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The unforeseen effects of melting glaciers on Arctic coastal ecosystems

In an interdisciplinary cooperation project of the EU-projects FACE-IT, ECOTIP, and SEA-Quester, scientists investigated the consequences of climate change in the Arctic. They focused on a group of organisms that form the very basis of Arctic coastal ecosystems—brown macroalgae, known as kelps, which form dense and extensive underwater forests along rocky coastlines.

The ecological role of kelps can be compared to trees on land: they provide food, habitat, and a nursery ground for a variety of organisms and thereby maintain complex ecosystems. The researchers focused on the effects of climate change on kelps in order to draw conclusions about the ecological and socio-economic consequences.

Their new findings in Arctic coastal ecology have been in Scientific Reports by Sarina Niedzwiedz and Kai Bischof from the University of Bremen and MARUM—Center for Marine Environmental Sciences and their team of co-authors.

Warming increases run-off intensities and influences element concentrations

The Arctic region is warming at a rate that is far above the global average. Consequently, snow, glaciers, and permafrost are melting—all of which are contributing to coastal run-off plumes.

The run-off plumes change water parameters drastically as large volumes of fresh water reduce the salinity, washed-in sediments reduce the light availability, and, depending on the lithogenic and organic material in the run-off, the elemental composition changes.

While many of the elements that are being washed into the fjords can act as micronutrients for kelps (e.g., sodium, magnesium, potassium), harmful elements, such as heavy metals (e.g., cadmium, lead, mercury) have also been found in higher concentrations.

The researchers collected kelps exposed to different levels of run-off intensities and analyzed their elemental composition. Across all investigated elements, the team found the same pattern: as run-off intensity increases, so do element concentrations.

In the case of mercury, kelps that were highly influenced by run-off were characterized by a 72% higher mercury content compared to kelps from the control area.

Changing microbiome

Further, the researchers analyzed how different run-off rates affect the kelp microbiome. The microbiome is highly important for the ecological function of kelps, such as their nutritional value or elemental cycling in the ecosystem. They found that the microbiome also changed with different run-off rates.

Both of these climate-related changes on kelps are likely to have cascading consequences for the entire ecosystem. The ingestion of metal-contaminated kelps was shown to have negative impacts, such as reduced development, growth, and reproduction, and might lead to a bioaccumulation of harmful elements across the Arctic food web.

Eventually, this might also have socio-economic consequences. The high biosorption potential of kelps has to be considered in the implementation of maricultures.

However, harvesting kelps in fjords with high levels of meltwater and metal contamination might be an environmentally friendly method to harvest rare earths (phytomining). Rare earths are increasingly being used in key technologies such as renewable energies and electronics.