Benthic Communities in the Polar Night

Scientists generally believe that the products of photosynthesis raining down from above support the community of organisms living on the ocean bottom deeper than light can reach. Consequently, we have assumed that during the Polar Night, when there is insufficient light for photosynthesis, these communities enter a stage of torpor, and little occurs that is significant for the ecosystem. We review our limited knowledge of bottom-dwelling organisms and communities during the Polar Night, and while much remains unexplored, unexpected activity at many levels of the benthic system puts previous beliefs of a general dormancy into question. Studies have revealed that some animals grow and reproduce during the Polar Night, presumably relying on stored resources or on detrital and advected sources of nutrition, and some species of marine macroalgae even grow during this dark period by using stored energy. We conclude that some processes occurring during the Polar Night may be important for understanding Arctic marine ecosystems and the organisms that comprise them. Furthermore, we suggest that changing food supply and increased winter metabolic requirements caused by warming temperatures make it difficult to predict the impact of climate change on these communities. Scientists need to learn more about the basic biology of Arctic organisms (life-history strategies, food sources) to more fully understand their ecosystem roles throughout the year. Furthermore, they must take advantage of opportunities to use new technologies and observation platforms to conduct year-round studies of Arctic benthos. Only then will we understand the importance of this long dark period in driving the structure and functioning of marine benthic communities.