Spatial and temporal patterns of microcrustacean assemblage structure and secondary production in a wetland ecosystem

1. In contrast to extensive studies of zooplankton in lakes, the role of microcrustaceans in wetlands is not well studied. In this study, spatial and temporal patterns of microcrustacean assemblage structure and secondary production were quantified over a 2-year period in a southeastern U.S.A. wetland.
2. Thirty-two species, including 19 cladocerans, 10 copepods and three ostracods, generated different temporal patterns of density and production between vegetated ( Nymphaea ) and non-vegetated (open-water) zones reflecting species-specific differences in life histories.
3. Summer assemblages were dominated by small, planktonic filter-feeders, typified by high annual production/biomass ( P / B ) and daily production. In contrast, winter assemblages were dominated by larger, epibenthic detritivores with low P / B and high biomass. Seasonal shifts in the relative importance of planktonic species in the warmer months to benthic and epiphytic species in the cooler months suggest that energy flow pathways through microcrustaceans may vary seasonally.
4. Total annual production was higher during both years in the Nymphaea zone (13.0 g and 13.6 g DM m⁻² year⁻¹) than the open-water (8.2 and 6.3 g DM m⁻² year⁻¹), and was similar between years for the entire wetland pond (12.3 and 12.2 g DM m⁻² year⁻¹).
5. Although wetland ecosystems have been the subject of considerable ecological research in the past 20 years, our study is one of the few to demonstrate a highly diverse and relatively productive microcrustacean assemblage. Such comprehensive production studies can be used to quantify the ecological importance of microcrustaceans in freshwater wetland ecosystems.