Impacts and effect of ocean warming on deepsea communities

• The deep sea covers a vast proportion of the planet (50% below 3000 m) and supports both a wide rangeof habitats and biological communities. Its very nature, i.e. deep and remote, has resulted in difficultiesin studying this region as well as being extremely expensive to do so. The number of in-depth studiesundertaken is restricted to a small number of locations.• Increases in the atmospheric and upper ocean water temperatures are not quickly transferred to the deepsea. However, the increase in deep ocean water temperature is projected to continue for centuries after theatmospheric temperatures have levelled off or even decreased.• The deep sea plays an essential role in absorbing (~25%) and storing (>35,000 Gt) vast amounts of carbonfrom the atmosphere, however, this will impact the regulating capacity that the deep sea currently undertakesand will no longer be able to reduce the impacts of climate change globally.• Currently 2.5 Gt of frozen methane hydrate are stored in the sea floor at water depths of 200 – 2000 m. Increasingwater temperature could release this source of carbon into the ocean and ultimately into the atmosphere.• Impacts of climate change on deep sea faunal communities are not fully known. It is hypothesized that longterm changes in surface productivity, as a result of a warming ocean, will lead to fundamental changes in thedeep sea community as they are reliant on this flux of material reaching the sea floor.• Currently there are few data to base predictions of current and future impacts of ocean acidification. However,it can be expected that calcifying fauna such as deepsea corals and bivalves are, and will be, under threat.• The lack of long-term time-series studies i.e. a baseline, therefore makes it difficult to envisage the impact offuture climate-driven changes against natural biological variability over time.