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1. cleaning up the seas
Managing the OceansPosted: 10 Oct 2000
1. Cleaning up the seas
by Bruce McKay and Kieran Mulvaney
Coastal seas and the wider ocean have become the sink for thousands of chemicals and heavy metals with widespread but uncertain impact on marine wildlife. Here, Bruce McKay and Kieran Mulvaney provide a fresh assessment of the causes, effects and future of marine pollution.
Around the world, some 70,000 substances are now in use as industrial compounds, cleaning agents, pesticides, fertilisers, pharmaceuticals, food additives and for other purposes. According to rough estimates by the US National Research Council, 1,000 new chemicals are introduced into the environment each year.
Chemical discharge into the Mersey
© Robert Brook/The Environmental Picture Library
Global levels of other chemicals already in wide use are expected to increase; and while some contaminants are being phased out, their replacements are being found at environmentally-deleterious levels in various coastal regions.
Though rigid scientific proof is often lacking, chemical groups such as the organochlorines such as DDT, toxaphene and PCBs, polycyclic aromatic hydrocarbons (PAHs), dioxins and furans, and organotins - all ubiquitous in marine environments - have been implicated in a tremendous variety and number of marine wildlife impacts, increased levels of many heavy metals.
A few examples include declines in the population of some European harbour seal populations due to PCBs; cancer and various chronic diseases in St. Lawrence beluga whales from a wide variety of contaminants; decline in Alaskan spectacled eiders (a sea duck) from lead poisoning; malformation, chromosome abnormalities and mortality of fish eggs and larvae in the mid-west Atlantic; increased numbers of mortalities in disease-related marine mammal die-offs, including Mediterranean striped dolphins and US coastal bottlenose dolphins. Also affected have been white tailed sea eagles along the Baltic Sea whose numbers have declined due to various organochlorines; Baltic Salmon which are thought to have developed M-74 disease syndrome at least in part, due to dioxins and the Hawaiian blackfooted albatross which has been affected by the fishery bycatch impacts of PCBs, dioxins and furans.
Oiled gentoo penguin, South Georgia
© Roger Grace/The Environmental Picture Library
Meanwhile, oil spills and chronic oil pollution - as much as 25 million barrels are estimated to enter the ocean each year - continue, for example, to kill many thousands of seabirds; one study estimated that more than 42,000 Magellanic penguins alone die from oil pollution annually along the Argentinean coast.
One of the most pressing threats to the integrity of coastal ecosystems is over-enrichment by nutrients, primarily nitrogen, from the run-off of agricultural fertilisers, emissions from fossil fuel combustion, various land-use changes, and from the discharge of human and animal wastes. Many estuaries now receive over a thousand times more nutrients per unit surface area than heavily fertilised agricultural fields thus making them the most heavily fertilised ecosystems on the planet.
Excess nutrients and changes in nutrient balances have led to the growing eutrophication of numerous coastal waters worldwide including, for example, Chesapake Bay, the northern Adriatic Sea, the North and Baltic Seas, and the Black Sea. The partial or complete removal of dissolved oxygen from the water column (anoxia/hypoxia), a consequence of eutrophication, has had a wide range of effects including the mass mortality of benthic organisms, die-backs in seagrass meadows, and declines in biodiversity, and is considered to be an important contributory factor in the long-term decline of many coastal fisheries and to overall changes in the structure and function of estuarine and coastal environments.
In addition, the remarkable increase in the frequency, magnitude and geographic extent of algal blooms in numerous coastal environments, and the emergence of noxious and harmful species at unprecedented abundance, has in many cases co-occurred with elevated nutrient inputs and eutrophication. One example is Hong Kong, where increases of sewage discharge and nutrient levels in local waters have been matched by the progressive increase in blooms in the region, from three in 1977 to 36 by mid-1988. The cause of recurrent, massive fish kills since the 1980s along the North Carolina coastal waters of the United States was traced to potent toxins from what was previously an unknown organism - Pfiesteria piscicida - which researchers suspect may have been stimulated into ecological prominence by elevated nutrient influxes from human sewage and hog farms.
Any increase in harmful blooms or toxicity events obviously increases the potential for their often disastrous effects including human illness and death, spectacular fish kills, closed shellfish beds, and severe economic loss. Recent mass mortalities of marine mammals and seabirds, including those that are endangered such as the West Indian manatee, humpback whale, Hawaiian monk seal, and brown pelican, have also been attributed to toxic algae, although the relationship of these events to human activity, if any, is unknown.
Indeed, much remains unknown or unproved. Determining cause-and-effect relationships involving a wide range of pollutants on the one hand and changes in species populations and ecosystem function on the other is confounded by the tremendous complexity and natural variability of marine environments and the effects of other, now global-scale, human impacts. Fisheries, altered freshwater influxes as a result of dams, the onslaught of introduced species, increased UV-B radiation, and coastal habitat alteration and destruction, all exact tremendous environmental responses, themselves also poorly understood. Likewise, there is great uncertainty over the current or future effects of climate change.
Virtually nothing is known about the vast majority of marine species; most have even yet to be described. And there is a paucity of historical data to serve as a comparative baseline between past, pristine conditions and those of the altered present. In the United States, information on chemical toxicities to support risk assessments is available for less than 2 per cent of all the chemicals in commercial use. Even less is known of the interactive or cumulative effects of complex suites of contaminants, the typical environmental scenario.
The known and suspected environmental and human health effects of contaminants, the many uncertainties associated with them, and dramatic environmental "surprises" such as endocrine disruption or ozone layer depletion, have prompted numerous calls for a precautionary approach in dealing with the natural environment. This radical yet common-sense perspective advocates the prevention of damage in the first place, action before scientific proof on deleterious effects is established, and the reversal of the burden of proof onto the potential industry or regulatory body to show that the product/activity will not have a negative environmental impact.
Clean-up after Exxon Valdez oil spill, Alaska
© Vanessa Vick/Science Photo Library
Progress in some areas is being made. For example, the Ministerial Declaration of the Fourth International Conference on the Protection of the North Sea in 1995 stated that the guiding principle would be a precautionary approach and that this implies "continually reducing discharges, emissions and losses of hazardous substances thereby moving toward the target of their cessation within one generation (25 years) with the ultimate aim of the concentration in the environment near background values for naturally-occurring substances and close to zero concentrations for manmade synthetic substances."
Sustainability philosophies such as the 'Natural Step', gradually being applied in Sweden, or 'Clean Production' are being developed which move beyond the conceptual frameworks associated with chemical risk assessments, environmental assimilative capacity and pollution control (rather than prevention) as characteristically advocated by the status quo. For example, Clean Production Action, a UK-based advisory group, promotes consumption and production directions that question the necessity of a specific product in the first place while taking into account its full life-cycle environmental impact and its social benefits and costs. Such an approach helpfully asks questions such as: will the product end up as marine debris?
Yet change will not come easily. Much of humanity has developed a profound dependency on nitrogen-based fertilisers, fossil fuels, pesticides, and a host of other environmentally damaging goods and services. The causes of marine environment pollution, as in other global change phenomena, are the result of a complex mix of historical, cultural and psychological, and economic and political parameters with decision-making often in the hands of people and organisations who know little about the issues or who stand to gain from inaction. As individuals, notably for those of us in the 'developed' world, it would seem necessary to continuously strive to reduce our own ecological footprint while keeping alert for opportunities to promote public action.
Bruce McKay is the senior researcher for Sea Web: A Project of the Pew Charitable Trusts. Kieran Mulvaney is an environmental writer living in Washington and author of Whaling Diaries.