This project is a joint venture between the U.S. Army Corps of Engineers (USACE) and the Idaho Department of Fish and Game (IDFG).  The USACE will apply ammonium nitrate to the reservoir to promote an improved nitrogen (N) to phosphorus (P) ratio and increased food web efficiency. Increasing the N:P ratio is expected to increase primary productivity, favor beneficial algal taxa, increase zooplankton production, and improve growth and survival of kokanee. Increased size or abundance of kokanee is expected to improve recreational fishing, not only for kokanee, but also for piscivorous fish that use kokanee as a forage base. An increased N:P ratio is also expected to reduce N-fixing blue-green algae, which represent a public health hazard, and lead to inefficient transfer of carbon to fish populations (i.e. reduce fish production). The IDFG will be responsible for collecting limnological samples, which will be used for in-season management of nutrient supplementation, maintaining compliance with the NPDES permit, and continued evaluation of project effectiveness.  The USACE has contracted Advanced Eco-Solutions to provide the nutrient prescription, interpret the results of limnological sampling, and recommend in-season adjustments to the amount of fertilizer to be applied.  The USACE will further fund analysis of water and plankton samples collected by IDFG to monitor reservoir limnology. Fish monitoring will also be conducted by IDFG and, combined with limnological data, will allow for continued assessment of the nutrient additions.

This contract period will include an enclosure experiment which will allow us to determine the effects of nitrogen additions experimentally. Dworshak Reservoir is currently nitrogen limited and increasing available nitrogen through the addition of ammonium nitrate is expected to result in increased primary productivity and associated shifts in phytoplankton assemblage.  These shifts are expected to result in increased zooplankton forage available to kokanee. It has been demonstrated that increasing zooplankton forage will result in increased growth and biomass of kokanee. It is further expected that addition of ammonium nitrate will reduce the prevalence of potentially toxic, N-fixing blue-green algae. Testing N additions experimentally will allow us to infer causation of the additions as they relate to reservoir productivity and the prevalence of blue-green algae. It will further allow us to determine the true magnitude of these effects, by controlling for environmental variables, and fine tune the N additions to achieve the desired level of effect with the least amount of fertilizer.