Salton Sea Science — Where Do We Go From Here?

Fisheries Ecology of the Salton Sea

STATE OF THE SALTON SEA—OPENING COMMENTS

8505 Research Way, Middleton, WI 53562

A basic perspective for viewing the Salton Sea is to recognize its uniqueness as a waterbody within the geographic area referred to as the Salton Trough. The dynamic past of periodic flooding within this area that formed large waterbodies such as ancient Lake Cahuilla is history. Some of those waterbodies rose to sea level and higher elevations before evaporating to dryness. Such events no longer occur because of control of the Colorado River through a series of dams and allocation of waters to meet the needs of human society. Unlike the transient waterbodies of the past, the Salton Sea is a permanent waterbody that is primarily sustained by agricultural wastewater. The Sea is also unique because, despite being highly saline, it has rich biodiversity. The fish and bird components of this biodiversity are fundamental values that underlie support for restoration of the Sea. There is limited information about large-scale ecosystems of this type and even less knowledge of how to manage such environments. Science has joined management in the Salton Sea restoration effort by pursuing the knowledge needed to better understand the dynamics of this ecosystem and by providing guidance for the implementation of that knowledge to achieve restoration goals.

This second day of the Salton Sea Symposium addresses, "New Scientific Information and Discoveries". An exciting array of information is provided that separates fact from fantasy and replaces myth and innuendo with factual information about the current "State of the Salton Sea". The presentations provided address the physical and biological environments of the Sea and the fish and bird species that are dependent upon and affected by those factors. Today’s presentations are a milestone in our scientific understanding of this complex ecosystem. This milestone is "the end of the beginning", rather than an endpoint. This Symposium marks the end of an intensive 18-month effort to provide a foundation for decision processes that hopefully will result in actions for moving forward with restoration actions for the Salton Sea. The difficult task of evaluating the current "State of the Salton Sea" as a foundation for initiating such actions has been completed. The more difficult tasks lie ahead and, as for the task just completed, science has an important role in guiding the way to success. That role is described in the final presentation of this Symposium.

The geology of the Salton Sea basin provides a foundation for understanding the ecosystem of the Salton Sea and for making decisions on remediation facilities. Bottom sediments are important as substrates and nutrient sources for many of the Sea’s organisms. Although the geology of the basin is exceedingly complex, the geology of most relevance to understanding the ecosystem distills into the characteristics of sediment near and under the Sea. Sediment characteristics are controlled by bedrock sources, topographic characteristics of the land across which sediment is transported, and by its final depositional site (lake, stream, or alluvial fan). The bedrock geology of the area can be classified into five primary types, each of which erodes to form distinct sediment. For instance, schist and mudstone are very different rocks, but they each create clay-rich sediment such as that along the west side of the Sea. Evaluating the geology of the basin by using appropriately classified bedrock can therefore help in placing bottom sediments into a basin-wide context.

Geology is also an important factor for engineering design for remediation facilities from levees to pipelines. Part of the geologic complexity of the basin stems from its position on the San Andreas fault system, along which two of the Earth’s major tectonic plates, the North American and Pacific plates, move past one another. In addition, several parallel major faults in and near the basin, such as the Elsinore and San Jacinto faults, take up part of the plate motion, and all are seismically active. Earthquakes cause ground rupture and ground deformation that may damage and destroy engineered facilities located near the fault line; over wider areas earthquakes cause strong shaking that can cause damage far from an earthquake’s epicenter.

Plans for remediation facilities in the Salton Sea basin are developed as general plans that will be followed by more specific, detailed, plans. Planning for earthquake-caused ground rupture and strong shaking must likewise consider different scales, or resolutions, of information. Initial planning for the entire basin has used two information sources developed by California Division of Mines and Geology to make decisions on locations for facilities that will minimize hazards from earthquake-induced ground rupture: (1) existing information for state-mandated zones along active faults (Alquist-Priolo zones), and (2) regional maps of active faults. However, many poorly understood faults that lie in the basin do not have defined Alquist-Priolo zones, so initial design may require later improvement as fault information is developed.

After remediation options are determined and as detailed design work for facilities begins, detailed scales of geologic map information can provide the necessary framework for evaluating earthquake ground-rupture hazards and susceptibility to strong shaking. For example, in the San Gorgonio Pass area where detailed studies are underway by the U.S. Geological Survey, the two main splays of the San Andreas fault shown on regional maps and defined by the Alquist-Priolo zones are now known to comprise a set of compressional (thrust) faults that complicate an otherwise straightforward interpretation of the San Andreas zone. Detailed geologic study of remediation facility locations will provide information appropriate for more informed decisions relating to many hazards other than earthquakes, such as landsliding and floods.

Proposals presented to the Salton Sea Authority to control water levels and reduce salinity include schemes to isolate portions of this shallow water body to form fill-and-draw evaporation ponds to concentrate brines for ultimate export from the basin. These ponds, formed by dikes, could enclose areas of 10 to 20 percent of the Sea’s surface, primarily in the Southern Basin, and consequently significantly change natural wind-induced circulation. Under various proposed alternatives, the reconfigured Sea could ultimately be maintained at desired lower elevations to protect lands along the Sea’s periphery, stabilized consistent with balanced inflows of agricultural drainage, precipitation, and surface runoff and losses through water surface evaporation and deliberate export. By exporting salts concentrated by evaporation, the salinity of the Sea, now at levels that threaten its delicate ecosystem, could be regulated to decline gradually towards concentrations near ocean levels, closer to native salinity levels of the introduced fish species.

Physical modification of the Sea’s configuration and bathymetry, as envisioned in various alternative solutions of the water balance-salinity problem, is expected to change the distribution of wind shear stresses applied to the modified water surface and could hinder waters that circulate freely under present conditions. Possible consequences include increased scour and deposition of sediments, transport of nutrients and biota, and alteration of water quality levels that could be detrimental to the aquatic habitat. To assess quantitatively the potential consequences of physical changes in configuration and bathymetry, an established three-dimensional finite element hydrodynamic model has been modified and applied.

The numerical model, implemented on the computer, is comprised of a system of elements formed into a "grid" that represents the physical reality of the Sea, including the lower portions of three main tributaries that flow into the Sea. A set of equations that characterize fluid motions is solved in the model for a representative period of time to describe water motions, salinity, and temperature levels at all locations within the grid. When the model is provided with information on the direction and speed of winds over the Sea’s surface, it creates a corresponding field of velocities in the water body. The model was calibrated and verified against time-series of field observations of water velocities and temperatures obtained during a year-long field campaign performed during 1997.

The model solution contains time-series records of water velocity, temperature and salinity at all locations within the grid. By comparing model solutions with and without the evaporation ponds, the model can be used to determine potential changes in the water quality (temperature and salinity) and locations where increases or decreases in water velocity occur. Preliminary management scenarios have been performed for several pond structures under both present and future water surface elevations.

A one-year sampling program is being conducted to assess the current chemical and physical conditions in the Salton Sea. Analyses include general physical conditions and water quality parameters, nutrients, trophic state variables, major cations and anions, trace metals and organic compounds. Samples are collected from three locations in the main body of the lake and from the three major tributaries.

The Salton Sea was formed in 1905 when an accident caused the Colorado River to flow into the Salton Sink. The Salton Sea has a current water surface elevation of 227 feet below sea level and has no outlet other than evaporation. Salt concentrations have fluctuated over the years as the level of the Sea has changed, but levels have generally increased. The Salton Sea currently has a salinity of over 43 ppt, or about 30% greater than sea water. Proposed reductions in inflow volumes are expected to cause this level to increase.

Nutrient concentrations are high and lead to frequent algal blooms, which in turn contribute to low dissolved oxygen concentrations. The tributaries have a much lower salt content, but consist primarily of agricultural return flows with high nutrient levels. Concentrations of trace metals and organic compounds do not appear to be of major concern.

Once monitoring has been completed, data will be used to develop information on nutrient and suspended solids loading to the Salton Sea. The geochemical model, PHRQPITZ, will be used to evaluate potential chemical reactions limiting the solubility of selected water quality variables.

The study conducted by LFR Levine Fricke included collection of sediment samples from 73 separate locations within Salton Sea. The sediment sampling assessed and measured contaminant concentrations and evaluated particle size distribution in the bottom sediment of Salton Sea using both surface sediment grab samples and core sediment samples which provided information to sediment depths up to approximately 6 feet. This sampling effort encompassed the entire Sea plus approximately 1 mile up each of its three main tributaries: the Whitewater, the Alamo, and the New rivers.

Chemicals found at elevated concentrations and of potential ecological concern were cadmium, copper, molybdenum, nickel, zinc, and selenium. Selenium and molybdenum were found to be the most elevated inorganic constituents relative to background concentrations. Concentrations of selenium in general were elevated over much of the northern half of the Sea. The highest chemical concentrations (such as selenium, cadmium, and copper) were generally limited to the upper 1 foot of sediment.

The most common organic compounds found at the Sea included volatile organic compounds (acetone, 2-butanone, carbon disulfide) that appear to be associated with natural biological processes occurring within Salton Sea sediment. One of the most significant findings of this study was the number of organic chemicals commonly used in agriculture earlier this century that were not detected at elevated concentrations, such as DDT. Chemicals not detected above the laboratory detection limit in sediment samples include many semivolatile organic compounds, chlorinated pesticides and PCBs, organophosphate and nitrogen pesticides, and chlorinated herbicides.

Dissolved solids or chloride as an indicator, Colorado River water = 750 mg/L TDS. Looking at agricultural processes that control dissolved solids. Possibly show DH/O18O16 plot that indicates that evaporation is the main process controlling dissolved solids concentrations in the subsurface drainwater of the Imperial Valley tile water = median. Tail water = similar to Colorado River water Surface Drains = median from 49 drain samples New and Alamo River’s at outlet to Salton Sea = medians from detailed study. Salton Sea water = 44,000 mg/L and 15,000 mg/L chloride.

Colorado River water 2 ug/L, Subsurface drainwater - In May 1988 measured subsurface drainwater at 119 sumps and gravity tiles had median 25 ug/L (1-360 ug/L).

In 1994-5 - sampled 820 sites within the Imperial Valley – Discharge and specific conductance were measured at all 820 sites. Laboratory analyses at 304 of the sites had Median selenium concentration of 28 ug/L ranging from 1-311 ug/L. Selenium in tile water increases by evaporative concentration in a similar manner to chloride or dissolved solids. Give Se/Cl ratios that demonstrate that highest selenium concentrations have similar ratio to Colorado River water and median subsurface drainwater and also Alamo River Tail water 2-3 ug/L. Surface Drains - August 1994 sampled 49 sites had median of 6 ug/L (2-52 ug/L). New and Alamo River’s at outlet to Salton Sea median 4 ug/L and 8 ug/L.

Interface area – Alamo River 200 feet seaward of the end of the levee on the left bank - water 3 ft deep – at a depth of 1.3 feet sp cond 5,000 uS, DO 4.2 mg/L (56%) and Se 8ug/L. At 3 feet – sp cond 51,000 uS, DO 1.2 mg/L (18%) and Se1.0 ug/L. Special sample collected in June 1989 on river side of interface had total Se of 6.35 ug/L with 2.56 ug/L in the +4 selenite state and 3.79 in the +6 selenate oxidation state. At interface total Se 2.4 ug/L (<method specific reporting limit) with 1.79 ug/L at +4 selenite and <0.2 in the +6 selenate state. Salton Sea water 1 ug/L. None of selenium is in the highly oxidized +6 selenate state.

Colorado River if available. Soils from fields in Imperial Valley (270 soil cores representing 15 fields have median concentration of 0.2 ppm selenium ranging from <0.1 to 1.3 ppm. Bottom sediment from 48 surface drains in Imperial Valley have median concentration of 0.5 ppm ranging from 0.1 to 1.7 ppm. Bottom sediment in Salton Sea 11 sites have median concentration of 2.7 ppm with range from 0.58 to 11 ppm. Compare to particle size distribution table and contour plot – Very fine sediment <0.002 mm in deepest parts of Salton Sea have highest selenium concentrations. Composed of highly organic matter, low density detritus.

Invertebrates from Salton Sea had Se concentrations ranging from 0.8 to 12.1 ug/g dry weight – critical dietary threshold is 5 ug/g – only pileworms had concentrations exceeding the threshold – very limited sampling in numbers and area. Fish in the Sea had higher concentrations than fish in the freshwater drain/river system.

NIWQP focus has been on selenium concentration in food chain of both fresh water system and in the Salton Sea. Bioaccumulation and biomagnification of selenium.

Nitrogen – Nitrate plus nitrite Ammonia

East Highline 0.22 mg/L 0.03 mg/L

Subsurface drainwater 12.0 mg/L 0.07 mg/L

Surface drainwater 4.95 mg/L 0.19 mg/L

Salton Sea 0.1 mg/L 1.41 mg/L

Organic nitrogen at 2.95 mg/L and Organic carbon 42 mg/L

In the Salton Sea, as in many aquatic ecosystems, the small organisms rule. They drive the system. They carry out most of the photosynthesis and most of the decomposition. Their metabolic and biogeochemical activities are a major determinant of water chemistry and water quality. They serve as the base of the foodweb that sustains the fish and bird populations at the Sea. Not much happens without their involvement. Some are pathogens or toxic. In this session, we will hear talks by specialists on seven different aspects of the biology of these little critters. Each speaker will give both general background information plus their recent findings. There are also six posters on different aspects of the little critters available for your viewing. The present talk aims to provide an introduction and context for these oral and poster presentations.

The Salton Sea's biology has received little serious study despite its relevance to the lake's value to man and wildlife. In the 1950s a small group of scientists from UCLA and the California Department of Fish and Game carried out a two-year survey of the lake's limnology and fish following the successful stocking of the lake with marine fish, invertebrates and algae during the previous decade. In 1968-69 the Federal Water Pollution Quality Control Administration carried out a study of nutrient inputs to the lake and phytoplankton populations. Other biological investigations at the lake have been of a very sporadic and limited nature. The work reported in this session represents the most thorough study of the Sea's little critters ever carried out. The work is still in progress. It is being done primarily by scientists and graduate students at six different institutions around the country with funding from the Environmental Protection Agency, Salton Sea Authority, and other sources.

Two general types of studies will be reported, systematic and ecological. The systematic studies represent the attempt by some of the nation's top specialists in different taxonomic groups of organisms to determine what species are in the Salton Sea, a task more difficult than it may sound. Small organisms are hard to identify and classify and non-specialists often err when they attempt this. Five groups with large numbers of species were selected for special attention: cyanobacteria, diatoms, dinoflagellates, ciliates, and amebas. We also enlisted, on an ad hoc basis, specialists to identify new species found in less species-rich groups - the rotifers, roundworms, flatworms, segmented worms, and crustaceans. Altogether, as a result of this biotic inventory, the number of cyanobacterial, algal, protozoan, and invertebrate species known from the Sea has gone this year from about 70 to about 360 and is still climbing. At least a couple of dozen of these species are completely new to science, not just to the Salton Sea.

Four studies predominantly ecological in character are reported. The benthos and plankton have been sampled at regular intervals over a year or more to document their seasonal dynamics and spatial variability. These are the food supply for the rest of the system, and a number of important interactions with the physical-chemical environment have been documented. Ectoparasites of fish have also been monitored since 1997; they often cover baby fish so densely as to suggest their effects on juvenile mortality could drive fish population dynamics in the lake. Finally, the potential role of algal toxins in fish or wildlife mortality events has been assessed by extracting with organic solvents phytoplankton samples obtained from different blooms and testing them for toxicity to brine shrimp and mice.

Diatoms are unicellular, eukaryotic (cells in which the nucleus is separated from the cytoplasm by a nuclear membrane; i.e. structurally more complex than prokaryotic bacteria), photosynthetic (i.e. they require light for the process of photosynthesis) microorganisms ranging from ca. 2 µm to ca. 2 mm in size. They are found just about anywhere there is light and moisture. They are far more diverse and abundant in freshwaters, where they are the most common organism and make up the base of many freshwater food pyramids. In the oceans, diatoms are most abundant in areas of upwelling (coastal and open ocean), where oceanic currents bring up the nutrients from deeper waters to the photic zone, and in polar latitudes. In these regions, they are the most important organisms at the base of the food chain.

Diatoms have a highly differentiated cell wall, which is impregnated with opaline silica, so that their growth is subject to the availability of silicon in the water. The diatom skeleton (frustule) is composed of two valves that fit together in a nested, overlapping fashion like a Petri dish. Diatom classification is based on the features of the skeleton.

Diatoms are important ecological indicators because they are sensitive to such factors as salinity, temperature, pH and pollution. In limnology, freshwater diatoms are the primary tool for reconstructing lake conditions, especially changes in pH and fertility. They play a key role in monitoring acid rain and the pollution of the world's freshwater. With the objective of documenting the diversity of diatoms in the Salton Sea and thus expanding the limited knowledge about these single-celled algae from this extreme environment we set out to identify and photograph all diatom species encountered in the phytoplankton and the phytobenthos of the Salton Sea (see poster). A catalogue of the diatom assemblages is being prepared which will serve as a guideline to the diatom flora of the Sea for use by future students and researchers.

In the Salton Sea there are four general categories of diatoms. Those that live in the plankton float freely about with the water currents. Some diatoms live on the bottom mud or in the algal mats, these are the benthic diatoms. Others, the epiphytic diatoms, attach to the macroscopic green algae which grow on the rocks and other hard surfaces near the shore. Also present in the Sea are diatoms that get washed in by the rivers and other inflows. Many of these probably don’t live long in the high salinity but their valves are found infrequently in the water or sediments.

We have found a great diversity of diatoms; 92 taxa were distinguished on their basis of their morphological features at the light- and electron microscope level. These were found after examining samples collected at 19 different sites (including shore and open water samples). Whenever possible, taxa were identified to the level of species using published literature. Some of these are new to science. In addition, a few taxa showed peculiar morphological features, probably as a response to adaptation to the extreme environment of the Salton Sea, and are documented as "morphotypes" in need of further taxonomic work. The most abundant diatoms are marine planktonic species which is not surprising given the salinity and history of the lake. They dominate the phytoplankton assemblage in the summer and fall with densities of about 10⁶ cells per liter. Other common species are mostly found in salt lakes or are usually found in fresh or brackish water.

It is clear that diatoms are a major component of the microorganisms in the Salton Sea. Preliminary studies on the sediments reveal a rich flora preserved in the sediments which holds clues to the past history of the Salton Sea.

Ciliates are unicellular microorganisms that make up the Phylum Ciliophora in the Kingdom Protista. They are eukaryotic with dimorphic nuclei. They usually have proteinaceous projections, termed cilia, that cover portions of the cell and function primarily in locomotion and food-gathering. Another distinguishing characteristic for this group of protists is the presence of complex structures known as kinetids. All ciliates display some form of heterotrophic nutrition. In aquatic environments ciliates are important as grazers of bacteria, algae, and other protozoans, and in turn serve as food for small invertebrates and fish. When abundant in the Salton Sea plankton they can give the water a grayish color.

The major objective of the present study was to begin an inventory of the ciliate species found in the Salton Sea. Prior to this study, no ciliates from the Salton Sea had ever been identified. Two one-week sampling trips (in January and June 1999) were made to the Sea for collection purposes, and some additional samples were sent by SDSU biologists. Specimens were collected, observed live, catalogued, preserved with a fixative, stained, observed with standard light microscopy and identified to genera and, where possible, species. Approximately 664 microscope slide preparations were made and analyzed. Representatives from eight separate classes in the phylum Ciliophora were identified, on the basis of kinetid morphology and nuclear number and arrangements.

A total of 140+ different species of ciliates have been found in bottom sediment, algal mat and plankton samples from our twelve collecting sites. Of these, there are 40+ new to science, i.e. have never been found anywhere before. Of major interest was the finding in June of 35 species not found in January, even though the very same sites were sampled on both occasions. Factors that varied between the two trips included water temperature and dense blooms of planktonic dinoflagellates in January. Diatoms and bacteria, but not dinoflagellates, could be seen in the food vacuoles of some ciliates. Ciliates are clearly one of the most species-rich groups of organisms in the Salton Sea. To fully analyze and catalog this diversity will require great deal of work, as will the deciphering of the influence ciliates exert on the rest of this ecosystem.

Protozoa are unicellular microorganisms that include amoeboid, flagellated and ciliated organisms. They all display heterotrophic nutrition, that is, they consume organic material usually in the form of other microbes such as bacteria, other protozoa and unicellular algae. Because they are generally considered to be the major micro-consumers in ecosystems, it is important to understand the nature of the different protozoan groups within the microscopic community.

Amoebae without an obvious cell covering are termed "naked amoebae" and are different from other amoeba that live within a walled cell with openings for food ingestion. They are united by the fact that they are all eukaryotic (i.e. structurally more complex than prokaryotic bacteria) single cells that produce pseudopodia (literally ‘false feet’) of one form or another which they use for locomotion and feeding. Naked amoebae are often small (less than 20 thousands of a mm), transparent and attached to particles making them difficult to see in freshly collected samples. Their constantly changing shape also makes them difficult to identify since they have few rigid diagnostic features for identification purposes. In 1979, the marine microbiologist Sieburth commented that investigators who examine planktonic or benthic samples seem to shy away from amoebae. Today, some 20 years later, little has changed and amoebae remain an understudied group despite the fact that they often number several thousand per liter in marine waters.

The objective of the present study was to document the diversity of naked amoebae in the Salton Sea and to provide a first estimate of their numerical importance. Since they are virtually invisible in fresh samples, they had to be cultivated in the laboratory to make them conspicuous in the collected samples. Of course, this enrichment procedure only worked for those amoebae amenable to laboratory cultivation and the results must be considered underestimates of the true biodiversity.

A total of 45 different types of amoebae were distinguished on the basis of their morphological features at the light microscope level. These were found after examining water collected at 19 different sites (15 shore samples and 4 open water samples). Wherever possible, these ‘morphotypes’ (presumed to be different species) were identified to the level of species or genus using published keys. However, because amoebae are an understudied group and because the Salton Sea is species-rich, we estimate that around 18 of the isolates (that’s 40%) are new to Science. A diversity of 45 species can be put into perspective if we consider that a recent review of all the literature on naked amoebae from European marine waters yielded just 74 species (Rogerson & Goodkov, 1999 unpublished). In other words, more than half the biodiversity of amoebae in European waters can be found in the Salton Sea. Preliminary counts, also based on enrichment cultivation methods, showed that amoebae in the water column ranged from 14,560 to 237,120 cells per liter. These densities, also underestimates, are far higher than for any previously examined marine water sample.

It is clear that the Salton Sea is rich in microbial life and that naked amoebae constitute a significant part of the microbial assemblage. The ecological importance of high numbers and high diversity of amoebae is unknown. But it should be noted that amoebae are unique amongst micrograzers in that they prey on tightly associated microbes (those attached to the surface of particles). As such amoebae may be important in the cycling of carbon and nutrients in the Salton Sea. The view that amoebae may be important consumers in situ deserves further consideration.

Aquatic environments like the Salton Sea represent extreme environments that mimic, in some ways, the extreme environments present in the early earth. The high concentrations of sulfur, for example, are toxic to many photosynthetic micro-organisms but can be tolerated by cyanobacteria. Cyanobacteria are among the most primitive oxygen-evolving photosynthetic organisms; they are more closely related to heterotrophic bacteria than higher plants. As a group, they are extremely diverse in the Salton Sea with most genera of common marine cyanobacteria represented by at least one species. We have been able to create pure cultures of many of these forms and have focused special attention on those which form long filaments. This type of cyanobacteria is found in large, slimy, visible mats along the shoreline at certain times of year; our observations suggest that these mats form near the bottom, in layers where hydrogen sulfide concentrations are high.

Center for Inland Waters and Department of Biology, San Diego State University.

Objectives:

This study focuses on the distribution and seasonal abundance of the benthic (bottom-dwelling) invertebrate species which serve as a major food source for fish and many types of birds in the Salton Sea. Its purpose is to document the diversity of species and their abundance within three major habitats: the sea bottom at depths of 2–12 m, the shoreline barnacle shell sand, and on rocky shorelines.

Methods:

We surveyed each habitat bimonthly throughout 1999. We sampled the offshore sediments using a grab off of our research boat. The grab removes a 225 cm2 sample of the sea floor, which is rinsed through a screen. Animals retained on the screen are preserved for later sorting and enumeration back in the lab. We sampled the Sea bottom along 3 transects, each containing 6 stations at depths of 2, 4, 6, 8, 10, and 12 m, collecting a total of 320 samples. We sampled the shoreline sand at 3 locations on the east side of the Sea using a coring device which removed the top 10 cm of a .01 m2 area for a total of 54 samples. Finally, we scraped off all the living material from within 60 10 x 10 cm squares on both barnacle- and algae-covered rocks to determine the abundance of invertebrate species in this habitat.

Important Results:

Ours is the first scientific survey of the invertebrate life in the Salton Sea since 1956, and we have discovered 4 species of worms new to the Sea. The macroinvertebrate community now consists of 5 worms, 2 amphipod crustaceans, and 1 barnacle. The pileworm Neanthes succinea is the key food chain organism for fish and birds, and is the dominant species on the sea bottom between depths of 2-12 m. However, its abundance varies greatly over the year, due to the seasonally decreasing oxygen levels in the water column. In spring, the pileworm was abundant at all depths and locations sampled, but disappeared by September from all sediments deeper than 2 m, and from the shoreline sand habitat. In contrast, densities of all invertebrate species increased throughout the year on the rocky shoreline, which harbors the highest numbers of organisms. In this habitat, Neanthes was present in densities of up to 85,540/m2, and the crustacean Gammarus mucronatus was seen at densities of up to 125,780/m2. This demonstrates the importance of the rocky shoreline both as a refuge for Neanthes, and as a habitat that should be maintained to ensure the availability of these food organisms for fish and birds.

The plankton of a lake ecosystem is very important to its functioning. Photosynthetic algae in the plankton form the base of the food web, directly providing food to the zooplankton and planktivorous fish such as the tilapia. Algae also produce dissolved organic matter (DOM). Bacteria and heterotrophic flagellates use the DOM and then are fed upon by planktonic ciliates which in turn can be fed upon by larger zooplankters and fish.

The concentration of chlorophyll in the water provides a good index of phytoplankton abundance. Chlorophyll concentration was highest in late winter, declined to a minimum in late summer, and then increased throughout the fall mixing period. Phytoplankton decline during the warm season probably is a consequence of reduced nutrient levels in surface waters. This would be caused by the limited mixing of bottom and surface waters as a result of the thermal stratification present during most of this season. In early fall when the lake first starts to cool and mix from top to bottom daily, the nutrients nitrogen and phosphorus are brought up from below and stimulate the winter blooms of dinoflagellates that color the water dark brown. Chlorophyll levels were usually highest in the surface water stratum, reflecting the ability of some phytoplankters to swim toward the light. Secchi disk readings ranging mostly from 0.5 to 1.5 m suggest self-shading may often limit growth of phytoplankton.

The dominant species present in the phytoplankton have changed since the 1950s, but most of the major groups (dinoflagellates, diatoms, chlorophytes, euglenoids, and cryptomonads) are the same. One exception is an alga in the raphidophyte group, which may be toxic to fish and has not been reported previously from the lake (see poster on Chattonella marina). The prominent dinoflagellates in the 1950s were Prorocentrum spp. and Heterocapsa niei. Now Gyrodinium uncatenum, several Gymnodinium spp., and a Scrippsiella sp. dominate, along with the Heterocapsa. The dominant diatoms in the 1950s were Cylindrotheca closterium and an unidentified Cyclotella. We now find Thalassionema nitzschioides, Pleurosigma ambrosianum and a very small Cyclotella to be the dominant ones (see the diatom poster).

Summer has the highest total zooplankton density, mainly due to the high numbers of the copepod, Apocyclops dengizicus, and a rotifer, Brachionus rotundiformis. In late summer, there are sometimes abrupt decreases in zooplankton populations. In 1998 an especially dramatic decline in zooplankton occurred when hydrogen sulfide was found throughout the water column and oxygen levels fell to almost zero following a mixing event. This simultaneous scarcity of phytoplankton and zooplankton in late summer, together with low oxygen availability, may represent a time of serious stress to fish. Zooplankton species now dominant are the same as or similar to those found in the 1950s. Three species of rotifers alternate dominance during the year. These feed mostly on algae and other small organisms. One of them, Brachionus rotundiformis, may have been present in 1955. Two species of Synchaeta, a genus of rotifer not previously been reported from the Sea, are now very common in the winter. Larvae of the benthic barnacle (Balanus amphitrite) and polychaete worm (Neanthes succinea) are also found in the zooplankton. These larvae were scarcest in summer. This possibly was due to 1) summertime reduction of adult barnacles by a drop in lake level that left many 'high and dry' and 2) anoxia that rendered most of the lake bottom uninhabitable by adult polychaetes.

Algal toxins have been known to cause disease and mortality in fish, birds, marine mammals, and even humans. Several algal groups contain species that are commonly known to produce toxins including Prymnesiophyceae, Dinophyceae and Raphidophyceae and Bacillariophyceae. Although algae in these groups have been found in the Salton Sea, no humans have been affected. One health hazard to humans in coastal areas is consumption of mollusks contaminated with algal toxins. Mollusks, however, are not found in the lake. Fish, birds, and invertebrates, however, could be susceptible to any toxins present. In response to the 1992 and 1994 unexplained bird mortality events, we surveyed for algal toxins in the Salton Sea. The goals of this survey were to determine if and when algal toxins are present in the lake and to document the phytoplankton community structure at those times.

Phytoplankton samples were taken from the water surface and from the top 50-100 cm of the water column using various methods, beginning in January 1999. One portion of each sample was extracted with organic solvents and screened for toxicity using a brine shrimp lethality assay. Samples that showed activity in the screening process were then analyzed using a mouse toxicity bioassay. A second subsample was preserved in Lugol’s solution for identification and counting of types of algae present.

Several species of prymnesiophytes (Prymnesium sp., Chrysochromulina sp.) are occasionally found in the lake in low densities. In this same group, a coccolithophore (Pleurochrysis pseudoroscoffensis) was seen in very high densities in surface films during spring and summer 1999. Although samples taken from these films showed activity in the brine shrimp lethality assay, they showed no activity toward mice. Samples dominated by Chattonella marina (Raphidophyceae), a species known to cause fish kills in oceanic systems, were taken during summer and fall months. Several samples dominated by dinoflagellates (Heterocapsa niei, Gyrodinium uncatenum, Gymnodinium sp., Scrippsiella sp.) were also taken throughout the year. Samples dominated by C. marina and by dinoflagellates again showed moderate to high lethality in the brine shrimp assay but were negative in the mouse bioassay. No potentially toxic diatoms were observed. While some blooms at the Salton Sea show toxicity to invertebrates, those tested so far are inactive when tested in a vertebrate system (mice). This limited study is not sufficient, however, to rule out toxic algae as a factor in major mortality events in birds or fish at the Salton Sea.

During the summer of 1999, the Ecological Planning and Assessment Group of the U.S. Bureau of Reclamation (Reclamation) conducted a survey of the desert pupfish community within shoreline pools of the Salton Sea (Sea), agricultural drains that discharge directly into the Sea, and lower Salt Creek tributary for the Salton Sea Restoration Project (Project). The objectives of this study were to determine the movement of pupfish within and between various habitat types within one summer season and to address the purposes (i.e., feeding, breeding, dispersal, and avoidance of predators) for which pupfish were utilizing these areas. This information would help determine the importance of the Sea as a corridor to movements among various habitats and allow mixing of the gene pool. Information from this study could be used to determine how various proposed Salton Sea restoration actions might affect the desert pupfish, such as the construction of a desert pupfish channel around a series of concentration ponds to allow movements among habitats.

Irrigation drains, shoreline pools, and a tributary (Salt Creek) were sampled every two weeks from the end of June to the middle of September (6 sample trips) during the summer of 1999. Fish were captured using small minnow traps. Movements of pupfish were determined by a marking and recapturing technique. Collected pupfish were marked by injecting a small fluorescent plastic material just under the skin. Unique markings were used for each site. Feeding habits were determined by examining the stomach contents of 10 desert pupfish.

Movements of desert pupfish were documented between different, adjacent habitat types. Of the 3,239 desert pupfish captured during the study at all sites, 278 were recaptures, including 27 recaptures at areas different from where they were initially marked.

The best evidence of desert pupfish movements between habitats was observed in the southwestern area of the Sea between an irrigation drain and a connected shoreline pool. Of the 1,441 pupfish captured in the drain during the study, 214 were recaptures from this drain and 19 were recaptures from the shoreline pool. In the shoreline pool, 308 pupfish were collected, including 13 recaptures from this pool and 7 recaptures from the drain. Although some pupfish were moving between these habitats, a large proportion remained where they were initially marked. There was no clear explanation for this behavior. Since the shoreline pool was always open to the Sea, there is a good probability that some pupfish moved into other habitats via the Sea. However, no marked pupfish from this drain or shoreline pool were recaptured in other nearby habitats.

Movements of desert pupfish from lower Salt Creek into the shoreline pool south of Salt Creek were confirmed when one marked pupfish from Salt Creek was recaptured in the shoreline pool. Movements were also supported from the catch rate data which showed the densities of pupfish declining in Salt Creek while the numbers in the shoreline pool increased during the summer. The movements into the shoreline pool were probably a result of deteriorating habitat conditions in lower Salt Creek (e.g., drying channel and dying aquatic vegetation). Access from the shoreline pool to the Sea was blocked by a barnacle bar throughout the study.

The limited stomach analyses suggested a shift in diet from primarily plankton to small fish and fish eggs as the spawning season progressed.

Decreases in the size of isolated shoreline pools during the season were observed and may require maintenance of the connectivity between habitats to prevent pupfish from becoming stranded within habitats that cannot sustain them for prolonged periods.

Great concern recently has been expressed about the fate of the Salton Sea ecosystem because of increasing salinity, contamination from agricultural and urban sources, disease outbreaks, and large die-offs of waterbirds. Particularly hard hit in the 1990s were the Eared Grebe (150,000 in 1992, unknown causes); American White Pelican (9,000 in 1996, botulism); Brown Pelican (1,200 in 1996, botulism); and waterfowl, shorebirds, and waders (>11,000 in 1998, avian cholera). Concern is heightened because connections with other important ecosystems in western North America link the health of populations of many species of waterbirds to that of the Salton Sea. Additionally, because of the loss or degradation of other major wetland systems in the Pacific Flyway, including the nearby Río Colorado Delta region, birds have become increasingly dependent on the Salton Sea.

As part of the Salton Sea Reconnaissance Survey, designed to gather primary data on the Salton Sea ecosystem, we synthesized prior bird data, and in 1999 initiated baseline studies of bird use of the Salton Sea and adjacent Imperial Valley. These studies used a suite of standardized methods to gather data on current population sizes, seasonal abundance patterns, and local distribution patterns and habitat associations of the key groups of birds in this area.

Prior and current data demonstrate that the Salton Sea supports large numbers and a great variety of avian species and is arguably one of the most important wetlands to birds in North America. The Salton Sea hosts hundreds of thousands, and at times low millions, of migratory, wintering, and breeding birds and is the destination for many post-breeding birds moving north from Mexico. Populations in the Salton Sea area of a number of species – Eared Grebe, American White Pelican, White-faced Ibis, Ruddy Duck, Mountain Plover, Black Tern, and Burrowing Owl – are of regional, continental, or worldwide importance. Colonial breeding species with significant populations at the Sea include the Double-crested Cormorant, Cattle Egret, Gull-billed Tern, Caspian Tern, and Black Skimmer. The Sea also supports notable populations of a number of additional taxa of conservation concern, such as the Fulvous Whistling-Duck, Least Bittern, Wood Stork, Yuma Clapper Rail, Black Rail, and Snowy Plover.

Although waterbirds are widely distributed in various habitats at the Salton Sea and Imperial Valley, studies in 1999 documented particularly large concentrations of waterbirds at both the north and south ends of the Sea. Isolated river deltas and islands were very important refugia for large flocks of roosting and colonial nesting birds.

Future research should continue to focus on diseases and contaminants; the reproductive success, ecology, diet, and habitat use of key species; and life history needs of species that move between the Sea and adjacent agricultural habitats or to and from distant wetlands. Ongoing research and monitoring is needed to understand seasonal and long-term population dynamics and to assess the effectiveness of any large scale projects implemented to resolve the Sea’s ecological problems.

The two North American pelican species, the brown pelican (Pelecanus occidentalis) and American white pelican (P. erythrorhynchos), both importantly occupy the Colorado Delta Region (the "Delta")(including the Salton Sea and extending into the northern Gulf of California) during major portions of their annual cycles. This is unusual in that the two species seldom ecologically overlap significantly in other parts of their ranges (other than as occasional mixed-species roosting groups or rare mixed-species feeding groups). Both species have historically bred or currently breed at the Salton Sea or in other parts of the Colorado Delta region, but major habitat utilization for both species comes during migration and post-breeding dispersal. American white pelicans that utilize the Delta region are comprised and dominated by individuals from the declining western population segment, so that events in the Delta will importantly affect the status of this entire population segment in other parts of western North America. The source of all Salton Sea brown pelicans are from much larger populations in the Gulf of California, and the Delta Region supports only a small proportion of "global" brown pelican population numbers. But the recent range expansion of this formerly endangered species as a breeder into the Salton Sea represents a developing ecological and behavioral phenomenon of seabird range expansion, a potentially important expansion into the United States, and the first inland occurrence of this species as a breeding bird. As a case-history, both species of North American pelicans then abundantly demonstrate what has been shown for other avifauna of the Delta region–that this area is a unique and valuable binational treasure that represents a vital element in the connectivity of the Pacific Flyway for pelicans and many other avian species.

The Salton Sea was formed in 1905 when an accident caused the Colorado River to flow into the Salton Sink. The Salton Sea has a current water surface elevation of 227 feet below sea level and has no outlet other than evaporation. Salt concentrations have fluctuated over the years as the level of the Sea has changed, but levels have generally increased. The Salton Sea currently has a salinity of over 43 ppt, or about 30% greater than sea water. Proposed reductions in inflow volumes are expected to cause this level to increase.

A one-year sampling program was conducted to assess the current chemical and physical conditions in the Salton Sea. Analyses included general physical conditions and water quality parameters, nutrients, trophic state variables, major cations and anions, trace metals and organic compounds. Samples were collected from three locations in the main body of the lake and from the three major tributaries.

Nutrient concentrations are high in the Salton Sea and lead to frequent algal blooms, which in turn contribute to low dissolved oxygen concentrations. However, the tributaries have a much lower salt content, but consist primarily of agricultural return flows with high nutrient levels. Lastly, concentrations of trace metals and organic compounds do not appear to be of major concern in the water column.

Among the environmental factors having greatest impact on the organisms that live in and on the Salton Sea are water temperature, the mixing of surface and bottom waters, and concentration of dissolved oxygen. Here, we report the results of our 1997-1999 monitoring of the thermal, mixing, and oxygen regimes of the Sea, interpret them in relation to weather and climatic variables, and discuss the numerous ways in which these processes may be affecting plankton, benthos, fish, and aquatic birds of the Sea.

Temperature and dissolved oxygen were measured at three mid-lake stations at 2-5 week intervals from January 1997 to December 1999. Two additional near shore stations were added in January 1999. Measurements of conductivity were begun in July, 1998 and hydrogen sulfide measurements were made in July - September, 1999. Daily weather data was obtained from 4 meteorological stations surrounding the Salton Sea.

The lake has a warming period from early January to July-September, followed by a 4-5 month cooling period. Thermal stratification exists during most of the warming period but this is interrupted by periodic wind-driven mixing events, especially in early spring. Mixing events are less frequent in the summer, but when they occur they sometimes result in the entire water column becoming anoxic with measurable quantities of hydrogen sulfide in surface waters. These may be responsible for crashes in plankton populations often observed at these times. During stratification anoxia and high concentrations of hydrogen sulfide, up to 5 mg/L, are found in bottom waters. For a large part of the warming period, few fish are found in midlake and macroinvertebrates are absent over most of the lake bottom as a result of these conditions. By the end of the warming period mean water column temperature in midlake is 31-34°C. During the cooling period, convectional circulation in the water column supplements wind-generated turbulence and the whole water column mixes more or less daily. Oxygen levels during this period are almost always >3 mg/L at all depths. By the end of the cooling period mean midlake water column temperature is 13-15°C. Lake hydrodynamics are complex, influenced by freshwater inflows at the south end and a double-gyre current system. Dissolved oxygen profiles differed markedly with distance from shore. In general, during the warming period the well-oxygenated layer is thicker in nearshore areas than in midlake. Salinity gradients have been found in the southeastern sector of the lake, upcurrent from the New and Alamo River inflows. Such gradients will inhibit mixing of bottom and surface waters wherever they occur.

The Salton Sea has been accumulating chemical constituents delivered by its tributary streams for nearly 100 years because it has no outlet. The buildup of chemicals that are highly soluble and unreactive, such as chloride, has resulted in the development of a quasi-marine lake. In contrast, chemicals that react to form insoluble phases ultimately enter the sediment that accumulates on the floor of the Sea. Solubility properties are especially relevant for two important contaminants, selenium (Se) and nitrogen (N). The Se is contained in Colorado River water used for irrigation, and N is derived mostly from chemical fertilizer. Both are delivered to the Salton Sea as highly soluble oxyanions by the Alamo and New Rivers, which are relatively high in oxygen at their outlets to the Salton Sea, but are removed as reduced species in anoxic sediment on the Sea’s floor. Without this removal mechanism, Se concentration would presently be about 400 parts per billion (ppb) and N would be 100 parts per million (ppm) in the Salton Sea’s water, rather than the observed concentrations of only about 1 ppb and 5 ppm, respectively. Ironically, anoxic conditions responsible for producing the noxious odors and leading to periodic dieoffs of large numbers of fish in the Salton Sea have prevented aqueous Se and N from reaching levels that could indeed pose an extreme environmental hazard.

Does all the Se and N ever discharged to the Salton Sea still reside in its sediment, or has some been lost? It is well known that certain bacteria are capable of converting both elements into gases that can then be volatilized to the atmosphere. By comparing concentrations of Se and N with those of molybdenum and uranium, elements with similar geochemical properties, this study concluded that there is now little, if any, Se and N loss to the atmosphere. It is important that any engineering changes made to the Salton Sea do not result in reintroduction of these contaminants from sediment into the overlying water.

Dissolved N concentration in the Salton Sea is apparently several times higher today than it was in the mid-1950’s; yet dissolved phosphorus (P) concentration has changed little, if at all. Why have P levels not increased? One possible explanation is that phosphate is efficiently removed from the water column by incorporation with calcium as apatite minerals--the material that composes bone. If so, attempts to slow or reverse excessive biological productivity (eutrophication) through large-scale harvesting of fish may not result in lowering the dissolved P concentration that would thereby improve the trophic status of the Salton Sea.

During prehistoric times, the Colorado River occasionally meandered into and filled the Salton Sea Basin, creating several huge inland lakes, variously called Lake LeConte or Lake Cahuilla. Previous researchers have identified high stands of these ancient lakes using standard survey methods. The objective of this investigation was to further delineate the prehistoric shorelines using satellite imagery, global positioning system (GPS) and geographic information system (GIS) technologies. Using one-meter digital orthophotographs, points were selected in the laboratory and were located in the field using a GPS. Point data were integrated with a digital elevation model (DEM) and elevation contours were plotted on Landsat-TM images, generating a range of prehistoric shorelines. Contours were then correlated with archaeological site data, geomorphic features, and other factors to reconstruct Early American settlement patterns for Lake Cahuilla. The combined GIS coverages of ancient Lake Cahuilla and cultural resources may be used together as a cultural resources constraints model, identifying areas of high cultural resource sensitivity for evaluation of potential impacts as a result of implementation of Salton Sea restoration project alternatives.

  The Salton Sea basin is criss-crossed by a mosaic of faults, many of which are active in the sense that they are considered capable of destructive earthquakes and associated ground rupture along the fault line. The faults of this basin are particularly complex because the basin contains the San Andreas fault system, along which two of the Earth’s major tectonic plates, the North American and Pacific plates, move past one another. The San Andreas fault system in the basin undergoes a big jog or step. At the step, the basin is sinking and young volcanic materials are intruding into the sediment; this rapidly sinking part of the basin forms the southern Salton Sea. In addition, several parallel major faults in and near the basin, such as the Elsinore and San Jacinto faults, take up part of the plate motion.

Earthquakes cause ground rupture and ground deformation that may damage and destroy engineered facilities located near the fault line; over wider areas earthquakes cause strong shaking that can cause damage far from an earthquake’s epicenter. Damage due to shaking is difficult to predict without extensive information on the earth materials on which a facility is built.

Planning for earthquake-caused ground rupture in the Salton Sea basin must consider different scales, or resolutions, of information. Initial planning for the entire basin can use the two information sources developed by California Division of Mines and Geology to make decisions on locations for facilities that will minimize hazards from earthquake-induced ground rupture: (1) existing information for state-mandated zones along active faults (Alquist-Priolo zones), and (2) regional maps of active faults. However, many poorly understood faults that lie in the basin do not have defined Alquist-Priolo zones, so initial design may require later improvement as fault information is developed.

After remediation options are determined and as design work for facilities begins, detailed scales of geologic map information can provide the necessary framework for evaluating earthquake ground-rupture hazards. For example, in the San Gorgonio Pass area where detailed studies are underway by the U.S. Geological Survey, the two main splays of the San Andreas fault shown on regional maps and defined by the Alquist-Priolo zones are now known to comprise a set of compressional (thrust) faults that complicate an otherwise straightforward interpretation of the San Andreas zone. Detailed study of remediation facility locations will provide information appropriate for more informed decisions relating to many hazards other than earthquakes, such as landsliding and floods.

Parasites of fish and invertebrates are integral parts of aquatic ecosystems. Especially in water bodies with poor environmental conditions they can exert a strong regulatory effect on populations. Environmental stresses can depress host immunity. Fish become more susceptible to infections and these can become more severe, even fatal. Sick and dead fish can become a source of disease for piscivorous birds and can present serious threats to their health.

For many decades, the Salton Sea has been the site of an unprecedented series of die-offs of fish and water birds. These mortality events have been associated with critical combinations of high temperature and salinity, low oxygen tension, and toxic algal blooms. Recently, bacterial and viral pathogens have been documented or suspected as a cause of some of the massive birds and fish kills. Until 1997 nothing was known about parasites and their roles in fish disease at the Salton Sea.

Parasitological monitoring was carried out in 1997-1999. A total of 1,512 fish were examined from 6 locations along the shoreline of the Salton Sea. The young of tilapia, croaker, and longjaw mudsucker were found infected by ectoparasites that is parasites that attach to the external body surfaces. Some permanent and persistent infestations of fish by such parasites were discovered around the perimeter of the Salton Sea at Varner Harbor, Bombay Beach, Red Hill Marina and Salton City. Invertebrates such as pile worms and copepods that represented the major food items for fish were also infected.

We found that fish from the Salton Sea are infected by three species of parasitic protozoans: the dinoflagellate Amyloodinium ocellatum, the ciliate Ambiphrya ameiuri; and the flagellate Cryptobia branchialis, and two species of parasitic flatworms, Gyrodactylus olsoni and Gyrodactylus imperialis. The protozoans range from 7.5 µm to 129 µm in length, the flatworm from 261µm to 312 µm. These parasites are dangerous and sometimes spread pathogens for fish in aquaculture facilities. In nature, however, infestations by these parasites are usually low. At the Salton Sea, parasitic protozoans infected fish from spring through fall with extremely high intensity. In summer months of 1997-1999, 100% of fish from 6 locations examined were infected by the dinoflagellate A. ocellatum. Hundreds of these dangerous and destructive parasites were attached to fish gills. In spring and autumn during 1997-1999, about 100% of fish fry from the same locations along the shoreline were heavily infected by the ciliate A. ameiuri, which completely covered fish skin, fins and, rarely, gills. In autumn 1997, an outbreak of fish infestation by C. branchialis was found at Bombay Beach. Parasites tightly covered the gill surface. Parasitic flatworms G. olsoni and G. imperialis infected gills longjaw mudsucker and tilapia in different seasons. Their numerous hooks penetrated deeply into epithelial tissue of gills, skin and fins, heavily damaging it.

All these ectoparasites affect fish gills and skin, which are the major respiratory organs for young fish. Both parasitic protozoans and flatworms changed the general structure of fish gills and skin and caused numerous lesions, local erosion, and severe irritation at sites of their attachment to epithelial tissues. These alterations of fish gills and skin may suppress respiratory functions and cause fish suffocation. The numerous sites of epithelial damage also represent portals of entry for bacterial, viral and fungal infections.

The pile worm, Neanthes succinea, was heavily infected by peritrich Epistylis sp., individuals of which were attached to their body segments and locomotory organs. Another peritrich, Rhabdostyla vernalis, was distributed over the body surface of the copepod Apocyclops dengizicus. It is suggested that heavily infected invertebrates have decreased locomotor capabilities and become easy prey for predators.

Parasites appear to be an important stressor affecting fish populations in this unique water body. If they are a major cause of juvenile fish mortality, as seems likely, they may play a major role in determining fish population dynamics in the Salton Sea.

The last detailed examination of the biota of the Salton Sea was carried out in the 1950s. A biotic inventory is currently being conducted by researchers at SDSU and other universities. As part of this, we are attempting to document all invertebrates in the Salton Sea with scanning electron microscopy (SEM) and light microscopy (LM). General morphology and ultrastructure of representatives of 11 major taxonomic groups of invertebrates are demonstrated in this portfolio of images and brief descriptions. Forms illustrated include different stages of their development of both planktonic and benthic organisms.

1. Larvae of barnacle, Balanus amphitrite saltonensis. Found in greatest abundance in nearshore

waters in January through April. Adult forms live attached to hard substrates. Extensive deposits of barnacle shell form major structural habitats for other invertebrates in the Sea.

2. Larvae of pile worm, Neanthes succinea. Most abundant in March, scarce in summer, increases starting in November. Prey for fish and birds feeding in water column.

3. Rotifer, Brachionus rotundiformis. Most numerous organism in the summer zooplankton. Plays an important role in nutrient cycling. Prey for copepods and fish.

4. Cyclopoid copepod, Apocyclops dengizicus. Dominates summer zooplankton. Prey for small fish. Feeds on algae, protozoans and rotifers.

5. Adult pile worm. Major item in diet of several fish and eared grebes. Most abundant in winter on mud at a depth of 5-8 m. Estimated biomass is up to 13 million kg for the entire Sea.

6. Polychaete worm, Streblospio benedicti. First found in the Salton Sea in January 1999.

7. Amphipod, Gammarus mucronatus. Lives in algal mats, among living barnacles, and on various other bottom substrates. Eaten by fish, eared grebes and other birds feeding in shallow water.

8. Amphipod, Corophium sp. Lives in small tubes on submerged rocks.

9. Harpacticoid copepod, Cletocampus deitersi. Abundant among algae and detritis on rocks and also present in the mud.

10. Ostracod, Cyprideis beaconensis. Lives in algal mats and in the sediments, but can swim up into the water column.

11. Flatworm (Turbellaria), an as yet unidentified species. Lives in the sediments. Probably feeds on bacteria, protozoans, and algae.

12. Roundworms (Nematoda). Several species have been found in sediments and are being identified.

Current proposals for solving the problems of the Salton Sea all fall short of the mark. They are classic examples of the idea of a technological fix, the idea that scientists and engineers can provide the solution to what are fundamentally social and political problems. When called to the rescue, the scientists and engineers are happy to look for these technological fixes on behalf of the politicians, who usually need to claim "progress made" before the next election cycle. The scientists and engineers know the fixes will not help much in the long run, and may even delay attention to the real problems. But a "fix search" can provide a job, research funds, per diem for travel to interesting places and conferences, and other perks. So we are happy to oblige, to be 'good soldiers' and not question orders. To avoid offense, to maintain our positions, and to keep the funds flowing, we refrain from pointing out to the politicians the lack of vision and courage that keeps them from dealing with the important issues. This poster attempts to depart from these self-serving and myopic traditions.

The long-term health of the Salton Sea requires four things: removal of salts, continued large inflows of wastewaters, some additional freshwater inputs for dilution purposes, and removal of phosphorus from the Sea at a rate faster than it is coming in. However, the last three of these will be very difficult if not impossible given the high rate of population growth, especially in California, Arizona, and Baja California. Should large amounts be invested in the proposed technological fixes for the Sea if the politicians are not willing, at the same time, to deal with the social and political issue of population management so that the 'fixes' can bear real fruit? We suspect not.

In the U.S., population growth is driven primarily by immigration. The U.S. Census Bureau estimates that under current immigration policies, immigration will account for about 80 million of the 122 million increase in the U.S. population predicted for 2050. Increasing population and increasing environmental degradation go hand in hand. In a very real sense, immigration is the greatest controllable cause of environmental problems in the U.S., including those confronting the Salton Sea. Our high average standard of living (nice cars, nice homes, nice industries, nice agriculture, nice daily showers, etc.) is a bigger cause, of course, but even the 'greenest' individuals seem disinclined to give up much of this.

The poster presents a collage of information on problems of eutrophication and water supply at the Salton Sea, their relation to population growth and immigration, the failures of the executive and legislative branches of the U.S. government to deal effectively with immigration issues, and the smear tactics and cognitive dissonance with which some organizations attempt to suppress rational discussion of them.

An information packet with materials from different organizations on these issues will be available to symposium registrants. A resolution for forwarding to the President and Congress of the United States will also be available for signing by interested persons. This will present the Salton Sea as just one example of the collision between high rates of population growth and the need to reduce environmental degradation, and will ask for appropriate government action, so that expenditures on engineering projects at the Salton Sea, among other places, have a chance of purchasing more than white elephants.

Chattonella marina, an alga in the raphidophyte group, was identified from the Salton Sea in 1997. Algae in this genus are known to be extremely toxic and produce brevetoxins and superoxide radicals, both of which may be lethal to fish. Massive fish kills, especially in aquaculture operations, have occurred world-wide due in part to this organism. Fish collected at the height of the Chattonella bloom showed damage to their gills similar to that caused by Chattonella in experimental studies. To our knowledge, this is the first recorded of a species of Chattonella in a salt lake.

We report on high abundance of Chattonella marina in the phytoplankton of the Salton Sea from April to November in 1997. Maximum mean density was over 600 cells/ml mid-lake which exceeds the density known to kill fish in studies of this organism in Japan. It was not detected from January 1997 to March 1997 or in January and February 1998. We believe that this alga forms cysts and spends the cold months in the sediment.

Hermisinum adriaticum is a rare and unusual non-photosynthetic microscopic flagellate that has a skeleton made of silicon. Skeletons of Hermesinum have recently been found in large numbers in the surface of sediment of the Salton Sea and also infrequently in algal mat and the plankton. It has previously been reported as present in the Salton Sea. In fact, the greatest abundance of this organism ever seen anywhere was in the Salton Sea in the 1950's’(450 cells/ml).

This study adds to the knowledge of how this organism reproduces. In some samples of sediment, many newly forming skeletons were found in al stages of development. This allowed the study of the way the new daughter skeleton is formed as the cell gets ready for divisions. Scanning electron microscope images give a three dimensional view of each stage.

The Salton Sea is a saline (46g/L), highly eutrophic lake in the southeast corner of California, USA. Small numbers of unidentified coccolithophores were seen in earlier (1955-1956) studies of the lake. Recently, we have identified this coccolithophore as Pleurochrysis pseudoroscoffensis (Prymnesiophyceae). To our knowledge, this is the first record of the presence of this species in any lake. This species was found only in small numbers in the water column and in surface sediment samples before 1999. In February, June, and July of this year, however, dense accumulations of P. pseudoroscoffensis on the surface film were seen at several locations around the Salton Sea. The community compositions of these blooms were analyzed and samples were taken for determination of possible toxicity.

Phytoplankton samples were taken from the water surface and from the top 50-100 cm of the water column using various methods. One portion of each sample was extracted with organic solvents and screened for toxicity using a brine shrimp lethality assay. Samples that showed activity in the screening process were then analyzed using a mouse toxicity bioassay. A second subsample was preserved in Lugol’s solution for identification and counting of types of algae present.

Coccolithophorids are noted for producing blooms that are non-toxic. In a preliminary study, however, P. pseudoroscoffensis collected from a surface scum caused high mortality in a brine shrimp assay (100% lethality at 400 m g/mL). Several large samples have since been collected for toxicity analysis using both the brine shrimp lethality assay and standard mouse bioassay. Although all samples showed some level of activity in the brine shrimp assay, they were negative in the mouse bioassay. This evidence shows that blooms of P. pseudoroscoffensis are most likely not toxic to vertebrates and are not contributors to the various mortality events of birds and fish that occur in the Salton Sea.

Benthic (bottom-dwelling) invertebrate animals form a major part of the diets of fish and many types of birds at the Salton Sea, and can be extremely numerous within different habitats. In fact, on submerged rocks, several thousand invertebrates can be collected from an area the size of a slice of bread! How are these animals collected from the different habitats? Our poster illustrates three techniques commonly used by ecologists for collecting animals: grab sampling, quadrat sampling, and sediment coring. In addition to depicting how we sampled the environments at the Salton Sea, we include images and natural history details of the animals collected by these methods.

Funding for this project is entirely from USGS. The principal objectives originally indicated preliminary contaminant analyses and population surveys, but peer review comments noted that much of what we proposed for preliminary work had previously been done, or was being contracted for under the auspices of the Science Coordinating Committee. Furthermore, the peer reviewers commented that the available funding would not allow for any meaningful data collection beyond what was already known with respect to contaminants. We then decided to begin with population (nesting) surveys in a manner which would least likely conflict with other funded research activities.

Now in our second year of field work, we can expand our work into examining avian movements via satellite telemetry. Peer reviewers and other researchers view this avenue of research as the most productive use of limited resources and the type of research necessary to move beyond reconnaissance level science.

The study plan was completed and field work was initiated in April 1999. Consultations with Sonny Bono Salton Sea National Wildlife Refuge (SBSSNWR) staff, National Wildlife Health Research Center, Point Reyes Bird Observatory, and others led to the selection of a small colony of Great blue herons (GBH) and Great egrets (GREG) for intensive nest monitoring. Nesting structures at the Ibis Road colony were visited and inspected weekly between April and late July to ascertain egg numbers (presence or absence), number hatched, condition and number of young, stage of development, nest structure integrity, and hatchling status. Forty nests were established during this period, 27 GBH, 12 GREG, and 1 unknown. Only four GREG nest survived to the point of producing hatchlings, and no GREG nest survived to fledging. Seven GBH nests remained intact and produced fledglings. The Salton Sea routinely experiences severe wind storms during the spring and summer, and the particular area of the Ibis Road colony seems to be especially prone to severe, prolonged high wind events (SBSSNWR staff pers. comm.). These extreme winds rip apart fragile nesting structures and the nest themselves. A contract was issued for the development of a book on the historical status and distribution of birds of the Salton Sea and surrounding areas. This book is currently in development for publication during FY2000. Anticipated research for FY2000 includes a continuation of nest monitoring efforts at the Ibis Road Colony, publication of the Salton Sea book on birds, and satellite telemetry on Double-crested cormorants to document localized and long-range movements for a small number of birds. Information gained from this research effort should provide a thorough analysis of avian occurrence and distribution data, much of which has been sequestered in a variety of published journals, gray literature, and field notes. Moreover, this research will document movement patterns of Double-crested cormorants and provide insight into the potential for the dispersal of Newcastle disease.

Recent disease outbreaks at the Salton Sea have killed large numbers of birds. These events have resulted in a national focus on the Sea and issues associated with restoration actions. This presentation highlights the avian diseases occurring at the Sea, addresses their importance as a factor in the conservation of migratory birds and highlights what is being done to combat avian disease at the Sea. A review of existing information on disease occurrence at the Sea was conducted from historical records, National Wildlife Refuge Narrative Reports and the National Wildlife Health Center epizootic and diagnostic databases.

There has been a substantial increase since the late 1980s in the importance of disease as a cause of bird mortality at the Sea. Disease outbreaks have occurred since at least the 1920s. With the exception of 1932, annual outbreaks occurred during the period of 1925-1935, with each of those events killing a substantial number of birds. Type C botulism is the likely cause of those outbreaks. The frequency of outbreaks was much less during the period of 1936-1945 before increasing again since 1946. With few exceptions, the magnitude of bird deaths associated with individual disease outbreaks during the period of 1936-1987 has been low. Since 1987, the magnitude of losses from disease has increased substantially and there have been a number of catastrophic die-offs. During 1992, an estimated 155,000 birds died at the Sea, including an estimated 150,000 eared grebes. This was approximately 7 percent of the continental population of this species. The cause of this event and recurring grebe mortality at the Sea has not been determined despite extensive diagnostic evaluations. The 1996 outbreak of type C botulism was even more devastating regarding population impacts. That outbreak killed approximately 15-20 percent of the western population of white pelicans and killed more than 1,000 endangered California brown pelicans. During 1997 and again in 1998, all hatchlings from the double-crested cormorant colony on Mullet Island died from Newcastle disease. Avian cholera and salmonellosis are other important diseases that have appeared at the Salton Sea during recent years.

Environmental quality is a factor in many disease events. Therefore, the Salton Sea Restoration Project focus on improving the environmental quality of the Sea is a fundamental action required to reduce the probability for major losses from disease. Current actions taken include enhanced surveillance to provide early detection of disease occurrences and aggressive response to outbreaks that occur. In addition, studies have been initiated to gain a greater understanding of the ecology of disease at the Sea. Findings from those studies will be of considerable value in guiding management actions to achieve the Restoration Project Goal to:

"Provide a safe, productive environment at the Sea for resident and migratory birds and endangered species."

Achievement of this goal is important because more than 90 percent of inland wetland acreage that was part of the California landscape no longer exists. As a result, millions of migratory birds within the Pacific Flyway have become highly dependent upon the habitat provided by the Salton Sea.

OBJECTIVES

The Salton Sea has become an important resource for wildlife. Recent mortality of fish and birds at the Sea has prompted a high level of concern by many resource agencies. A more intensive survey to document the distribution of known and potential microbial pathogens in the Salton Sea ecosystem was needed to provide baseline information for those tasked to evaluate proposed engineering projects at the Sea. This study was to determine the prevalence of Pasteurella multocida (avian cholera), Salmonella spp., Aeromonas spp., Vibrio spp., Yersinia spp., Erysipelothrix spp. in the sediments and water of the Salton Sea ecosystem at various times of year. Isolates will be evaluated through molecular methods to determine potential epidemiological linkages and providing better insights into the their characterization and distributions.

Water and sediment samples were collected monthly at the Sea, frozen, and shipped for analysis. Samples were collected at the inflows to the Sea on a monthly basis and from six other sites at the Sea on a quarterly basis. Primary isolation of selected bacterial pathogens included both direct plating and selective enrichment culturing. Enrichment media for the enhanced recovery of Pasteurella, Yersinia, and Salmonella spp. and selective/differential media for the isolation of Aeromonas, Vibrio spp., and Erysipelothrix spp. were used. All bacterial colonies were screened based on typical colony morphology and biochemical reactions on selective or differential media. Isolates were biochemically characterized and identified using an appropriate system. Selected isolates are to be further analyzed by ribotyping, a method to compare the genetic material of the isolates to determine, not only the identification, but also relatedness of the isolates. Samples collected will also be screened by a polymerase chain reaction (PCR), a method to look for the genetic evidence of some of these pathogens.

The study is still on-going at this point. A full year of water collection has been completed but the analysis is still pending on some samples. At this point, the expected water-borne pathogens, Aeromonas and Vibrio spp. are present in many samples collected throughout the year. Although Aeromonas and Vibrio spp. are both occasionally pathogenic to wildlife and humans, the real threat from these organisms to both wildlife and human health has not yet been established. The identification and further characterization of these isolates is pending. The potential wildlife and human pathogen, Salmonella,spp. have been isolated from only two samples so far. The other pathogens of interest in this study have not been isolated yet. Screening of the samples using polymerase chain reaction (PCR) is pending.

During the summer of 1996, nearly 15,000 pelicans and other fish-eating birds died at the Salton Sea from type C avian botulism. This die-off was the largest documented loss of pelicans in the U.S., killing nearly 15% of the western white pelican (Pelecanus erythrorhynchos) population and many endangered California brown pelicans (Pelecanus occidentalis californicus), although a number of brown pelicans were treated and released. Since 1996, outbreaks of type C botulism have occurred in fish-eating birds every year at the Sea, however the losses have not been as extensive. These outbreaks are unusual for several reasons and may be unique to the Salton Sea. Type C botulism typically afflicts waterfowl and shorebirds, and although the disease has been previously documented in freshwater wetlands surrounding the Salton Sea, fish-eating birds were not involved and do not usually contract type C botulism. Also, it was apparent that sick and dying fish were the probable source of toxin for pelicans in these recent outbreaks, however, the role of fish is unclear. Some evidence suggests that fish may ingest toxin and contract the disease, making them easy prey for feeding pelicans and other birds. Other evidence suggests that fish become sick from other bacterial infections, allowing botulinum spores in their guts to germinate and produce toxin. A better understanding of the role that fish play in precipitating botulism outbreaks in birds and the contributing environmental conditions are necessary to evaluate how proposed engineering projects in the Sea may affect occurrence of this disease.

Currently the USGS/ National Wildlife Health Center, in conjunction with the USGS/Western Fisheries Research Center, Mississippi State University and others, are working to identify the key factors that initiate these unique die-offs on the Salton Sea. Research efforts will focus on determining the linkages between type C botulism outbreaks in pelicans and their predominant prey, tilapia (Tilapia mossambicus). Laboratory experiments will be conducted to evaluate the sensitivity of tilapia to type C botulism and the interactions between toxin production in fish and other bacterial infections. Field studies will also be conducted to evaluate patterns of botulism mortality in fish-eating birds in relation to water chemistry, sediment microbiology, fish kills, and the abundance of botulinum toxin and toxin-producing bacteria in fish.

In separate, but related studies, we are also determining the distribution of type C botulinum cells and spores in the Sea and its major tributaries, evaluating the risk of type C avian botulism in freshwater wetlands surrounding the Sea, and assessing the risk of type E botulism in fish in the Salton Sea. Last, we will evaluate the feasibility of vaccinating endangered brown pelicans brought in for rehabilitation purposes in order to prevent them from contracting the disease again upon their release.

Background: In late 1991 and early 1992, an undiagnosed disease occurred in eared grebes (Podiceps nigricollis) at the Salton Sea. Carcasses of 46,040 eared grebes were picked up and estimates of total mortality for this event were as high as 145,000. This was the largest eared grebe epizootic ever documented, resulting in the death of approximately 10% of the North American population of this species. Several significant mortality events have occurred in eared grebes at the Salton Sea since the 1991-1992 die-off. Affected grebes often exhibit unusual behaviors, such as coming out on shore and preening excessively, and congregating at freshwater drains where they drink water. The feathers of affected grebes frequently appear disheveled or wet. A total of 160 eared grebe carcasses from the Salton Sea have been necropsied at the National Wildlife Health Center since 1991, but the primary cause of these mortality events remains unknown. Avian cholera (caused by the bacterium, Pasteurella multocida) and avian botulism type C (caused by toxin produced by the bacterium, Clostridium botulinum) have been diagnosed in 21% and 4%, respectively, of eared grebes necropsied since 1991, but no other bacterial or viral pathogens were consistently isolated. No cause of death could be determined for 46% of the grebes examined. Pulmonary, hepatic, and skin lesions were observed during necropsies, but were not severe enough to account for the death of the birds. Exposure to salt and selected contaminants were investigated, but were ruled out as primary causes of mortality.

Future studies: Continued mass mortality of eared grebes at the Salton Sea is a potential threat to the population of this species. During fiscal year 2000, we initiated a 3-year study with the primary goal of identifying the cause(s) of undiagnosed eared grebe mortality at the Salton Sea. We will use field and laboratory studies to:

The Salton Sea Database Program has undertaken a project to identify and map the vegetation in the Salton Sea Restoration Project area. The objectives of this effort were to produce an accurate map of the dominant plant communities of the project area in order to facilitate Salton Sea restoration project planning efforts. Vegetation mapping for the project was produced at two levels of resolution: a low-resolution vegetation map for the entire watershed; and a high-resolution coverage for the immediate shore zone plant communities and adjacent wetlands.

The low-resolution vegetation map utilizes U.S.G.S. Landsat-TM images as the base map at a scale of 1:250,000. This coverage is based upon a modified Cal-GAP vegetation classification system developed by U.C. Santa Barbara. The vegetation map was clipped to the watershed boundary, including an area of approximately 8,300 square miles. This coverage identifies dominant plant communities within the entire basin.

A high-resolution, wetlands map has been produced on digital orthophotograph quarter-quadrangles (DOQQs). The DOQQs correspond to one-fourth of a 15-minute U.S.G.S. topographic quadrangle, at a scale of 1:12,000, with a resolution of approximately one-meter. The high-resolution vegetation mapping effort focussed on the immediate shore zone area and adjacent wetlands. Ground validation of the preliminary wetland map was accomplished during the Spring-Summer ’99 season. The resultant map identifies dominant and associated species for the shoreline and adjacent wetlands, managed wetlands, and riparian wetlands, including the Whitewater River delta, Salt Creek, San Felipe Creek, and the New and Alamo Rivers to the Mexico border.

Annual Christmas bird counts (CBCs) have been conducted at the Salton Sea since 1969. Two census areas have been established—one at the north end centered near the Whitewater River delta, and the other at the south end of the Sea centered near the National Wildlife Refuge. The counts are conducted on a designated day within a week or so of Christmas Day each year in a 7.5-mile radius circle at each location. All birds observed are tallied.

The CBCs represent the longest standing data set of winter bird use at the Salton Sea. Thirty-year trends have been calculated for each species, family, guilds (shorebirds, waterfowl, piscivorous birds, waders, etc.), individual census totals, and combined north-south census data.

The oral and poster presentations of this Symposium clearly illustrate that we have learned a great deal about the Salton Sea that was previously unknown. In general, we now know that the biological complexity of the Sea is far greater relative to species diversity than was previously recognized and that there has been considerable adaptation by some of the species to allow them to thrive in this highly saline environment. We have also gained considerable insight relative to the biological importance different areas of the Sea provide for various species. One of the most important contributions of the science effort that has taken place is the "bridge" that has been built joining science and management in a collective and collaborative effort to improve the environmental quality of the Sea. Science has become a component of the restoration project that is issue driven rather than being an independent, exploratory activity.

The science displayed at this Symposium is a good beginning and needs to continue as a strongly integrated science effort that is relevant for the restoration project. Learning from pilot projects and adaptive management will be important aspects of the science activities from this point on. The establishment of baseline values against which change can be monitored and carrying out appropriate monitoring activities will be major scientific activities along with focused investigations to address specific information needs. A Strategic Science Plan has been developed as the conceptual framework for guiding this science effort.

The key component of the Strategic Science Plan is a Science Office dedicated to the restoration project. That Office would provide the link between scientists and managers but would not carry out scientific investigations. The basic roles would be science planning, coordination, evaluation, and contract awards and administration. The Office would be assisted in its efforts by two external bodies, a stakeholder advisory committee and a science advisory committee of technical specialists from various science disciplines. Another component of the Strategic Science Plan is a small common-use field facility at the Sea to facilitate field investigations undertaken as part of the restoration project.

The scientific and management challenges that lie ahead are formidable. However, failure is not an option. These are the types of challenges that must be overcome if we are to sustain global biodiversity and, by doing so, serve human values and needs through the benefits derived. These relations are expressed in the following quotation:

"The nation’s biological resources are the basis of much of our current prosperity and an essential part of the wealth that we will pass on to future generations." (Pulliam 1995)

The Salton Sea Restoration Project and the science effort that is part of this undertaking is an opportunity to "make a difference". By doing so we will provide a lasting tribute to the memory of Congressman George Brown.

Beginning in 1929, large introductions of over 20 marine species were planted into the Salton Sea, CA from offshore San Felipe, Gulf of California. Of these, only the orangemouth corvina (Cynoscion xanthulus), bairdiella (Bairdiella icistia) and sargo (Anisotremus davidsoni) established and flourished in the Sea. In 1964-65, an aggressive exotic species from Africa, the tilapia (family Cichlidae), escaped to the Sea by two routes: (1) an aquarist fish farm near Niland, and (2) from irrigation ditches where it was stocked purposefully by California and Arizona fisheries agencies for the control of nuisance aquatic weed and insect species (Costa-Pierce and Doyle 1997). In the 1970's-80's, the tilapias quickly dominated the fish community of the Salton Sea as the salinity rose to hypersaline levels. We conducted a large, bimonthly fisheries sampling program of the Salton Sea Ecosystem (SSE) that set four, 50-m long multi-panel, multi-mesh gill nets overnight (two bottom and two surface nets at each station) at nine stations in the Sea. Our preliminary observations are: (1) eight species have been sampled, and their size and age distributions determined,, (2) the Alamo and New Rivers are not refugia for any of the fish species in the Sea with the exception of threadfin shad, (3) highest catch per unit efforts (CPUEs) were in nearshore and estuarine stations, (4) a remnant threadfin shad population is present at southern stations, (5) tilapia CPUEs are higher than reported in tropical lakes worldwide, (6) there is a narrow population size-frequency distributions for bairdiella and tilapia, and many tilapia are 1.5-2.0 years old, (7) there is evidence for large scale seasonal in/offshor movements that result in a "bathtub ring"of fish in the summer, (8) there is no evidence of widespread deformities or external abnormalities in the corvina, sargo, tilapia, and croaker populations.