Scientists have warned that deep-sea ecosystems, occupying 60 percent of the Earth’s surface, could be vulnerable to the effects of global warming.
“Global-scale models are now estimating that climate change will affect the supply of organic matter from surface waters upon which most deep-sea ecosystems depend,” study co-author Dr. Henry Ruhl of the National Oceanography Centre, Southampton.
Most scientists believe that the burning of fossil fuels (gas, coal and oil) for energy by humankind is largely responsible for global warming. The resulting increases in sea temperature change the availability of nutrients and light needed by tiny marine plants called phytoplankton for growth. When phytoplankton die, their remains sink down through the water column, and a small but significant proportion of this organic carbon ends up on the seabed where it drives one of the largest ecosystems on Earth.
“Essentially, deep-sea communities are coupled to surface production,” said Dr Ken Smith of the Monterey Bay Aquarium Research Institute and lead author of the paper. “Global change could alter the functioning of these ecosystems and the way that carbon is cycled in the ocean,” he added. No one is really sure yet whether global climate change is already having major impacts on deep-sea ecosystems. But what seems certain is that climate variation can and does affect them. Unprecedented long-term studies over the last two decades have revealed unexpectedly large changes in deep-ocean ecosystems that are clearly linked to changes in the surface ocean resulting from variation in climate.
Much of the new understanding has come from two key sites - Station M in the NE Pacific and the Porcupine Abyssal Plain (PAP) in the NE Atlantic, with water depths of around 4100 and 4850 metres, respectively.
“Data from these two widely-separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes,” according to the researchers. “Disruption of deep-sea ecosystems could result from long-term changes in the supply of organic matter caused by global climate change,” said Dr Ruhl. “This could occur through a combination of known mechanisms, including increased stratification of the water column, changes in ocean up-welling and mixing, aerosol and dust nutrient input, increased acidity, and even changes in water clarity,” he added. The researchers warn that even “seemingly subtle changes that persist for centuries, as projected by the IPCC (Intergovernmental Panel on Climate Change), could have important implications for biogeochemical processes and other ecological interactions that affect the functioning of the oceans as a whole.”