The most likely type of slick of human origin in coastal waters and along beaches is oil, or an oil based product, released in bilge water from boats or spilled down stormwater drains. More rarely, an oil slick might be caused by a shipping accident or accident at an offshore oil well. To date the occurrence of oil slicks in Territory waters has been rare, due partly to the low level of shipping and mining activities. While the amount of activity and therefore the risk of oil spills is increasing, cooperation between relevant groups has resulted in the development of oil spill prevention and contingency plans for those areas most at risk. These plans have been prepared for Darwin Harbour , and for the offshore oil exploration industry in the Timor Sea and Territory coastal waters.
Oil slicks are relatively easy to distinguish.
Depending on the type and amount of oil and the period of time the oil has been floating on the water, the slick may be a filmy brown or rainbow coloured sheen, it may be thick and frothy or sticky, or may have broken up into tan coloured balls. There is almost always an oily smell and feel to an oil slick. Which Occur Naturally A more likely cause of slicks in Territory waters is natural. Algal Blooms Many species of marine algae occur as single cells or small clusters of cells which float suspended in the water column and are referred to as planktonic algae. Under certain conditions some species are able to reproduce so rapidly that the accumulation of cells form rafts or slicks on the water surface and these may be washed ashore by prevailing winds.