Response of deep-water sponge fauna to oil drilling discharges: linking molecular and biological parameters

The RESPONSE project aimed at evaluating the response of deep water sponge fauna to particulate oil drilling discharges, and to initiate the development of new tools (biomarkers) for exposure based studies to link molecular and biological stress responses. To achieve this, the RESPONSE project brought together key national and international scientific experts in "sponge biology and ecology" and "ecotoxiciology research". Using a number of controlled laboratory studies, the cold deep-water sponge Geodia barretti was exposed to different sediment types (i.e. natural sediment, simulated drill cuttings ? crushed rock, bentonite and barite) at ecologically relevant concentrations between 10 and 500 mg l-1. G.barretti individuals were exposed to these different sediment treatments over different time periods, from 4 hours to 50 days, and in some experiments were given the opportunity to recover. From the results of the different experiments, the concentration sensitivity appears to be set at around 10 mg/L with clear shifts in pumping behavior, cellular integrity, anti-oxidant stress and metabolism. Responses measured are highly dependent on sediment type, with a reduced capacity to recover (when presented with a 30 day recovery period) when exposed to barite sediments compared to the other sediment types. The results obtained are highly topical for the petroleum and gas industry, but could also be extrapolated to the mining industry and bottom trawling activities. Follow on projects should build on these experiments through multi-stressor studies, focusing on the interactive effects of suspended sediments and climate stressors (Temperature and ocean acidification) and other environmental changes (hypoxia, salinity and food availability). Furthermore, field based studies in and around petroleum exploratory drilling should also be considered to compare back to existing laboratory studies.

Drilling fluids (DF) and drill Cuttings (DC) are the largest volume of particulate wastes discharged directly from oil and gas drilling activities in marine habitats. These particulate wastes, negatively impact the biology and ecology of different benthic fauna, however, their impacts on marine sponges remain poorly investigated. This is surprising given that sponges are important components of benthic communities (i.e. in terms of diversity and biomass) in areas of drilling activity and they are also sen sitive to changes in their ambient environment. More research is needed to investigate the effects of regular discharges of DF and DC on deep-water sponge fauna and to develop tools and methodologies to improve methods of detection for exposure assessmen ts. Using the model sponge Geodia barretti, this project will develop and link molecular (i.e. gene expression and metabolomics) and biological (i.e. physiological and histopathological) markers of stress with specificity to exposure to suspended DC and DF. These biomarkers will be developed for different exposure concentrations, durations and frequencies, and will provide solid tools to measure biological effects and stress levels of sponges exposed to DF and DC in the field. Threshold values for conce ntration, duration and frequency of exposure of DC and DF on sponges will also improve current modelling tools for environmental risk assessment of offshore oil drilling activities. Strengthening this knowledge is vital in developing effective management strategies to mitigate environmental and ecological impacts to marine benthic habitats. Furthermore, this project will measure key physiological and biological parameters of deep-water sponges, which is a currently lacking in the literature. This increa sed knowledge is important to enhance the awareness of the sensitivity and importance of these marine benthic organisms and the need to manage them more effectively.