Salmon are potentially susceptible to changes in water quality caused by both natural fluctuations in chemical concentrations and climate variability, as well as anthropogenic introduction of pollutants and changes in land-use patterns.  Non-point-source pollution, including any resulting from agriculture and commercial logging operations, can affect water chemistry in the rivers. 

A 2002 report to the Maine Atlantic Salmon Technical Advisory Committee titled “Water Quality Issues as Potential Limiting Factors Affecting Juvenile Atlantic Salmon Life Stages in Maine Rivers” postulated that acidification from acid rain could be adversely affecting the survival of Atlantic salmon in some Maine rivers.  This report was prepared by an Ad Hoc Committee on Water Quality, made up of scientists from the Atlantic Salmon Commission, Department of Environmental Protection (DEP), University of Maine, Penobscot Indian Nation (PIN), U.S. Fish and Wildlife Service (USFWS), United States Geological Survey (USGS), and Maine Department of Inland Fisheries and Wildlife (MDIFW).

In 2003, the Atlantic Salmon Commission began collaborative efforts with the Senator George Mitchell Center for Environmental and Watershed Research at the University of Maine (GMC) to investigate baseline and precipitation event driven chemical conditions that exist in Maine salmon rivers during different hydrologic conditions.  The Mitchell Center has been involved for over 15 years in watershed research, developing new methods and operating under EPA QA/QC guidelines and reporting requirements.  The Center has been the laboratory for EPA Long Term Monitoring in Maine since 1983.

The first objective of the pH survey was to create three seasonal snapshots of pH related water chemistry in Maine salmon rivers.  This sample scheme allowed for comparisons both within and among watersheds under similar flow and precipitation conditions.  Water samples were collected on the same day in spring, summer, and fall from 74 sites across 13 Downeast and central Maine river systems, including all eight drainages with Endangered population of Atlantic salmon.  Samples were analyzed at the Mitchell Center for closed-cell pH, air-equilibrated pH, acid neutralizing (buffering) capacity (ANC), apparent color, and conductivity.  A cation/anion series was also analyzed for. The spring and fall sample days each coincided with peak flow conditions following significant rain events.  The summer sample occurred at normal low flow conditions.

The project was funded by the Atlantic Salmon Commission.

Spring 2003: May 7

Summer 2003: July 29

Fall 2003: October 28

Spring 2004: April 6

Summer 2004: July 27

Fall 2004: October 26.