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Map of the week – Coral (coralligenous) Habitats

Published on: Fri, 13/12/2019 - 11:25
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    On the occasion of COP25, our Map Of The Week features one of the most vulnerable marine habitats, coral reefs, threatened in several ways by climate change.

    During the last two weeks, the UN Climate Change Conference COP 25 in Madrid discussed measures to mitigate and reduce the impacts of the climate emergency on our planet. Designated as the “Blue COP”, this high impact International Conference focussed in particular on how climate change will affect the oceans, marine life and the people depending on them.

    One of the most vulnerable marine habitats are coral reefs, marine invertebrates that accumulate a skeleton of calcium carbonate, building complex three-dimensional structures over thousands of years. While these habitats only cover 0.5% of the ocean floor, they account for up to 25% of all marine species, making them the most biodiverse ecosystems on earth1. Furthermore, they provide many ecosystem services to human society, from protection against storm flooding to sustaining the fishing and tourism industries1.

    Climate change is threatening these “rainforests of the ocean” in several ways2. The absorption of the elevated atmospheric CO2 into the ocean makes the water more acidic, which may negatively impact the coral skeleton. Sea level rise and changes in precipitation and runoff may enhance the input of pollutants and sediments in coral reef environments, smothering the corals. Changes in storm patterns may destroy the reef structure and altered ocean currents could disrupt the ability of the corals to feed or disperse their larvae. Finally, the most serious effect may be due to the increased ocean temperatures. The thermal stress causes corals to expel the algae living inside them, so called “coral bleaching”, which starves the coral of food and makes them vulnerable to disease.

    Also in European waters, coral reefs are under threat, in particular in the Mediterranean Sea. Here, corals reefs and maerl beds (coralline algae) form an important part of the marine ecosystem but they are exposed to ever increasing water temperatures3. A first step towards protecting them is to understand where these ecosystems occur. The Map of the week shows a modelled spatial distribution of these coralligenous (coral) habitats which indicate the likeliness of coral occurrence.

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    The data in this map were provided by EMODnet Seabed Habitats.