Code of Maine Rules
06 - DEPARTMENT OF ENVIRONMENTAL PROTECTION
096 - DEPARTMENT OF ENVIRONMENTAL PROTECTION - GENERAL
Chapter 581 - REGULATIONS RELATING TO WATER QUALITY EVALUATIONS
Section 096-581-6 - Great Ponds Trophic State

A. Trophic state is the ability of a body of water to produce algae and other aquatic plants. The trophic state of a body of water is a function of its nutrient content and may be estimated using the Maine Trophic State Index (TSI) as follows:

All Lakes:

TSI = 70 log (mean chlorophyll a + 0.7)

Lakes with water color <30 SPU:

TSI = 70 log (.33 mean total phosphorus + 0.7) or,

TSI = 70 log ( 105 + 0.7 )

mean Secchi disk

Standardized data requirements for calculating TSI shall be determined by the Department.

B. Algal bloom. - An algal bloom is defined as a planktonic growth of algae which causes Secchi disk transparency to be less than 2.0 meters.

C. Stable or decreasing trophic state. A GPA water shall be considered to have stable or declining trophic state unless it exhibits (1) a perceivable and sustained increase in its trophic state as characterized by its Trophic State Index or other appropriate indices, or (2) the onset of algal blooms.