Sweeping Climatic changes in biogeochemistry will affect every part of global oceans by 2100.

Previous studies have stressed on ocean warming and acidification caused by climate changes and emission of greenhouse gases. This led many researchers to underestimate the consequences of climate change.  Keeping in mind all influencing factors like depletion of dissolved oxygen in seawater and a decline in productivity of ocean ecosystems, researchers of a new study predict that no part of the global ocean will be left unaffected by climate changes.

"When you look at the world ocean, there are few places that will be free of changes; most will suffer the simultaneous effects of warming, acidification, and reductions in oxygen and productivity," said lead author Camilo Mora, assistant professor at the Department of Geography in the College of Social Sciences at the University of Hawai'i at Mānoa (UH Mānoa). "The consequences of these co-occurring changes are massive-everything from species survival, to abundance, to range size, to body size, to species richness, to ecosystem functioning are affected by changes in ocean biogeochemistry."

Using models of projected climate change, researchers measured co-occurrence of changes in temperature, pH, oxygen, and primary productivity based on two scenarios. The first scenario is an uncontrolled one where concentration of carbon dioxide in the air could reach 900 ppm by 2100 and the second scenario is a controlled one when CO2 concentrations would reach only 550 ppm by the same year.

The results revealed that by 2100 every inch of the world's ocean will be affected by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity.

"Even the seemingly positive changes at high latitudes are not necessary beneficial. Invasive species have been immigrating to these areas due to changing ocean conditions and will threaten the local species and the humans who depend on them," said co-author Chih-Lin Wei, a postdoctoral fellow at Ocean Science Centre, Memorial University of Newfoundland, Canada.

In another part of the study, researchers used available data on human dependency on ocean goods and services and social adaptability to estimate the vulnerability of coastal populations to the projected ocean biogeochemical changes.

Humans will not be left unaffected by this occurrence. It will also impact food chains, fishing, and tourism. Multiple ocean biogeochemical changes may also lead to comprises in ocean goods and services. This will, in turn, affect the 470 to 870 million of the world's poorest people who rely heavily on the ocean for food, jobs and revenue.

"The impacts of climate change will be felt from the ocean surface to the seafloor. It is truly scary to consider how vast these impacts will be," said co-author Andrew K. Sweetman, who helped to convene the original team of investigators and now leads the deep-sea ecosystem research group at the International Research Institute of Stavanger, Norway. "This is one legacy that we as humans should not be allowed to ignore."