John Luft’s research while affiliated with Salt Lake Community College and other places

Millions of wetland-dependent birds annually depend on saline lakes and associated wetlands in the western United States. Understanding the population status and trends of birds with different life histories and habitats can guide efforts to secure water resources needed to sustain bird habitats. We used a 21-year dataset to examine population trends for 24 survey units for migratory shorebirds, waterfowl, and other waterbirds at Great Salt Lake and associated wetlands. We found stable or positive trends for 36 of 37 species or groups in fall, spring, or both seasons when considering survey units in aggregate. Stable, positive, and negative trends were observed in individual survey units. Foraging technique, migration distance, and taxonomic groupings were unrelated to trend direction. Research is needed to test whether survey units represent high-quality habitat. With declining regional water resources, stable and positive aggregate trends reinforce the importance of surveyed units at Great Salt Lake and associated wetlands to wetland-dependent birds. Ensuring continuation of stable and positive trends will require identifying environmental factors—including water quantity and quality—driving trends, and require coordinated regional management and monitoring of wetland-dependent birds.

Using laboratory and field experiments as well as spectral analysis of satellite images, we demonstrate that surface aggregations of brine shrimp (Artemia) cysts (BSC) in salt lakes can be identified unambiguously in satellite imagery. This is because of the unique reflectance spectral shapes of the BSC image slicks, where a sharp and monotonic increase in reflectance is found at wavelengths >550 nm and two inflection points are found around ~550 nm and ~ 650 nm. Such spectral characteristics differentiate BSC slicks from other floating matters. Based on this principle, a deep learning model is developed to extract BSC features from MERIS (Medium Resolution Imaging Spectrometer, 2002–2012) and OLCI (Ocean and Land Color Instrument, 2016 - present) satellite images to quantify BSC abundance, spatial distribution patterns, and their temporal changes in the Great Salt Lake (GSL), the world's largest contributor of BSC commercial products. A clear seasonality is found in BSC abundance, with the primary peak in April – May and secondary peak in October – November. The two peaks may be explained by food availability to brine shrimp. The inter-annual variability and the recent increasing trend in BSC abundance, on the other hand, are difficult to explain by fluctuations in wind, temperature, or salinity, while recent increase in commercial harvest does not appear to be associated with the variability in BSC abundance estimated by satellites. Because many salt lakes around the world, for example the Aral Sea, Lake Urmia, and the Dead Sea, also show BSC slicks in satellite imagery, this study suggests that it is possible to perform a systematic evaluation of BSC abundance and possibly brine shrimp populations in all major salt lakes, especially under a changing climate and increased human activities.

en The value of saline lakes and associated wetlands as habitats in the xeric Great Basin is dependent on having water of sufficient quantity and quality to support wetland-dependent birds. To inform conservation and management of these habitats, models are needed to link birds and hydrological changes due to climate and human water use. We modeled seasonal relationships between counts for 35 migratory shorebird, waterfowl, and other waterbird species or taxonomic groups and hydrological metrics at Bear River Bay, a globally Important Bird Area at Utah’s Great Salt Lake. We found that increased fall surface flows to the bay increased counts of 13 species, including American Avocets (Recurvirostra americana), American White Pelicans (Pelecanus erythrorhynchos), American Wigeons (Mareca americana), Northern Pintail (Anas acuta), Redheads (Aythya americana), and Ruddy Ducks (Oxyura jamaicensis). Increased spring surface flows increased counts of Forster’s Terns (Sterna forsteri) and the sandpiper group, whereas intermediate spring flows produced peak counts for American White Pelicans. Thus, conservation or management actions that increase seasonal flows to Bear River Bay are expected to increase bay use by diverse members of the avian community. Counts for 11 species or taxonomic groups responded positively or negatively to the seasonal elevation of Great Salt Lake, and these responses are hypothesized to reflect the relative availability of habitats within the bay versus the lake as a whole. Our models provide tools that allow managers to understand how hydrological changes associated with climate change and human water use will affect birds in Bear River Bay. Addressing lake-wide and regional population implications of changing hydrological conditions at Bear River Bay, Great Salt Lake, and other locations across the Great Basin will require a regionally coordinated assessment of hydrology, habitat, and bird movements in response to changing habitat conditions. RESUMEN es La hidrología afecta aves playeras, anátidas y otras aves acuáticas en Bear River Bay, una Área de Importancia Global para las Aves El valor como hábitat de los lagos salinos y humedales asociados en el Great Basin xérico depende de tener suficiente calidad y cantidad de agua para dar soporte a las aves dependientes de humedales. Para informar la conservación y el manejo de estos hábitats, se necesitan modelos que vinculen a las aves con los cambios hidrológicos relacionados al clima y el uso humano del agua. Modelamos la relación estacional entre los conteos de 35 aves playeras, anátidas y otras especies acuáticas migratorias o grupos taxonómicos, y métricas hidrológicas en Bear River Bay, un Área de Importancia para las Aves en el Great Salt Lake de Utah. En otoño, encontramos que el incremento de flujos de superficie a la bahía aumentó los conteos de 13 especies, incluyendo a Recurvirostra americana, Pelecanus erythrorhynchos, Mareca americana, Anas acuta, Aythya americana y Oxyura jamaicensis. En primavera, el incremento de los fujos de superficie aumentó los conteos de Sterna forsteri y varios playeros, mientras que los flujos intermedios produjeron conteos pico de Pelecanus erythrorhynchos. Por ello, se espera que las acciones de conservación o manejo que incrementen los flujos estacionales a Bear River Bay a su vez aumente el uso de la bahía por diversos miembros de la comunidad de aves. Los conteos de 11 especies o grupos taxonómicos respondieron positiva o negativamente a la elevación estacional del Great Salt Lake y tenemos la hipótesis de que estas respuestas reflejan la disponibilidad relativa de hábitats al interior de la bahía versus la del lago completo. Nuestros modelos proveen herramientas que permiten a los gestores entender cómo los cambios hidrológicos asociados con el cambio climático y el uso humano del agua afectarán a las aves en Bear River Bay. Entender las implicaciones del cambio de condiciones hidrológicas en todo el lago y en poblaciones regionales de Bear River Bay, Great Salt Lake, así como en otras localidades a lo ancho del Great Basin, requerirá de una caracterización regionalmente coordinada de la hidrología, hábitat y movimientos de las aves en respuesta a las cambiantes condiciones de sus hábitats.

Millions of wetland-dependent birds annually depend on saline lakes and associated wetlands in the western United States. Understanding the population status and trends of birds with different life histories and habitats can guide efforts to secure water resources needed to sustain bird habitats. We used a 21-year dataset to examine population trends for 24 survey units presumed to be high-quality habitat for migratory shorebirds, waterfowl, and other waterbirds at Great Salt Lake and associated wetlands. As expected for high-quality habitats, we found stable or positive trends for 36 of 37 species or groups in fall, spring, or both seasons when considering survey units in aggregate. Despite stable or positive aggregate trends, negative trends did occur in some individual survey units. Foraging, migration distance, and taxonomic groupings were unrelated to trend direction. Research is needed to test whether survey units represent high-quality habitat. With declining regional water resources, stable and positive aggregate trends reinforce the importance of surveyed units at Great Salt Lake and associated wetlands to wetland-dependent birds. Ensuring continuation of stable and positive trends will require identifying environmental factors - including water quantity and quality - driving trends, and require coordinated regional management and monitoring of wetland-dependent birds.

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.

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.

We examined mercury (Hg) speciation in water and sediment of the Great Salt Lake and surrounding wetlands, a locale spanning fresh to hypersaline and oxic to anoxic conditions, in order to test the hypothesis that spatial and temporal variations in Hg concentration and methylation rates correspond to observed spatial and temporal trends in Hg burdens previously reported in biota. Water column, sediment, and pore water concentrations of methylmercury (MeHg) and total mercury (THg), as well as related aquatic chemical parameters were examined. Inorganic Hg(II)-methylation rates were determined in selected water column and sediment subsamples spiked with inorganic divalent mercury ((204)Hg(II)). Net production of Me(204)Hg was expressed as apparent first-order rate constants for methylation (kmeth), which were also expanded to MeHg production potential (MPP) rates via combination with tin reducible 'reactive' Hg(II) (Hg(II)R) as a proxy for bioavailable Hg(II). Notable findings include: 1) elevated Hg concentrations previously reported in birds and brine flies were spatially proximal to the measured highest MeHg concentrations, the latter occurring in the anoxic deep brine layer (DBL) of the Great Salt Lake; 2) timing of reduced Hg(II)-methylation rates in the DBL (according to both kmeth and MPP) coincides with reduced Hg burdens among aquatic invertebrates (brine shrimp and brine flies) that act as potential vectors of Hg propagation to the terrestrial ecosystem; 3) values of kmeth were found to fall within the range reported by other studies; and 4) MPP rates were on the lower end of the range reported in methodologically comparable studies, suggesting the possibility that elevated MeHg in the anoxic deep brine layer results from its accumulation and persistence in this quasi-isolated environment, due to the absence of light (restricting abiotic photo demethylation) and/or minimal microbiological demethylation. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

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.