Clay Perschon’s research while affiliated with Salt Lake Community College and other places
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Survivability of diapausing (cryptobiotic) life stages over time in nature, beyond maximum observed time for viability, is not well understood. Because these life stages are an adaptation to overcome harsh conditions, survivability over time is assumed to be high. Brine shrimp (Artemia franciscana) diapausing eggs (cysts) permit overwinter survival to initiate the population each spring. An experiment was designed to examine overwinter survival of brine shrimp cysts for 17 yr in Great Salt Lake (Utah, U.S.A.). Initial hatchability entering the winter (17.8–78.8%) and overwinter survivability (9.9–65.9%) of cysts varied dramatically among years. Better maternal nutrition increased initial hatchability. Overwinter survival of cysts decreased in part because some cysts hatch when it is too cold for the hatchlings to feed (0.8–39.4% among years), so they starve. However, overwinter cyst survival decreases the most with warmer waters in winter, and with better maternal nutrition, as both factors lead to diapause being easier to break. Annual variation in initial hatchability and survival is shown to be important to Great Salt Lake brine shrimp populations. Therefore, cryptobiotic life‐stage ecology needs to be better understood, as these life stages may have highly variable hatchability and survivability with normal environmental stresses.
Great Salt Lake (Utah, USA) is one of the world's largest hypersaline lakes, supporting many of the western U.S.'s migratory waterbirds. This unique ecosystem is threatened, but it and other large hypersaline lakes are not well understood. The ecosystem consists of two weakly linked food webs: one phytoplankton-based, the other organic particle/benthic algae-based. Seventeen years of data on the phytoplankton-based food web are presented: abundances of nutrients (N and P), phytoplankton (Chlorophyta, Bacillariophyta, Cyanophyta), brine shrimp (Artemia franciscana), corixids (Trichocorixa verticalis), and Eared Grebes (Podiceps nigricollis). Abundances of less common species, as well as brine fly larvae (Ephydra cinerea and hians) from the organic particle/benthic algae-based food web are also presented. Abiotic parameters were monitored: lake elevation, temperature, salinity, PAR, light penetration, and DO. We use these data to test hypotheses about the phytoplankton-based food web and its weak linkage with the organic particle/benthic algae-based food web via structural equation modeling. Counter to common perceptions, the phytoplankton-based food web is not limited by high salinity, but principally through phytoplankton production, which is limited by N and grazing by brine shrimp. Annual N abundance is highly variable and depends on lake volume, complex mixing given thermo-and chemo-clines, and recycling by brine shrimp. Brine shrimp are food-limited, and predation by corixids and Eared Grebes does not depress their numbers. Eared Grebe numbers appear to be limited by brine shrimp abundance. Finally, there is little interaction of brine fly larvae with brine shrimp through competition, or with corixids or grebes through predation, indicating that the lake's two food webs are weakly connected. Results are used to examine some general concepts regarding food web structure and dynamics, as well as the lake's future given expected anthropogenic impacts.
The Great Salt Lake (GSL) is an important region for millions of migratory waterbirds. However, high concentrations of some trace elements, including Hg and Se, have been detected within the GSL, and baseline ecotoxicological data are lacking for avian species in this system. We collected common goldeneye (Bucephala clangula), northern shoveler (Anas clypeata), and green-winged teal (A. crecca) from the GSL during the winters of 2004-2005 and 2005-2006 to evaluate sources of variation in liver trace element concentrations. Hg concentrations were among or exceeded the highest values reported in the published literature for common goldeneye, northern shoveler, and green-winged teal. Average Hg (total) concentrations of common goldeneye peaked in midwinter, whereas average Se concentrations peaked during late winter. During late winter, 100% and 88% of female goldeneye contained elevated concentrations of Hg [>or=1.0 microg/g wet weight (ww)] and Se (>or=3.0 microg/g ww), respectively, and 5% and 14% contained potentially harmful amounts of Hg (>or=30.0 microg/g ww) and Se (>10.0 microg/g ww), respectively. Similarly, 30% and 16% of male goldeneye contained potentially harmful concentrations of Hg and Se, respectively. Concentrations of Hg and Se were elevated in 100% and 79%, respectively, of northern shoveler samples (sexes combined) collected during February. We suggest that waterfowl contain biologically concerning amounts of Hg and Se during winter while on the GSL and further research is needed to evaluate the effect of these elements on GSL waterbirds.
a b s t r a c t Despite the ecological and economic importance of Great Salt Lake (GSL), little is known about the input and biogeochemical cycling of nutrients and trace elements in the lake. In response to increasing public concern regarding anthropogenic inputs to the GSL ecosys-tem, the US Geological Survey (USGS) and US Fish and Wildlife Service (USFWS) initiated coordinated studies to quantify and evaluate the significance of nutrient and Hg inputs into GSL. A 6‰ decrease in d 15 N observed in brine shrimp (Artemia franciscana) samples collected from GSL during summer time periods is likely due to the consumption of cyanobacteria produced in freshwater bays entering the lake. Supporting data collected from the outflow of Farmington Bay indicates decreasing trends in d 15 N in particulate organic matter (POM) during the mid-summer time period, reflective of increasing proportions of cyanobacteria in algae exported to GSL on a seasonal basis. The C:N molar ratio of POM in outflow from Farm-ington Bay decreases during the summer period, supportive of the increased activity of N fixation indicated by decreasing d 15 N in brine shrimp and POM. Although N fixation is only taking place in the relatively freshwater inflows to GSL, data indicate that influx of fresh water influences large areas of the lake. Separation of GSL into two distinct hydrologic and geochemical systems from the construction of a railroad causeway in the late 1950s has created a persistent and widespread anoxic layer in the southern part of GSL. This anoxic layer, referred to as the deep brine layer (DBL), has high rates of SO 2À 4 reduction, likely increasing the Hg methylation capacity. High concentrations of methyl mercury (CH 3 Hg) (median concentration = 24 ng/L) were observed in the DBL with a significant proportion (31–60%) of total Hg in the CH 3 Hg form. Hydroacoustic and sediment-trap evidence indicate that turbulence introduced by internal waves generated during sustained wind events can temporarily mix the elevated CH 3 Hg concentrations in the DBL with the more biologically active upper brine layer (UBL). Brine shrimp collected during the summer/fall time periods contained elevated Hg concentrations (median concentration = 0.34 mg/kg, dry weight (dw)) relative to samples collected during the spring (median concentration < 0.2 mg/kg, dw). Higher Hg in brine shrimp during the summer and fall may reflect the higher propor-tion of adult brine shrimp during this time period, resulting in an increased time for bioac-cumulation of Hg. Eared grebes (Podiceps nigricollis) consume brine shrimp from GSL during the fall molting period. Median Hg concentrations in eared grebe livers increased by almost three times during the 3–5 month fall molting period. Selected duck species utilizing GSL have consistently exceeded the US Environmental Protection Agency (USEPA) screening 0883-2927/$ -see front matter Published by Elsevier Ltd.
The Great Salt Lake (GSL) is the fourth largest terminal lake in the world and is an important region for migratory and breeding waterbirds. Because the GSL is a closed basin, contaminants associated with industrial and urban development may accumulate in this system. Recently, water and sediment samples from the GSL revealed high concentrations of Hg and Se and methylmercury concentrations in GSL water samples were among the highest ever recorded in surface water by the USGS Mercury Laboratory. Thus, GSL waterbirds are likely exposed to these contaminants and elevated contaminant concentrations may adversely affect survival and reproduction in waterfowl. Our objectives were to 1) estimate mercury (Hg), selenium (Se), cadmium (Cd), copper (Cu), and zinc (Zn) concentrations in wintering waterfowl from GSL and, 2) evaluate relationships between measures of waterfowl body condition and internal organ masses (hereafter body condition) with trace metal concentrations. We collected common goldeneye (COGO), northern shoveler (NSHO), and American green-winged teal (AGWT) from the GSL during early winter. We used ICP-MS to analyze liver and muscle tissue samples for contaminant concentrations. We developed species specific regression models for each of 5 condition indices, including ingesta-free plucked body mass (IFPBM), abdominal fat mass, spleen, liver, and pancreas masses. Independent variables were comprised of Hg, Se, Cd, Cu, and Zn and we included sex and age as covariates in each regression. We used Akaike's Information Criterion adjusted for small sample size to select best and competing models. Subsequently, we used partial correlations to depict inverse relationships identified in competing models. Hg concentrations in COGO and NSHO muscle tissue generally exceeded or approached the 1 ppm wet weight (ww) threshold considered unsafe for human consumption in fish and game. Hg concentrations in liver tissue exceeded or were among the highest reported in published literature for COGO, NSHO, and AGWT. Se concentrations in liver tissue for all 3 species were below the 10 ppm, ww threshold suggested for potential harmful effects in non-breeding ducks. Cd, Cu, and Zn concentrations in liver tissues were generally within normal background levels for all 3 species. IFPBM was inversely correlated with Se (r = -0.29) in COGO, Cu (r = -0.30) and Zn (r = -0.32) in NSHO, and with Zn (r = -0.62) in AGWT. Abdominal fat mass was inversely correlated with Se (r = -0.32) in COGO, Cu (r = -0.23) and Zn (r = -0.21) in NSHO, and with Zn (r = -0.81) in AGWT. Spleen mass was inversely correlated with Hg (r = -0.42) in COGO, and Se (r = -0.36) in AGWT. Liver mass was inversely correlated with Hg (r = -0.56) and Zn (r = -0.71) in AGWT, and with Se (r = -0.47) in NSHO. Pancreas mass was inversely correlated with Zn in (r = -0.70) AGWT. Our results indicate GSL waterfowl may experience reduced body condition due to environmental contaminants. However, these relationships should be evaluated in other annual cycle periods and GSL waterbirds. Contaminant pathways to waterfowl need to be elucidated and water quality standards for GSL should be developed. Finally, human consumption of COGO and NSHO from GSL should be limited.
... Samples exhibiting abnormally high reflectance in SWIR2 were eliminated, presuming that these pixels were overlapping dry land, or the pixel retained some cloud or cloud shadow pollution. We also compared water depth to the concentration of Chl a to determine if samples in shallower water resulted in abnormally high Chl a concentration (>200 mg L −1 ) [31], thus identifying samples whose Chl a concentration may have been influenced by the churning of the lake bottom by the boat propeller. To further address shallow water depth, we examined the change in the coefficient of determination between our spectral index and sampled Chl a concentration as samples were systematically removed by increasing water depth. ...
... The GSL has no outlet al.lowing for the accumulation and concentration of minerals over time, giving the lake its trademark salinity [3]. While the extraction of minerals such as lithium, magnesium, and potassium sulfate from the GSL are of major economic importance, GSL sediments also contain toxic metals such as iron, aluminum, copper, lead, arsenic, and mercury which is attributable to upstream natural sources and possibly being juxtaposed to one of the world's largest copper mines [4,5]. As shown later, GSL sediments also harbor natural and anthropogenic chemicals. ...
... In 2007, human consumption advisories were issued for three species of ducks found in marshlands adjacent to Great Salt Lake due to high levels of mercury in the bird tissue [40]. Subsequent geochemical studies revealed very high concentrations of methylmercury in the deep brine layer [17,30,32] suggesting the DBL may have been the source for the mercury observed in the water fowl [1,44]. However, exact sources and pathways of mercury in Great Salt Lake ecosystem have yet to be definitively worked out [32,51]. ...