Effects of dispersed oil droplets and produced water components on growth, development and reproduction of Arctic pelagic copepods

The RCN-funded project with acronym PWC-Arctic investigated the effects of oil spills and produced water from oil production activities on Arctic zooplankton species, more specifically on copepods of the genus Calanus. These copepods are at the bottom of the Arctic marine food chain and are preyed upon by numerous organisms including juveniles of many fish species. A decline in copepod populations would therefore affect fish production directly. Arctic copepods build up a stock of fat which constitutes raw material for egg production. Their high fat content makes them suitable feed for fish and other animals, but fat also readily assimilates fat-soluble chemicals, and these copepods can filter and ingest small oil droplets. Calanus species can therefore contribute to the uptake of oil components into the food chain. Oil components stored in Calanus fat can be transferred to the eggs, thereby possibly increasing mortality or delaying development and growth of the next generation. Investigating this issue has been one objective of the project. A second objective has been to examine developmental effects of continuous exposure to oil components. Particular focus has been on early development stages and stage transitions which are known to be critical in copepods; hatching to the first naupliar stage, transition from the second to the third naupliar stage, and transition from the last naupliar stage to the first copepodite stage. We suspected that oil components can cause changes in energy budget use such as increasing metabolic rate in these animals, thereby stealing vital energy required to fuel these challenging transitions. A third objective has been to reveal how fast and how much of oil-related substances are taken up into the animals and how long it takes before the substances are excreted again during recovery in clean water. Such data are crucial for the evaluation of effects and for mathematical models describing the effects of oil and oil components on populations and ecosystems. Through close collaboration between the Norwegian University of Science and Technology (NTNU), SINTEF Ocean, BioTrix and the Technical University of Denmark (DTU), we successfully carried out experiments at 3 different locations: at Ny-Ålesund, Svalbard, at Qeqertarsuaq, Greenland, and in Trondheim, Norway. Two Arctic Calanus species were employed in our exposure studies, Calanus glacialis and Calanus hyperboreus, as well as their boreal relative Calanus finmarchicus for comparison. The PWC-Arctic project was developed around 3 hypotheses: (1) elimination of produced water components in Arctic copepods is slow and related to the size of their lipid reservoir; (2) early developmental transition stages are particularly sensitive to produced water exposure; (3) maternal exposure to produced water components results in reduced fecundity and altered development and growth of offspring. Hypothesis 1 was confirmed. Lipid-poor individuals of arctic copepod species take up potentially toxic oil components such as polyaromatic hydrocarbons (PAHs) faster but also excrete PAHs faster than lipid-rich individuals of the same species. This is particularly true for larger, more fat-soluble PAH molecules. Generally, hypothesis 2 could be rejected. We found no profound effects of a mix of selected PAHs on early life stages of C. hyperboreus when exposed continuously to environmentally relevant concentrations. Similarly, few, if any effects of maternal exposure to produced water could be observed on reproduction and offspring growth and development. Hence, hypothesis 3 was also rejected. In conclusion, our findings suggest that produced water and crude oil components have limited physiological effects on arctic Calanus species. However, when in lipid-rich state, these arctic copepods accumulate toxic oil and produced water compounds such as PAHs which can be transferred up the food chain, thereby potentially affecting organisms of higher trophic levels. During the course of PWC-Arctic, several new methods have been developed. We established a handling and treatment procedure for produced water from oil platforms to maintain its original characteristics as much as possible. We also developed a novel method to directly extract lipids from the fat sac of Calanus species to study the distribution of oil and produced water components within the body of a copepod. Moreover, we managed to maintain a population of C. hyperboreus at the facilities of NTNU Sealab for 3 years. Importantly, the data generated by PWC-Arctic allowed us to validate and improve existing mathematical models such as the OMEGA bioaccumulation model. This will improve future predictions of the uptake an elimination rates of oil and produced water components in Arctic Calanus species, and become a useful tool in the sustainable management of copepod and fish stocks in the presence of oil production activities.

Through increased international scientific collaboration between the Norwegian partners (NTNU, SINTEF, BioTrix) and the Technical University of Denmark (DTU), data were generated that allowed us to validate and improve existing mathematical models used as a tool in the sustainable ecosystem based management of copepod and fish stocks in the presence of oil production activities. The results from PWC Arctic are therefore of high value for national and international stakeholders and policy makers that deal with sustainable management of natural resources. In the long term, our findings can be used in the political decision process related to the licensing out of marine areas for oil exploration and exploitation, or the implementation of improved water treatment of effluents from oil platforms, in order to safeguard ecologically and economically important fish stocks as well as food safety.

As the Oil & Gas industry moves north towards the Arctic, it is crucial to understand and be able to predict the potential for detrimental effects of regular (produced water) and accidental oil spills on Arctic organisms, which often are characterized by high lipid content. Organisms with high lipid content are susceptible to accumulation of lipophilic organic components like produced water components (PWC) including oil droplets. Limited data exist on accumulation of oil components in Arctic lipid-rich species which are parameterized so they can be applied as input to models predicting bioaccumulation and body residues as a function of exposure time/concentration. Even less data exist where body residues of oil components are explicitly linked to sub-lethal and delayed effects (e.g. on offspring). Finally, the potential contribution of oil droplets to bioaccumulation has never been studied in Arctic species. The present project aims at i) providing parameterized data on uptake/elimination kinetics and internal administration (partitioning coefficients between lipids and body fluids) for PW components in the Arctic lipid-rich copepods Calanus glacialis and C. hyperboreus; ii) determine effect concentrations for PW components on early life stages of these copepods; and finally iii) assess the potential for maternal transfer of PW components to eggs by exposing females prior to egg-laying and determine potential developmental effects in early stages developing in clean sea water. The parameterized data collected in this project will provide direct input to numerical models aimed at predicting impact of PW on Arctic organisms. The approaches and methodologies used are based on extensive experience from previous toxicological studies on the two Arctic species and in particular the related boreal species Calanus finmarchicus.