Summary of the Workshop on Ecological Effects of Hydrocarbon Spills in Alaska

Résumé

In any study of the effects of the introduction of an organic compound, such as oil, into a particular environment, such as the Arctic we should, at the outset separate two basic responses: the responses of those organisms (largely bacteria and fungi) to whom the oil is a nutrient to be attacked and eventually decomposed, from the responses of those organisms (largely plants and animals) to whom the oil is a physical and chemical agent of potential toxicity to be tolerated with varying degrees of success. ... both groups really function as mixed populations that exhibit dynamic responses to environmental changes, such as oil spills, but our perception of the effects of these changes is largely population-oriented in the decomposers and species-oriented among higher organisms. ... The actual removal of oil from the Arctic environment depends on a combination of physical weathering and microbial decomposition .... Thus a general principle of microbial ecology is sustained here in that the addition of an organic material to a system stimulates the development of a specific microbial population capable of using that material as a nutrient. The rate of this decomposition process is of maximum importance and it obviously depends on the robustness of the initial microbial population and on nutrient limitation. ... One of the special problems of the Arctic is the very slow rate at which these decomposer populations develop significant activities ... and accessory nutrient supplementations may be required to achieve acceptable rates of hydrocarbon decomposition. A very important facet of oil degradation is the relative rates at which the different components of oil are broken down by bacteria and fungi. ... There are many reasons why oil may be toxic to animals .... Oil appears to constitute a fairly general "contact herbicide" whose direct application is most often toxic to plants. ... plants vary in their sensitivity to this "contact herbicide" and sensitivity mapping ... and bioassays of the sensitivity of specific plants under field conditions are very valuable. ... oil exerts direct and immediate toxic effects on certain plants and animals, in both aquatic and terrestrial systems, and ... more subtle toxic effects are often detected only with the passage of time. Whole populations react in the expected manner in that oil-resistant forms proliferate and then lead the recolonization of the system as the toxic hydrocarbons are removed by weathering or by microbial decomposition. The extent of severe ecological damage from oil spills is, therefore, a function both of the oil-sensitivity of the plant and animal populations and of the rates at which oil is removed by human intervention, weathering or microbial decomposition. ... In the decomposition studies perhaps the most promising development is the advent of rate studies which should be extended to cover the major classes of oil constituents and a very wide variety of ecological systems. ... In many cases it is clear that microbial decomposition, aided by fertilizer application ... will reduce the level of hydrocarbons below the toxic level for the indigenous plants and animals at a satisfactory rate. ... This entire program, with its emphasis on rates of microbial decomposition and on differential sensitivity of both species and populations of higher organisms, is basically well designed and offers a scientific basis for the development ... [of] rational oil spill clean-up policies in the sensitive Alaskan ecosystem.