Ecosystem Effects of Waterbird Predation on Keystone Chironomid Larvae in a Highly Productive Wetland of Great Salt Lake, UT, USA

Disentangling multiple predator effects in biodiversity and ecosystem functioning research

Great Salt Lake (GSL) is the largest hypersaline lake in North America and is the fall staging area for a high proportion of North America’s Wilson’s Phalaropes (Phalaropus tricolor) and Red-necked Phalaropes (Phalaropus lobatus). Unfortunately, diversion of freshwater for agriculture and development has decreased the size of GSL by 48%. To assess the potential impact of a smaller GSL on phalaropes, we collected data from 2013 to 2015 from sites where large, dense flocks of phalaropes congregated and sites where there were no phalaropes. At each site, we measured the densities of invertebrates that were preyed upon by phalaropes, including larval and adult brine flies (Ephydridae), adult brine shrimp (Artemia franciscana), chironomid larvae (Chironomidae), and corixid adults (Corixidae). Abiotic characteristics measured included water depth, water salinity, water temperature, wind speed, and benthic substrate. We analyzed high-salinity sites separately from low-salinity sites because they contained different invertebrates. High-salinity sites were in Carrington and Gilbert bays and were relatively deep (mostly <2 m). At the high-salinity sites, phalaropes exhibited a preference for sites with an abundance of adult brine flies and for microbialite substrates. The low-salinity sites were in Ogden and Farmington bays and were shallow (<1 m). At low-salinity sites, large phalarope flocks were more likely to occur at sites that were shallower, less saline, and had a high biomass of benthic macroinvertebrates. Our results indicate that physical features and prey availability are both important in determining phalarope habitat use at GSL. Phalaropes prefer to use shallower parts of GSL and brackish waters. These areas will be especially impacted by decreased freshwater inflow into GSL.

Eared grebes ( Podiceps nigricollis ) are colonial‐nesting waterbirds that breed in Canada and northern United States. Great Salt Lake (GSL), Utah, is vital to the survival of this species because all eared grebes in North America stage in the fall either on the GSL or Mono Lake, California. The importance of GSL and its surrounding wetlands for breeding eared grebes is unknown. We studied eared grebe nesting status and chronology in the freshwater wetlands around GSL and found over 4,280 nests distributed among 35 colonies during 2018 and 5,794 nests among 23 colonies during 2019. We also located the 2 largest colonies of this species ever recorded (902 and 1,492 nests). Mean clutch size differed between years and was 2.4 eggs during 2018 and 2.0 during 2019; clutch sizes were lower at GSL than in colonies located in more northern latitudes, perhaps due to a local paucity of invertebrate prey during the egg‐laying period. Grebe nests around the GSL were constructed with, and anchored to, growing Stuckenia pectinate . Eared grebes near GSL started laying eggs in the first week of June during 2018 and a week later during 2019. The number of incubated nests per colony peaked on 27 June during 2018 and 9 July during 2019. Nests continued to be incubated into August in both years. These dates are later than those reported in more‐northern colonies. The later nesting in GSL colonies could be due to the birds' need to wait for Stuckenia pectinata to form mats at the water surface. This plant species needs a water depth of 38 to 45 cm to thrive, and increasing amounts of freshwater from the GSL watershed are diverted for agriculture and human development. If this trend continues, there may not be enough water to maintain the required water depth for dense stands of Stuckenia; the loss of which may prevent the grebes from nesting. © 2021 The Wildlife Society.

In November and December of 2013, a large mortality event involving 15,000 to 20,000 eared grebes (Podiceps nigricollis) occurred at the Great Salt Lake (GSL), UT. The onset of the outbreak in grebes was followed by a mortality event in >86 bald eagles (Haliaeetus leucocephalus). During the die-off, West Nile virus (WNV) was detected by reverse transcription-PCR (RT-PCR) or viral culture in the carcasses of grebes and eagles submitted to the National Wildlife Health Center. However, no activity of mosquitoes, the primary vectors of WNV, was detected by the State of Utah's WNV monitoring program. The transmission of WNV has rarely been reported during the winter in North America in the absence of known mosquito activity; however, the size of this die-off, the habitat in which it occurred, and the species involved are unique. We experimentally investigated whether WNV could survive in water with a high salt content, as found at the GSL, and whether brine shrimp, the primary food of migrating eared grebes on the GSL, could have played a role in the transmission of WNV to feeding birds. We found that WNV can survive up to 72 h at 4°C in water containing 30 to 150 ppt NaCl, and brine shrimp incubated with WNV in 30 ppt NaCl may adsorb WNV to their cuticle and, through feeding, infect epithelial cells of their gut. Both mechanisms may have potentiated the WNV die-off in migrating eared grebes on the GSL.IMPORTANCE Following a major West Nile virus die-off of eared grebes and bald eagles at the Great Salt Lake (GSL), UT, in November to December 2013, this study assessed the survival of West Nile virus (WNV) in water as saline as that of the GSL and whether brine shrimp, the major food for migrating grebes, could have played a role as a vector for the virus. While mosquitoes are the major vector of WNV, under certain circumstances, transmission may occur through contaminated water and invertebrates as food.

Research Article| November 01, 1990 Geology of Salt Lake City, Utah, United States of America WILLIAM R. LUND; WILLIAM R. LUND Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar GARY E. CHRISTENSON; GARY E. CHRISTENSON Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar KIMM M. HARTY; KIMM M. HARTY Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar SUZANNE HECKER; SUZANNE HECKER Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar GENEVIEVE ATWOOD; GENEVIEVE ATWOOD Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar WILLIAM F. CASE; WILLIAM F. CASE Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar HAROLD E. GILL; HAROLD E. GILL Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 *Present address: Gregg and Associates, 808 South Edwards Drive, Suite 6, Tempe, AZ 85281 Search for other works by this author on: GSW Google Scholar J. WALLACE GWYNN; J. WALLACE GWYNN Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar ROBERT H. KLAUK; ROBERT H. KLAUK Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 **Present address: Warzyn Engineering, Inc., 11270 West Park Place, Suite 400, Milwaukee, WI 53224 Search for other works by this author on: GSW Google Scholar DON R. MABEY; DON R. MABEY Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 ***Present address: Castle Valley Star Route, Box 2408, Moab, UT 84532 Search for other works by this author on: GSW Google Scholar WILLIAM E. MULVEY; WILLIAM E. MULVEY Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar DOUGLAS A. SPRINKEL; DOUGLAS A. SPRINKEL Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar BRYCE T. TRIPP; BRYCE T. TRIPP Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar BILL D. BLACK; BILL D. BLACK Utah Geological and Mineral Survey, 606 Black Hawk Way, Salt Lake City, UT 84108-1280 Search for other works by this author on: GSW Google Scholar CRAIG V. NELSON CRAIG V. NELSON Salt Lake County Public Works Planning Division, 2001 South State Street, #N3700, Salt Lake City, UT 84190-4200 Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (1990) xxvii (4): 391–478. https://doi.org/10.2113/gseegeosci.xxvii.4.391 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation WILLIAM R. LUND, GARY E. CHRISTENSON, KIMM M. HARTY, SUZANNE HECKER, GENEVIEVE ATWOOD, WILLIAM F. CASE, HAROLD E. GILL, J. WALLACE GWYNN, ROBERT H. KLAUK, DON R. MABEY, WILLIAM E. MULVEY, DOUGLAS A. SPRINKEL, BRYCE T. TRIPP, BILL D. BLACK, CRAIG V. NELSON; Geology of Salt Lake City, Utah, United States of America. Environmental & Engineering Geoscience 1990;; xxvii (4): 391–478. doi: https://doi.org/10.2113/gseegeosci.xxvii.4.391 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Salt Lake City is the capital of Utah and is a major financial, trade, and transportation center for the western United States. Founded in 1847, Salt Lake City presently (1990) has a population of about 158,000. However, the metropolitan area of the city, which includes most of the Salt Lake Valley, contains both incorporated and unincorporated suburbs that increase the population to nearly 705,000.Geologic exposures in the Salt Lake City region record a long history of sedimentation and tectonic activity extending back to the Precambrian Era. Today, the city lies above a deep, sediment-filled basin flanked by two uplifted range blocks, the Wasatch Range and the Oquirrh Mountains. The Wasatch Range is the easternmost expression of major Basin and Range extension in north-central Utah, and is bounded on the west by the Wasatch fault zone (WFZ), a major zone of active normal faulting. During the late Pleistocene Epoch, the Salt Lake City region was dominated by a succession of inter-basin lakes. Lake Bonneville was the last and probably the largest of these lakes. By 11,000 years BP, Lake Bonneville had receded to approximately the size of present-day Great Salt Lake. Lake Bonneville sediments bury most older deposits in the valley below an elevation of about 5,200 ft (1,585 m). Lake sediments include near-shore beach, delta, spit, and bar deposits and silt and clay deposited in deeper water. Post-Bonneville deposits include Holocene alluvium along the Jordan River and its tributaries and alluvial fans along mountain fronts.Repeated normal-slip faulting has occurred at the ground surface in northern Utah during late Pleistocene and Holocene time. Most of this activity has been on the WFZ which traverses the Salt Lake City metropolitan area. West-facing scarps of a few to tens of feet high are common, as are graben, horsts, and other fault-related features. Paleoseismic data show that the average recurrence interval for surface-fault displacement on the Salt Lake City segment of the WFZ is 4,000 ±1,000 years. However, the city can expect to experience strong ground shaking associated with a large earthquake somewhere on the WFZ every 340 to 415 years. The West Valley fault zone (WVFZ) is an east-dipping, normal fault that trends to the north-northwest through the central part of the Salt Lake Valley. The WVFZ has had at least six surface-faulting events in the past 13,000 years. Despite the close proximity to active faults, Salt Lake City has not yet been subjected to a large, destructive earthquake. Felt events have occurred, but only a few have caused appreciable damage.Geologic units in the Salt Lake City metropolitan area generally provide adequate foundation conditions. The principal foundation problems are compressible, low bearing-strength soils; collapse-prone soils; and liquefaction. Some shale units and the soils derived from them may be expansive. Use of underground space is restricted to the nearby Wasatch Range and Oquirrh Mountains and includes storage of documents and valuables, water storage, and mining-related uses.Numerous geologic hazards exist in the Salt Lake City metropolitan area. Movement on faults may cause ground rupture, ground shaking, tectonic displacement, ground failure including liquefaction, and seiches on the Great Salt Lake. Steep slopes create the potential for landslides, rock falls, debris flows, and snow avalanches. Streams and the Great Salt Lake experience flooding, and high ground-water conditions are common.Water for the Salt Lake City metropolitan area comes principally from streams in the Jordan and Colorado River drainages. Ground water from wells and springs is also used. Major surface storage reservoirs are considered inadequate and additional storage is being constructed. Basin-fill aquifers provide the largest existing source of stored water.Most of the Salt Lake City metropolitan area is served by public sewers. Wastewater is treated at municipal treatment plants and solid waste is placed in county and municipal sanitary landfills. Hazardous waste sites include disposal sites for cement kiln dust; mine, smelter, and oil refinery wastes; and various chemical wastes. Three hazardous waste disposal sites are on the Environmental Protection Agency's current Superfund National Priority List.Mineral resources have played an important role in the development of Salt Lake City. A variety of salines and metals are recovered from Great Salt Lake brines. The Bingham mining district in the Oquirrh Mountains is one of the world's largest copper producers. The Big and Little Cottonwood mining districts and the Hot Springs mining district, all in the Wasatch Range, are no longer active, but have produced a variety of precious and base metals. Industrial rocks and minerals include cement, construction aggregate, crushed stone, industrial sand, and clay. The oil and gas potential of the Salt Lake Valley has not been thoroughly explored, but probably is low. Geothermal water is used to heat greenhouses and part of the Utah State Prison.The Great Salt Lake presents Salt Lake City with unique geologic hazards and engineering geology problems. Fluctuations in lake level occur daily, seasonally, and on a long-term basis. The rise of the lake during the period 1983–1985, due to above-normal precipitation, caused over $240 million in damages and initiated construction of the West Desert Pumping Project. In addition to flooding, development near the lake must also consider the effects of earthquakes on the lake and sensitive lake-bottom sediments, low bearing-strength soils, and rafting-ice impact on in-lake structures. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Great Salt Lake (GSL) is recognized as a site of “Hemispheric Importance” for shorebirds by the Western Hemisphere Shorebird Reserve Network. An estimated ten million birds visit GSL every year for breeding, staging, and for some species, as a wintering destination. American white pelicans (Pelecanus erythrorhynchos) rely on GSL for both breeding and foraging habitat. Surveys conducted by the Utah Division of Wildlife Resources (UDWR) during mid-September 1997 estimated over 85,000 pelicans using GSL wetlands for foraging and loafing. Gunnison Island, situated in the northwestern section of GSL, is home to one of the largest breeding colonies of American white pelicans in North America. Aerial counts completed by the UDWR have shown up to 20,000 breeding pelicans on the island. Naturally protected by water and the island’s remoteness, pelicans have been able to breed and raise their young free from predation and disturbance from red fox (Vulpes vulpes), coyote (Canis latrans), and humans. Lower water availability and threats of increasing pressure on water resources in recent years has caused increased attention to, preparation for, and response to losses of aquatic habitat. The population of American white pelicans in Utah has remained stable over time, but the potential effects of local and regional stressors on pelicans and their habitat are poorly understood. Recent research provides an eye into the lives of American white pelicans in Utah and to the broader watershed and flyway dynamics.

In tropical freshwaters, different species of water bugs (Heteroptera) constitute a guild sharing similar prey resources including chironomid and mosquito larvae. Assuming possibilities of intraguild predation (IGP) among the constituent members, an attempt was made to evaluate the effects of prey and predator density on the mortality of mosquito and chironomid larvae (shared prey), using Laccotrephes griseus Guérin-Méneville (Hemiptera: Nepidae) and Ranatra filiformis Fabricius (Hemiptera: Nepidae) as IG predators and Anisops bouvieri Kirkaldy (Hemiptera: Notonectidae) as IG prey. The predation on mosquito and chironomid larvae varied with the density and combinations of the predators. When present as conspecific IG predators, L. griseus exhibited greater effect on the prey mortality than R. filiformis. The effects on shared prey suggest that the two predators are not substitutable in terms of the effect on the shared prey mortality. The mortality of A. bouvieri (IG prey) at low shared prey density was significantly different (p < 0.05) from high shared prey density. In view of predatory effect of the heteropteran predators on the dipteran larvae, the results suggest possible interference by the presence of A. bouvieri as an intermediate predator. It seems that the presence of heteropteran predators including A. bouvieri as IG prey may benefit the dipteran prey under situations when the density is low in tropical waters. The intensity of the predatory effect may differ based on the species composition at IG predator level. For mosquito biological control, the interactions between the predators may not be substitutable and are independent in their effects.

Eared Grebes (Podiceps nigricollis Brehm, 1831) use saline ecosystems throughout much of their life cycle, and greater than 90% of the North American population stage during fall at two hypersaline lakes. At one of these lakes, Great Salt Lake (GSL), Utah, a commercial harvest of brine shrimp (Artemia franciscana Kellogg, 1906) cysts occurs during fall and may impact Eared Grebe populations. We used photo surveys on the other hypersaline lake, Mono Lake, California, and on the GSL, as well as aerial counts on the GSL, to describe population fluctuations of Eared Grebes staging on these lakes. The long-term (1997–2012) Eared Grebe population was 1.4 million on the GSL and 1.0 million on Mono Lake. Populations changed on GSL and Mono Lake in synchrony, indicating population regulation is likely occurring at wintering, not staging, areas and is influenced by El Niño effects. Location of Eared Grebes on the GSL was influenced by brine shrimp densities and did not overlap with concentrations of commercial harvest boats. Spatial segregation of commercial harvesters and Eared Grebes reduces negative impacts of anthropogenic disturbance on Eared Grebes. Knowledge of population changes within and among staging areas will help managers monitor long-term abundances and reduce negative impacts between Eared Grebes and commercial harvesters.

Summary 1. Positive interactions driven by ecosystem engineers have been determined to be important community forces in stressed environments. By ameliorating habitat conditions, ecosystem engineering can create available ecological niches for other species. In poorly oxygenated sediments of freshwater wetlands, small invertebrates such as tubificid worms and chironomid larvae are known to function as active bioturbators; however, their effects on the growth and physiology of organisms which are constrained by low oxygenation of sediments have never been studied. 2. We examined whether the common bioturbator, Tubifex tubifex, significantly influences the growth and the physiological state of two plant species, Elodea canadensis and Myriophyllum spicatum, in experimental systems simulating a water–sediment interface of wetlands. We also quantified the influence of plant–animal interactions on biogeochemical processes (fluxes of oxygen and nitrogen at the water–sediment interface) and microbial compartment in sediments. 3. Tubificid worms stimulated growth of aboveground and belowground biomasses of the two plants through reduction in the anoxic stress in sediments. Myriophyllum spicatum, which was the best adapted to sedimentary anaerobic conditions, essentially increased its biomass whereas E. canadensis, less adapted to anaerobic conditions, shifted its root metabolism from anaerobic to aerobic. 4. Biogeochemical processes were not significantly influenced by plant–animal interactions: (i) oxygen flux from overlying water to sediments probably reached a threshold that could not be raised by the increased plant biomass induced by worms and (ii) nitrogen fluxes were essentially linked to bioturbation activities of worms. 5. Our study confirmed that the reduction in constraining variables by physical habitat modifications (ecosystem engineering) may play a crucial role in community and ecosystem processes. The fact that positive interactions measured between ecosystem engineers and plant species in anoxic wetland sediments were highly dependent on the ecophysiology of plant species suggests an extension of this first study to a wide range of macrophytes in order to determine the main plant functional traits driving plant–animal interactions in wetland sediments.

Saline lakes provide a prey-rich, predator-free environment for birds to utilize during migration and stopover periods. The Great Salt Lake (GSL), Utah is the largest salt lake in North America and is utilized by millions of migratory birds. It also is host to multiple commercial endeavors. Proposed expansion of commercial use of the GSL would result in increased impounded area and water extraction for mineral production, which may increase the GSL's salinity and negatively impact invertebrate abundance. I review previous literature and synthesize diets of avian species utilizing the GSL to determine the importance of each invertebrate species, including brine shrimp (Artemia franciscana) and brine flies (Ephydra spp.), and clarify the anthropogenic impacts on food sources and avian populations. Species considered are eared grebes (Podiceps nigricollis), northern shovelers (Anas clypeata), green- winged teals (Anas crecca), common goldeneyes (Bucephala clangula), American avocets (Recurvirostra americana), black-necked stilts (Himantopus mexicanus), Wilson's phalaropes (Phalaropus tricolor), red-necked phalaropes (Phalaropus lobatus), and California gulls (Larus californicus). Brine shrimp and brine fly adults are consumed by all species considered. Alterations in prey abundance due to increased salinity may alter the ability of the GSL to support large avian populations.

Ecosystem engineers shape ecological communities worldwide by modifying the habitats of other taxa. Engineering activities may generate feedbacks that benefit the engineers themselves, though such evidence is sparse. The superb lyrebird (Menura novaehollandiae), a ground‐dwelling species of moist eucalypt forests in south‐eastern Australia, engineers habitats by extensively modifying litter and soil layers (~155 tonnes/ha/year in suitable habitat) whilst foraging for invertebrates.We examined whether this engineering activity by lyrebirds serves to promote a ‘farming’ effect on their prey, by increasing the biomass and taxonomic richness of the invertebrates on which they feed and altering the composition of invertebrate communities. We experimentally isolated the effects of engineering (soil/litter modification) from predation effects (on invertebrates) by establishing a manipulative experiment with three treatments: (1) lyrebird‐free, fenced exclosures (‘control’; no engineering or predation); (2) fenced exclosures with raking (‘raked’; engineering effects only); and (3) unfenced plots accessible to lyrebirds (‘lyrebird’; engineering and predation effects).Biomass and taxonomic richness of invertebrates were higher in ‘raked’ treatments compared with ‘control’ treatments, due to the engineering effects of raking. Biomass and richness were lower in ‘lyrebird’ treatments, due to predation effects by lyrebirds. Whilst the composition of invertebrate communities showed no significant change due to engineering, it was significantly influenced by predation. Lyrebird foraging actions that mix, turn over, and aerate litter and soil layers create a positive feedback loop that actively replenishes the biomass and diversity of their invertebrate prey, compensating for offtake by predation. These results provide evidence that lyrebirds ‘farm’ their prey resource.This process of farming by the superb lyrebird operates at a spatial scale that is unprecedented in non‐human vertebrates, extending across millions of ha in moist forest ecosystems. The enhanced diversity and biomass of invertebrates generated via lyrebird foraging has potentially far‐reaching implications for the structure and function of forest ecosystems; and for the temporal dynamics of forests and their response to disturbance processes, such as wildfire. Reported examples of such positive feedback loops arising from ecosystem engineering activities are scarce, but may be more common than thought and have extensive impacts on ecosystem function.

Six months-long experiment was carried out in a fish pond at Bangladesh Agricultural University (BAU), Mymensingh from September 2008-February 2009 to evaluate the limnological parameters affecting monthly abundance of Chironomid larvae and their role in the diet of catfish, Clarias batrachus. The water-quality and soil parameters were monitored and found to be within suitable range for freshwater aquaculture. The composition of the benthic macro-invertebrates at the bottom indicated that Chironomidae was most dominant group in this pond. The body-weight percentage of the organisms showed that Chironomids and Oligochaetes were major two groups. The quantitative and qualitative studies of Chironomid larvae indicated that there was monthly variation in the abundance of Chironomids where Chironomus was most dominant. The highest (3585.19 m-2) and the lowest (548.15 m-2) abundance of Chironomids in 3 samples were recorded in the month of lanuary 2009 and October 2008, respectively. Gut content analysis suggested that Chironomids was dominant food item in the diet of Clarias batrachus. The maximum 768 and minimum 25 occurrences were recorded in the months of December and October 2008, respectively in 5 fishes sampled from the experimental pond. The electivity indices suggested a shifting to Chironomid larvae from negative selection to positive selection in different months. © 2013 Asian Network for Scientific Information.

Physical, chemical and biological variables were measured in the Great Salt Lake during 1985–87, when salinity in the mixolimnion was near 50 g/L, much lower than the 250 g/L maxima recorded in 1963. Decreased salinity has been accompanied by a change in macrozooplankton from one species (Artemia franciscana), to an assemblage with one rotifer, two copepods, Artemia, and the corixid Trichocorixa verticalis. Predation by the corixid may now limit Artemia to low densities (&lt;100∙m−3). The low biomass of Artemia and other zooplankton has reduced grazing pressure on the algal community so that high chlorophyll levels (5-44 mg∙m−3) and low Secchi depths (0.8–2.7 m) are now present throughout the year. The algae presently reduce soluble reactive phosphorus and inorganic nitrogen in the mixolimnion to below 5 and 50 μg∙L−1, respectively. Shading in the 7-m thick mixolimnion by algae, and by purple-sulfur bacteria in the chemocline, decreases light penetration so that the monimolimnion now maintains a nearly constant temperature (9–11 °C) throughout the year. The data support the hypothesis that the effects of corixid predation have cascaded through the Great Salt Lake, affecting herbivores, nutrients and thermal stratification.

Effect of microplastics on ecosystem functioning: Microbial nitrogen removal mediated by benthic invertebrates

The introduced grass Phragmites australis (hereafter Phragmites) is one of the most widespread invasive plants in North American wetlands. Phragmites has been extensively studied in some regions of North America, such as the Chesapeake Bay and the Great Lakes. However, little research has evaluated the extent of Phragmites invasion in the Intermountain West and the environmental drivers that have promoted its spread, particularly in the critically important Great Salt Lake (GSL) wetlands. Here we use high-resolution multispectral imagery to map the current distribution of Phragmites around GSL. We then identify factors associated with Phragmites presence in GSL using a species distribution model using the Random Forest algorithm. We contrast these findings with what is known about Phragmites invasion in other regions. We estimate that Phragmites occupies over 93 km2 around GSL. Phragmites was more likely to be found in wetland areas close to point sources of pollution, at lower elevations with prolonged inundation, and with moderate salinities. Results from our study will assist wetlands managers in prioritizing areas for Phragmites monitoring and control by identifying likely areas of prime Phragmites habitat.