Continuing Analysis of Phytoplankton Nutrient Limitation in Farmington Bay and the Great Salt Lake

Farmington Bay is a nutrient-enriched, highly eutrophic embayment of the Great Salt Lake. The highly variable salinity of the bay influences what species of plankton can survive there. Previous analyses suggested that cyanobacteria (blue-green algae) may not be able to survive or fix atmospheric nitrogen at high salinities, thus maintaining the lake in a nitrogen-limited state. To determine the interacting influence of nutrients and salinity on the growth and nitrogen fixation of plankton we performed a 28-day bioassay with water from Farmington and Gilbert Bays in October 2004. We tested the response of the plankton to additions of nitrogen (N) and phosphorus (P) at salinities of 3%, 5%, 70/0, 9% or 11 %. Algal inocula from a variety of salinities were added to provide colonists for the cultures

Analysis of Phytoplankton Nutrient Limitation in Farmington Bay and the Great Salt Lake

The Great Salt Lake is bordered to the south and east by a growing metropolitan area that contributes high nutrients to Farmington Bay. This large bay is eutrophic, and there is concern that continued increases in effluents from the Salt Lake City area could extend to impact the much larger, and currently less productive, Gilbert Bay. This study focused on determining how nutrient supplies might limit, and therefore control, algal populations in Farmington Bay and Gilbert Bay at different salinities. We tested both short and long-term responses of algal growth using laboratory nutrient addition bioassays in the summer and fall of 2003. Because some phytoplankton can alleviate nitrogen deficiency by fixing atmospheric nitrogen, we also determined how nutrients and salinity influenced nitrogen fixation

Hydrogen Sulfide in Farmington Bay and the Great Salt Lake: A Potential Odor-Causing Agent

Odors from Farmington Bay and/or the Great Salt Lake frequently impact residents of Salt Lake and Davis counties, but the agent causing the problem and the origin of the odor is uncertain. Hydrogen sulfide (H2S) gas is produced in the deeper layers of water in Farmington Bay and Gilbert Bay in the Great Salt Lake, but these deeper waters are generally part of high salinity deep-brine layers that are resistant to wind mixing. Hydrogen sulfide has a rotten-egg odor and is a likely component contributing to the lake stink. The goals of this study were to determine (1) whether wind driven mixing events drove mixing of the deep-brine layers in Farmington and Gilbert Bays, (2) determine the amount of hydrogen sulfide present in each of these bays, and (3) determine the potential of each area of the lake to release hydrogen sulfide from those deep-brine layers and cause odor events. We found that in Farmington Bay, which was \u3c1.5 m (5 ft) deep during the study, the deep-brine layer was entrained (mixed) four times in three months during high-wind events. By contrast, in Gilbert Bay, which has a deeper water column and more stable deep-brine layer, the brine layer was never completely entrained. However, the top 0.9 m (3 ft) of the deep brine layer eroded between July and October. Hydrogen sulfide concentrations in the surface mixed layers of both bays were insignificant on each sampling date, but concentrations in the deep-brine layers were significant. In Farmington Bay H2S concentrations reached 8 mg/L in the deep-brine layer. In Gilbert Bay H2S concentrations in the deep-brine layer ranged from 11 mg/L in late July to 4 mg/L in November 2003. The higher concentrations in Gilbert Bay are likely due to decreased mixing and therefore increased time intervals of hydrogen sulfide accumulation in Gilbert Bay. Both bays may release H2S into the airshed, and thus contribute to odor problems. Large releases of H2S into the water columns could result in rapid deoxygenation and toxicity to aquatic organisms. Detailed whole water column monitoring of oxygen, salinity, and H2S concentrations in both bays should be undertaken to assess these potential threats. It will necessary to do these studies at a variety of lake levels in order to fully understand the driving mechanisms creating H2S and allowing it to be released from the lake

Ecological Analysis of Nutrient, Plankton and Benthic Communities in Farmington Bay and the Great Salt Lake, Utah (2004)

In Fall 2004, the Aquatic Ecology Practicum class at Utah State University finished a third year of research on limnological and ecological characteristics of Farmington Bay and Gilbert Bays of the Great Salt Lake. Our previous research has produced interesting findings in Farmington Bay, including hypereutrophy (Marcarelli et a!. 2001), high phosphorus loading into the Bay, overnight water column anoxia linked to high winds (Wurtsbaugh et a!. 2002), potential predator control of brine shrimp, and high levels of hydrogen sulfide in the sediment and deep brine layer (Marcarelli et a!. 2003). These class findings have lead to increased interest in Farmington and Gilbert Bays. Because of the breadth of research now occurring in Farmington Bay, the topics studied by the students this fall encompassed a wider range of research than ever before. The reports ranged from an expanded analysis of nutrients entering Great Salt Lake, including external loading and biological nitrogen fixation, benthic ecology of Gilbert Bay including analyses of stromatolites and brine shrimp cysts in sediments, and more focused experiments on brine shrimp survival and predation by corixids in Farmington Bay. Key findings of the students are identified below

Nutrient limitation of algae and macrophytes in streams: Integrating laboratory bioassays, field experiments, and field data

Successful eutrophication control strategies need to address the limiting nutrient. We conducted a battery of laboratory and in situ nutrient-limitation tests with waters collected from 9 streams in an agricultural region of the upper Snake River basin, Idaho, USA. Laboratory tests used the green alga Raphidocelis subcapitata, the macrophyte Lemna minor (duckweed) with native epiphytes, and in situ nutrient-limitation tests of periphyton were conducted with nutrient-diffusing substrates (NDS). In the duckweed/epiphyte test, P saturation occurred when concentrations reached about 100 μg/L. Chlorophyll a in epiphytic periphyton was stimulated at low P additions and by about 100 μg/L P, epiphytic periphyton chlorophyll a appeared to be P saturated. Both duckweed and epiphyte response patterns with total N were weaker but suggested a growth stimulation threshold for duckweed when total N concentrations exceeded about 300 μg/L and approached saturation at the highest N concentration tested, 1300 μg/L. Nutrient uptake by epiphytes and macrophytes removed up to 70 and 90% of the N and P, respectively. The green algae and the NDS nutrient-limitation test results were mostly congruent; N and P co-limitation was the most frequent result for both test series. Across all tests, when N:P molar ratios \u3e30 (mass ratios \u3e14), algae or macrophyte growth was P limited; N limitation was observed at N:P molar ratios up to 23 (mass ratios up to 10). A comparison of ambient periphyton chlorophyll a concentrations with chlorophyll a accrued on control artificial substrates in N-limited streams, suggests that total N concentrations associated with a periphyton chlorophyll a benchmark for desirable or undesirable conditions for recreation would be about 600 to 1000 μg/L total N, respectively. For P-limited streams, the corresponding benchmark concentrations were about 50 to 90 μg/L total P, respectively. Our approach of integrating controlled experiments and matched biomonitoring field surveys was cost effective and more informative than either approach alone

Eutrophication and Metal Concentrations in Three Bays of the Great Salt Lake (USA)

The Great Salt Lake, bordered by several major population centers in the State of Utah, has received heavy loading of various pollutants that until recently have received little attention. However, during the last decade management agencies and environmental groups have become concerned that these contaminants might limit the beneficial uses of the lake. Recent work by the Utah Department of Environmental Quality, The Utah Division of Forestry, Fire and State Lands, universities, and federal agencies have focused on how selenium, mercury, eutrophication and salinity may influence recreational use of the lake and the migratory bird populations that rely on the lake for feeding and nesting

Climate, snowmelt dynamics and atmospheric deposition interact to control dissolved organic carbon export from a northern forest stream over 26 years

Increasing concentrations of dissolved organic carbon (DOC) have been identified in many freshwater systems over the last three decades. Studies have generally nominated atmospheric deposition as the key driver of this trend, with changes in climatic factors also contributing. However, there is still much uncertainty concerning net effects of these drivers on DOC concentrations and export dynamics. Changes in climate and climate mediated snowfall dynamics in northern latitudes have not been widely considered as causal factors of changes in long-term DOC trends, despite their disproportionate role in annual DOC export. We leveraged long-term datasets (1988–2013) from a first-order forested tributary of Lake Superior to understand causal factors of changes in DOC concentrations and exports from the watershed, by simultaneously evaluating atmospheric deposition, temperature, snowmelt timing, and runoff. We observed increases in DOC concentrations of approximately 0.14 mg C l−1 yr−1 (mean = 8.12 mg C l−1) that were related with declines in sulfate deposition (0.03 mg SO24− l−1 yr−1). Path analysis revealed that DOC exports were driven by runoff related to snowmelt, with peak snow water equivalences generally being lower and less variable in the 21st century, compared with the 1980s and 1990s. Mean temperatures were negatively related (direct effects) to maximum snow water equivalences (−0.71), and in turn had negative effects on DOC concentrations (−0.58), the timing of maximum discharge (−0.89) and DOC exports (indirect effect, −0.41). Based on these trends, any future changes in climate that lessen the dominance of snowmelt on annual runoff dynamics—including an earlier peak discharge—would decrease annual DOC export in snowmelt dominated systems. Together, these findings further illustrate complex interactions between climate and atmospheric deposition in carbon cycle processes, and highlight the importance of long-term monitoring efforts for understanding the consequences of a changing climate

Comparative Analysis of Pollution in Farmington Bay and the Great Salt Lake, Utah

Farmington Bay covers 94 mi2 (260 km2) in the SW comer of the Great Salt Lake, and is essentially a separate lake because it is enclosed by Antelope Island and a causeway leading to the island from the mainland. The bay has received wastes from the adjoining Salt Lake City metropolitan area for decades. Because of water quality concerns for Farmington 8ay, the Aquatic Ecology Laboratory class at Utah State University studied the bay and a nearby control site (Bridger Bay) in the Great Salt Lake during the fall of 2001. Field sampling and laboratory experiments, as well as other data sources, demonstrated the bay is severely eutrophic and is one of the most polluted water bodies in the state of Utah. A preliminary nutrient loading estimate for the bay indicates that total phosphorus coming into the system is a-times higher than necessary for the bay to be classed as eutrophic. Sewage treatment plants discharging directly to the bay contribute approximately 500/0 of the nutrients. Metrics of eutrophication (chlorophyll, Secchi depth and total phosphorus) all indicated that the bay was hypereutrophic and the combined Trophic State Index was 91, higher than any other lake or reservoir in the state. Oxygen was supersaturated in the surface waters of Farmington Bay during the day, but the bottom water was anoxic. During the night, nearly the entire water column became anoxic due to respiratory demand of the biota. The anoxic conditions allowed high concentrations \u27Of foul-smelling hydrogen sulfide to be produced. Brine shrimp were not abundant in Farmington Bay and the community was dominated by rotifers. In contrast, water quality in Bridger 8ay located on the main lake, was good and brine shrimp were abundant there. Our results, although restricted in scope, corroborate existing monitoring data from this bay. Water quality characteristics in Farmington Bay do not meet those mandated for the protection of aquatic life. Odor problems from the bay likely impact more people than are affected by any other polluted water body in the state. The impact of eutrophication and anoxia on the biota in Farmington Bay may also be substantial, although inadequate data exists to determine these impacts. There are substantial technical challenges to be overcome if water quality in the bay is to be improved to meet its designated use. However, before these technical issues can be solved, the responsible agencies will need to address the problem, and begin studies that may eventually lead to a solution to this serious water quality issue

Fostering effective and sustainable scientific collaboration and knowledge exchange: a workshop-based approach to establish a national ecological observatory network (NEON) domain-specific user group

The decision to establish a network of researchers centers on identifying shared research goals. Ecologically specific regions, such as the USA’s National Ecological Observatory Network’s (NEON’s) eco-climatic domains, are ideal locations by which to assemble researchers with a diverse range of expertise but focused on the same set of ecological challenges. The recently established Great Lakes User Group (GLUG) is NEON’s first domain specific ensemble of researchers, whose goal is to address scientific and technical issues specific to the Great Lakes Domain 5 (D05) by using NEON data to enable advancement of ecosystem science. Here, we report on GLUG’s kick off workshop, which comprised lightning talks, keynote presentations, breakout brainstorming sessions and field site visits. Together, these activities created an environment to foster and strengthen GLUG and NEON user engagement. The tangible outcomes of the workshop exceeded initial expectations and include plans for (i) two journal articles (in addition to this one), (ii) two potential funding proposals, (iii) an assignable assets request and (iv) development of classroom activities using NEON datasets. The success of this 2.5-day event was due to a combination of factors, including establishment of clear objectives, adopting engaging activities and providing opportunities for active participation and inclusive collaboration with diverse participants. Given the success of this approach we encourage others, wanting to organize similar groups of researchers, to adopt the workshop framework presented here which will strengthen existing collaborations and foster new ones, together with raising greater awareness and promotion of use of NEON datasets. Establishing domain specific user groups will help bridge the scale gap between site level data collection and addressing regional and larger ecological challenges

Global Patterns and Controls of Nutrient Immobilization On Decomposing Cellulose In Riverine Ecosystems

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature