38573d6e_International_Joint_Commission__Delisting_Guideline
[BUI] DEGRADATION OF PHYTOPLANKTON AND ZOOPLANKTON POPULATIONS [Listing Guideline] When phytoplankton or zooplankton community structure significantly diverges from unimpacted control sites of comparable physical and chemical characteristics. In addition, this use will be considered impaired when relevant, field- validated, phytoplankton or zooplankton bioassays (e.g. Ceriodaphnia; algal fractionation bioassays) with appropriate quality assurance/quality controls confirm toxicity in ambient waters. [Delisting Guideline] 
When phytoplankton and zooplankton community structure does not significantly diverge from unimpacted control sites of comparable physical and chemical characteristics. Further, in the absence of community structure data, this use will be considered restored when phytoplankton and zooplankton bioassays confirm no significant toxicity in ambient waters.
International Joint Commission
Delisting Guideline