Effect of electromagnetic fields from renewable energy subsea power cables on righting reflex and physiological response of coastal invertebrates.

Offshore renewables are expanding, yet more information is required to understand their possible impacts on the environment. Little is known about the effects of Electromagnetic Fields (EMF) from subsea power cables on marine life. This study simulated an EMF of 500 µT, as modelled for an export cable over a rocky shore, where the industry standard cable burial would not be possible. Righting reflex, refractive index of haemolymph/coelomic fluid, and total haemocyte/coelomocyte counts were measured for four coastal invertebrates (Asterias rubens, Echinus esculentus, Necora puber, and Littorina littorea). No significant differences were found in either behavioural or physiological responses. This was the first study to investigate EMF exposure on righting reflex, and the first ever EMF study on edible sea urchins and periwinkles, and only one of a couple for common starfish and velvet crabs. It therefore, provides valuable data for environmental impact assessments, marine spatial planning, and commercial fisheries.

Human impacts on deep-sea sponge grounds: Applying environmental omics to monitoring.

Sponges (Phylum Porifera) are the oldest extant Metazoans. In the deep sea, sponges can occur at high densities forming habitats known as sponge grounds. Sponge grounds can extend over large areas of up to hundreds of km2 and are biodiversity hotspots. However, as human activities, including deep-water hydrocarbon extraction, continue to expand into areas harbouring sponge grounds, understanding how anthropogenic impacts affect sponges and the ecosystem services they provide at multiple biological scales (community, individual and (sub)cellular levels) is key for achieving sustainable management. This chapter (1) provides an update to the chapter of Advances in Marine Biology Volume 79 entitled "Potential Impacts of Offshore Oil and Gas Activities on Deep-Sea Sponges and the Habitats They Form" and (2) discusses the use of omics as a future tool for deep-sea ecosystem monitoring. While metagenomics and (meta)transcriptomics studies have contributed to improve our understanding of sponge biology in recent years, metabolomics analysis has mostly been used to identify natural products. The sponge metabolome, therefore, remains vastly unknown despite the fact that the metabolome is a key link between the genotype and phenotype, giving us a unique new insight to how key components of an ecosystem are functioning. As the fraction of the metabolome released into the seawater, the sponge exometabolome has only just started to be characterised in comparative environmental metabolomic studies. Yet, the sponge exometabolome constitute a unique opportunity for the identification of biomarkers of sponge health as compounds can be measured in seawater, bypassing the need for physical samples which can still be difficult to collect in the deep sea. Within sponge grounds, the characterisation of a shared sponge exometabolome could lead to the identification of biomarkers of ecosystem functioning and overall health. Challenges remain in establishing omics approaches in environmental monitoring but constant technological advances and reduction in costs means these techniques will become widely available in the future.

Potential Impacts of Offshore Oil and Gas Activities on Deep-Sea Sponges and the Habitats They Form.

Sponges form an important component of benthic ecosystems from shallow littoral to hadal depths. In the deep ocean, beyond the continental shelf, sponges can form high-density fields, constituting important habitats supporting rich benthic communities. Yet these habitats remain relatively unexplored. The oil and gas industry has played an important role in advancing our knowledge of deep-sea environments. Since its inception in the 1960s, offshore oil and gas industry has moved into deeper waters. However, the impacts of these activities on deep-sea sponges and other ecosystems are only starting to become the subject of active research. Throughout the development, operation and closure of an oil or gas field many activities take place, ranging from the seismic exploration of subseafloor geological features to the installation of infrastructure at the seabed to the drilling process itself. These routine activities and accidental releases of hydrocarbons during spills can significantly impact the local marine environment. Each phase of a field development or an accidental oil spill will therefore have different impacts on sponges at community, individual and cellular levels. Legacy issues regarding the future decommissioning of infrastructure and the abandonment of wells are also important environmental management considerations. This chapter reviews our understanding of impacts from hydrocarbon exploration and exploitation activities on deep-sea sponges and the habitats they form. These impacts include those (1) at community level, decreasing the diversity and density of benthic communities associated with deep-sea sponges owing to physical disturbance of the seabed; (2) at individual level, interrupting filtration owing to exposure to increased sedimentation; and (3) at cellular level, decreasing cellular membrane stability owing to exposure to drill muds. However, many potential effects not yet tested in deep-sea sponges but observed in shallow-water sponges or other model organisms should also be taken into account. Furthermore, to the best of our knowledge, no studies have shown impact of oil or dispersed oil on deep-sea sponges. To highlight these significant knowledge gaps, a summary table of potential and known impacts of hydrocarbon extraction and production activities combined with a simple "traffic light" scheme is also provided.