¹Lake Superior Ecosystem Research Center, Michigan Technological University, Houghton, Michigan 49931
²Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
³School of Marine Science and Technology, University of Massachusetts- Dartmouth, New Bedford, Massachusetts 02742

Summary

         Because so many species enter and leave coastal planktonic communities, there is debate about biodiversity and the intensity of biotic (predator-prey, competitive) interactions. Lake Superior is characterized by one of the most diverse zooplankton communities, with species falling into three broad categories (embay¬ment, coastal, and open-water). To what degree is diversity a reflection of spatial and temporal scale? Here we advocate application of a new perspective (metacommunity) to examine if embayment and coastal zooplankton communities conform to an exchange-dispersal structure. Both assemblages (embayment and coastal) are seasonal warm-water communities that recruit largely from overwintering eggs or stages. Because of the restricted spatial distribution of viable resting eggs and “egg banks”, we postulate that embayment communities contribute species to developing coastal assemblages, as water is periodically pumped out of openings and long-shore currents disperse individuals from these multiple sources around the coastal zone. Circumnavigation is risky, interrupted by eddies and offshore excursions, potentially iso¬lating populations in different embayments along an irregular coastal zone.
Modeling and experimental paleoecological approaches offer opportunities to test the metacommunity concept. Linked embayment-coastal zone models offer insight into mechanisms of dispersal of endoge¬nous and introduced species. Diapausing eggs can be retrieved from embayment sediment cores to docu¬ment species colonization, extinction, and turn-over rates. Embayment sediments can be dated by a combination of radioisotope (¹³⁷Cs and ²¹⁰Pb) techniques and varves, and the timing and successional responses to perturbations (deforestation, mining, eutrophication) quantified. Moreover, diapause eggs can be hatched from different sediment levels for genetic characterization (allozyme electrophoresis, mDNA 12S/16S, microsatellite sequences) and "common garden" experiments. Preliminary studies docu¬ment active species exchange between coastal waters and embayments.