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  • Title

    Integrated Science and Management of Nutrient, Salt, and Mercury Export from San Joaquin River Wetland Tributaries to the Delta

    Lead University of California - Merced [UC Merced]
    Description Mercury, salinity, and nutrients such as nitrogen and phosphorus are major contaminants of concern and are an understudied source of water quality impairment to the Delta. This study will (1) examine seasonal variation and transfer of salt, nutrients, and mercury out of managed wetlands;(2) establish and verify whether other routinely monitored water components can serve as reliable alternatives (proxies) for detecting mercury and nutrients;(3) integrate monitoring data and proxy relationships to estimate levels of contaminants;and (4) develop science-based strategies for adaptive co-management of salt, nutrients, and mercury from seasonal wetlands to improve water quality in the Delta. Outcomes from this study will provide improved best practices and guidelines for management of salt, nutrients, and mercury in wetlands. Results will also address key knowledge gaps identified in the Delta Nutrient Research Plan and provide support for the Delta Mercury Control Plan.
    Science topics Nutrients, Salinity, Hg and methyl mercury
    Updated April 29, 2022
  • Title

    Understanding the Effects Of Nutrient Forms, Nutrient Ratios and Light Availability on the Lower Food Web of the Delta

    Lead University of Maryland - Center for Environmental Science
    Description This proposed study addresses how changes in nutrient form, ratio and loading (water quality) affect the lower pelagic food web that ultimately determines the quality and quantity of food for Delta fishes. Shifts in algal composition and food availability have been implicated in fish decline, but identifying the changes at the base of the food web that are linked to changes in nutrients has been difficult because of the complexity of factors contributing to stress on the food web. Nutrients may shape community composition in complex ways;they do not have to be limiting to be important drivers of plankton communities. Elevated nutrients, particularly chemically reduced forms of nitrogen (N), may be inhibitory rather than stimulatory. We hypothesize that when NO3- is proportionately abundant relative to NH4+ (and the N:P ratio is suitable), diatoms will dominate, but when NH4+ is proportionately abundant, cyanobacteria or flagellates will dominate. Reduced light availability will lead to communities with higher bacterial abundance, and/or higher proportions of flagellates able to alter their nutrition towards mixotrophy. This proposal will directly test these relationships by conducting experimental manipulations with different ambient communities from different sites and seasons. Data will be interpreted with respect to the long-term trends reported for the Bay Delta and supplied as an integrated product for management efforts concerned with water quality and fisheries.
    Science topics Nutrients, Food webs
    Updated April 29, 2022