Ship paints may lead to sea otter deaths

Hull paint: Bad for sea otters?

By Environmental News Network staff

(ENN) -- Chemicals used in ship paint to prevent hulls from becoming encrusted with barnacles may have contributed to the deaths of hundreds of sea otters found on the shores of California, according to a researcher at the University of Michigan.

Tests run on the dead sea otters reveal high levels of the anti-fouling agent tributyltin (TBT) and other butyltin (BT) compounds, which, according to Dr. Kurunthachalam Kannan, may have attributed to immunosuppression in the otters and increased their susceptibility to infections.

Sea otters that died of infectious diseases contained greater concentrations of BTs in their tissues than those that died of trauma or unknown causes.

Butyltins are organic tin compounds used in marine ship paints to prevent hulls and docks from becoming encrusted with barnacles.

However, the chemicals have been found to have negative impacts on organisms such as mollusks and gastropods and, more recently, marine mammals such as dolphins.

In 1989, TBT was banned in all states on vessels of 25 meters or less in length. However, because BTs persist in sediment for years, wildlife continues to be exposed to them. In addition, BTs are still used on larger vessels and aluminum-hulled boats.

Large harbors, such as California's Monterey Bay, that handle a plethora of ships greater than 25 meters in length and thus are legally painted with TBT, continue to experience high inputs of BTs.

Since sea otters tend to hang out in harbors, they are particularly vulnerable to this contamination. Sea otters feed on such species as scallops, mussels, rock crabs and sea urchins, which accumulate high levels of BTs. As a result, levels of BT contamination in some sea otters found dead along the California coast were as high as those found in dead finless porpoises from Japan and diseased bottlenose dolphins from the United States.

A paper on the findings, written by Kannan and colleagues, will appear in a forthcoming issue of Environmental Science and Technology.

Copyright 1998, Environmental News Network, All Rights Reserved

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