In-stream biomonitoring is an integral component of the watershed-based water quality management program. Its importance is underscored in the Clean Water Act that stresses the need to restore the biological integrity of the nation's waters and achieve a water quality which provides for the protection and propagation of aquatic life. DWM biologists perform habitat assessments and conduct biological sampling to determine aquatic life use-support status, the fish consumption use, and to supplement other water quality monitoring and management programs.
Assessment of Aquatic Community Health
DWM assesses the condition of resident macroinvertebrate, fish and algal populations in streams to provide a direct measure of the ecological response to cumulative effects of pollutant loadings and habitat degradation. Physico-chemical water data can provide a "snapshot" of conditions prevailing at the time of sampling; however, due to their temporal variability, solutes must be measured with some degree of replication in order to draw conclusions with respect to the overall quality of the water. Furthermore, surrogate chemical analytes are less reliable than the more direct biological assessment of instream "health". For example, whereas satisfactory dissolved oxygen values may provide the means for predicting that a given stream is supporting aquatic life, a survey of the organisms that spend all or a portion of their life-cycles in the water furnishes direct evidence that this use is or is not supported. Thus, the analysis of aquatic community structure and function indicates the general condition of the aquatic ecosystem which, in turn, is dependent upon such factors as the quality of the habitat, water quality and flow regime.
Rapid bioassessment protocols (RBPs), based on those developed by EPA, are used to monitor the health of benthic macroinvertebrate communities. These methods were developed to minimize laboratory time requirements for taxonomic identification and enumeration of benthos. Kick-net samples are collected at sites for upstream/downstream comparisons, comparisons against a regional or surrogate reference, or for long-term trend monitoring. Two different levels of analysis are employed, RBP II or RBP III, depending on the objectives to be served.
Based on scoring of several metrics, three categories of impairment are discerned by the RBP II (nonimpaired, moderately impaired, and severely impaired), while the RBP III distinguishes between four (nonimpaired, slightly impaired, moderately impaired, severely impaired). Benthic macroinvertebrate RBPs are conducted at up to 75 sampling sites per year.
The analysis of the overall structure and function of the finfish community as a measure of biological integrity is also a component of the DWM water quality monitoring program. Fish bioassessment data quality and comparability are assured through the use of qualified fisheries professionals and the application of consistent methods. The DWM utilizes a standardized method based on the EPA Rapid Bioassessment Protocol V (RBP V) to improve data comparability among wade-able sampling sites throughout the state.
The fish collection procedures employ a multihabitat approach that allows for sampling of habitats in relative proportion to their local availability. A representative 100-meter stream reach is selected and delineated such that primary physical habitat characteristics of the stream are included (i.e., riffle, run, and pool habitats). Electrofishing has generally proven to be the most comprehensive and effective single method for collecting stream fishes, and is therefore the preferred method for obtaining a representative sample of the fish community at each sampling site. Fish (except young-of-the-year) collected within the study reach are identified to species (or subspecies), counted, and examined for external anomalies, (i.e., deformities, eroded fins, lesions, and tumors). Aquatic life use-support status is derived from a knowledge of the environmental requirements (e.g., water temperature and clarity, dissolved oxygen content, etc.) and relative tolerance to water pollution of the fish species collected. This information may also be used to corroborate findings of other community analyses or water quality testing.
Algae represent a third community that may be assessed as part of DWM biomonitoring efforts. The analysis of the attached algae or periphyton community in shallow streams, or the phytoplankton in deeper rivers and lakes employs an indicator species approach whereby inferences on water quality conditions are drawn from an understanding of the environmental preferences and tolerances of the species present. Algal indicators of the presence of elevated metals concentrations, nutrient enrichment, or other pollutants are noted. Because the algal community typically exhibits dramatic temporal shifts in species composition throughout a single growing season, results from a single sampling event are generally not indicative of historical conditions. For this reason the information gained from the algal community assessment is more useful as a supplement to the assessments of other communities that serve to integrate conditions over a longer time period. In some instances, where information pertaining to primary production is required, algal biomass analysis or chlorophyll determinations may be performed. Results of these analyses are used to evaluate the trophic status of lakes, ponds, and impoundments. Similar information from riverine and coastal waters is used to identify those waterbodies subjected to excessive nutrient enrichment.
In addition to the community analyses described above, DWM also collects some aquatic organisms to be assayed for the presence of toxic contaminants that may be sequestered in their tissues. The goal of this monitoring element is primarily to provide data for the assessment of the risk to human consumers associated with the consumption of freshwater finfish. In the past fish collection efforts were generally restricted to waterbodies where wastewater discharge data or previous water quality studies indicated potential toxic contamination problems. More recently, concerns about mercury contamination from both local and far-field sources have led to a broader survey of waterbodies throughout the Commonwealth. In both cases, nonetheless, the analyses have been restricted to edible fish fillets. This "Toxics-in-Fish" monitoring program is a cooperative effort of the MADEP, the Department of Fisheries, Wildlife, and Environmental Law Enforcement (DFWELE), and the Department of Public Health (DPH). Uniform protocols, designed to assure accuracy and prevent cross-contamination of samples, are followed for fish collection, processing and shipping. Fish are typically obtained with electroshocking gear or gill nets. Lengths and weights are measured, and fish are visually examined for tumors, lesions, or other indications of disease. Data are provided to the DPH which is the agency responsible for performing the risk assessments and issuing public health advisories.
The use of tissue bioassays to trace the fate and transport of toxic contaminants in the aquatic environment has been explored on a limited basis, as time and resources permit. Caddisfly and crayfish bioassays have been used to identify possible sources of PCB's in selected watersheds. However, the effects of potentially toxic chemicals on the organisms that accumulate them are often not well understood, rendering tissue contaminant data of limited value for inferring aquatic life use support.