Spatio-Temporal Variation of Primary Production Rates in Lake Erie

Session: Poster Session

Hunter Carrick, Central Michigan University, [email protected]
David Millie, Palm Island Enviroinformatics, [email protected]

Abstract

Limited primary production data exists for large lakes, given the difficulties inherent in sampling during all seasons and conducting shipboard experiments.  Lake Erie exhibits strong spatio-temporal gradients in phytoplankton biomass that manifest themselves among the three basins.  For instance, seasonal occurrences of cyanobacterial harmful algal blooms (cyano-HAB) are observed in the western basin, while seasonal hypoxia in the central basin is a persistent lake feature.  Both conditions currently exist despite improvements in Lake Erie water quality conditions over the past 3 decades.  That said, few studies exist that document the changes in the seasonal production of phytoplankton throughout the lake.  In this study, >70 primary production experiments were performed to evaluate spatio-temporal variation in production rates during the 2002-2005 period; time-dependent changes in oxygen concentrations were measured in light-dark bottle experiments (modified Winkler technique).  Offshore net production rates were comparable with historic rates (typically 1-10 mgC/m3/h) and were closely balanced against respiration rates.  Nearshore net production rates in the vicinity of the Maumee and in Sandusky River inflows, were some of the highest recorded for the Great Lakes (250-833 mg C/m3/h).  These results suggest that evaluations of hypoxia in the central basin should consider sources of nearshore primary production.