Project
Effects of phosphorus limitation on the quantity and quality of lower food web plankton in Lake Huron
Dikameg (lake whitefish, Coregonus clupeaformis) are a cold-water fish species of critical importance to the Saugeen Ojibway Nation (SON), having been a major component of SON diet, economy and culture for thousands of years. Over the last two decades, dikameg have declined in abundance. A major concern in the ongoing recovery of dikameg in SON territory and the Great Lakes, is limited food for larval fishes, likely induced by phosphorus limitation. One possible dikameg restoration strategy of interest to SON is nutrient enrichment. However, several knowledge gaps remain in our understanding of the effects of nutrient limitation on plankton in nearshore waters. While resource limitation of dikameg recruitment success has been explained primarily in terms of food quantity, it is also possible that nutrient limitation in the water column has cascading effects on phytoplankton and zooplankton nutrient content (stoichiometry), with consequences on larval dikameg. We still do not know the extent to which phosphorus limitation induces changes in phytoplankton and zooplankton quality and quantity. Here, we propose a pilot lab experiment paired with partnership building efforts, in order to generate new knowledge that can inform next steps in dikameg restoration efforts and strengthen relationships among partners to maintain a knowledge co-production framework in this and future work. In our lab experiments we will test the following hypotheses: H1) Phosphorus limitation decreases the growth rates of phytoplankton, and induces a shift in the nutritional value of these phytoplankton H2) Phosphorus limitation cascades from phytoplankton to zooplankton stoichiometry H3) Zooplankton feeding on phosphorus-limited phytoplankton will have reduced growth rates and H4) Zooplankton feeding on a community of phytoplankton will maintain closer to optimal stoichiometry. This pilot experiment is the first step in building a better understanding of how change in the lower food web is related to recovery trajectories for dikameg in the Great Lakes. How to proceed toward this larger goal will require inputs from stake- and rightsholders, so building relationships with SON in support of knowledge co-production, will be an equal objective with developing methods and generating pilot data here.