Impact of Episodic Transport and Resuspension on Coastal Phytoplankton Processes:
A Case Study of the Lake Michigan Recurrent Coastal Plume

G. Fahnenstiel, S. Lohrenz, O. Schofield, D. Millie, L. Goad, and M. Julius

Biological production in coastal waters serves an important role in assimilating terrestrially-derived inputs, in sustaining fisheries, and in influencing the global carbon cycle. The complex and dynamic nature of the coastal environment makes it difficult to determine how specific phytoplankton assemblages will respond to this environmental variability. Identification of taxon-specific and community responses to environmental forcing is of central importance to our understanding of the variations in coastal phytoplankton biomass, growth, and production.
The duration and extent of the highly-turbid, recurrent coastal plume (RCP) in late winter/early spring makes Lake Michigan an ideal locale to examine and compare impacts on phytoplankton rate processes of episodic physical forcing in relation to more persistent seasonal scale variability. Although the RCP coincides with the initiation of the basin wide spring diatom bloom, linkages between the duration and intensity of the plume and the prominent role of light availability in regulating Lake Michigan phytoplankton growth during the spring isothermal period have been postulated, but not verified. As such, the concurrent physical and biological events provide a novel opportunity to examine how specific environmental parameters (particularly light) influence phytoplankton rate processes at both the species and community-levels, and how variations in biological rate processes, coupled with transport and resuspension phenomena associated with the RCP, affect the distributions of organisms, evolution of communities, and growth and primary production of Lake Michigan phytoplankton.
The proposed research is an interdisciplinary effort which will greatly improve our understanding of ecophysiological mechanisms controlling phytoplankton and community structure during episodic, physical forcing events within the Laurentian Great Lakes The measurement of cellular, species, group, and community processes coupled with state-of- the-art, big-optical instrumentation will allow for a unique comprehensive examination of the taxon-specific and community responses to distinct physical forcing factors We will also further develop, evaluate, and improve the current big-optical production model for Lake Michigan and assist in efforts developing (related) remote-sensing algorithms elsewhere in this NSF/NOAA Coastal Ocean Processes Program (see Appendix).