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Seagrass: revealing impact of climate change on marine environments

Marine ecosystems are increasingly pressurised by global climate change and its impacts. New research reveals that seagrasses, underwater flowering plants found worldwide, make excellent case studies showing how ecosystems in general could suffer or thrive.

Climate Change and Environment

Global warming and ocean acidification are two major environmental stressors linked to climate change. Acting alone or combined, these stressors force organisms to burn more energy in order to survive in the warming and more acidic oceans forecast for this century. The EU-funded SEAMET project set out to determine how marine ecosystems could respond under future climate change scenarios. The project posed two main questions: will the plants and associated organisms in these ecosystems survive in the future, because they are resilient to such stressors? If not, what will be the repercussions for the ecosystems they are part of? “We focused on seagrasses physiology as a descriptor of their health and how they perform as a whole ecosystem, because these plants are a vital ecosystem service provider and economically valuable,” says Nick Kamenos, coordinator of the project at the University of Glasgow in the United Kingdom. “As a ‘model system’, seagrass is ideal to assess the pressures linked to global climate change for marine ecosystems.”

Home for many fish, birds and invertebrates

This habitat-forming plant is home for a wide variety of marine life, helps to recycle nutrients and improves water quality. Seagrass coastal ecosystems cover some 40 million hectares and they naturally capture and store ‘blue carbon’, the human-produced carbon dioxide in the atmosphere and oceans. “Our researchers built a global picture of seagrass, selecting a range of sites with specific characteristics that make them representative of what the average future oceans will look like,” adds Kamenos, who conducted the research with the support of the Marie Skłodowska-Curie Actions programme. “They measured the organisms’ physiology, such as rate of photosynthesis, and its size, to see how well they were surviving in those sites.” Sites were in Europe (France, Portugal and Scotland), East Africa (Réunion Island) and Mexico, thus covering the Atlantic, Pacific and Indian Oceans and the Mediterranean. Although the project concentrated on the seagrass species Zostera marina, two other species (Cymodocea nodosa and Syringodium isoetifolium) were also considered in experiments and field work. Teams were from Glasgow with collaborations involving researchers from France, Mexico and Portugal.

Combined lab and field studies

“All experiments included climate change’s two main environmental drivers, which are temperature and carbon dioxide concentrations and thus ocean acidification. We also accounted for geographic latitudinal gradients and other environmental factors,” notes Kamenos, who has a doctorate in marine biology from the University of London. They collected the plants by snorkelling, and carried out field experiments using a specially designed apparatus to measure oxygen produced during photosynthesis. “SEAMET data provided insights into seagrass capacity to cope with climate change in the oceans of the future. That’s essential for scientists and policymakers, as seagrass habitats play a key role as blue carbon sinks and by locally buffering ocean acidification,” Kamenos concludes. He highlights another project first, a ‘latitudinal gradient of responses’. This reveals how seagrasses that have experienced a different temperature history respond to climate change, depending on their latitude. Moreover, the project contributes to the new EU Biodiversity Strategy, since seagrass habitats are considered hotspots of biodiversity.

Keywords

SEAMET, blue carbon, climate change, marine ecosystems, marine biology, ocean acidification, seagrass, stressors, temperature

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