Ocean acidification locks algal communities in a simplified state – Watts Up With That?

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Ocean acidification locks algal communities in a simplified state – Watts Up With That?

Researchers at Tsukuba University find that ocean acidification is limiting algal communities to a state of low biodiversity and complexity

UNIVERSITY OF TSUKUBA

Research news

Tsukuba, Japan – Out with the old, in with the new, as the New Year's saying goes, but not in relation to the marine environment. Researchers from Japan have found that ocean acidification is keeping algal communities in a simplified state of low biodiversity.

In a study published in Global Change Biology on January 11, 2021, researchers from Tsukuba University showed that the biodiversity and ecological complexity of marine algal communities decrease with increasing oceanic carbon dioxide levels.

Ocean acidification is the continuous increase in the acidity of the Earth's oceans caused by the absorption of atmospheric carbon dioxide (CO2). The largest contributor to this acidification is the human-made CO2 emissions from burning fossil fuels.

"Ocean acidification is detrimental to many different marine organisms," says the study's lead author, Professor Ben P. Harvey. "This affects not only ecosystem functions, but also the goods and services that humans obtain from marine resources."

To study the changes caused by CO2-enriched water in algae communities, the researchers anchored tiles in the ocean for the algae to grow on. The tiles were placed under reference conditions (i.e. those representing the structure and function of biological communities exposed to no / very little human-induced disturbance) and acidified conditions. The team used a natural CO2 seep for the acidified conditions to plot CO2 conditions at the end of this century and compared the differences between the cooler months (January to July) and the warmer months (July to January).

“We found that under acidified conditions, the tiles were taken over by turf algae and the communities were less diverse, complex, and biomass less,” explains Professor Harvey. "This pattern was consistent throughout the season and kept these communities trapped in simplified, low-biodiversity systems."

The team also transplanted established communities between the two conditions. The transplanted communities ultimately agreed with the other communities around them (i.e. high biodiversity, complexity and biomass under the reference conditions and vice versa under the acidified conditions).

"If we understand the ecological processes that are changing community structure, we can better gauge how ocean acidification is likely to change communities in the future," says Professor Harvey.

The results of this study show that if atmospheric CO2 emissions are not reduced, more algal habitats (like kelp forests) may be lost. But the study also shows that shallow-water marine communities can recover if CO2 emissions are significantly reduced, as required by the Paris Agreement.

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The article "Ocean acidification blocks algae communities in a species-poor early succession stage" was published in Global Change Biology at DOI: 10.1111 / gcb.15455

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