Science & Technology

Changing dynamics and biodiversity loss in temperate marine ecosystems

Researchers at the University of Tsukuba have discovered that the combined effects of ocean warming and acidification in temperate marine ecosystems have led to the loss of kelp habitat and the transition to a predominant ecosystem of simple turf. did. These changes lead to the loss of ecosystem services provided by highly productive large algae forests and coral reefs dominated by tropical corals. These results highlight the need to reduce greenhouse gas emissions.Credit: University of Tsukuba

Researchers at the University of Tsukuba have discovered that ocean warming and acidification are shifting temperate coastal reefs to simple turf-dominated ecosystems.

In Japan’s Shikinejima, kelp forests and abalone fishing were once common, but have disappeared in the last 20 years. Now, Japanese researchers have discovered that these temperate coastal marine ecosystems are becoming “simpler”, losing biodiversity, complexity, and their aesthetic value.

In a study published this month, researchers at the University of Tsukuba and international collaborators investigated how the combined effects of ocean warming and acidification are altering temperate coastal marine ecosystems. ..

Tropical coastal waters are synonymous with coral reefs. As the seawater temperature cools towards the poles, coral is replaced by kelp as the main habitat-forming species. The transition from coral to kelp is clearly visible along Japan’s 2000 km coastline, and changes in these ecosystems are already underway.

“Kelp forests are lost worldwide as a result of rising sea surface temperatures and heat waves,” says lead author Dr. Sylvain Agostini. “In Japan, this” rocky shore “, that is, the” burnt coast “is widespread. As seawater temperatures continue to rise, hot water corals can move northward to temperate reefs, replacing cold water species. “

As coastal species move, three scenarios are possible. Temperate reefs can become more tropical, with warm water corals, fish and other species predominant. Alternatively, coral reefs may become dominated by tropical seaweeds and turf algae.

However, ocean acidification, another effect of increased greenhouse gas emissions, complicates the matter. Acidification reduces the amount of carbonate in the ocean. This is necessary for the coral that builds the reef to create its structure. Decreased carbonate levels may limit the colonization of new areas by fast-growing coral species.

To investigate possible changes along the coast of Japan, the team used three locations at the same latitude representing three different scenarios (currently ocean warming, ocean warming and acidification). They investigated the existing community, then transplanted kelp and coral seeds and measured growth and survival in different locations.

The team found that due to both ocean warming and acidification, coastal ecosystems are likely to lose kelp forests, but may not be able to obtain reef-building corals. As a result, lawn-dominated habitats are simplified.

“Warmer water promotes the growth and colonization of reef-building corals,” explains Dr. Ben Harvey. “But ocean acidification seems to negate these benefits, and kelp transplants did not survive in warm water, mainly because they were eaten by warm-water fish.”

“The result of these changes is that temperate temperate coastal waters face significant simplification, which is evident in the deterioration of seascapes,” said Ecole’s co-author and artist. Pointed out and documented by Professor Nicolas Floc’h. Européenne Supérieure d’Art de Bretagne. Lost kelp forests could be replaced by simpler turf-dominated communities that provide some of the more biodiversity tropical coral reef ecosystem services. Overall, the results highlight the urgent need to control carbon emissions and limit the impetus for ocean change.

Reference: “Ocean acidification confine algae communities to an early continuous stage with few species” by Ben P. Harvey, Kon Koets, Sylvain Agostini, Shigeki Wada, Jason M. Hall Spencer, 2021 1 10th of the month Global change biology..
DOI: 10.1111 / gcb.15455

Changing dynamics and biodiversity loss in temperate marine ecosystems Changing dynamics and biodiversity loss in temperate marine ecosystems

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