Wildlife Diseases, Die-offs and Declines in U.S. Waters

by Bruce McKay

Originally published in Sea Technology 41(1): 97 (2000).

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The recovery of more than 70 dead bottlenose dolphins along Florida's far west coast this past autumn was another in a remarkable series of disturbances involving the nation's marine wildlife. Earlier in the year some 225 harbor porpoise carcasses were found along mid-Atlantic shores, and an estimated 300 gray whales died along those of the Pacific. California sea otters and northern Puget Sound orcas continued their mysterious decline. A large-scale sea urchin die-off occurred in Maine waters, while a disease in lobsters from Long Island Sound prompted calls for the area to be declared a federal disaster due to the projected loss of $30-50 million to the local economy.

Indeed, over the past few years there has been a litany of die-offs, plummeting populations, and novel disease events in U.S. marine waters -- involving everything from coral and seagrasses to sea turtles and whales. For example, black abalone populations throughout southern California have been decimated by 'withering syndrome', a disease which first emerged in abalone in the Channel Islands during the mid-1980s. The disease has now struck red abalone. New diseases have been noticed in northern fur seals (Alaska), in sea otters (California), and in manatee (Florida), while die-offs of bottlenose dolphins, such as the event late last year, have become commonplace in the Gulf of Mexico. Green sea turtles in Hawaii and Florida continue to suffer from an epidemic of fibropapillomas, a disease characterized by grotesque external tumors. Virtually unheard of before 1985, this disease has just recently appeared in loggerhead and olive ridley sea turtles in the Caribbean.

There have been precipitous declines in numbers of Steller's sea lion, harbor seal, and sea ducks in Alaska, stretching back for years. Monk seal numbers in Hawaii continue to fall. Coral diseases are substantially reducing reef cover and biodiversity in parts of the Florida Keys. Disease was noted at 26 (out of 160) coral monitoring stations in the Keys in 1996; by 1998, however, 131 stations had diseased coral while the number of species affected rose from 11 to 31. A host of new coral diseases have emerged there as well. Meanwhile, the first reported epidemic of mycobacterium-induced sores in wild striped bass -- as high as 40 percent of caught fish in some areas -- is bedeviling the Chesapeake Bay. This disease is usually found in fish farms. New diseases have just recently been discovered in salmon and lobster in Maine.

There are many more such examples. However, very little is typically known about the underlying environmental changes and conditions that may be at the heart of these events. This should be cause for concern simply because environmental problems are revealed through their effects on wildlife. Co-occurring as they do with the well-documented issues of eutrophication and "dead zones" from nutrient pollution, expanding harmful algal blooms or "red tides", declining fish populations, burgeoning coastal development, increasing numbers of introduced species -- and their pathogens -- wide-scale chemical pollution and now, apparently, a changing climate, suggests an important human component.

Of course, disease and strandings, fish kills and other die-offs, and population fluctuations in wildlife can be entirely natural and may result from normal disease processes, toxic algal blooms, or climatic conditions such as El Nino. Increasing awareness, research, and numbers of people along our coasts also mean that such events are much more likely to be reported.

Yet the sheer number, uniqueness and seriousness of recent disturbances point to other factors.

Pesticides and industrial chemicals can induce disease and reproductive impairment in wildlife, and fertiliser run-off, sewage discharge, and nitrogen emissions can stimulate the development or increase the severity of harmful algal blooms. Ballast water discharge and aquaculture translocations have introduced pathogens and toxic phytoplankton to areas where they did not previously exist. Dams and water diversions alter salinity levels and water temperatures in estuaries thus stressing resident flora and fauna. Overfishing of much of the nation's fish is increasing pressure on fish-eating mammals and birds. Climate change can lead to increased water temperatures allowing various aquatic pathogens to thrive or expand their range.

Yet with mounting evidence of an increase in marine wildlife diseases, die-offs and declines, little attention is being paid to their overall significance. Attempts to gain better understanding are often piecemeal, species- or event-specific, and divided among government agencies and research institutions. Nearly all are woefully under funded. Large-scale patterns are most certainly being missed and our ability to recognise, predict -- and effectively respond to -- marine environment change is sorely lacking.

Part of what is needed is federal leadership -- notably in terms of technical support and research, rapid response protocols and contingency plans, and effective nationwide monitoring programs -- such as is generally in place for agricultural crop and livestock diseases. Nonetheless, the effects of human activity on our coastal ocean waters are profound and probably growing. Yet more than enough is now known to begin acting accordingly and with precaution. Changes in agricultural practices involving massive reductions in fertilizer and pesticide use are required. Coastal wetlands as natural filtering bodies need to be protected and restored. Our use of fossil fuels needs to be greatly reduced and clean, renewable energy sources must be brought on line. Closed-loop industrial processes and the phasing out of persistent organic chemicals are likewise necessary. The onslaught of alien species arriving via ballast water must be halted with efficient ballast cleaning operations at ports. Our fisheries require management and habitat protection programs aimed at restoring depleted populations, while a system of marine protected areas needs to be developed. And while some of these directions may appear daunting, it may be worthwhile considering, after all, what is at stake in terms of public health, fisheries and coastal economies, and our natural heritage. It should now be the time to focus attention on what our marine wildlife is telling us -- and the important task of ocean protection.