The Effects of Copper on Salmon - A Review of the Scientific Literature

Posted 8.23.07 by Renewable Resources Coalition

Copper (Cu) is an element which is essential to healthy metabolism and growth of all living organisms, including fish, although fatal Cu deficiencies remain undocumented for any aquatic species (Sorensen 1991,Carbonell and Tarazona 1994, Eisler 2000). Cu is highly toxic to aquatic organisms and may cause irreversible harm at concentrations just over that required for growth and reproduction (Hall et al. 1988, Eisler 2000, Baldwin et al. 2003). The U.S. Environmental Protection Agency (1980) and a recent review by Eisler (2000) indicates toxicity of Cu to fish and their food chains depends on many factors including:
• Cu species and concentration;
• water quality including: pH, temperature, hardness, salinity, suspended solids, and organics;
• Cu interactions with other local elements;
• Organisms, age, size and species of affected fish and prior Cu exposure

Recent large scale industrialized mining proposals in Alaska’s pristine salmon-rich watersheds instigated this review. Here, highlights of published scientific literature are presented with an emphasis on potential effects of increasing bioavailable Cu to salmon and their freshwater food chains. In Alaska, the state Cu water quality standard for protection of freshwater species is 9 parts per billion (ppb) calculated on 100 mg/L hardness (CaCO3) while the standard for drinking water is 1,300 ppb (Alaska Department of Environmental Conservation 18 AAC 2006).

Sublethal effects to fish and the aquatic food chain can occur at less than 9 ppb Cu (Eisler 2000) and data to accurately assess ecosystem impacts from increased Culoads are lacking. The following facts are important to consider relative to developments that will increase bioavailability of Cu to freshwaters:

1. Toxicity tests to determine lethal levels and sublethal effects of Cu and other heavy metals are lacking for most Alaskan fish species, all of which are used for subsistence.

2. Many species of freshwater plants and animals die within 96 hours at waterborne concentrations of 5.0 to 9.8 ppb and sensitive species of mollusks, crustaceans and fish die at 0.23 to 0.91 ppb within 96 hr (Eisler 2000)

3. There is a lack of information on how multispecies aquatic food chains are affected by Cu and how aquatic organisms cycle Cu through aquatic ecosystems.

4. Numerous elements in addition to Cu, such as zinc, cadmium, mercury, iron, lead, aluminum, and selenium are released at hard rock mining sites in a unique “cocktail”; such effects of multiple element releases are not well studied nor understood and effects may be additive, synergistic, or antagonistic. Federal and State water quality limits for metals do not take these effects into account.

5. The numerous parameters affecting Cu toxicity dictate site and species specific studies to determine acceptable exposure levels in the specific ecosystems of interest.

The Effects of Copper on Salmon - A review of the scientific literature

by Dr. Carol Ann Woody