Meiofauna Abundance and Distribution in Chesapeake Bay: Relationships with Environmental Stressors, Sediment Toxicity and Macrofauna

Macrofauna-based biocriteria to assess impairment in aquatic communities are well-developed and have been widely accepted as useful for coastal monitoring programs worldwide. Meiofauna-based methods are not as well developed, but meiofauna are intimately associated with sediments through their life cycles and are functionally important. Thus, an understanding of meiofauna relationships with environmental quality is also important. Relationships between the abundance and composition of major meiofauna taxa for two shallow water habitat types (protected, with muddy sediment; exposed, with sandy sediment) were investigated along gradients associated with changing land use, sediment contamination and environmental stressors in Chesapeake Bay. Principal component analysis shows that urbanization, eutrophication and sediment contamination affect shallow water sites in the lower Chesapeake Bay, Virginia ecosystem. Multidimensional scaling ordination of meiofauna community data reveals gradients associated with human activities and major habitat types. Both sediment enrichment (high percent organic carbon and percent nitrogen) and sediment toxicity were associated with shifts in meiofauna community composition in muddy sediment. Benthic Foraminifera, known to be pollution sensitive, were rare or absent in collections from sites with sediment enrichment or toxicity. Nematodes were abundant at a site with enrichment, but not at a site with significant sediment toxicity. Major meiofauna taxa also differed clearly between protected and exposed sites, with greater abundances in collections from mud versus sand sediment. Results of analyses matching biotic to environmental patterns point to the importance of regional historic salinity and chlorophyll-a levels in addition to other habitat properties, including sediment organic carbon, total nitrogen and sediment toxicity as predictors of meiofauna community structure. The Benthic Index of Biotic Integrity (B-IBI) developed for Chesapeake Bay based on macrofauna was negatively correlated with nematode abundance at muddy sites when a site with significant sediment toxicity was excluded. There were no other significant relationships between meiofauna metrics and the B-IBI. The ratio of nematodes to copepods was not effective for discriminating relationships among sites relative to anthropogenic effects