Editorial: Extreme benthic communities in the age of global change

The sea floor represents the largest solid ecosystem on our Planet. This heterogeneous realm consists of many different features shaped by millions of years of geological and chemical events, and biological and environmental evolution. “Extreme” benthic environments, defined as having abiotic conditions that demand organisms and resident communities be adapted in order to survive and thrive, are widespread and offer many opportunities for investigating the biological responses and adaptations of organisms to “abnormal” life conditions. At the same time, these adapted organisms may give insights into future ecosystem responses, as today's extreme ecosystems can be considered natural analogs of “normal” environments that may change under future climate change conditions. With continuing climate change and increased anthropogenic pressures, very few seafloor areas will remain untouched. Hence the future of the benthos will depend on how organisms, species, populations and communities will respond. Benthic communities are especially useful in long-term comparative investigations such as studying the effects of climate change and other pressures because most of their species are sessile or have low mobility, can be long-lived, and integrate the effects of environmental change over time. In addition, macro-, meio-, and microbenthos of hard and soft bottoms are found in almost any marine environment, including the most hostile or unusual, rendering them ideal to assess the impacts of environmental change and other pressures, as well as effects of multiple, simultaneous pressures. The continuous discovery of communities in extreme environments and the study of their variability, heterogeneity, and their relation to climate change and anthropogenic impacts, are slowly expanding as more evidence and long-term observations become increasingly available.