In the context of climate change, the Arctic is experiencing some of the most rapid and pronounced warming in the world. As a result, ecosystems in the region are undergoing significant transformations. In an interdisciplinary cooperation project involving three major EU-funded initiatives—FACE-IT, ECOTIP, and SEA-Quester—scientists have explored the ecological consequences of this warming, with a particular focus on the keystone organisms that shape the region’s coastal ecosystems. These organisms are brown macroalgae, more commonly known as kelps, which form extensive underwater forests along rocky coastlines. These forests are not just beautiful and iconic; they play a vital role in maintaining the ecological integrity of Arctic coastal ecosystems.
Kelps are often compared to trees on land due to their extensive ecological role. Just like forests, kelp forests provide food, habitat, and nursery grounds for a wide variety of marine organisms, supporting complex and diverse ecosystems. The researchers involved in this project sought to understand how climate change, particularly warming temperatures and increasing run-off intensities, affects kelps, as this could have far-reaching consequences not only for the Arctic ecosystems but also for human communities that rely on these environments.
The research team, led by Sarina Niedzwiedz and Kai Bischof from the University of Bremen and MARUM—Center for Marine Environmental Sciences, along with their colleagues, published their findings in Scientific Reports. Their study offers a comprehensive analysis of how climate-driven changes are influencing the biological and ecological functions of kelps, specifically focusing on the impacts of increased run-off intensities as a result of melting snow, glaciers, and permafrost in the Arctic.
Warming and its Effect on Coastal Run-Off
One of the most striking features of climate change in the Arctic is the rate at which the region is warming. The Arctic is warming at a pace that is approximately four times faster than the global average, leading to the accelerated melting of snow, glaciers, and permafrost. This melting has profound consequences for the surrounding ecosystems, especially in coastal areas. As snow and ice melt, they contribute to a phenomenon known as coastal run-off, which brings large volumes of fresh water into fjords and coastal zones.
The increase in run-off has significant ecological implications. As fresh water enters the coastal waters, it lowers the salinity, which alters the physical and chemical properties of the water. Additionally, meltwater carries sediments, both organic and inorganic, which affect light availability in the water, an essential factor for the growth of kelps and other marine plants. But the effects of run-off go beyond physical changes; it also brings various elements into the water. Some of these elements may be beneficial for kelps, while others can be harmful.
The researchers observed how changes in run-off intensity influenced the elemental composition of kelps. They found that, as run-off intensified, there was a corresponding increase in the concentration of elements within the kelps. For example, elements like sodium, magnesium, and potassium, which can act as micronutrients for kelps, were found in higher concentrations. However, there was also a concerning increase in the levels of toxic heavy metals such as cadmium, lead, and mercury, which were being washed into the fjords from the land.
This increased concentration of heavy metals in the kelps raised serious ecological concerns. In particular, the team found that kelps exposed to higher run-off levels had a 72% higher mercury content compared to kelps in unaffected areas. This spike in mercury levels could have significant consequences for the health of organisms that depend on kelp forests for food, as mercury is known to bioaccumulate through the food chain, leading to toxicity in higher trophic levels.
The Kelp Microbiome and Climate Change
In addition to studying the physical and chemical changes in kelps, the research team also explored the impact of varying run-off intensities on the kelp microbiome. The microbiome refers to the diverse community of microorganisms, including bacteria, fungi, and algae, that live on and inside the kelp. This microbiome plays a critical role in the ecological functions of kelps, including nutrient cycling, growth, and elemental transformation. The microbiome also contributes to the kelp’s ability to cope with environmental stresses, such as pollution or changing temperatures.
The researchers found that the kelp microbiome also changed significantly with different levels of run-off. As run-off intensity increased, the microbial community associated with the kelps underwent shifts that could affect the kelp’s overall health and ecological function. These microbial shifts might alter the kelp’s ability to grow, cycle nutrients, and interact with other organisms in the ecosystem, thereby further complicating the cascading effects of climate change on Arctic coastal ecosystems.
Cascading Ecological Consequences
The combination of altered element concentrations and shifts in the kelp microbiome has profound implications for the Arctic ecosystem. Kelp forests serve as a critical food source for a variety of marine species, including herbivores, invertebrates, and fish. These species, in turn, are preyed upon by higher trophic level predators. If the quality and nutritional value of kelp are compromised—due to metal contamination or changes in the microbiome—it could disrupt the entire food web.
Moreover, the ingestion of contaminated kelps by marine animals could lead to a bioaccumulation of harmful metals in these species. This process could have cascading effects throughout the food web, potentially harming fish populations and, by extension, the communities that rely on these fish for food and income. This could also extend to human populations in the Arctic that depend on marine resources for their livelihoods, leading to socio-economic impacts, particularly for Indigenous communities whose traditional way of life depends on the health of the coastal ecosystem.
Socio-Economic Implications
The implications of these findings are not confined to the natural world. As kelps play a vital role in supporting local economies through fisheries and other marine industries, changes to kelp forests could lead to broader socio-economic challenges. A decline in kelp health, due to increased metal contamination or altered microbiomes, could impact the productivity of local fisheries, tourism, and other sectors that rely on the health of marine ecosystems.
However, there may also be some unexpected opportunities. The researchers noted that kelps, due to their high biosorption potential, might be useful in the extraction of rare earth elements from polluted waters—a process known as phytomining. Rare earth elements are critical for the production of high-tech devices, including renewable energy technologies and electronics. The use of kelps to extract these valuable elements from contaminated waters could provide an environmentally friendly and sustainable method of harvesting these resources. This potential, however, would need to be balanced against the broader ecological consequences of contaminating the environment with heavy metals.
More information: Sarina Niedzwiedz et al, Run-off impacts on Arctic kelp holobionts have strong implications on ecosystem functioning and bioeconomy, Scientific Reports (2024). DOI: 10.1038/s41598-024-82287-w