Benthos Sample Clauses

Benthos. Benthos refers to the suite of organisms that live on or in the lake bottom, referred to here as macroinvertebrates. Because macroinvertebrates live in close association with the sediments and are relatively immobile, they are good bioindicators of levels of persistent compounds in the sediments, especially trace metals and organic chemicals (pesticides, petrochemicals, PCBs, PAHs, etc.). Therefore, one of the criteria used for assessing benthic impairment is when toxicity of sediment-associated contaminants at a site is significantly higher than reference controls. Highly toxic sediments produce profound, but sometimes non-specific, reductions in benthic abundance, richness (numbers of species), and community composition. Lower levels of contaminants may cause sublethal effects in invertebrates, just as they do in vertebrate animals (impairment of growth or development, morphological deformities, chromosomal abnormalities, or production of stress proteins). Contaminant breakdown products are often more toxic than the parent compounds. However, some benthos may tolerate persistent compounds because they lack the ability to break the pollutants down into compounds that can be excreted. Because benthic invertebrates may bioaccumulate these toxic compounds, their body burdens can serve as indicators of the amount of bioavailable contaminants in the environment, and of the transfer potential to predators at higher trophic levels (fishes, birds, etc.). Bioaccumulation factors for some chemicals can be extrapolated to anticipate whether burdens of top predators are likely to approach toxic thresholds. For the Lake Erie LaMP assessment, the benthic communities found in contaminated sediments may be designated impaired if one or more of the following occur: • The community is degraded; • Bioassays using sediment from an area indicate toxicity to benthic organisms; • Macroinvertebrates collected from the sediments have significantly elevated incidences of deformities or other abnormalities; • The contaminant burden of benthic animals is great enough that predators may be at risk of bioaccumulating toxic concentrations of the contaminants. Impairment was assessed in each of six lake zones: tributaries, wetlands, shorelands, embayments, nearshore and offshore. Draft conclusions, by basin and zone, for benthic impairments due to contaminated sediments are summarized in Table 4.5. Benthic impairments that are due to causes other than contaminated sediments are addresse...

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Benthos. Data is needed for benthic community composition in Canadian wetlands, shorelands in both Canada and the U.S., central basin nearshore, especially Canadian waters, and central basin profundal zone. • An improved understanding is needed of benthic-pelagic processes and benthic biotic/ physical feedback loops, especially in the western basin. • A GIS facilitated, integrated data-base of all historical and current benthic data is needed. S e c t i o n 4 36

Benthos. The collection of organisms attached to or resting on the bottom (benthic) sediments and those which bore or xxxxxx into the sediments. Berm An engineered (earth) bank forming a raised barrier separating two areas. Best Practicable Environmental Option (BPEO) Procedure which results in identification of the option that causes least damage to the environment at acceptable cost.

Benthos. To protect, maintain and, where in the past impacts have occurred, restore where appropriate to levels characteristic of natural ecosystems:

Benthos. To protect, maintain and, where in the past impacts have occurred, restore where appropriate: