Effects of Climate Change on Spring-Winter Runoff and Lake Productivity

This project will look at the effects of ongoing changes in the seasonality of winter – spring streamflow on lake productivity. Our initial hypothesis is: Changes in the timing of spring runoff, with more runoff occurring in the winter and early spring, will lead to reduced productivity and phytoplankton biomass during the summer stratified period. We expect the above might be true since nutrients delivered to a lake during colder deeply mixed and possibly ice covered conditions could be less effective at stimulating phytoplankton growth. To test the hypothesis we would like to collect data from a large variety of lakes which meet the following minimal requirements:

• In a geographic location where snow accumulation and melt significantly impact the seasonality of stream discharge.
• A lake with data from 1990 or earlier and continuing to present. There should be multiple samples per year that cover at least the period of thermal stratification.
• Lake measurements of chlorophyll profiles during thermal stratification and/or measurements of hypolimnetic oxygen at the onset and just before the loss of thermal stratification.
• Stream discharge measurements of a major inflow to the lake starting in 1990 or earlier, or measurements from a nearby stream or river than can be used to provide an index of lake inflow.