Biological effects of water soluble fraction of crude oil on the Arctic sea ice amphipod Gammarus wilkitzkii

With increasing petroleum related activity in the Barents Sea and the subsequent risk of accidents, there is a demand for knowledge about the effect of oil pollution in Arctic ecosystems. In the present study, the sea ice amphipod Gammarus wilkitzkii was exposed to a water soluble fraction (WSF) of oil in two experiments, using a rock column system. First, three groups of adult females were exposed for 36 days for control (n=9), low dose (n=10) (initial and final oil concentration: 14, 115 and 120 g/l) and high dose (n=10) (initial and final oil concentration: 78, 764 and 395 g/l). Total oxyradical scavenging capacity (TOSC), malondialdehyde (MDA), catalase activity (CAT), respiration rate and mortality were measured. In the second experiment, moulting rate was measured in immature individuals of two groups, control (n=10) and exposed (n = 20), over 113 days. No mortality was observed in either of the experiments. There was a dose-related significant increase in respiration rate (40.69 (+/- 22.82), 55.63 (+/- 20.98), 94.57 (+/- 22.80)) mg O-2 h(-1) g ww(-1) in control, low dose and high dose, respectively. A higher MDA level was detected in the low dose group (25.04 (+/- 6.00) nmol g(-1) of tissue) compared to both control (20.44 (+/- 2.62) nmol g(-1) of tissue) and high dose groups (20.93 (+/- 4.79) nmol g(-1) of tissue). Likewise, the low dose group had the highest value of TOSC towards hydroxyl (727.74 (+/- 475.58), 1157.58 (+/- 278.62), 1067.30 (+/- 369.22) TOSC unit value mg-1 of protein for control, low and high dose, respectively). Although no difference in the catalase activity between control and exposed groups was detected, higher activity was measured at 0 degrees C (average: 248 mol(-1)min(-1)mg(-1) of protein) than at the standard temperature for catalase measurement of 25 degrees C (average: 140 mol(-1)min(-1)mg(-1) of protein), indicating a need to optimise the standard operational procedure when working with Arctic organisms. No effect of WSF exposure on moulting rate was detected. In conclusion, little mortality was observed during the experiments, indicating some degree of tolerance levels. However, the biomarker results indicated sub-lethal effects in G. wilkitzkii after exposure to WSF.