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Requested News Item
| 8/18/2002 |
Special Issue of Hydrobiologia on Salton Sea, USA |
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S. B. Barlow and P. Kugrens. 2002. Cryptomonads from the Salton Sea, California
Hydrobiologia 473(1-3):129-137
Using freshly collected field samples and enrichment cultures, eight genera of cryptomonads from the Salton Sea are recorded for the first time. Comparative data from light and scanning electron microscopy were utilized to identify these genera and species. The genera included Chroomonas, Falcomonas, Hemiselmis, Plagioselmis, Pyrenomonas/Rhodomonas, Storeatula, Teleaulax, and the kathablepharid Leucocryptos. One putative genus remains unidentified and may represent a new taxon. SEM has not been conducted on this cryptomonad, but it has been isolated and is being maintained in culture. The genera and species identified from the Salton Sea are typical of marine rather then freshwater environments and may play an important role in primary productivity and as preferred food organisms for zooplankton.
J. E. Buckles, K. Kashiwase and T. Krantz. 2002. Reconstruction of prehistoric Lake Cahuilla in the Salton Sea basin using GIS and GPS
Hydrobiologia 473(1-3):55-57
During prehistoric times, the Colorado River occasionally meandered into and filled the Salton Sea Basin, creating several huge inland lakes, variously called Lake LeConte and 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 model for cultural resource constraints, identifying areas of high cultural resource sensitivity for evaluation of potential impacts as a result of implementation of Salton Sea restoration project alternatives.
C. B. Cook, G. T. Orlob and D. W. Huston. 2002. Simulation of wind-driven circulation in the Salton Sea: implications for indigenous ecosystems
Hydrobiologia 473(1-3):59-75
The Salton Sea, the largest 'man-made' water body wholly within California, was formed in 1904 as the result of a levee failure along the Colorado River. Initially, flow into the Salton `Sink' created a fresh water lake about 24 m deep with a water surface about 85 m below the level of the ocean. Salinity of the water body, at first roughly the same as the river, rose rapidly due to solution of previously accumulated residual salt, then following levee repair, adjusted to the combined influence of agricultural drainage accretions and evaporative losses. Water levels adjusted accordingly, at first declining then rising slowly until the mid 1930s when a level about 75 m below ocean level was reached. Thereafter, both water levels and salinity gradually rose, so that at present the surface elevation of the Sea stands near -69.5 m and salinity is approaching 45 g l(-1), about 30% above ocean salinity. The Salton Sea Authority is seeking practical methods for reducing water levels and controlling salinity within ranges that will protect beneficial uses of the Sea, its adjacent lands, and its indigenous ecosystems, both aquatic and avian. Proposed solutions include various physical changes in the bathymetry and configuration of the Sea, especially its southern basin. Because circulation in the Sea is driven primarily by wind stresses imposed on the water surface, and circulation changes are likely to affect the Sea's quality and ecology, a methodology for quantifying the effects of specific alternatives is required. For this purpose a mathematical model for simulation of the hydrodynamic behavior of the Sea has been developed, calibrated to data gathered by a field investigation conducted in 1997, and applied to alternative schemes that will isolate sections of the southern basin, thus changing the natural wind induced circulation in areas that are ecologically sensitive. The Salton Sea Hydrodynamic/Water Quality Model is constructed using the finite element method to represent the bathymetry of the Sea as it currently exists, or may subsequently be modified, in a three-dimensional grid. Given certain boundary conditions, for example wind stresses imposed on the surface, the model solves the three dimensional equations of motion and continuity, the advection-dispersion equation, and an equation of state dependent upon temperature and salinity, to obtain temporal and spatial descriptions of velocities and temperatures over a specified period of time. Using data derived from 1997 field measurements of velocities using acoustic Doppler current profilers and temperature sensors, the model was calibrated to reproduce mathematically the historic experience of field observation. The model successfully replicated principal features of the Sea's behavior, especially the persistence of a counterclockwise gyre in the southern basin and seasonal stratification. Once calibrated, the model was applied to evaluate the possible effects of changing water surface elevations in the Sea and altering its configuration to isolate sections for evaporative concentration of salts. These effects, evident in changes in velocity, were quantified with regard to their possible impacts on the aquatic habitat and the health of the Salton Sea ecology. A comparative evaluation of alternatives is presented.
P. M. Detwiler, M. F. Coe and D. M. Dexter. 2002. The benthic invertebrates of the Salton Sea: distribution and seasonal dynamics
Hydrobiologia 473(1-3):139-160
The Salton Sea, California's largest inland water body, is an athalassic saline lake with an invertebrate fauna dominated by marine species. The distribution and seasonal dynamics of the benthic macroinvertebrate populations of the Salton Sea were investigated during 1999 in the first survey of the benthos since 1956. Invertebrates were sampled from sediments at depths of 2-12 m, shallow water rocky substrates, and littoral barnacle shell substrates. The macroinvertebrates of the Salton Sea consist of a few invasive, euryhaline species, several of which thrive on different substrates. The principal infaunal organisms are the polychaetes Neanthes succinea Frey & Leuckart and Streblospio benedicti Webster, and the oligochaetes Thalassodrilides gurwitschi Cook, T. belli Hrabe, and an enchytraeid. All but Neanthes are new records for the Sea. Benthic crustacean species are the amphipods Gammarus mucronatus Say, Corophium louisianum Shoemaker, and the barnacle Balanus amphitrite Darwin. Neanthes succinea is the dominant infaunal species on the Sea bottom at depths of 2-12 m. Area-weighted estimates of N. succinea standing stock in September and November 1999 were two orders of magnitude lower than biomass estimated in the same months in 1956. During 1999, population density varied spatially and temporally. Abundance declined greatly in offshore sediments at depths >2 m during spring and summer due to decreasing oxygen levels at the sediment surface, eventually resulting in the absence of Neanthes from all offshore sites >2 m between July and November. In contrast, on shoreline rocky substrate, Neanthes persisted year round, and biomass density increased nearly one order of magnitude between January and November. The rocky shoreline had the highest numbers of invertebrates per unit area, exceeding those reported by other published sources for Neanthes, Gammarus mucronatus, Corophium louisianum, and Balanus amphitrite in marine coastal habitats. The rocky shoreline habitat is highly productive, and is an important refuge during periods of seasonal anoxia for Neanthes and for the other invertebrates that also serve as prey for fish and birds.
M. Friend. 2002. Avian disease at the Salton Sea
Hydrobiologia 473(1-3):293-306
A review of existing records and the scientific literature was conducted for occurrences of avian diseases affecting free- ranging avifauna within the Salton Sea ecosystem. The period for evaluation was 1907 through 1999. Records of the U.S. Department of Agriculture, Bureau of Biological Survey and the scientific literature were the data sources for the period of 1907-1939. The narrative reports of the U.S. Fish and Wildlife Service's Sonny Bono National Wildlife Refuge Complex and the epizootic database of the U.S. Geological Survey's National Wildlife Health Center were the primary data sources for the remainder of the evaluation. The pattern of avian disease at the Salton Sea has changed greatly over time. Relative to past decades, there was a greater frequency of major outbreaks of avian disease at the Salton Sea during the 1990s than in previous decades, a greater variety of disease agents causing epizootics, and apparent chronic increases in the attrition of birds from disease. Avian mortality was high for about a decade beginning during the mid-1920s, diminished substantially by the 1940s and was at low to moderate levels until the 1990s when it reached the highest levels reported. Avian botulism (Clostridium botulinum type C) was the only major cause of avian disease until 1979 when the first major epizootic of avian cholera ( Pasteurella multocidia) was documented. Waterfowl and shorebirds were the primary species affected by avian botulism. A broader spectrum of species have been killed by avian cholera but waterfowl have suffered the greatest losses. Avian cholera reappeared in 1983 and has joined avian botulism as a recurring cause of avian mortality. In 1989, avian salmonellosis (Salmonella typhimurium) was first diagnosed as a major cause of avian disease within the Salton Sea ecosystem and has since reappeared several times, primarily among cattle egrets (Bubulcus ibis). The largest loss from a single epizootic occurred in 1992, when an estimated 155 000 birds, primarily eared grebes ( Podiceps nigricollis), died from an undiagnosed cause. Reoccurrences of that unknown malady have continued to kill substantial numbers of eared grebes throughout the 1990s. The first major epizootic of type C avian botulism in fish-eating birds occurred in 1996 and killed large numbers of pelicans ( Pelecanus occidentalis & P. erythrorhynchos). Avian botulism has remained as a major annual cause of disease in pelicans. In contrast, the chronic on-Sea occurrence of avian botulism in waterfowl and shorebirds of previous decades was seldom seen during the 1990s. Newcastle disease became the first viral disease to cause major bird losses at the Salton Sea when it appeared in the Mullet Island cormorant (Phalacrocorax auritus) breeding colony during 1997 and again during 1998.
G. C. Holdren and A. Montano. 2002. Chemical and physical characteristics of the Salton Sea, California
Hydrobiologia 473(1-3):1-21
A 1-year sampling program was conducted to assess current chemical and physical conditions in the Salton Sea. Analyses included general physical conditions and a suite of water quality parameters, including 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 in the Salton Sea are high and lead to frequent algal blooms, which in turn contribute to low dissolved oxygen concentrations. The tributaries 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. Two geochemical models, PHRQPITZ and PHREEQC, were used to evaluate potential chemical reactions limiting the solubility of selected water quality variables. Modeling indicated that the Salton Sea is supersaturated with respect to calcite, gypsum, and other minerals. Precipitation of these minerals may serve as a sink for phosphorus and limit the rate of salt accumulation in the Salton Sea.
J. R. Jehl and R. L. McKernan. 2002. Biology and migration of Eared Grebes at the Salton Sea
Hydrobiologia 473(1-3):245-253
The Eared Grebe (Podiceps nigricollis Brehm) is the North American bird species most closely associated with highly saline habitats, and in winter and early spring it is the most abundant waterbird at the Salton Sea. During the fall, the great majority of the North American population stages at hypersaline lakes in the Great Basin, departing in early winter for wintering areas in southern California and Mexico, principally in the central Gulf of California. On the northward return flight, nearly all the population passes through the Salton Sea, where concentrations of >1 million have been reported in February-March. After staging for several weeks, grebes leave in March-April and migrate toward breeding grounds in the northern United States and southern Canada. The Sea's development as the species' major spring staging area may be as recent as the 1960s, and presumably awaited the establishment of appropriate prey populations of marine worms. In the past decades, two major dieoffs at the Sea each resulted in the undiagnosed death of tens of thousands of birds. Whether the cause(s) are endemic to the Sea or involve the grebes' migration routes and stopover locations is unknown. Because of problems in estimating numbers, the significance of these mortality events is hard to evaluate. Population trends are better studied at fall staging areas, especially Mono Lake, where population turnover is inconsequential, grebes are virtually the only species present, and numbers can be ascertained by aerial photography.
B. I. Kuperman, V. E. Matey and S. B. Barlow. 2002. Flagellate Cryptobia branchialis (Bodonida : Kinetoplastida), ectoparasite of tilapia from the Salton Sea
Hydrobiologia 473(1-3):93-102
An infestation of young tilapia, Oreochromis mossambicus Peters, by the flagellate Cryptobia branchialis was observed at the Salton Sea, California, in September, 1997. This is the first report of C. branchialis in a highly saline water-body (43 g l(-1)). Ultrastructure of C. branchialis as well as its effect on the gills of tilapia were studied using the scanning and transmission electron microscopy. No direct effect of C. branchialis on the epithelial cells of fish gills was observed. However, alterations of gill general structure, such as deposition of copious mucus on the gill surface, swelling of filaments, reduction of respiratory lamellae and their transformation into short club-shaped structures were found in infected fish. This suggests mortality of young tilapia may arise from decreased gill function in response to Cryptobia infestation.
B. I. Kuperman, V. E. Matey, D. M. Dexter and M. A. Tiffany. 2002. Invertebrates of the Salton Sea: a scanning electron microscopy portfolio
Hydrobiologia 473(1-3):203-216
Scanning electron microphotographs of 16 Salton Sea invertebrate species are presented within this portfolio. A wide spectrum of invertebrates was investigated including foraminiferans, a flatworm, a rotifer, annelids, crustaceans and insects. Additional information is provided on the morphology and function of structures visible in the images.
C. B. Lange and M. A. Tiffany. 2002. The diatom flora of the Salton Sea, California
Hydrobiologia 473(1-3):179-201
We report on diatom species of the Salton Sea, a highly saline (43 g l(-1)) inland lake in California. We identified and photographed all diatom taxa encountered in the phytoplankton and benthos of the Salton Sea and its immediate tributaries. Ninety-four taxa were distinguished based on their morphological features using light- and electron microscopy. In the Salton Sea, there are four general categories of diatom assemblages related to their habitats: (1) A planktonic assemblage composed of Chaetoceros muelleri var. subsalsum, Cyclotella choctawhatcheeana, Cyclotella sp., Cylindrotheca closterium, Pleurosigma ambrosianum, Thalassionema sp.; (2) a benthic assemblage with diatoms that live on the bottom (e.g. genera Caloneis, Diploneis, Entomoneis, Gyrosigma, Plagiotropis, Pleurosigma, Surirella and Tryblionella), or in algal mats ( Proschkinia bulnheimii, several species of Navicula and Seminavis gracilenta); (3) an epiphytic community attached to the macroscopic green algae which grow on the rocks and other hard surfaces near shore (e.g. Achnanthes brevipes, Licmophora ehrenbergii, Tabularia parva); and (4) a freshwater assemblage composed of species that get washed in by the rivers and other inflows discharging into the Sea (e.g. Achnanthidium minutissimum, Cocconeis pediculus, Cyclotella atomus, C. scaldensis, Nitzschia elegantula, T. weissflogii). The most striking feature of the phytoplankton is the abundance of species formerly known only from marine environments; this is not surprising given the high salinity and the peculiar history of the lake.
K. M. Reifel, M. P. McCoy, T. E. Rocke, M. A. Tiffany, S. H. Hurlbert and D. J. Faulkner. 2002. Possible importance of algal toxins in the Salton Sea, California
Hydrobiologia 473(1-3):275-292
In response to wildlife mortality including unexplained eared grebe (Podiceps nigricollis) die-off events in 1992 and 1994 and other mortality events including large fish kills, a survey was conducted for the presence of algal toxins in the Salton Sea. Goals of this survey were to determine if and when algal toxins are present in the Salton Sea and to describe the phytoplankton composition during those times. A total of 29 samples was collected for toxicity analysis from both nearshore and midlake sites visited biweekly from January to December 1999. Dinoflagellates and diatoms dominated most samples, but some were dominated by a prymnesiophyte ( Pleurochrysis pseudoroscoffensis) or a raphidophyte (Chattonella marina). Several types of blooms were observed and sampled. The dinoflagellate Gyrodinium uncatenum formed an extensive, dense (up to 310 000 cells ml(-)1) and long-lasting bloom during the winter in 1999. A coccolithophorid, Pleurochrysis pseudoroscoffensis, occurred at high densities in surface films and nearshore areas during the spring and summer of 1999. These surface films also contained high densities of one or two other species (an unidentified scrippsielloid, Heterocapsa niei, Chattonella marina). Localized blooms were also observed in the Salton Sea. An unknown small dinoflagellate reached high densities (110 000 cells ml(-1)) inside Varner Harbor, and an unidentified species of Gymnodinium formed a dense (270 000 cells ml(-1)) band along part of the southern shoreline during the summer. Three species known to produce toxins in other systems were found. Protoceratium reticulatum (= Gonyaulax grindleyi) and Chattonella marina were found in several samples taken during summer months, and Prorocentrum minimum was found in low densities in several samples. Extracts of most samples, including those containing known toxic species, showed a low level (<10% mortality across all concentrations) of activity in the brine shrimp lethality assay and were not considered toxic. All sample extracts tested in the mouse bioassay showed no activity. One sample extract taken from the bloom of the small dinoflagellate was highly active (100% mortality across all concentrations) in the brine shrimp lethality assay, but the active material could not be isolated. While dense algal blooms are common at the Salton Sea, no evidence gathered in this study suggests that algal toxins are present within phytoplankton cells; however, toxins actively excreted by cells may have been missed. Blooms of phytoplankton likely contribute to wildlife mortality at the Salton Sea. Possible mechanisms including intoxication due to ingestion of feathers in grebes and waterlogging caused by changes in surface tension are discussed.
R. Riedel, L. Caskey and B. A. Costa-Pierce. 2002. Fish biology and fisheries ecology of the Salton Sea, California
Hydrobiologia 473(1-3):229-244
Studies of the fisheries ecology and fish biology of the Salton Sea, California, were conducted in 1999 and 2000 using 50 m gill nets in river, nearshore, pelagic, and estuarine areas. Total lengths and weights were measured for all fish captured, and sub-samples were dissected for gonad weights and aging. Ten fish species were captured of which a hybrid tilapia ( Oreochromis mossambicus x O. urolepis hornorum) was dominant by number and weight. Nearshore and estuarine areas had highest catch rates (over 11 kg h(-1) net(-1) for tilapia). Rivers were richest in the number of species (6 of 10 species were exclusively riverine), but lowest in fish abundance. Orangemouth corvina (Cynoscion xanthulus), bairdiella (Bairdiella icistia), sargo (Anisotremus davidsoni), and tilapia grew faster, but had shorter life spans than conspecifics elsewhere and Salton Sea conspecifics of 50 years ago. Reproduction occurred mostly in the nearshore and estuarine areas. Onset of reproduction of bairdiella and sargo was in the spring and extended through the beginning of summer. Reproduction of orangemouth corvina started in the summer and of tilapia in the spring. Reproduction of orangemouth corvina and tilapia extended through the fall. Gender ratios of tilapia were skewed toward males in all areas, except the rivers, where females predominated. All four species aggregated along the nearshore and estuarine areas in the summer when dissolved oxygen in the pelagic area was limited. Any restoration alternative for the Salton Sea should consider areas close to shore as primary areas for fish reproduction and survival.
A. Rogerson and G. Hauer. 2002. Naked amoebae (Protozoa) of the Salton Sea, California
Hydrobiologia 473(1-3):161-177
The Salton Sea is an inland lake in California with an average salinity of ca. 44 g l(-1). This productive water body, which supports substantial fish and migratory bird populations, is under threat because of increasing salinity levels. The present study was the first to examine the naked amoeboid protozoa of the Salton Sea and provide a first estimate of their numerical importance. Over a six-month sampling period (June-December, 1999), 45 different morphospecies (considered to be species) of amoebae were isolated. Wherever possible, isolates were identified to species or genus using diagnostic features recognizable by light microscopy. For each isolate, illustrations and brief notes on the diagnostic characters used in the identifications are given. These will allow this paper to be used as an identification guide to amoebae of the Salton Sea in future studies. Of the 45 taxa, around 18 of the isolates (i.e. 40%) are probably new to Science. Preliminary counts, based on enrichment cultivation methods, showed that amoebae in shoreline waters ranged from 14 560 to 237 120 cells l(-1) (mean 117312+/-86075 S.D.). The ecological importance of high numbers and high diversity of amoebae is unknown. But it should be noted that several of the amoebae were actively grazing cyanobacterial and algal filaments and filaments of the bacterium Beggiatoa. Others were predominately associated with suspended particulates. As such, amoebae may be important in the cycling of carbon and nutrients in the Salton Sea.
R. A. Schroeder, W. H. Orem and Y. K. Kharaka. 2002. Chemical evolution of the Salton Sea, California: nutrient and selenium dynamics
Hydrobiologia 473(1-3):23-45
The Salton Sea is a 1000-km(2) terminal lake located in the desert area of southeastern California. This saline (similar to44 000 mg l(-1) dissolved solids) lake started as fresh water in 1905-07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr(-1) show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.
W. D. Shuford, N. Warnock, K. C. Molina and K. K. Sturm. 2002. The Salton Sea as critical habitat to migratory and resident waterbirds
Hydrobiologia 473(1-3):255-274
Concern about the Salton Sea ecosystem, based on potential impacts of increasing salinity, contaminants, disease outbreaks, and large die-offs of birds, is heightened because of tremendous prior loss and degradation of wetland habitat in western North America. In 1999, we used a variety of survey methods to describe patterns of abundance of birds at the Salton Sea and in adjacent habitats. Our results further documented the great importance of the Salton Sea within the Pacific Flyway to wintering, migratory, and breeding waterbirds. Exclusive of Eared Grebes, we estimated about 187 000 individual waterbirds at the Salton Sea in January, 88 000 in April, 170 000 in August, and 261 000 in November. Additional surveys of Eared Grebes in November and December suggested the total population of all waterbirds was about 434 000 to 583 000 in those months, respectively. We also documented breeding by about 14 000 pairs of colonial waterbirds. Waterbirds were particularly concentrated along the northern, southwestern, southern, and southeastern shorelines and river deltas. By contrast, some species of wading birds (Cattle Egret, White-faced Ibis, Sandhill Crane) and shorebirds (Mountain Plover, Whimbrel, Long-billed Curlew) were much more numerous in agricultural fields of the Imperial Valley than in wetland habitats at the Sea. Various studies indicate the Salton Sea is of regional or national importance to pelicans and cormorants, wading birds, waterfowl, shorebirds, and gulls and terns. Important taxa are the Eared Grebe, American White Pelican, Double-crested Cormorant, Cattle Egret, White-faced Ibis, Ruddy Duck, Yuma Clapper Rail, Snowy Plover, Mountain Plover, Gull-billed, Caspian, and Black terns, and Black Skimmer. Proposed restoration projects should be carefully assessed to ensure they do not have unintended impacts and are not placed where large numbers of breeding, roosting, or foraging birds concentrate. Similarly, plans to enhance opportunities for recreation or commerce at the Sea should aim to avoid or minimize disturbance to birds. Future research should focus on filling gaps in knowledge needed to effectively conserve birds at the Salton Sea.
R. J. Sutton. 2002. Summer movements of desert pupfish among habitats at the Salton Sea
Hydrobiologia 473(1-3):223-228
Summer movement behavior of native desert pupfish (Cyprinodon macularius Baird and Girard) was evaluated among various habitats around the Salton Sea, located in southern California. Agricultural drains, shoreline pools, and Salt Creek were sampled six times between June 28 and September 16, 1999. Collected pupfish were marked using fluorescent elastomer implants. Unique marks were used at each site. Movements were detected from locations of recaptured pupfish. Desert pupfish were found in 10 of 12 sites sampled. Of 3239 pupfish captured during the study, 278 were recaptures, including 27 recaptures at areas different from where they were initially marked. The best evidence of pupfish movements was in the southwestern area of the Salton Sea between a drain and a connected shoreline pool. Movements were also observed from lower Salt Creek into a shoreline pool at the mouth of the creek as the water level dropped. The use of the Salton Sea as a migration corridor between habitats was not documented during this short study. The marking technique was successful and showed promise for future mark and recapture studies of desert pupfish.
M. A. Tiffany, B. K. Swan, J. M. Watts and S. H. Hurlbert. 2002. Metazooplankton dynamics in the Salton Sea, California, 1997- 1999
Hydrobiologia 473(1-3):103-120
The dynamics of metazooplankton populations were studied over 3 years at the saline (43 g l(-1)) Salton Sea, California's largest lake. Total abundance was highest in summer following late winter/early spring phytoplankton blooms. At this time, metazooplankton consisted mostly of the copepod, Apocyclops dengizicus, and the rotifer, Brachionus rotundiformis. In August or September, severe crashes in the metazooplankton populations occurred each year in mid-lake due to strong wind events which increased mixing and caused low oxygen and high sulfide concentrations throughout the water column. Larvae of the polychaete worm, Neanthes succinea and the barnacle, Balanus amphitrite were present mostly in late winter and spring. Their scarcity in summer is due in part to persistent anoxic bottom conditions that decrease adult populations and in part to predation by tilapia, an omnivorous fish that has become abundant in the lake since the 1960s. Two Synchaeta species, rotifers not previously reported from the Sea, were abundant in winter and spring and predation on these may have permitted the copepod to persist at low levels through the winter. There were two major changes in metazooplankton dynamics since 1954-1956 in addition to the appearance of the two synchaetid rotifers in the fauna. First, there are now much lower densities of barnacle and polychaete larvae in the fall, probably due to the invasion of the zooplanktivorous fish, tilapia. Second the precipitous crashes now seen in metazooplankton densities, especially the copepod, in late summer-early fall did not occur in the 1950s possibly because fall overturn events did not result in such high sulfide levels.
M. A. Tiffany. 2002. Skeletal development in Hermesinum adriaticum Zacharias, a flagellate from the Salton Sea, California
Hydrobiologia 473(1-3):217-221
Hermesinum adriaticum is a rarely reported unicellular biflagellated organism with a solid siliceous skeleton. Live specimens were not observed but many skeletons were found in sediments and, in small numbers, in cyanobacterial mats and the water column of the Salton Sea, a salt lake in California, U.S.A. Stages of the developing skeleton were studied with scanning electron microscopy, and the progression from small tetraxial daughter skeletons to complete asymmetrical adult skeletons is presented. Some variability in the adult skeletons is illustrated.
R. A. Vogl and R. N. Henry. 2002. Characteristics and contaminants of the Salton Sea sediments
Hydrobiologia 473(1-3):47-54
This was the first comprehensive study to evaluate the distribution of sediment types and sediment contaminants throughout the Salton Sea. The sampling effort encompassed the entire Sea plus its three main tributaries, and included collection of sediment samples from 73 locations. The agricultural runoff that keeps the Sea alive is loaded with salts, pesticides, selenium, and other metals. Metals and metalloids found at elevated concentrations and of potential ecological concern were cadmium, copper, molybdenum, nickel, zinc, and selenium. The most significant metalloid of concern was selenium, which was limited to the upper 30 cm of sediment. There did not appear to be any strong correlation between the sand, silt, or clay content with the areas of elevated metals and metalloids. Acetone, 2-butanone, and carbon disulfide were also widespread but appeared to be associated with natural biological processes within the sediments. One of the most significant findings of this study was the absence of elevated concentrations of organic chemicals commonly used in agriculture earlier this century, such as dichlorodiphenyltrichloroethane (DDT).
R. M. Warwick, D. M. Dexter and B. Kuperman. 2002. Freeliving nematodes from the Salton Sea
Hydrobiologia 473(1-3):121-128
Thirteen species, or putative species, of freeliving nematodes are recorded from a variety of habitats in the hypersaline Salton Sea, the largest inland lake in California. This doubles the number of species of multicellular invertebrates known to occur in the lake. All species are referable to known marine genera, and are regarded as having a marine coastal origin. The range of taxa present is representative of the full taxonomic spread found in marine coastal habitats, suggesting that a wide range of marine nematode taxa are capable of adapting to the hypersaline conditions. The broad spectrum of feeding types present suggests that nematodes play a variety of ecological roles within the lake.
A. M. Wood, S. R. Miller, W. K. W. Li and R. W. Castenholz. 2002. Preliminary studies of cyanobacteria, picoplankton, and virioplankton in the Salton Sea with special attention to phylogenetic diversity among eight strains of filamentous cyanobacteria
Hydrobiologia 473(1-3):77-92
Cyanobacterial diversity in the Salton Sea, a high-salinity, eutrophic lake in Southern California, was investigated using a combination of molecular and morphological approaches. Representatives of a total of 10 described genera (Oscillatoria, Spirulina, Arthrospira, Geitlerinema, Lyngbya, Leptolyngbya, Calothrix, Rivularia, Synechococcus, Synechocystis) were identified in the samples; additionally, the morphology of two cultured strains do not conform to any genus recognized at present by the bacteriological system. Genetic analysis, based on partial 16S rRNA sequences suggested considerable cryptic genetic variability among filamentous strains of similar or identical morphology and showed members of the form-genus Geitlerinema to be distributed among three major phylogenetic clades of cyanobacteria. Cyanobacterial mats, previously described from the Sea were, in fact, composed of both filamentous cyanobacteria and a roughly equivalent biomass of the sulfur-oxidizing bacterium Beggiatoa, indicating their formation in sulfide rich regions of the lake. Flow cytometric analysis of the water samples showed three striking differences between samples from the Salton Sea and representative marine waters: (1) phycoerythrin-containing unicells, while abundant, were much less abundant in the Salton Sea than they were in typical continental shelf waters, (2) Prochlorococcus appears to be completely absent, and (3) small (3-5 mum) eukaryotic algae were more abundant in the Salton Sea than in typical neritic waters by one-to-two orders-of- magnitude. Based on flow cytometric analysis, heterotrophic bacteria were more than an order of magnitude more abundant in the Salton Sea than in seawater collected from continental shelf environments. Virus particles were more abundant in the Salton Sea than in typical neritic waters, but did not show increases proportionate with the increase in bacteria, picocyanobacteria, or eukaryotic algae.
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