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January 13-14, 2000 Miracle Springs Hotel & Spa, Desert Hot Springs, California
Program of Talks
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Day 1 |
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Registration |
9:00 A.M |
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Introduction |
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10:00 A.M. |
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Supervisor Tom Veysey |
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Restoration Report |
10:20 A.M |
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David Hayes, Deputy
Secretary, Department of the Interior |
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Federal Legislators |
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Senator Dianne Feinstein |
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State Legislators |
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Assemblyman Jim Battin |
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Local Legislators - Salton Sea Authority Board of Directors |
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President Tom Veysey,
Supervisor - Imperial County |
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Tribal Legislators - Torres Martinez Desert Cahuilla Tribe |
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Mary Belardo, Tribal
Chair |
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LUNCH |
Senator Dianne Feinstein |
12:15 P.M. |
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A Careful Balancing Act MIRAGE BALLROOM |
2:00 P.M. |
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Mike Madigan - Chairman, California Water Commission - Moderator |
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Mike Bracken - Economic
development |
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Roles and Responsibilities |
3:00 P.M. |
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Joe Findaro, McClure Gerard & Neuenschwander, Inc. - Moderator |
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Bob Johnson - Federal |
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BREAK |
4:00 P.M. |
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The Sea in Context |
4:15 P.M. |
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Phil Gruenberg, Executive Officer, Regional Water Quality Control Board-Moderator |
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Dan Taylor - The Pacific
Flyway |
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WINE RECEPTION/ HOST BAR
/ POSTER SESSION |
5:00 P.M. |
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DINNER |
Congresswoman Mary Bono |
6:30 P.M. |
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DAY 2 |
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Registration |
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7:30 A.M. |
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Introduction |
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8:00 - 8:15 A.M. |
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"State
of the Salton Sea
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Session I - Physical Environment of the Sea |
8:15 - 9:50 A.M. |
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John F. Elder, U.S. Geological Survey - Moderator |
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Oral Presentations: |
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"Geology
and Seismicity of the Salton
Basin." |
8:15 - 8:35 A.M. |
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"A
Three-dimensional hydrodynamic model of the Salton
Sea.." |
8:35 - 8:55 A.M. |
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"Overview
of physical and chemical limnology at the Salton
Sea." |
8:55 - 9:15 A.M. |
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"Characteristics
of Salton Sea Sediments." |
9:15 - 9:30 A.M. |
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"Contaminants
in the Salton Sea and its Drainage
Basin," |
9:30 - 9:50 A.M. |
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BREAK AND POSTER SESSION
JOSHUA
TREE |
9:50 - 11:00 A.M. |
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Session II - Biological
Environment of the Sea |
11:00 - 2:30 P.M. |
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Doyle Stephens, U.S. Geological Survey - Moderator |
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"Overview
of the Little Critters." |
11:00 - 11:20 A.M. |
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"The Salton Sea: Hotspot for Microbial Diversity" |
11:20 - 12:00 P.M. |
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"Diatom
flora of the Salton Sea" |
11:20 - 11:30 A.M. |
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"Ciliate
diversity in the Salton Sea" |
11:30 - 11:40 A.M. |
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"Naked
amoeboid protozoa of the Salton
Sea" |
11:40 -11:50 A.M. |
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"Cyanobacteria
of the Salton Sea" |
11:50 - 12:00 NOON |
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LUNCH GRAND BALLROOM |
12:00 - 1:30 P.M. |
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Session II - Biological Environment of the Sea, cont. |
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"The benthic invertebrates of the Salton Sea: distribution seasonal dynamics." Paul Detwiler, Marie Coe, and Deborah M. Dexter, and Lindsey M. Harrington, Department of Biology, San Diego State University, San Diego, CA. |
1:30 - 1:50 P.M. |
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"Phytoplankton and zooplankton population dynamics in the Salton Sea." Mary Ann Tiffany, Brandon K. Swan, James M.Watts and Stuart H. Hurlbert, San Diego State University, San Diego, CA. |
1:50 - 2:10 P.M. |
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"The
possible importance of algal toxins:findings and
prospects"
Kristen M. Reifel,
Michael P. McCoy, Mary Ann Tiffany, Stuart H. Hurlbert,
and D. John Faulkner, San Diego State University and Scripps
Institution of Oceanography, San Diego, CA. |
2:10 - 2:30 P.M. |
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BREAK AND POSTER SESSION
JOSHUA TREE |
2:30 -3:00 P.M. |
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Session III - Fish, Wildlife, and Vegetation |
3:00 - 4:40 P.M. |
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Dick Zembal, U.S. fish and Wildlife Service - Moderator |
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Oral Presentations: |
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"Fisheries
Ecology and Fish Biology of the Salton
Sea." |
3:00 - 3:20 P.M. |
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"Desert
Pupfish of the Salton Sea." |
3:20 - 3:40 P.M. |
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"The Importance of the
Salton Sea to Pacific Waterbirds." |
3:40 - 4:00 P.M. |
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"The
Importance of the Salton Sea to Pacific
Waterbirds." |
4:00 - 4:20 P.M. |
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"American
White Pelicans." |
4:20 -4:40 P.M. |
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4:40 -5:00 P.M. |
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Dr. Milton Friend,
Executive Director, Salton Sea Science Subcommittee |
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POSTER PRESENTATIONS
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Geology and Lake History |
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Physical and Chemical Limnology |
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Nutrient Dynamics in the Salton Sea--Implications from Calcium: Uranium, Molybdenum and Selenium |
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Seasonal Variation of Nutrient, Major Ion, and Metal Concentrations in the Salton Sea, 1999 |
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Thermal, Mixing and Oxygen Regimes of the Salton Sea, 1997-1999 |
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Biology of Plankton and Benthos |
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Invertebrates of The Salton Sea: A Scanning Electron Microscopy Portfolio |
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Chattonella marina, A Potentially Toxic Alga in the Salton Sea, California |
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Pleurochrysis pseudoroscoffensis in the Salton Sea, California, USA |
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Fish, Birds and Vegetation |
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Population Surveys and Preliminary Contaminant Analysis of Birds on the Salton Sea |
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Eared Grebe Mortality at The Salton Sea in the 1990s: Review of Findings and New Studies |
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Christmas Bird Counts at the Salton Sea--Presenting 30 Years of Wintering Bird Data |
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Implications of Regional Population Growth |
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Population
Growth and the Salton Sea: The Major Long-term Issue, Out
from Under the Rug |
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ABSTRACTS OF ORAL AND POSTER PRESENTATIONS
STATE OF THE SALTON SEA--OPENING COMMENTS
Milton Friend, Salton Sea Science
Subcommittee
8505 Research Way, Middleton, WI 53562
contact: milton_friend@usgs.gov
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.
GEOLOGY AND SEISMICITY OF THE SALTON BASIN
David M. Miller,
U.S. Geological Survey, 45 Middlefield Road, MS 975, Menlo Park, CA
94025,
contact: dmiller@usgs.gov
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.
THREE DIMENSIONAL HYDRODYNAMIC MODELING OF THE SALTON SEA
C. B. Cook, G. T. Orlob, and D. W. Huston
Department of Civil and Environmental Engineering
University of California, Davis, CA 95616<
contact: cbcook@ucdavis.edu
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.
CHEMICAL/PHYSICAL LIMNOLOGY OF THE SALTON SEA
G. Chris Holdren and Andrew Montaño
Bureau of Reclamation, P.O. Box 25007 (D-8220), Denver, CO
80225
contact: choldren@do.usbr.gov;
amontano@do.usbr.gov
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.
CHARACTERISTICS AND CONTAMINANTS OF THE SALTON SEA SEDIMENTS
Richard A. Vogl and Ryan N. Henry, LFR
Levine·Fricke, Irvine, CA
Douglas S. Lipton, Ph.D., LFR Levine·Fricke, Healdsburg,
CA
contact: richard.vogl@lfr.com;
doug.lipton@lfr.com
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.
CONTAMINANTS IN THE SALTON SEA
Jim Setmire, Hydrologist USGS/USBR
contact: jsetmire@lc.usbr.gov
Contaminants of Concern: Selenium, Nutrients, DDE, Boron, SedimentDissolved 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.
Selenium:
Colorado River water 2 µg/L, Subsurface drainwater - In May 1988 measured subsurface drainwater at 119 sumps and gravity tiles had median 25 µg/L (1-360 µg/L).
In 1994-5 - sampled 820 sites within the Imperial Valley &endash; Discharge and specific conductance were measured at all 820 sites. Laboratory analyses at 304 of the sites had Median selenium concentration of 28 µg/L ranging from 1-311 µg/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 µg/L. Surface Drains - August 1994 sampled 49 sites had median of 6 µg/L (2-52 ug/L). New and Alamo River's at outlet to Salton Sea median 4 µg/L and 8 µg/L.
Interface area &endash; Alamo River 200 feet seaward of the end of the levee on the left bank - water 3 ft deep &endash; at a depth of 1.3 feet sp cond 5,000 µS, DO 4.2 mg/L (56%) and Se 8ug/L. At 3 feet &endash; sp cond 51,000 µS, DO 1.2 mg/L (18%) and Se1.0 µg/L. Special sample collected in June 1989 on river side of interface had total Se of 6.35 µg/L with 2.56 µg/L in the +4 selenite state and 3.79 in the +6 selenate oxidation state. At interface total Se 2.4 µg/L (<method specific reporting limit) with 1.79 µg/L at +4 selenite and <0.2 in the +6 selenate state. Salton Sea water 1 µg/L. None of selenium is in the highly oxidized +6 selenate state.
Selenium in sediments:
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 &endash; Very fine sediment <0.002 mm in deepest parts of Salton Sea have highest selenium concentrations. Composed of highly organic matter, low density detritus.
Selenium in biota:
Invertebrates from Salton Sea had Se concentrations ranging from 0.8 to 12.1 µg/g dry weight &endash; critical dietary threshold is 5 µg/g &endash; only pileworms had concentrations exceeding the threshold &endash; 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 &endash; 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
OVERVIEW OF THE LITTLE CRITTERS
Stuart H. Hurlbert,
Department of Biology and Center for Inland Waters
San Diego State University, San Diego 92182
contact: shurlbert@sunstroke.sdsu.edu
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 lakes'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.
THE DIATOM FLORA OF THE SALTON SEA, CALIFORNIA
Carina B. Lange and Mary Ann Tiffany
Scripps Institution of Oceanography, 9500 Gilman Drive La Jolla,
CA 92093-0244
and San Diego State University, Department of Biology, San Diego, CA
92182
contacts: clange@ucsd.edu; mtiffany@sunstroke.sdsu.edu
[Complete poster on The Diatom Flora of the Salton Sea, California]
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.
CILIATE DIVERSITY IN THE SALTON SEA, CALIFORNIA
Eugene B. Small and Glenn F. Gebler
Department of Biology, Room 0221
University of Maryland at College Park, College Park, MD 20742
contacts: es20@umail.umd.edu; gebler@wam.umd.edu
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.
NAKED AMOEBOID PROTOZOA OF THE SALTON SEA, CALIFORNIA
Andrew Rogerson and Gwen Hauer
Oceanographic Center, Nova Southeastern University,
8000 N. Ocean Drive, Dania Beach, FL 33004
contacts: arogerso@nsu.acast.nova.edu;
ghauer@nsu.acast.nova.edu
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 forlocomotion 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.
CYANOBACTERIA OF THE SALTON SEA
A. Michelle Wood, Scott Miller, and Richard
Castenholz
Department of Biology, University of Oregon, Eugene, OR 97403
contacts: miche@darkwing.uoregon.edu;
rcasten@darkwing.uoregon.edu
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.
THE
BENTHIC INVERTEBRATES OF THE SALTON SEA: DISTRIBUTION
AND SEASONAL DYNAMICS
Paul M. Detwiler, Marie M. Coe,
Lindsay M. Harrington and Deborah M. Dexter
Department of Biology and Center for Inland Waters,
San Diego State University, San Diego, CA 92182
contacts: detwiler@sunstroke.sdsu.edu;
mfcoe@ucdavis.edu; ddexter@sunstroke.sdsu.edu
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&endash;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.
PLANKTON AND ZOOPLANKTON DYNAMICS IN THE SALTON SEA
Mary Ann Tiffany, Brandon K. Swan, James Watts
and Stuart H. Hurlbert
Department of Biology and Center for Inland,
San Diego State University, San Diego, CA 92182
contacts: mtiffany@sunstroke.sdsu.edu; swan@rohan.sdsu.edu;
jwatts@sunstroke.sdsu.edu; shurlbert@sunstroke.sdsu.edu;
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.
THE POSSIBLE IMPORTANCE OF ALGAL TOXINS: FINDINGS AND PROSPECTS
Kristen
M. Reifel1, Michael P. McCoy2, Mary Ann
Tiffany1,
Stuart H. Hurlbert1, and D. John Faulkner2
1Department of Biology and Center for Inland
Waters,
San Diego State University, San Diego, CA 92182
2Scripps Institution of Oceanography, University of
California at San Diego
La Jolla, CA 92093-0212
contacts: kreifel@sunstroke.sdsu.edu;
mtiffany@sunstroke.sdsu.edu;
shurlbert@sunstroke.sdsu.edu; jfaulkner@ucsd.edu
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.
FISHERIES ECOLOGY AND FISH BIOLOGY OF THE SALTON SEA
Barry A. Costa-Pierce1, Ralf
Riedel1, J. Butler2, Lucille
Helvenston3
and Stuart H. Hurlbert3
1Institute of Marine Sciences, University of Southern
Mississippi, Ocean Springs,
MS 39564, 2 Southwest Fisheries Science Center,
La Jolla, CA 92038, USA, 3Department of Biologyand Center
for Inland Waters,
San Diego State University, San Diego, CA 92182
contacts: b.costapierce@usm.edu; jbutler@ucsd.edu;
lucilleh@sgilj.ucsd.edu;
shurlbert@sunstroke.sdsu.edu
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 specis from Africa, the tilapis (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 Salto 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 i 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/offshore 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, or croaker populations.
SALTON SEA DESERT PUPFISH MOVEMENT STUDY
Ron Sutton, U.S. Bureau of Reclamation,
Denver, CO 80225
contact: rsutton@do.usbr.gov
SummaryDuring 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.
Methods
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.
Conclusions
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.
THE IMPORTANCE OF THE SALTON SEA TO PACIFIC FLYWAY WATERBIRDS
Nils Warnock, W. David Shuford and Kathy
Molina
Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson
Beach, CA 94970
contact: nilsw@prbo.org; kmolina@prbo.org
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 &endash; Eared Grebe, American White Pelican, White-faced Ibis, Ruddy Duck, Mountain Plover, Black Tern, and Burrowing Owl &endash; 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.
Joseph R. Jehl, Jr.
Hubbs-SeaWorld Research Institute, San Diego, CA 92109
contact: jjehl@hswri.org
From December through April, the Eared Grebes is probably the most numerous waterbird at the Salton Sea. Several tens of thousands winter there. In spring migration daily estimates have exceeded 1 million, and it appears that the majority of the entire North American population (about 4 million) passes through and stages there before moving to breeding grounds in the interior. Accordingly, the sea in its current condition represents one of the most important single localities for this species. At the same time, it is a potentially hazardous place, as indicated by occasional and still-unexplained dieoffs that have killed tens of thousands of birds.From intensive studies at the major fall staging areas--Mono Lake and Great Salt Lake--over the past two decades, the biology and ecological requirements of the Eared Grebe are now well known. Accordingly, one can make reasonable predictions about how the grebes' status at the Salton Sea would be affected by changes in water level, salinity, and prey base.
In this paper I will review the species' history and status at the Salton Sea. I will also outline salient aspects of its biology in the non-breeding season, its adaptations for exploiting the highly saline habitats that other grebes and waterbirds avoid, and the nature of its fall and spring migrations. Such information is essential for considering the potential causes of mass mortality. Even though the Salton Sea holds a larger fraction of the North American Eared Grebe population than any other single area, efforts to monitor the size and health of the population through local studies will be largely uninterpretable--and therefore futile--unless they are integrated with knowledge from the major fall staging areas.
BOTH NORTH AMERICAN PELICAN SPECIES CO-OCCUPY HABITATS AND SHARE MANAGEMENT/CONSERVATION PROBLEMS OF THE COLORADO DELTA REGION
Daniel W. Anderson1, Leopoldo A.
Moreno1,2, and Kenneth Sturm3
1Department of Wildlife, Fish, &
Conservation Biology, University of California, Davis, CA 95616;
2California Environmental Protection Agency, Department of
Pesticide
Regulation-Endangered Species Project, 830 K Street, Sacramento, CA
95814-3510;
3U.S. Fish & Wildlife Service, Sonny Bono Salton Sea
National Wildlife Refuge,
Post Office Box 120, Calipatria, CA 92233.
contacts: dwanderson@ucdavis.edu;
ken_sturm@mail.fws.gov
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&endash;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.
SALTON SEA SCIENCE--WHERE DO WE GO FROM HERE?
Milton Friend, Salton Sea Science
Subcommittee,
8505 Research Way, Middleton, WI 53562
contact: milton_friend@usgs.gov
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.
Andrew Montano and G. Chris Holdren
U. S. Bureau of Reclamation, P.O. Box 25007 (D-8220), Denver, CO
80225
contact: amontano@do.usbr.gov;
choldren@do.usbr.gov
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.
Brandon K. Swan, James M. Watts, Mary A.
Tiffany, and Stuart H. Hurlbert
Department of Biology and Center for Inland Waters,
San Diego State University, San Diego, CA 92182
contacts: swan@rohan.sdsu.edu; jwatts@sunstroke.sdsu.edu;
mtiffany@sunstroke.sdsu.edu;
shurlbert@sunstroke.sdsu.edu
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.
NUTRIENT
DYNAMICS IN THE SALTON SEA--IMPLICATIONS FROM
CALCIUM, URANIUM, MOLYBDENUM AND SELENIUM
Roy A. Schroeder and William H. Orem,
U.S. Geological Survey, San Diego, CA and U.S. Geological Survey,
Reston, VA
contact: raschroe@usgs.gov
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
