An examination of environmental factors affecting macroinvertebrate communities in the Merrimack River basin

Cotter-Brown, Maire
Joy Ackerman, PhD
Department of Environmental Studies
This project was conducted to assist the National Water Quality Assessment Program in the New England Coastal Basin Study area. Data on the macroinvertebrate communities in the basin was taken from the Merrimack River Bi-State Biomonitoring Report (Baczynski et al., 1997) and summarized using Principal Component Analysis (PCA). Supplemental data was gathered at five sites in Massachusetts. The greatest amount of variability in macroinvertebrate communities was due to differences in the percentages of the communities composed of the orders Ephemeroptera and Plecoptera. Variability in biometrics measurements emphasized differences in richness and diversity. Correlation analysis suggests that optimal velocity/depth regimes and bank conditions, as well as minimal channel alteration, are associated with healthy macroinvertebrate communities in the Merrimack River Basin. High levels of Nitrogen and Phosphorus have negative impacts on macroinvertebrate communities in the basin. Land use analysis indicates that community composition is affected by the percent of land covered by water. This study promotes the use of PCA and Geographic Information Systems in water quality investigations, particularly in studies involving large numbers of variables. For this reason, these techniques may be useful for the National Water Quality Assessment Program.

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