Researchers at the University of Adelaide in South Australia have constructed a three-level food web to show how ocean acidification combined with warmer sea temperatures could destroy marine biodiversity over the next century.
Published today in Global Change Biology, the researchers found that high CO2 expected by the end of the century which causes ocean acidification will boost production at different levels of the food web.
However, ocean warming cancelled this benefit by causing stress to marine animals, preventing them using the increased resources efficiently for their own growth and development, leading to a food web collapse.
It is the most comprehensive study of its kind that looks at how global warming affects multiple layers of an ecosystem instead of individual species only.
The Great Barrier Reef is the world’s largest coral reef system that stretches out for about 2300km along Australia’s east coast.
Last year, increasing ocean temperatures caused a bleaching phenomenon where sections of the reef began to rapidly deteriorate, sparking global environmental concern.
Project leader Ivan Nagelkerken said the protection of natural habitats, such as the Great Barrier Reef, needed to be made a priority to help slow the effects of climate change.
“Climate change is happening as we speak with the acidification of oceans and warmer temperatures, where it is rising up half a degree in some areas,” Professor Nagelkerken said.
“The consequences for marine ecosystems are likely to be severe – oceans in the future may provide less fish and shellfish for us to eat.
“Obviously more work needs to be done but once you have more information about the effects of all these stressors, human and environment, you can identify which species and which habitats need most protection, then develop appropriate mitigation strategies and conservation efforts.”
Researchers used 12 large aquaria filled with imitation seagrass, open sand and rocky reef habitats to simulate real-world environments. It also included artificial tidal movements with circular currents.
Each 2000-litre container (pictured right) consisted of plants such as algae, small invertebrates to graze on the plants and fish that preyed on the invertebrates to complete the food web.
The food webs were exposed to the levels of ocean acidification and warming predicted for the end of this century. Over several months, the researchers assessed the basic processes that operate in food webs such as predation and growth of organisms.
The researchers found that ocean warming would be an overwhelming stressor that made food webs less efficient, neutralised the “fertilising” effect of elevated carbon dioxide and threw the fragile relationship between predators and prey off balance.
Professor Nagelkerken said the stressed ecosystem would result in the fish on the higher end of the food chain to eliminate their prey.
According to NASA, CO2 levels in the air are at 405.6ppm, the highest it has been in 650,000 years.
“Both acidification and warmer oceans are indirect results of human CO2 emissions into the atmosphere,” Professor Nagelkerken said.
“Ideally we need to continue to work towards reducing carbon emissions similar to what was put out in the Paris Agreement but who knows if all those countries take action?”
South Australia’s capital Adelaide has three long-standing public universities, Flinders University, University of South Australia and the University of Adelaide, each of which are consistently rated highly in the international higher education rankings.Jump to next article