Harmel, a tiny marine worm with superpowers, the big “winner” of global warming?

A tiny marine worm that builds large reefs on European shores, the hermel should see its favored area expand rapidly under the effects of global warming. But according to a study unveiled on Thursday, it may also be infesting French coasts locally.

This study, published in the International Journal Global Change Biology, shows “Hermel is the species to win from climate change by 2050”, underlines Stanislas Dubois, researcher in coastal benthic ecology at the French Research Institute for the Exploitation of the Sea (IFRAMER), quoted in a press release.

While the habitats of many species are at risk from global warming, this publication, which is based on a scenario of a temperature increase of 2 °C in 2050, could serve as rare good news among COP27 in Egypt.

These insects provide many ecological services

Because hermaphrodites provide many ecological services. These 3 cm long marine worms, which live in tubes they make by sticking sand and shell pieces together, filter sea water and serve as food for crabs or fish.

But above all, the reefs they form over hundreds of hectares from Morocco to Scotland are home to a rich biodiversity and protect the coast against erosion.
“they absorb the energy of the waves, they have a buffer effect”, describes Amelia Curd, research engineer at Iframer and co-author of the article.

“The Largest Cattle Building in Europe”

The bay of Mont-Saint-Michel thus hosts the largest rock of the Hermels of Saint-Anne, which extends over a hundred hectares and constitutes “Europe’s largest continuous surface animal building”Underlines the researcher.

According to a model established by Ifremer researchers in collaboration with the universities of Porto (Portugal), Bangor (Wales) and Plymouth (England), the distribution area of ​​hormels should increase by 27.5% by 2050.

Predictably enough, areas suitable for their habitat would move north, particularly the Irish Sea, the English Channel and the Scottish coasts.

“The overall figure is relatively optimistic but it is more nuanced when you look at the details”, However, Amelia warns Curd. Because the researchers did not limit themselves to an overall assessment. They also took into account a whole range of environmental variables to investigate species development at a microscopic scale: water and air temperature but also salinity, wave height or tidal amplitude, orientation winds, etc.

local deletion

According to their findings, the Harmels reef may be over-expanded in some areas, which could lead to local extinction of the species. One of the characteristics of this species actually lies in the fact that its larvae develop in water and are carried away by the current before attaching themselves to a rock.

“The further apart the reefs are from each other, the more difficult it is for the larvae to reach them. Gradually these initial local reefs can become territorial.” Mr. DuBois explains.

In 2050, hermel could thus have disappeared from some central areas of its current range, in Charente-Maritime or Vendée, where its reefs cover several hundred hectares, sometimes more than a meter high.

These local extinctions can have widespread impacts on reef-hosted ecosystems.

Already at risk from trampling by foot fishermen or the spread of green algae, the Hermel reef has still not benefited from any effective protection at national and European level.

a protection that the authors of the study call for “Stop the degradation of this sensitive and useful natural habitat for our coastal ecosystems”, Mr. Dubois says.