Passage Three

In recent years there has been an increasing number of large oil spills. These spills, some of which have occurred directly at the site of extraction and others during transportation, have had in adverse effect on marine organisms. Because of the importance of these organisms in the life cycle, research has been carried out in order to identify more accurately the reactions of these organisms to oil. A recent study has revealed that it is essential to understand that there is not one but rather, at least four possible ways in which oil can affect an organism. First, as a result of an organism’s ingestion of oil, direct lethal toxicity (毒性), that is, death by poisoning, can occur. However, in cases where the effect is less extreme, sub-lethal toxicity occurs. While cellular and physiological processes are involved in both cases in the latter, the organism continues to survive. Second, in some cases, oil forms a covering on the organism. This covering, referred to as coating, can result in smothering, that is, death of the organism due to lack of air. In instances where the effects of coating are less severe, interference with movement and loss of insulated properties of feathers or fur may occur. The third effect of oil on marine organisms is the tainting or contamination of edible organisms. This results from the incorporation of hydrocarbons (碳化氢) into the organism, thus it unfit for human consumption. The final effect which this study has revealed is that of habitual changes. The alterations in the physical and chemical environment brought about by oil spills result in a change in the species composition of a region. The implications of this must recent study are far-reaching. An oil spill in a particular region could critically upset the balance of nature, the total effect only becoming apparent after many years.

The effect of oil spills can be seen______.