Macrofauna Associated With Submarine Groundwater Discharge Sites and a Cold Seep in Svalbard Fjords

ABSTRACT

Submarine groundwater discharge (SGD) is the flow of subsurface water into the ocean. To assess its impact on the Svalbard benthos, the composition of macrobenthos was investigated in relation to sediment physico‐chemical conditions. SGD has been seen to generate seep‐like ecosystems in subarctic locations through the transport of reduced chemicals such as methane. Therefore, we compared the benthos of three Svalbard fjord SGD locations to a Svalbard shelf seep location. However, contrary to our expectations, the SGD locations did not resemble the sampled cold seep. Methane was not detectable in sediment porewater, free sulfide concentrations were low, and diversity and abundance were extremely low, despite shallow water depths (40–117 m). It is possible that the combination of freshwater stress, limited chemosynthetic primary production, and high glacimarine sedimentation rates typical of glacier‐proximal fjord environments together result in an inhospitable environment for many marine benthic taxa at Svalbard fjord SGD locations. As the Arctic warms and glaciers transition from marine‐ to land‐terminating, SGD fluxes may change and the sedimentary overprint on SGD‐related ecological effects may diminish. Whether SGD will eventually emerge as an ecologically relevant process in Arctic fjord systems remains an open question, but one that will become increasingly pertinent as permafrost thaws and glaciers continue to retreat.