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Habitat, Chemistry, Community Structure, and Mercury in Benthics and Blacknose Dace Deerfield River Watershed, Massachusetts and Vermont. Presented by Peter Mitchell. Study Objectives. Assess habitat and water chemistry conditions
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Habitat, Chemistry, Community Structure, and Mercury in Benthics and Blacknose Dace Deerfield River Watershed, Massachusetts and Vermont Presented by Peter Mitchell
Study Objectives • Assess habitat and water chemistry conditions • Collect and identify stream macroinvertebrates and blacknose dace for the purposes of community assessment, and tissue analysis • Investigate the variability in mercury concentrations in macroinvertebrates and blacknose dace using standard physical, chemical, and biological variables
Mercury (Hg) • Most toxic of all non-radioactive heavy metals • No known function in any human biological process • Ingestion is most prevalent toxicant pathway • Exposure may result in: chromosomal breakage, CNS damage, birth defects, death • May be aerially deposited to areas of no point source discharge • Anthropogenic sources: waste and sludge incineration, sewage treatment plant operation, fossil fuel combustion
Forms of Environmental Hg • Elemental (metallic) mercury Hg0 • Divalent (mercuric) mercury Hg++ • Methylmercury CH3Hg+ • Dimethylmercury (CH3)2Hg
Upwind emission and proximal deposition Aquatic habitats rich in organic matter CPOM and FPOM processing and transport Diminished pH and ANC Elevated temperature Dissolved oxygen flux Microbial activity Community structure Number of trophic levels Conditions Affecting Mercury
Width and depth Mean bank angle Substrate type Gradient Canopy coverage Aspect and sinuosity Watershed area Number of unimpounded 1st, 2nd, and 3rd order streams Number of unimpounded ponds and wetlands Upstream and abutting landuse Habitat Assessment MeasuresStream Reach Measure Watershed Measure
Chemical Measures • Air Temperature (oC) • Water Temperature (oC) • Conductivity (µmhos) • pH • Acid Neutralizing Capacity (ANC) • Dissolved Oxygen (DO) • Total Organic Carbon (TOC) • Discharge (cms)
Taxa Richness Eveness Diversity Functional Feeding Groups Tolerance Dominance Habit Mass Macroinvertebrate Community Metrics
Tissue Analysis • Sample Type……..Homogenized, Freeze-Dried • Sample Type..……Liquid Organic Extraction • Lab……………….Xral (Toronto, Canada) • Detection Limits…5ppb (Total and Organic) • Tissue Standards…Three (DOLT-1, DOLT-2, TORT-2) • Accuracy…………95%
Multiple Regression:EPT, TOC, Scraper / Filterer, and Wetland / Pond over Organic Mercury
Increase riparian vegetative zone Decrease organic inputs Increase variety of discharge Set limits on mercury fuel content Dam removal Sewage treatment plant design Incinerator design Remediation National Watershed