Integrated Benthic Macroinvertebrate Community Assessment of the Tittabawassee River (MI) to Support Risk-Based Remedial Decisions

摘要

Background/Objectives. A benthic macroinvertebrate community study was conductedon the Tittabawassee River in the vicinity of The Dow Chemical Company Michigan Operationsfacility in Midland, Michigan. The objectives of this study were to: (1) evaluatethe condition of benthic macroinvertebrate communities in the river, comparing sitespecificdata (including data collected from Sediment Management Areas) to upstreamreference conditions (USEPA approach) and to eco-regional reference conditions(MDNRE approach); (2) evaluate spatial trends in the condition of benthic communitieslocated adjacent to and downstream from the Dow facility; (3) assess potential relationshipsbetween benthic community indicators/metrics, sediment contaminant concentrations,and non-contaminant habitat factors; and (4) compare results from this benthiccommunity assessment with results from similar rivers in Michigan.Approach/Activities. Standardized, quantitative sampling and analysis methods wereused based on United States Environmental Protection Agency (USEPA) and MichiganDepartment of Natural Resources and Environment (MDNRE) published guidance.Sampling was conducted from September-October 2010 using sediment grabs, artificialsubstrates, and sweep nets at 21 locations including several upstream reference sites. Amulti-metric approach following USEPA and MDNRE methods was used to quantify andcompare habitat and benthic community scores based on metrics such as diversity/richness, proportion of sensitive taxa, etc. Results for Tittabawassee River stationsadjacent to and downstream from the Dow facility were compared with results for upstreamreference stations and other similar Michigan rivers. Stations were assignednarrative descriptors for habitat condition and benthic community structure.Results/Lessons Learned. Benthic community scores for stations from the TittabawasseeRiver ranged from “excellent” to “tending toward excellent” when compared to theMDNRE eco-regional reference approach, and from “non-impaired” to “slightly impaired”when compared to upstream reference areas using the USEPA approach.Statistical testing on a “river reach” basis (i.e., groups of nearby stations) did not identifyany significant differences in community structure between reference reaches and inreaches adjacent to and downstream of the Dow facility. Two stations exhibited benthicassemblages that were significantly different from those observed at reference locations.These station-specific results (i.e., high densities of tubificid worms) were indicative oforganic enrichment, suggesting potential localized effects from nutrient inputs (i.e.,municipal wastewater or stormwater). Non-chemical habitat limitations were also shownto influence benthic communities in the Tittabawassee River. These results demonstrate