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HAVKYST-Havet og kysten

Insights into the sensitivity of cold-water communities to drilling mud: enhancing diagnosis and decision-making with emphasis on Lophelia

Awarded: NOK 8.1 mill.

We need to know more about the impact of offshore oil and gas exploration on cold-water corals (CWC). The main objective was to assess the effects of exposure to drill cuttings (DC) on the reef-building CWC Lophelia pertusa. Laboratory experiments were de signed to provide information on important physiological responses for corals based on treatments with varying food availability, how sedimentation from DC particles affected these responses and the consequences for coral fitness. Even with no or little a dded food, L. pertusa survived and grew for long periods (26 weeks). This demonstrated their high tolerance to minimal resource of food added and their likely adaptation to using other food sources from their surroundings. Other measures showed that both mucus and the mucus-associated microbes were modified under the different food regimes. The effects of DC loads from 2 to 52 mg particles/l on coral physiology and other parameters were measured in long-term and short-term exposures. Respiration rate, gro wth and total tissue lipid storage were unaffected during repeated or constant DC scenario exposures. The mucus production was first enhanced, but then decreased with duration of exposure. Prey ingestion measured in clean water was not modified by the DC exposure but polyp activity was. Corals catch food with their polyps.Using time-lapse shooting, we saw that polyp activity increased rapidly following DC exposure over 10 mg/l and remained high throughout the exposure periods. During recovery, the polyp a ctivity returned rapidly to basal levels, but for some corals there was a gradual decrease in activity after high concentration of DC. Sedimentation of DC on coral surfaces, particularly on those lacking their protective tissue (coenosarc), was revealed a nd DC remained on these surfaces even when corals were maintained long in clean water. In the mucus, we found potential microbial markers indicating a change in coral condition. Further, we found a reduction of egg maturation in female coral tissue.,There was also a significant dose-response decrease of L. pertusa larval survival from DC above 0.1 mg/ml. The data from this work will be used to develop a Dynamic Energy Budget (DEB) model for end-users. Even though L. pertusa can apparently tolerate relativ ely high DC sedimentation, the long-term effects of DC reported here warrants the use of precautionary measures for CWC management policy relative to exploration.

Compared to shallow-water reefs, cold-water coral reefs and communities have received political and management attention only recently. These cold-water reefs are biodiversity and biomass hot spots in the deep ocean, and should also be regarded as a natu ral heritage of the past, due to their long lifetimes, that need safeguarding. Oil companies are expanding their search into new remote areas and this exploration releases large volumes of drilling mud (DM) into the sea that may affect these ecosystems. L ittle is known about deep communities sensitivity to DM and so research is desperately needed. Also, oil operators and policy makers should have at hand the means to document and predict how DM may affect these critical habitats. The general objectives ar e to generate specific diagnostic tools to document impairments of health with the main emphasis on Lophelia pertusa coral and to enhance our ability to predict impacts using a biological model. In WP1, we will generate new diagnostic methods based on pro tein signatures and coral-associated microbial fauna (mucus), and gene expression (polyps). A link between early diagnosis and actual effect parameters will allow assessing the ecological meaning and consequence of exposing L. pertusa to drill cuttings. T his will be assessed by growth, oxygen consumption, structural changes, survival and reproductive traits (WP2). A Dynamic Energy Budget (DEB) model existing for corals will be extended with a DM module in WP3 to infer which coral traits are affected by DM and use that to support decision-making and coral management (WP3). Finally, some of the methodological tools used for corals will be adapted to sponges (Geodia baretti) (WP4) revealing important information of these communities. This project will provid e new insights and provide guidelines that can be used by policy makers, contribute to important societal debates and decisions like those related to the oil search in the Lofoten-Vestrålen area of Norway

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HAVKYST-Havet og kysten