Nigel A. D'souza
I am currently working with Dr. Mike McKay on a project aimed at understanding primary production in ice-covered Lake Erie.
Lake Erie is the southernmost of the Laurentian Great Lakes. Its relatively shallow depth results in 80-90% ice cover during winter months. In spite of its unique nature, very little is known about the winter processes in the lake.
Loss of oxygen in the hypolimnion of the central basin Lake Erie in the summer is well documented and of binational concern due to internal loading of nutrients into the lake during the summer that can lead to proliferation of harmful algal blooms. Hypoxia can also result in loss of habitat to benthic macrofauna and fish and if persistent, can lead to noxious gas emissions. The exact cause of this hypoxia remains unresolved to date. The reduction of oxygen that occurred in the hypolimnion did not seem to be coupled directly to phytoplankton biomass present in the lake in spring and early summer.
In February 2007 members of MELEE (Microbial Ecology of Lake Erie Ecosystems) consortium (Wilhem, Bullerjahn, Mckay and Twiss) voyaged the length of the lake in an attempt to measure phytoplankton and bacterial abundance actoss the lake to answer the question: “What microbes are in the lake in the dead of winter, and what are they doing?” The group documented high phytoplankton biomass dominated by a nutrient replete, low light adapted, filamentous centric Diatom Aulacoseira spp. Preliminary work by the group suggests that rapid diatom proliferation occurs in winter in Lake Erie and can be associated with ice cover, thus exerting an influence on the biogeochemistry of this lake months later. As such, any changes in winter growing conditions (ice cover, surface temperatures) could dramatically influence the net productivity of this ecosystem. Export of this biomass to the hypolimnion and its respiration in summer could explain the hypoxia observed.
My current research involves further characterization of the winter phytoplankton and looks at a possible link between winter production and the hypolimnetic hypoxia in the central basin of the lake in summer. The work would involve culturing these organisms in the lab, their characterization, understanding the primary production parameters, the role of the winter and summer phytoplankton biomass in biogeochemical cycling in the lake and the use of biochemical and molecular markers in tracing the fate of the biomass in the lake.
