Forsøksdyr: Sensitivity of polar cod early life stages to a changing Arctic: A study of the impact of petroleum and warming

Godkjenningsdato 19.01.2018

Interest in oil and gas development in the Arctic shelf seas increases the risk of accidental spills. Laboratory studies simulating oil spills have provided important information of sub-lethal effects on organisms. However, there are still important gaps of knowledge related to the sensitivity of Arctic species and especially their early life stages (ELS). Polar cod are the most abundant pelagic fish species in the Arctic and play a key role in the food web. Unlike adult fish, ELS of polar cod found in the surface waters, are most prone to exposure to toxic oil compounds as they lack the ability to swim away from potential oil spills. Polar cod ELS have shown to be sensitive to extremely low levels of the water-soluble fraction (WSF) of crude oil showing reduced growth and deformities (Nahrgang et al. 2016). The present study aims at examining the sub-lethal effects of embryonic exposure to low levels of crude oil WSF on exogenously feeding larvae. Additionally, this experiment will investigate the additional effects of warmer water (i.e. climate change) on the sensitivity of ELS. The knowledge gained in this study will firstly aide our understanding of the potential consequences of an oil spill and/ or elevated water temperature on a key arctic species. Secondly, the data will be used to develop a Dynamic Energy Budget (DEB) model that can be coupled to ecological risk-based modeling frameworks. Ultimately, such a framework is of great interest for stakeholders, such as the industry and environmental managers, in order to predict the potential effects of oil spill on key species and ecosystems.

In January 2018, mature polar cod specimens will be stripped for eggs and sperm and eggs will be fertilized and distributed to 34 conical incubators. Embryos will be exposed through an oiled rock column system, designed to deliver low and exponentially decreasing levels of crude oil WSF to the incubators over time. The highest concentration of hydrocarbons will be in the upper ng/L range and represent environmentally relevant concentrations post oil spill. Exposure will be stopped at the onset of hatching. The experimental design consists of 34 incubators (17 incubators in each temperature regime [0˚C and 3 ˚C]) and containing ca 5000 embryos each, total 160000 eggs. Natural mortality is expected to be high in these life stages and further removal before first feeding will reduce the number of larvae (i.e. a transitional life form) to approx. 200 larval fish per incubator and 6400 in the total experiment. Each temperature will be further divided into three “oil” treatment groups with four replicates per group and a control with five replicates. The two extra control incubators, one at each temperature regime, will provide additional embryos to follow the development without perturbing the main experimental units. The experiment will be carried out until approx. 10 weeks after hatching (120 days after fertilization at 0˚C). Physiological changes in growth, development, behavioral activities (swimming and feeding) and respiration will be studied on exogenously feeding larvae.