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Bioassessment and Biocriteria Program Status for Maine: Streams and Wadeable Rivers

State Program Contact

Maine DEP Water Biomonitoring Exit

Water Quality Standards

WQS Information
The link to Maine's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
  • Water Quality Standards Regulations: Maine
The state of Maine provided information and links to sections of their administrative code on designated aquatic life use, biological criteria, antidegradation as well as technical support documents and information on its bioassessment and biocriteria programs. These are included for your convenience and may or may not reflect the most recently EPA approved WQS. The following links exit the site Exit

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Designated Aquatic Life Uses
ALU designations are based on multiple thresholds and use categories. Benthic macroinvertebrate and algal communities are assessed in rivers, streams, and wetlands to address Maine’s aquatic life standards.

  • Class AA waters – Class AA shall be the highest classification and shall be applied to waters which are outstanding natural resources and which should be preserved because of their ecological, social, scenic or recreational importance
  • Class A waters – Class A shall be the 2nd highest classification
  • Class B waters – Class B shall be the 3rd highest classification
  • Class C waters – Class C shall be the 4th highest classification

Biological Criteria
__X__ Narrative, with quantitative implementation procedures or translators (stream algae)
__X__ Numeric (stream macroinvertebrates)
_____ No criteria

A waterbody shall be determined to be in attainment of the designated aquatic life uses and characteristics of its assigned water classification, if the association value, as determined according to Sections 3 and 4 of this chapter, following methods outlined in "Methods for Biological Sampling and Analysis of Maine’s Rivers and Streams" (DEP LW0387-B2002), is shown to be equal to or greater than 0.6 for that class or any higher class, or where the provisions for professional judgement determine that the water should be determined to be in attainment of its assigned water classification or any higher classification; and where other standards and criteria pertinent to protecting the aquatic life uses of the classification are determined to be attained (including, but not limited to, support of indigenous fish or other aquatic species, as required in the water quality classification law).

Antidegradation Policy
Chapter 579.5.C Subsection 4.F

Biological Assessment

What biological assemblages are used in the bioassessment program?
Benthic macroinvertebrates and periphyton. Fish IBI is under development. 

Are bioassessments used to support 303(d) listings? 
Yes. Listing methodology: Refer to sections "Assessment Methodology" and "Assessment Criteria" (especially subsection "Data Interpretation") in each Integrated Water Quality Monitoring and Assessment Reports

How are assemblages used to make impairment decisions?
Discriminant models and thresholds have been calibrated for macroinvertebrate assemblages in rivers/streams. Models and thresholds have been developed for algal assemblages in rivers/streams and for macroinvertebrate assemblages in wetlands. Models and thresholds are being developed for algal communities in wetlands. Assemblages are applied independently.

Other uses of biocriteria or bioassessment within the water quality program:
Refining ALU, TMDL development and assessment, antidegradation, non-point source assessments, BMP evaluation, 305(b) surface water condition assessments, and restoration goals.

Technical Support Information and Documents:

Reference condition:
Developed for streams and wetlands using the BCG approach as the basis.

Development of biocriteria involves the collection and interpretation of biological data –e.g. benthic macroinvertebrates, fish, and periphyton. During this process entities typically use biological metrics (usually aggregated into a multimetric index) and/or multivariate analysis to assess whether a waterbody is meeting its designated aquatic life use(s). The reference materials include standard operation procedures used in data collection, compilation, technical approaches used to develop biocriteria as well as its implementation procedures.

Technical reference material:
Classification Attainment Evaluation Using Biological Criteria for Rivers and Streams
Biomonitoring Program
Biological Water Quality Standards to Achieve Biological Condition Goals in Maine Rivers and Streams: Science and Policy (PDF) (87 pp, 8 MB, About PDF)

Stressor identification/causal analysis approach:
Linked stressor identification and causal analysis

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