Uses of copper include electrical wiring and electroplating, the production of alloys, copper piping, photography, antifouling paints and pesticide formulations. Major industrial sources include mining, smelting, refining and coal-burning industries. Certain of these anthropogenic sources may led to significant concentrations entering the aquatic environment (either directly via sewage or industrial discharges or through atmospheric deposition) but copper will also enter the aquatic environment through natural sources, e.g. from the weathering of or the solution of copper minerals (CCREM 1987).

The ambient levels of copper in seawater remote from source of pollution is estimated to be in the order of 1 µg l^-1 (Mance et al 1984).

Concentrations of copper have been measured in water and sediments as part of the National Monitoring Programme at sites throughout the UK in estuaries and coastal waters (MPMMG 1998). The results of the National Monitoring Programme are summarised in Appendix D. MPMMG (1998) should be consulted for further details.

Grimwood and Dixon (1997) compiled available monitoring data for copper in water, sediments and biota for marine sites of nature conservation importance in England.

As an example of the recorded levels of dissolved copper in the marine environment, the following concentrations have been reported by DETR (1998) for some English estuaries (see tables below) .

Minimum concentration (µg l^-1) of dissolved copper in the water column of some English estuaries (from DETR 1998)

Average concentration (µg l^-1) of dissolved copper in the water column of some English estuaries (from DETR 1998)

Maximum concentration (µg l^-1) of dissolved copper in the water column of some English estuaries (from DETR 1998)

Copper may exist in a natural water system, either in the dissolved form as the cupric (Cu²⁺) ion or complexed with inorganic anions or organic ligands or as suspended particles when present as a precipitate or absorbed to organic matter (Mance et al 1984). It can also be adsorbed to bottom sediments or exist as settled precipitates. The concentration of each of these forms depends on the complex interaction of many variables, including the concentration of copper and hardness, alkalinity, salinity, pH and concentration of bicarbonate, carbonate, sulphide, phosphate, organic ligands and other metal ions. Some of these variables are more relevant to freshwaters (e.g. hardness, alkalinity and pH) than for saltwaters. Complexes formed by copper with natural organic compounds are generally more stable than other metals such as cadmium, lead and zinc.

The high concentrations of particulate matter in most estuaries will facilitate the removal of copper from solution by adsorption to suspended particles which in turn may be deposited and accumulate in sediments. Estuarine sediments are thought to be the most important depositional site for particulate copper transported from rivers, although remobilisation may occur when sediment is disturbed. The remaining dissolved copper in the water column is likely to be present either as an organic complex or as the cupric ion. Copper in the form of the cupric ion is the most bioavailable.

An exhaustive literature review on the toxicity of copper to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (Mance et al 1984, Smith 1993 and Grimwood and Dixon 1997). The most sensitive groups of organisms have been identified.

Mance et al (1984) reviewed data on the toxicity of copper to saltwater organisms. They found that invertebrates exhibited slightly greater sensitivity to divalent copper than fish species tested. There were also indications of the moderation of toxicity in the presence of organic and inorganic ligands. Mance et al (1984) proposed an EQS (for the protection of saltwater organisms) of 5 µg l^-1 (expressed as a dissolved annual average concentration), although higher concentrations may be acceptable where high levels of dissolved organic carbon may reduce the potential for toxicity. This EQS is currently adopted in UK legislation (HMSO 1989). The EQS was established by applying an arbitrary factor of 10 to an effect concentration of 54 µg l^-1 reported in a life-cycle study conducted on the mysid shrimp Mysidopsis bahia.

A review of toxicity data by Smith in 1993 found no evidence to suggest that the EQS should be revised. In this later review, the lowest most reliable data were LOECs of 9 - 10 µg l^-1, reported for growth reduction in the amphipod Allorchestes compressa following 4 weeks exposure. Smith (1993) also reported some effect concentrations below the EQS, although for various reasons (e.g. nominal concentrations, poor controls) these were considered unreliable. Nevertheless, in light of these uncertainties, further research was recommended to validate the proposed EQS.

A more recent review by Grimwood and Dixon (1997) found no reliable toxicity data that indicated higher sensitivity of saltwater organisms had been reported for copper. The authors recommended that the EQS of 5 µg l^-1 (dissolved annual average) was appropriate for the protection of all saltwater life, although where there was concern that the health of communities at sites of nature conservation importance may be compromised as a result of the presence of particularly sensitive species, a lower value may be used as a guideline. However, in the absence of a suitable toxicity dataset, it was not possible to make any recommendations on such a value. This is particularly pertinent considering that if the EQS is lowered any further, the value would be at a level close to background concentrations.

Copper accumulates in sediments and can pose a hazard at concentrations above 18.7 mg kg^-1 according to Canadian interim marine sediment quality guidelines.

As an essential element, copper is readily accumulated by plants and animals. Bioconcentration factors ranging from 100 to 26,000 have been recorded for various aquatic species. However, whole-body concentrations tend to decrease with increasing trophic level. It is believed copper is regulated or immobilised in many species and is not biomagnified in food chains to any significant extent (CCREM 1987).

Potential effects include:

• acute toxicity to invertebrates, and to a lesser extent fish, at concentrations of dissolved copper above the EQS of 5 µg l^-1 (annual average) in the water column;
• accumulation in sediments and can pose a hazard at concentrations above 18.7 mg kg^-1 according to Canadian interim marine sediment quality guidelines.
• bioaccumulation in organisms posing a potential hazard to marine organisms, including fish, birds and Annex II sea mammals.

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