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Significant multiple regressions obtained for brine shrimp demography (partial correlations in parentheses).
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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/ben...
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... 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. ...
... A summary of the seasonal cycle in Chl a averaged over 20 years (2001-2021) and Artemia abundances from 1996-2004 [31,42] (Figure 9) shows that Chl a concentrations peak in March at approximately 37 µg L −1 and then decline to 3 µg L −1 by June, presumably due to strong grazing pressure by Artemia, which increases in population in the early summer months. With mean adult-equivalent densities of 3 L −1 in summer, Artemia can consume approximately 72% of the phytoplankton in the water column each day [43]. ...
... Additionally, the high chlorophyll concentrations in winter and lower concentrations in summer may not directly reflect rates of primary production, as the grazed populations in summer may feature proportionately higher production rates than the phytoplankton in winter in the absence of grazing [49], and cold temperatures can substantially suppress phytoplankton production rates when light is not limiting [50]. Nevertheless, the rich over-wintering phytoplankton biomass may play an important ecological role in annual lake food web dynamics, promoting rapid growth of Artemia in spring (Figure 9) [31] and thus food for migratory birds as well. ...
The Great Salt Lake (GSL) is the largest saline lake in the Western Hemisphere. It supports billion-dollar industries and recreational activities, and is a vital stopping point for migratory birds. However, little is known about the spatiotemporal variation of phytoplankton biomass in the lake that supports these resources. Spectral reflectance provided by three remote sensing products was compared relative to their relationship with field measurements of chlorophyll a (Chl a). The MODIS product MCD43A4 with a 500 m spatial resolution provided the best overall ability to map the daily distribution of Chl a. The imagery indicated significant spatial variation in Chl a, with low concentrations in littoral areas and high concentrations in a nutrient-rich plume coming out of polluted embayment. Seasonal differences in Chl a showed higher concentrations in winter but lower in summer due to heavy brine shrimp (Artemia franciscana) grazing pressure. Twenty years of imagery revealed a 68% increase in Chl a, coinciding with a period of declining lake levels and increasing local human populations, with potentially major implications for the food web and biogeochemical cycling dynamics in the lake. The MCD43A4 daily cloud-free images produced by 16-day temporal composites of MODIS imagery provide a cost-effective and temporally dense means to monitor phytoplankton in the southern (47% surface area) portion of the GSL, but its remaining bays could not be effectively monitored due to shallow depths, and/or plankton with different pigments given extreme hypersaline conditions.
... 24 Such rates are in line with what has been reported for highly eutrophic systems such as Lake Erie (Canada/United States), 38,39 as well as some other saline lakes. 36 In GSL, measured summertime aquatic fluxes tended to be higher than springtime fluxes, potentially reflecting typically low phytoplankton productivity in June and July, 37,40 likely associated with strong grazing pressure from brine shrimp (Artemia franciscana), 41,42 making these potentially peak months for aquatic GHG fluxes in GSL. Although we were unable to take more extensive aquatic flux measurements across other seasons within this study to confirm this for GSL, seasonality in lake surface CO 2 emissions tends to be highly variable, 43 particularly in eutrophic systems, 44 often being inversely related to primary productivity. ...
... Measuring Chl-a, which is present in all phytoplankton groups, is a well-known method for determining phytoplankton biomass in lakes (Winder and Cloern, 2010). However, high salinity and turbidity hinder further algal and Artemia growth in hypersaline lakes (Belovsky et al., 2011). As such, the sole use of Chl-a as an indicator of eutrophication is not sufficient, and complementary WQVs such as TP and SD should be used to better interpret the trophic state of lakes like LU and their ecosystem services. ...
... Furthermore, the high CTSI (SD) (ESMFigure S5) indicates the high turbidity of the north part of LU as a result of high TSS (because of the presence of a significant amount of the organic or non-organic suspended material). Previous studies discussed that the high salinity (TDS > 300 g/l) of water prevents organic matter from degradation (Belovsky et al., 2011). Thus, they may remain attached to the mineral-suspended particles and further reduce the lake's transparency (IWPCO, 2018). ...
... Integrating surface water information with climate patterns and human water usage factors offers an ecological perspective on evolving flyway conditions and addressing emerging migratory challenges (Donnelly et al. 2020). Despite the importance of the saline lake ecosystem for waterbirds, they are not well studied nor protected (Belovsky et al. 2011). ...
The hypersaline Lake Urmia, located in Iran, has undergone a significant reduction in size and is currently facing the risk of desiccation. The decrease in water levels, coupled with elevated salinity levels, has initiated ecological degradation, leading to a substantial decline in the region’s waterbird population. This study employs breakpoint analysis to determine the year when the drought event affecting the lake commenced. Additionally, canonical correspondence analysis (CCA) is utilised to elucidate the interaction between environmental parameters and the waterbird assemblages in Lake Urmia over the period 1970–2018. Our investigation identifies the year 2000 as the initiation of the water crisis in Lake Urmia, synchronously coinciding with the decline in the waterbird populations. This finding highlights a significant connection between the majority of waterbird species and the axes of CCA, intricately linked with water availability within Lake Urmia. This revelation underscores the pivotal role of fluctuations in water levels in shaping the dynamics of the lake’s waterbird assemblages. Furthermore, our observations emphasise the importance of even minor improvements in hydrological conditions of the lake, resulting in substantial positive impacts on waterbird populations.
... Nematodes are a nearly ubiquitous and diverse meiofaunal taxa. Although free-living nematodes have not been described in the GSL, several lines of evidence motivated further investigation [11]. As the most abundant animal phylum on the ocean floor and terrestrial biosphere, nematodes exhibit remarkable diversity with an estimated 250 000 species and at least 25 000 known extant species [12][13][14][15]. ...
Extreme environments enable the study of simplified food-webs and serve as models for evolutionary bottlenecks and early Earth ecology. We investigated the biodiversity of invertebrate meiofauna in the benthic zone of the Great Salt Lake (GSL), Utah, USA, one of the most hypersaline lake systems in the world. The hypersaline bays within the GSL are currently thought to support only two multicellular animals: brine fly larvae and brine shrimp. Here, we report the presence, habitat, and microbial interactions of novel free-living nematodes. Nematode diversity drops dramatically along a salinity gradient from a freshwater river into the south arm of the lake. In Gilbert Bay, nematodes primarily inhabit reef-like organosedimentary structures built by bacteria called microbialites. These structures likely provide a protective barrier to UV and aridity, and bacterial associations within them may support life in hypersaline environments. Notably, sampling from Owens Lake, another terminal lake in the Great Basin that lacks microbialites, did not recover nematodes from similar salinities. Phylogenetic divergence suggests that GSL nematodes represent previously undescribed members of the family Monhysteridae—one of the dominant fauna of the abyssal zone and deep-sea hydrothermal vents. These findings update our understanding of halophile ecosystems and the habitable limit of animals.
... Great Salt Lake (GSL), located in the state of UT, is the largest saltwater body in the USA and represents one of the most hypersaline and extreme environments in the world [1,2]. Its area spans five counties, including Weber, Box Elder, Salt Lake, Tooele, and Davis, and covers ∼4400 km 2 , though its area is rapidly shrinking due to climate change and water diversion [1,3,4]. ...
... Although the North Arm exhibits higher ion abundance than the South Arm, their ion compositions are similar [6,7]. However, the considerable differences in salinity significantly inf luence the microbiota between the two arms, creating two sub ecosystems within the lake [1,2,7,8]. A broader microbial diversity is observed in the South Arm compared to the North Arm, and this is primarily attributed to the differences in salinity [9,10]. ...
Great Salt Lake (GSL), located northwest of Salt Lake City, UT, is the largest terminal lake in the USA. While the average salinity of seawater is ~3.3%, the salinity in GSL ranges between 5% and 28%. In addition to being a hypersaline environment, GSL also contains toxic concentrations of heavy metals, such as arsenic, mercury, and lead. The extreme environment of GSL makes it an intriguing subject of study, both for its unique microbiome and its potential to harbor novel natural product–producing bacteria, which could be used as resources for the discovery of biologically active compounds. Though work has been done to survey and catalog bacteria found in GSL, the Lake’s microbiome is largely unexplored, and little to no work has been done to characterize the natural product potential of GSL microbes. Here, we investigate the bacterial diversity of two important regions within GSL, describe the first genomic characterization of Actinomycetota isolated from GSL sediment, including the identification of two new Actinomycetota species, and provide the first survey of the natural product potential of GSL bacteria.
... While 155 observations were collected in the study, only 58 of them (∼ 37%) had data available for chlorophyte concentration. Finally, during part of the period of study, chlorophyte populations dropped to unusually low levels [22,23], and outside of the periods of algal bloom (in all years), chlorophyte concentrations were often below the limit of detection, a problem which may be rectified with more modern equipment than that used in the study, which was conducted between 1994 and 2006. However, from an ecological standpoint, the algal bloom period is the most important time of year, since the algal bloom supports the GSL's brine shrimp population. ...
Since the mid-1800s, Utah's Great Salt Lake (GSL) has undergone dramatic changes. Due to the effects of climate change and an increase in agricultural, industrial, and residential water usage to support population growth, the present water level has fallen to about one-fourth of its highest recorded level in 1987. As Earth's global air and water temperatures continue to rise, evaporation rates from this closed basin will also rise, thus increasing the salinity of this already hypersaline lake. A shift in water chemistry from its current salinity of 15% to a halite saturation of 30% will negatively impact the populations of Dunaliella viridis — a halophilic species of green algae that form the basis of the simple but delicate food web in the South Arm of the GSL. Disruption of the D. viridis population through increased water temperature and salinity will spur a negative cascade throughout the food chain by reducing brine shrimp populations and thereby threaten local and migratory bird populations. Since increasing water temperature and salinity can have such deleterious ramifications on both D. viridis and the overall lake ecosystem, a predictive model that maps the impact of changing water temperature and salinity to specific growth values for D. viridis is needed for forecast-assisted management. In support of this goal, we developed a multiple linear regression model using twelve years of observational data consisting of chlorophyte (of which Dunaliella are the dominant species) population concentrations under co-varying water temperature and salinity. The resulting fitted data produced an R ² value of 0.17 with a RMSPE of 100.704, and additional diagnostics were conducted to verify the model. Overall, this model predicts that chlorophyte populations will decrease by 0.41 µg/L for each 1% increase in salinity and decrease by 0.74 µg/L for each 1°C increase in water temperature up to the extinction point of 30% salinity and 45°C. One limitation of the linear regression model is its inability to capture trace algal population concentrations at 0 μg/L. To address this, we also developed a zero-inflated Poisson regression model, which predicts similar decreases in chlorophyte populations for increasing water temperature and salinity as the linear regression model. The fitted data for this model produced a pseudo-R ² value of 0.35 with a RMSPE of 90.026. This model predicts that chlorophyte populations will decrease by 0.16 µg/L for each 1% increase in salinity and decrease by 0.13 µg/L for each 1°C increase in water temperature up to the extinction point of 30% salinity and 45°C. Even for a limited climate change scenario of an increase in air/water temperature of 2.5°C and an associated increase in salinity by 7.5%, the linear regression model predicts a potential loss of ∼224,000 kg total of chlorophytes from the South Arm of the GSL (based on the median chlorophyte concentration between 2001 and 2006), while the Poisson regression model predicts a potential loss of ∼173,200 kg of chlorophytes. Continued research will include model selection and error quantification. More broadly, future work aims to constrain chlorophyta population predictions based on D. viridis growth limits under maximum water temperature and salinity thresholds obtained from controlled laboratory experiments, which can be used to identify a microbial tipping point of the GSL.
... The nMDS results indicated overall high similarity (>40% similarity clustering) of most phytoplankton communities of salt lakes in Cyprus, independent of spatial and seasonal variability. The most diverse groups in terms of species richness were chlorophytes, followed by cyanobacteria and diatoms; this pattern is typical in many eutrophic lakes in the Mediterranean [64,65], and these groups have also been found to be important in salt lakes in other climate zones (e.g., Uldza-Torey saline lakes (Central Asia), Ethiopian and Kenyan Rift Valley lakes (Africa), Great Salt Lake (USA), Rauer Island lakes (East Antarctica) [23,[66][67][68]. The common feature of Cyprus' saline lakes phytoplankton community was the low compositional diversity (low species number) as a result of the harsh environmental conditions [10] compared to the rich phytoplankton communities of large freshwater lakes (e.g., [69,70]). ...
... This aligns with findings from other studies (e.g., [8,23]), wherein an increase in salinity from oligo-and mesohaline to hyperhaline levels is associated with a notable decrease in the species diversity of planktonic algae, leading to the development of a monodominant community. Blooms and extremely high productivity seem to be common phenomena not only in Cyprus, but also in other salt/hypersaline lakes [2,66]. In our study, the highly halotolerant chlorophyte Dunaliella was the main contributor to this high biomass in most cases, blooming under a wide range of salinity values (3 to 323‰). ...
The ephemeral saline lakes of Cyprus in the Mediterranean, situated in close proximity to each other, demonstrate pronounced seasonal and interannual fluctuations in their environmental conditions. Despite their extreme saline conditions, these lakes support phytoplankton diversity and bloom-forming species. Anthropogenic activities, particularly urban and artificial land uses within their catchments, contribute to eutrophication, warranting conservation attention within the context of European legislation. Over two years (2018–2019), we examined phytoplankton abundance and diversity alongside salinity in six lakes, with samples collected every three weeks. Chlorophytes were the dominant and most diverse group, followed by cyanobacteria and diatoms. Increasing salinity correlated with reduced compositional diversity and species richness. The proximity of lakes to each other suggested airborne microbe colonization from one lake to another as a significant factor in shaping these communities, while similar land use within each lake’s catchment impacted bloom formation. The highly halotolerant chlorophyte Dunaliella frequently dominated phytoplankton blooms, occasionally coexisting with other taxa in less saline lakes. Our findings provide insight into the phytoplankton community dynamics in temporal saline lakes, essential for developing effective conservation strategies and sustainable management practices.
... This makes them crucial habitat for Ephydra larvae, which depend on the microbialites for both food and pupation habitat [32,33]. The organisms that microbialite periphyton support feed in turn feed millions of birds that depend on the lake ecosystem [5,30,[32][33][34][35][36] (Fig 2A). Lake level fall is subjecting microbialites and their periphyton to desiccation. ...
Great Salt Lake hosts an ecosystem that is critical to migratory birds and international aquaculture, yet it is currently threatened by falling lake elevation and high lakewater salinity resulting from water diversions in the upstream watershed and the enduring megadrought in the western United States. Microbialite reefs underpin the ecosystem, hosting a surface microbial community that is estimated to contribute 30% of the lake’s primary productivity. We monitored exposure, desiccation, and bleaching over time in an area of microbialite reef. During this period, lake elevation fell by 1.8 m, and salinity increased from 11.0% to 19.5% in open-water portions of the outer reef, reaching halite saturation in hydrologically closed regions. When exposed, microbialite bleaching was rapid. Bleached microbialites are not necessarily dead, however, with communities and chlorophyll persisting beneath microbialite surfaces for several months of exposure and desiccation. However, superficial losses in the mat community resulted in enhanced microbialite weathering. In microbialite recovery experiments with bleached microbialite pieces, partial community recovery was rapid at salinities ≤ 17%. 16S and 18S rRNA gene sequencing indicated that recovery was driven by initial seeding from lakewater. At higher salinity levels, eventual accumulation of chlorophyll may reflect accumulation and preservation of lake material in halite crusts vs. true recovery. Our results indicate that increased water input should be prioritized in order to return the lake to an elevation that submerges microbialite reefs and lowers salinity levels. Without quick action to reverse diversions in the watershed, loss of pelagic microbial community members due to sustained high salinity could prevent the recovery of the ecosystem-critical microbialite surface communities in Great Salt Lake.
... The south arm aerobic microbiota is more diverse (Meuser et al., 2013), with a larger abundance of eukaryotic microalgae and cyanobacteria that serve as food for the brine shrimp and fly larvae that inhabit the water (Figs.1 & 2b) (Belovsky et al., 2011;Barrett and Belovsky, 2020;Brown et al., 2022). Microbial activities of the anaerobic compartments such as sediment and stratified deep brine layers in this region south of the causeway have been explored due to the concerning presence of deposited heavy metals (Domagalski et al., 1990;Wurtsbaugh, 2007;Naftz et al., 2008;Saxton et al., 2013;Boyd et al., 2017). ...
... Importantly, this prior sampling of brine assessed the aerobic compartment of GSL. Dissolved oxygen is low in this hypersaline surface water, but oxygen is replenished by wave action (Belovsky et al., 2011). The NHMU column remained capped and stationary without introduced oxygen or disturbance and thus, it likely reached the threshold that would enrich anaerobic species and not support obligate aerobes. ...
Sergei Winogradsky illuminated revolutionary concepts and produced a tool to visualize complex microbial communities and their metabolisms over time: columns displaying aquatic consortia with variety of niches. We worked with museums in Utah to create Winogradsky columns that would highlight aesthetic properties of the Great Salt Lake (GSL) ecosystem, which has a salinity gradient from the freshwater wetlands to salt saturation. One column, constructed using haloarchaea-rich hypersaline brine and oolitic sand of the lake’s north arm, was enriched with nutrients, and resulted in the desired pink hue over time. After a seven-year maturation period, we examined the microbial taxa present in the water through 16S/18S rRNA and Internal Transcribed Spacer (ITS) gene sequencing. A pigment analysis revealed an abundance of bacteriochlorophyll a. The presence of this pigment coupled with the DNA sequencing results, suggest that the haloarchaea that dominate the GSL brine, were not responsible for the pink coloration, but instead Gammaproteobacteria, especially Halorhodospira species. Among the eukaryotes, the lack of phytoplankton and the abundance of fungi were noteworthy observations. These data likely relate to the reduction of oxygen in a non-aerated sealed system over time. Our second exhibit had the goal of educating museum goers about the varying salinities of Great Salt Lake. Here we employed three distinct columns of water and sediment from this salinity gradient. Observations of these columns overtime gave us information about invertebrate communities in addition to the microbial consortia. Both installations taught us about comparing an artificial environment in a museum setting to the natural ecosystem. Taken together, we present the data collected and lessons learned from using Winogradsky columns in public spaces for teaching about an important saline lake.
