AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00442

ABSTRACT: Cold-water corals (CWC) have come under increasing pressure from human activities the last decades. Of particular concern in Norway is the potential impact of open-net pen aquaculture on CWC reefs formed by Lophelia pertusa, a threatened and declining habitat. We conducted a 1-year in-situ transplantation experiment and corresponding field measurements of 2 reefs located close to fish farms to elucidate the impacts of particulate organic waste released from the farms on coral colonies. Our study provided new evidence of negative impacts of organic effluents on L. pertusa eco-physiology. After 1 year, both naturally occurring and transplanted corals, at distances ranging from 250 m to 1 km downstream of what would be regarded an average-sized Norwegian fish farm, exhibited depressed metabolic rates compared to corals outside the main depositional footprint of the farms. The metabolic depression impeded energy acquisition, reducing growth and energy reserves by up to 70 and 50%, respectively. No clear threshold for significant biological impact could be detected along a distance gradient. Instead, a gradual decrease in metabolic rates, growth and lipid reserves occurred with increasing modelled sedimentation rate of organic waste from the farm. The strong statistical correlation between measured parameters and sedimentation rates implies that predictions of short-term impact of aquaculture effluents on L. pertusa eco-physiology and possibly CWC reef development may be carried out in the future, with added research. Such predictions would significantly improve the ability of management to make informed decision on the licensing of new farms near CWC reefs.