The underwater ecosystem of the Svalbard archipelago has changed in appearance over the last 20 years, with one disturbance leading to another, each of which calls into question the balance of the ecosystem. A study shows that the inhabitants of the sediments of a northern fjord are diversifying and could be multiplying.
Warm water currents are changing the Arctic Ocean on its surface by melting the sea ice and also transforming the sea floor in many places like the Svalbard archipelago. In 2006, such warm water upwellings led to a local extinction event among the benthic organisms of the Rijpfjorden fjord in northern Svalbard. It affected molluscs, worms, nematodes and bivalves, living on the surface of the sediment or in it. Such organisms are an important part of the food web and are the prey for fish, walrus and crustaceans. Following the incident, the fauna grew in number and diversity. This is shown by Norwegian, Polish and American researchers in a study published in early June in the journal Marine Environmental Research.
Between August and November 2006, water temperatures rose two degrees above normal. Warm water currents flowing up from the south hit the archipelago on its western flank, and wrapped around the underwater features. To the north, easterly winds pushed the currents into the Rijpfjorden fjord.
This prolonged episode coincided with a period of recurring anomalies between 2004 and 2008. Populations of bottom-dwelling animals such as nematodes plummeted. Since 2007, this fauna has entered a period of restoration. Species that can withstand a wider range of temperatures began to colonize the fjord, having previously lived along its edges, where water temperatures were more variable.
Such heat waves also occurred further offshore in the Fram Strait and Barents Sea. Further results suggest that in both Svalbard and in the Fram Strait, the benthic community may have increased in density and diversity. “It’s quite possible,” comments Laurent Chauvaux, a biologist and diver specializing in Arctic coastal ecosystems. After a disturbance, it’s unusual for the ecosystem to regain a state of equilibrium. There’s so much contingency in the relationships between species that a disturbance always reshuffles the cards in terms of species relationships.”
“For over 20 years, the fjords of Svalbard have been gradually losing the winter pack ice that protects them from swell,” explains Agnès Baltzer, a French sedimentologist who works regularly at Ny-Ålesund in Kongsfjorden with the French Polar Institute. Her team has also been working on the glacier’s retreat and has noticed that the flow of water has accelerated from the coast to the sea, bringing more fresh water and more sediment. Some sections of Kongsfjorden have decreased in depth by a metre in 10 years, and fish are feeding closer to the coast.
Laurent Chauvaux has been diving in the Kongsforden waters for over 10 years. “I’ve recently seen a proliferation of sea urchins,” he explains. There are sites at the foot of the village where the kelp forests have been nibbled away by sea urchins. So much so that they’re attacking the crabs, or eating each other. “Any kind of disturbance could have caused this proliferation of sea urchins,” he comments. The species of sea urchins is not new to the Arctic and also found near Newfoundland. But the changes they are experiencing are new.
Development of inshore fishing?
Such changes inevitably have consequences for fisheries for cod and crabs, which feed on bottom-dwelling prey. Arctic fisheries specialist Melina Kourantidou explains that “there is a desire to supply Svalbard residents with local fish, with the intention of supporting the local economy. Traditionally there used to be the coal mines, but today there’s only tourism and research.”
Changes in underwater coastal ecosystems could affect shellfish consumers such as walruses. Rising temperatures could favor the development of other bivalves, or introduce new pathogens such as Vibrio. Invasive and commercial species such as the snow crab could also benefit from the changes. “This is a more aggressive predator than the regular predatory species,” explains Laurent Chavaux. Yet, due to its commercial value, its development would be a boon for fisheries. But nobody could say for how long. “Often another species changes its behavior and regulates the population. This is what we saw with a bivalve introduced into the Brest harbor in France,” he adds.
It’s hard to predict whether the changes will be in favor of fisheries around Svalbard. If disturbances in these coastal areas are reshuffling the cards, then it’s fair to say that global change is completely changing the rules of the game.
Camille Lin, PolarJournal
Source: Jordà-Molina, È., Renaud, P.E., Silberberger, M.J., Sen, A., Bluhm, B.A., Carroll, M.L., Ambrose, W.G., Cottier, F., Reiss, H., 2023. Seafloor warm water temperature anomalies impact benthic macrofauna communities of a high-Arctic cold-water fjord. Marine Environmental Research 189, 106046. https://doi.org/10.1016/j.marenvres.2023.106046
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