Cold-water coral in the North Atlantic could be vulnerable to changes in large-scale weather systems due to climate change, according to researchers.These conclusions not only contribute to our scant knowledge of deep-sea ecosystems, but also provide vital information for people planning how best to protect the health of our oceans. They were published recently by a team led by Dr Alan Fox of the University of Edinburgh’s School of Geosciences, funded by the EU’s Horizon 2020 programme and part of the broader Horizon 2020 ATLAS (A Trans-AtLantic Assessment and deep-water ecosystem-based Spatial management plan for Europe) project.
Healthy coral matters. Coral reefs play an important role in the marine ecosystem as they provide other species with protection from predators and a safe place to reproduce. Scotland in particular has recently set up a network of Marine Protected Areas, designed to protect vulnerable ecosystems formed by cold-water corals.
Connecitivity is key
These protected areas do not exist in isolation but are connected by the movement of migratory species, larval life stages or simply the circulation of the elements. These transfers, known in the trade as connectivity, are essential for sea populations to thrive and prosper. So the extent to which a network of MPAs is capable of facilitating the connectivity of species and habitats is a core criteria for how effective they can be at safeguarding the marine ecosystem.
Choosing the Lophelia pertusa coral larvae as its species to study, Dr Fox’s team used computer models to simulate its migration across vast stretches of ocean. This tested the connectivity of the network of MPAs in the seas around Scotland and, by doing so, helped predict what effect changes in the weather could have on the long-term chances of survival of coral populations in the North Atlantic.
They found a striking degree of variation in the degree of connection within the network. Two strongly connected clusters of MPAs were identified in the west and north of the study area. Smaller clusters in the North Sea and elsewhere were found to be only weakly connected to the rest.
Changing winter conditions
These weaker and less frequent connections were found to be highly sensitive to weather phenomena such as the North Atlantic Oscillation or NAO, a pressure system over the North Atlantic which largely determines the severity of the winter in the Northern hemisphere. Changes in winter conditions in Western Europe is one of the predicted impacts of climate change.
If this happens, it would drive changes in ocean currents which could have a big impact on coral populations; it could carry migrating coral larvae away from the very sites were set up to protect them.
‘In summary, our new findings demonstrated significant climate-driven alterations in the connectivity of an established MPA network using biologically integrative particle tracking models,’ say the researchers in an article published in November 2016 in the journal ‘Royal Society Open Science’. ‘We conclude that the existing MPA network is not robust enough to atmospheric-driven changes in ocean circulation.’
Study lead Dr Fox said: ‘We can’t track larvae in the ocean, but what we know about their behaviour allows us to simulate their epic journeys, predicting which populations are connected and which are isolated. In less well connected coral networks, populations become isolated and cannot support each other, making survival and recovery from damage more difficult.’
Professor Murray Roberts, also of the University of Edinburgh’s School of GeoSciences and co-ordinator of the ATLAS project, commented: ‘Scotland’s seabed plays a unique role as a stepping stone for deep-sea Atlantic species. By teaming up with researchers in Canada and the US, we will expand this work right across the Atlantic Ocean.’