Kjell Westrheim

Sublethal effects of the water-soluble fraction of Ekofisk crude oil on the early larval stages of cod (Gadus morhua L.)

Abstract Low levels of dissolved oil hydrocarbons are demonstrated to produce sublethal effects on the early cod larval stages. These effects are discussed in relation to larval survival through the first critical stages. Continuous exposure of cod eggs and larvae to 0·05 and 0·25 ppm of the water-soluble fraction (WSF) of Ekofisk crude oil for 14 days caused significant reduction in growth and change in neutral buoyancy. The larvae exposed to 0·25 ppm showed malformation in the foremost part of the head and jaw, which reduced their ability to capture prey organisms at first feeding.

PETROLEUM HYDROCARBONS IN THE NORTH SEA

ABSTRACT Since May 1976, a number of water samples have been collected from various areas in the North Sea. Most of the samples were taken at 1 m depth, but samples were also obtained from depths d...

A flowthrough biotest system for continuous exposure of aquatic organisms to oil hydrocarbons

Abstract A biotest system for continuous exposure of aquatic organisms to the water soluble fraction of oil hydrocarbons is described. A stock solution was prepared in a separate tank, diluted with clean sea water to appropriate test concentrations, and continuously transferred to the exposure aquaria. The system was cleaned every week to avoid bacterial contamination. The hydrocarbon levels of aquaria and stock solution correlated with a coefficient of 0.96. Due evaporation, however, on the way from the stock solution tank to the aquaria, the oil concentration of the aquaria were 40–60 % lower than expected from the dilution ratios. The test solutions also contained traceable amounts of polar components which probably were oxidized compounds of oil hydrocarbon origin. These compounds could be of importance for the evaluation of eventual effects on test organisms.