Influence of Tributary Quality on Macroinvertabrate Communities in the St. Louis River Estuary

Macroinvertabrates are known indicators of aquatic ecosystem condition.  Anthropogenic stressors such as impervious surfaces and land conversion in a watershed can affect aquatic ecosystem condition.  The goal of this project was to determine if macroinvertabrate communities in tributary mouth wetlands in the St. Louis River Estuary (SLRE) are influenced by anthropogenic factors in tributary watersheds.  Samples were collected in tributary mouth wetlands in the SLRE using D-frame sweep nets.  In the lab samples were spread on a gridded tray with 5x5cm cells.  Cells were chosen at random and all macroinvertebrates were removed until a total of 150 macroinvertabrates were removed.  Macroinvertabrates were identified to family.  Relative abundance and richness metrics were calculated for each Order in each sample. Correlation coefficients between relative abundance-richness metrics and the anthropogenic stress score for each watershed were calculated using SPSS.  Of the 19 potential indicators investigated, only 1 metric was related to the stress gradient for macroinvertebrate communities in emergent vegetation.   In a previous study several potential indicators were significantly correlated with the stress gradient for macroinvertebrate communities in submergent vegetation.  I found that the macroinvertebrate community structure in emergent and submergent habitats was different.  Furthermore Order level relative abundance in emergent and submergent vegetation at the same sites was not correlated.  Because communities in these different habitats vary they will respond to anthropogenic watershed stresses differently.