About this Research Topic
The largest ecosystem on this Planet is the sea floor. This realm is not homogeneous, it consists of many different topological features and has been shaped by millions of years of geological, chemical and other environmental influences. Extreme benthic environments cover more than 50% of the Earth's surface and offer many opportunities for investigating the biological responses and adaptations of organisms to stressful life conditions. Extreme marine environments include mangroves, submarine caves, Polar ecosystems, hypersaline areas, hypoxic/anoxic environments, hydrothermal vents, cold seeps, carcasses/wood falls, deep-sea canyons, deep hypersaline anoxic basins, hadal zones, etc. Extreme conditions require the resident communities to be adapted in one way or another. With continuing climate change it has become obvious that no seafloor area will remain untouched by the changes, and the future of the benthos is one where organisms, species, populations and communities, their ecology, biology and interactions at different life stages will be modified in response.
Benthic communities are especially useful in long‐term comparative investigations such as in the context of studying climate change effects because most of the constituent species are sessile or have low mobility, are relatively long-lived, and integrate the effects of environmental change over time. Macro-, meio-, and microbenthos of hard and soft bottoms are also ubiquitous and can thrive in almost any marine environment, including the most extreme (i.e. Arctic, Antarctic, deep-sea, caves, hydrothermal vents, cold seeps, sulphidic, etc...), making them ideal subjects to assess climate change effects in extreme environments.
The discovery of communities in extreme environments and the study of their benthic variability, as well as their relation to climate change and other effects (anthropogenic such as eutrophication and pollution or otherwise), are still in progress as more evidence and long-term observations become more and more available. Climate change may modify population dynamics over time and space, phenology, and the geographical distribution of benthic communities and species. These modifications could result in habitat loss and species extinctions, with consequences for biogeochemical fluxes, ecosystem functioning, and biodiversity.
Global change and all the changes it entails generally has a negative impact on marine life, especially benthic organisms. The increase of atmospheric greenhouse gases is causing significant changes in the environmental properties of the oceans in terms of water column oxygenation, temperature, pH and food supply, with concomitant impacts on extreme deep-sea ecosystems. Projections suggest that abyssal ocean temperatures could increase by 1°C over the next 80 years, while abyssal seafloor habitats under areas of deep-water formation may experience significant reductions in water column oxygen concentrations. The ocean has become 30% more acidic since pre-industrial times and is predicted to increase in acidity with increased greenhouse gas emissions. The impact for marine benthos is that warmer seawater carries less oxygen and warmer water expands the low-oxygen zones in coastal areas. Acidic ocean environments hinder benthic organisms since it limits their ability to calcify (e.g. coralline algae, mollusk with shells, calcareous sponges, corals, bryozoans and various exoskeletons).
All studies related with benthos in extreme environments and how benthic populations react to Global Change pressures, including the consequences on ecosystem functioning and structure, as well as on the social benefits deriving from a healthy ocean in the future, are welcome.
Keywords: Benthos, Global change, Extreme environment, Ecosystem functioning, Biodiversity
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