Coastal ecosystems being ‘burned’ by double whammy of rising temperatures and ocean acidification

Coastal ecosystems being ‘burned’ by double whammy of rising temperatures and ocean acidification - University of Plymouth

New research from an international team of scientists has shown that when ocean warming and acidification combine, complex coastal habitats can be stripped of their variety and reduced to slime-covered barren grounds.

Across Japan, the team has found widespread evidence of ‘isoyake’ – or ‘burnt seashore’ – with the disappearance of kelp forests and abalone fisheries as temperate coastal marine ecosystems lose biodiversity and become more ‘simple’.

photo of pink corallines — Corallines (image: Paul Naylor)

In two studies published in Global Change Biology today (Friday 16/7), the team from the University of Plymouth, with counterparts in Japan, Italy, France and Spain, used the volcanic islands of Shikine-jima, approximately 160 kilometres south of Tōkyō, and Vulcano Island, off the coast of Italy, as living laboratories to analyse the impact of rising carbon dioxide and temperatures.

“Kelp forests are being lost globally as a result of warmer sea surface temperatures and heatwaves,” said first author, Dr Sylvain Agostini, from the Shimoda Marine Research Center, at the University of Tsukuba. “In Japan, this ‘isoyake’, or ‘burnt seashore’, is widespread. As ocean temperatures continue to increase, warm water corals are shifting northward into temperate reefs and could replace cold-water species.”

“At present, temperate waters are changing, becoming ‘tropicalized’ and dominated by warm water species of corals, fish and seaweeds,” added corresponding author Professor Jason Hall-Spencer, of the School of Biological and Marine Sciences, at the University of Plymouth. “But another effect of increasing greenhouse gas emissions – ocean acidification – complicates matters. Acidification reduces the amount of carbonate in the ocean, which is needed by reef-building corals to create their structure. Decreases in carbonate ion concentrations limits the poleward spread of corals.”

Professor Hall-Spencer said that global action is required to address the risk: “Temperate coastal waters are facing major degradation of seascapes due to the unseen hand of rising CO2 levels,” he concluded. “Overall, our results highlight the urgent need for control of carbon emissions and a limit to the drivers of ocean change.”