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.