Delayed effects of pyrene exposure during overwintering on the Arctic copepod Calanus hyperboreus.

Calanus hyperboreus is the largest copepod and a key species in the Arctic food web. During the spring bloom, C. hyperboreus builds up large lipid reserves, which enable it to survive and produce eggs during overwintering. The ecological effects of oil exposure on overwintering C. hyperboreus are unknown. The present study empirically tested if exposure to the polycyclic aromatic hydrocarbon (PAH) pyrene from crude oil affects the survival, egg production, and hatching success of overwintering C. hyperboreus. We also tested the delayed effects on faecal pellet production and lipid recovery in clean seawater. Direct exposure did not reduce survival and egg production, but reduced hatching success 3-18 times by the end of the exposure period. Remarkably, we documented strong delayed effects of pyrene on faecal pellet production and the recovery of lipid reserves. The current study reveals a high vulnerability of this key species of Arctic zooplankton to oil exposure during winter. Together with our previous study on C. glacialis, we complete the picture of the impact of oil on the largest and most lipid-rich copepod C. hyperboreus, which potentially can have huge ecological consequences for the fragile Arctic marine food web.

Effects of oil spill response technologies on marine microorganisms in the high Arctic.

We studied how exposure to oil spill response technologies affect marine microorganisms during Arctic winter and spring. Microorganisms were exposed to chemically dispersed oil (DISP), in situ burnt oil (ISB), and natural attenuated oil (NATT) in mesocosms from February to May. We subsampled the mesocosms and studied the effects of oil in laboratory incubations as changes in biomass of the major functional groups: bacteria, heterotrophic-nanoflagellates, dinoflagellates, ciliates, pico- and nanophytoplankton, and diatoms over two 14-day periods. In winter, the majority of polycyclic aromatic hydrocarbons (PAHs) remained encapsulated in the ice, and the low concentrations of PAHs in water led to minute changes in biomass of the investigated groups. In spring, however, when the PAHs were partially released from the melting ice, the biomass of many functional groups in DISP and NATT decreased significantly, while the changes in ISB were less pronounced. The overall biomass reduction, as observed in this study, could lead to a disrupted transfer of energy from the primary producers to the higher trophic levels in oil affected areas.

Impact of Pyrene Exposure during Overwintering of the Arctic Copepod Calanus glacialis.

While ongoing warming and sea ice decline threaten unique Arctic ecosystems, they improve the prospect of exploiting fossil fuels in the seafloor. Arctic Calanus copepods can accumulate oil compounds in the large lipid reserves that enable them to cope with highly seasonal food availability characteristic of the Arctic. While spending a significant part of their lives overwintering at depth, their vulnerability to oil contamination during winter remains unknown. We investigated effects of the hazardous crude oil component pyrene on overwintering Calanus glacialis, a key species in Arctic shelf areas. Females were exposed from December to March and then transferred to clean water and fed until April. We showed that long-term exposure during overwintering reduced survival and lipid mobilization in a dose-dependent manner at concentrations previously considered sublethal. After exposure, strong delayed effects were observed in lipid recovery, fecal pellet, and egg production. We showed that 50% lethal threshold concentrations were at least 300 times lower than expected, and that 50% effect thresholds for pellet and egg production were at least 10 times lower than previously documented. Our study provides novel insights to the effects of oil contamination during winter, which is essential to evaluate ecological impacts of Arctic oil pollution.

Effects of oil spill response technologies on the physiological performance of the Arctic copepod Calanus glacialis.

A mesocosm study with oil in ice was performed in Van Mijenfjorden in Svalbard to compare effects of the oil spill responses (OSR) in situ burning, chemical dispersion and natural attenuation on the physiological performance of the Arctic copepod Calanus glacialis. Seawater collected from the mesocosms in winter and spring was used in laboratory incubation experiments, where effects on fecal pellet production, egg production and hatching success were investigated over a period of 14 days. Polycyclic aromatic hydrocarbon (PAH) seawater concentrations were lowest in winter. Brine channel formation in spring resulted in an 18 times increase in PAH concentration in the chemical dispersion treatment (1.67 µg L-1), and a 3 fold increase in the natural attenuation (0.36 µg L-1) and in situ burning (0.04 µg L-1) treatments. The physiological performance of female C. glacialis was unaffected by the PAH seawater concentrations. However, a higher mortality and deformity of nauplii was observed in the chemical dispersion treatment, highlighting the importance of considering secondary effects on next generation in future environmental risk assessment of OSR. This study shows that during the ice-covered period, chemical dispersion of oil spills leads to higher PAH exposure than natural attenuation and in situ burning, with potential consequences for recruitment of Arctic copepods.