Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $24,340 Total Non-Federal Funds: $24,340
Principal Investigators: David Costello
Abstract: Recurring harmful algal blooms in Lake Erie are the result of excess loading of nitrogen (N) and phosphorus (P) from agricultural-dominated landscapes in the northwest Ohio. The streams that deliver nutrients to receiving ecosystems have the capacity to transform, store, and remove N and P, but in eutrophic ecosystems rates of in-stream processing slow and nutrients pass though unaltered. Trace metals are required by microbes (particularly algae) for key metabolic processes, and low concentrations of these elements are suggested to limit nutrient processing in eutrophic streams. It has been demonstrated that trace metals play an important role in marine and lake ecosystems, but relatively little is known about the spatial and temporal distribution of trace metals in streams and whether growth of stream organisms is limited by trace metals. I propose a collaboration with Heidelberg University’s National Center for Water Quality Research (NCWQR) to incorporate analysis of trace metals into their recurring water quality sampling of agricultural streams in northwest Ohio. I will collect additional samples from the Cuyahoga River drainage basin to provide information about trace metal and nutrient concentrations in streams draining forested and urban landscapes. Principals from ecological stoichiometry will be used to compare ratios of trace metals and nutrients in surface waters to biological requirements (estimated from tissue concentrations). Streams with surface water trace metal:nutrient ratios that are well below the physiological requirements of microbes will be identified as sites where microbial growth and nutrient assimilation is potentially limited by trace metals. For five streams identified as potentially limited by trace metals, I will complete in-stream trace metal nutrient diffusing substrate (tNDS) assays to directly measure growth limitation. For these studies, trace metals, nitrogen, and phosphorus will be added to tNDS separately and in combination, and biofilms growing on the tNDS providing the nutrient(s) limiting growth will grow to a greater biomass. Colonized tNDS grown under different nutrient conditions will be use for community metabolism and nutrient uptake assays, which will determine in-stream processing rates. I hypothesize, that tNDS delivering trace metals will contain a greater biomass of biofilms, and these biofilms will have greater metabolic rates, faster rates of nutrient uptake, and store more nutrients in their biomass. This proposed research will provide valuable information for researchers about coupled elemental cycles beyond the elements that are typically studied (C, N and P), and will demonstrate the role trace metals play in stream ecosystems. Holistic nutrient management approaches must consider the entire watershed, which includes tributary streams, and the information generated by this proposal will improve our understanding of in-stream processing of nutrients.