Effects of Ekofisk crude oil on an enclosed planktonic ecosystem

Publisher Website
Google Scholar
Abstract
There has been increasing concern about effects of peteroleum hydrocarbons and their derivatives on the highly productive North Sea waters. Possible effects of Ekofisk crude oil on planktonic communities enclosed in medium-scale controlled ecosystems were reported. A 5 mm layer of oil was added to 1 of 2 parallel bags filled before the diatom bloom started in March, and the development followed for 4 wk. Population sizes of bacteria, algae and zooplankton were estimated; chlorophyll .alpha., mineral nutrients and hydrocarbons were analyzed, and primary productivity was measured. In the oil-polluated bag, growth of diatoms and copepods was inhibited, while planktonic bacteria, choanflagellates and tintinnid ciliates increased. Phosphate probably limited the growth of algae and bacteria, and was rapidly reduced to low levels in the bags. The measured concentration of petroleum hydrocarbons and alteration products averaged 470 .mu.g/l. This level may have been acutely toxic to diatoms. The reasons for the bacterial developments observed, their role in hydrocarbon mineralization and the predominance of flagellates and tintinnid ciliates were discussed. Results from bag experiments may provide important clues to fate and effects of oil pollution at sea.