Freshwater Invertebrate Assemblage Composition and Water Quality Assessment of an Urban Coastal Watershed in the Context of Land-Use Land-Cover and Reach-Scale Physical Habitat

Abstract

Stream ecosystems provide invaluable ecosystem services but are highly impacted ecosystems in need of water quality monitoring for habitat change impacts. Freshwater macroinvertebrate (FWI) assemblages have been shown to be good indicators of water quality and are known to be vulnerable to land-use land cover (LULC) and other habitat changes. The goal of this case study was to use an existing dominant LULC analysis in the Neponset River watershed, Massachusetts, USA, as LULC sampling treatment groups to deliberately capture the influence of these LULC effects on meso-scale habitat quality, FWI assemblages, and FWI water quality indices at eight sampling reaches. To achieve this goal, we collected physical habitat measurements and FWI samples in the summers of 2010 and 2012 at eight reach-scale stations spread across four previously determined LULC sub-watershed types (forest, residential, industrial, and golf) in the watershed. We expected that LULC change would influence the habitat quality, which would influence the FWI assemblage water quality scores and composition. We also expected that the water quality at these LULC sub-watershed types would be reflected in the FWI assemblage composition. We identified five major findings from our study. Our first finding was that the habitat quality in the Neponset River watershed was somewhat degraded relative to pristine conditions. Our second finding was that our habitat characterization analysis reflected some separation of our reach-scale macrohabitat types at land-use land-cover treatment stations with some correlations with microhabitat variables. Our third finding was that the water quality base on FWI assemblages was generally degraded in reference to pristine conditions. Our fourth finding was that, contrary to our expectations, there was no significant correlation between our reach-scale EPA habitat quality scores and FWI water quality scores. Our fifth finding was that our FWI assemblage NMS showed separation of land-use land-cover sampling stations and that that low pollution-tolerant taxa dominated some of our LULC sampling treatment stations and influenced NMS groupings.