Can seepage of CO2 stored in sub-sea geological formations disrupt important behavioural traits in benthic invertebrates?

There is on-going technological development of methods to detect and accurately measure CO2 seepage from sub-sea geological storage. This project aims to provide important information for interpretation of such data to enhance its value with respect to de termining potential impacts from leakages on marine invertebrates that live in association with the sea bed overlying these storage areas. The project is evaluating the potential effects of CO2 seepage on the behavioural responses of representatives of tw o key benthic invertebrate groups (bivalve molluscs and crustacean decapods) and is expected to add significantly to the field of knowledge on the extent of impact from such leakages. A key step in this process has been the establishment of the threshold responses of the test organisms to indicate whether leakage events will have a serious impact on marine fauna both close to and more distant from a leakage source. The endpoints that are being examined are high level biological processes such that signif icant alteration away from normal predictable patterns would indicate an ecologically significant change. The central North Sea has had an active sub-sea storage system in use at the Sleipner site since 1986 and the region is also likely to host further s torage sites in the future. For this reason it serves as a suitable case study for examination of the potential effects of CO2 leakage. Species that form part of the benthic fauna found within the central to northern North Sea area are being used within t he project. An exposure system, which has already been successfully used in the laboratory at IRIS, has been used once again to deliver stepwise increasing volumes of CO2 gas that can ultimately reduce the seawater pH to 6.0. The system aims to mimic pote ntial seepage conditions in the field to determine if acute and or chronic exposure at these levels causes changes in behaviour of the exposed animals that could lead to reduced fitness or migration away from affected areas. The project is now reaching the end of its two year life and data analysis is continuing. The main findings so far indicate that the bivalve mollusc used, the Icelandic cyprine (Islandica arctica), responds with changes in its valve gape behaviour once the pH has fallen to 6.2. Fol lowing chronic exposure to this level of pH over 7 days, the behavioural response persisted for 1-2 days and then returned to the pre-existing level for the remainder of the exposure. There was no mortality associated with the tests either during the expo sure or for some weeks after and no difference could be detected between exposed and control animals in their ability to burrow into sediment immediately following the exposure. The activity patterns of the brown shrimp (Crangon crangon) have also been studied following their exposure to reduced pH seawater conditions and these experiments are now coming to a conclusion. Research carried out both by IRIS and LimCo international, an international partner in the project, have produced results that indica te that the shrimp respond with altered activity patterns when the seawater pH drops to around 7.0. This increased activity may indicate an attempt by the shrimps to migrate away from the reduced pH area. Shrimp continuously exposed to this reduced pH fo r 5 days, continued to show signs of disruption in their patterns of activity throughout the exposure, compared against control shrimp simultaneously maintained under normal seawater pH levels. Detection of chemical signals in seawater is a vital functi on for crustaceans, be it for finding partners for mating or for locating food. Experiments have been conducted by the University of Hull, an international partner in this project, to investigate whether reduced pH seawater conditions can affect this abi lity in the shore crab (Carcinus maenas). Results have shown that detection of sex pheromone was significantly reduced in crabs maintained in seawater with a pH of 7.7. This is a relatively small reduction in pH to produce such an important effect and ex periments are continuing to further establish the relationship between pH and sensory detection in these animals.

There is ongoing technological development of methods to detect and accurately measure CO2 seepage from sub-sea geological storage. This project aims to provide important information for interpretation of such data to enhance its value with respect to det ermining potential impacts from leakages on marine vertebrates that live in association with the sea bed overlying these storage areas. The project will evaluate the potential effects of CO2 seepage on the behavioural responses of representatives of two k ey benthic invertebrate groups (bivalve molluscs and crustacean decapods) and is expected to add significantly to the field of knowledge on the extent of impact from such leakages. A key step in this process will be the establishment of the threshold resp onses of the test organisms to indicate whether leakage events will have a serious impact on marine fauna both close to and more distant from a leakage source. The endpoints to be examined are high level biological processes such that significant alterati on away from normal predictable patterns would indicate an ecologically significant change. The central North Sea has had an active sub-sea storage system in use at the Sleipner site since 1986 and the region is also likely to host further storage sites i n the future. For this reason it will serve as a suitable case study for examination of the potential effects of CO2 leakage. Species that form part of the benthic fauna found within the central to northern North Sea area will be used within the project. An exposure system, which has already been successfully used in the laboratory at IRIS, will be used to deliver a stepwise increasing volume of CO2 gas that will ultimately reduce the seawater pH to 5.0 units. The system will aim to mimic potential seepa ge conditions in the field to determine if acute and or chronic exposure at these levels causes changes in behaviour of the exposed animals that could lead to reduced fitness or migration away from affected areas.