What climate change does to fragile coral

Sustainable and safe oceans and inland waterways

Erik Meesters is collaborating with French scientists to determine biodiversity in the coral reef off Bonaire. Photo: Erik Meesters

Estimated reading time: 9 minutes

Coastal areas around the world are under threat from climate change. Some parts of the coral reef off Bonaire, for example, have deteriorated seriously with disastrous consequences for biodiversity. Scientists at Wageningen University & Research are now collaborating with European colleagues to work out which factors exactly influence this process.

The world’s coastlines have a variety of marine ecosystems, from kelp forests and seagrass meadows to mangroves. These ecosystems are important for biodiversity because they form a habitat for thousands of species of plants, animals and microorganisms, which live together in sustainable harmony. But marine ecosystems are like carefully constructed houses of cards and those houses of cards are in danger of collapsing due to climate change. Which factors precisely are at play is the subject of research by a European consortium. Over the next four years, scientists from nearly all countries with North Sea, Atlantic or Mediterranean coastlines will be investigating what effect factors such as rising temperatures and acidification of the seawater have on the composition of species in marine ecosystems. The project is called MaCoBioS, which stands for Marine Coastal Ecosystems Biodiversity and Services in a Changing World. It is coordinated by the Centre for Blue Governance at the University of Portsmouth, which researches interactions between humans and the sea. The project extends beyond the European continent as it also encompasses the overseas territories of France, United Kingdom and the Netherlands. For example, researchers at Wageningen Marine Research will be collaborating with French colleagues to study the changes in the coral reef off the coast of Bonaire, which is deteriorating rapidly.

Important source of biodiversity

A coral reef is an irregularly shaped limestone structure made by polyps that have cup-shaped calcium skeletons. Coral reefs are ecosystems with an incredible wealth of species: plants, algae, microorganisms, crabs, crustaceans, echinoderms, molluscs and fish. In short, they are an important source of biodiversity. Coral reefs also serve other functions such as protecting the coast, providing food for fish and other animals, purifying the water and use by fisheries and tourism. The reef’s intrinsic value as a nature area is also an ‘ecosystem service’.

Coral reefs are ecosystems with an incredible wealth of species: plants, algae, microorganisms, crabs, crustaceans, echinoderms, molluscs and fish. Photos: Erik Meesters

Wageningen’s researchers are already familiar with Bonaire’s coastline because they have been collaborating with the Royal Netherlands Institute for Sea Research (NIOZ) on studies in this tropical area of the Netherlands for over 40 years. This data is being used in MaCoBioS to investigate the relationship between climate change and the state of the coral reef.

Rising temperatures and acidification

The data from these many years of research has already shown that in general the coral has deteriorated, says Erik Meesters, a marine biologist at Wageningen Marine Research in Den Helder, part of Wageningen University & Research (WUR). Meesters is in charge of the Dutch research contribution to MaCoBioS. “In the past, the deterioration was due to diseases, possibly caused by pollution of the water from human activities. But nowadays, the poor state of the coral reef is mainly down to climate change.” One of the main consequences of climate change pinpointed by Meesters is the rising seawater temperatures. “The temperature of the water doesn’t usually fluctuate much in the tropics and the coral reefs are adapted to that. Even a small rise in temperature can be disastrous for the survival of coral reefs. One consequence is bleaching, whereby the coral could die if it lasts more than a couple of days. This in turn has a negative effect on biodiversity as species that depend on the coral, whether directly or indirectly, leave.”

The main objective of MaCoBioS is to ensure efficient and integrated management and conservation strategies for European marine coastal ecosystems to face climate change. To this end, MaCoBioS has assembled a multidisciplinary team of experts to acquire knowledge about the impacts of climate on the most important marine coastal ecosystems (seagrass beds, coral reefs, mangroves, coralligenous and calcareous bio-concretion assemblages, salt marshes and kelp forests).

Another problem is the increased concentration of CO₂ in the water. This makes the seawater slightly more acidic and that is already having an effect on animals with calcium skeletons. That includes corals. The skeletons become somewhat more brittle and fragile, and the coral is much less effective as a natural breakwater during storms. Meesters: “There will undoubtedly be adaptations to compensate for this. All creatures will have to adapt to the new situation, but evolution takes time. At present, the changes are so significant and taking place so rapidly that it is nigh on impossible for the ecosystems and associated species to adapt in time.”

Underwater microphones

In MaCoBioS, Meesters will be working with French scientists. The first joint field trip is aimed at measuring biodiversity in the coral reef off Bonaire. They will be using equipment provided by the French researchers. “Many animals make sounds underwater. We can use those sounds to determine what species are present and how many there are. We capture the sounds with special underwater microphones that are installed at various locations in the sea. As a rough approximation, you can say the volume is an indicator of the number of creatures and the frequency gives you information on the species. It is a quick method for getting a picture of the biodiversity in an area.”

Nowadays, the poor state of the coral reef is mainly down to climate change

In addition to the acoustic data, Meesters will also be taking water samples. That will be used to draw up DNA profiles. “Every creature that passes through that water leaves a trace of DNA. There are animals such as sharks or whale species where the chance of spotting them is very small, but if they swam through the water we sample, we can still see that evidence in the water, even hours after the animals were there.”

Satellite images

Meesters also uses satellite images for his research to analyse changes in coral growth, for instance. “But of course they don’t show the details. In the case of underwater images, you can’t really use satellite images for depths of more than fifteen metres. We are however working with remote sensing specialists from Wageningen University & Research (WUR). European experts in remote sensing will also use our field data in combination with satellite photos taken by the European Space Agency, ESA.” Meesters explains that satellite photos are incredibly important because they give a good impression of the scale of the changes across the coral reef in successive years.

The Netherlands doesn’t have a “research diver” category. We are really behind the times

Coral reefs are in danger due to climate change. Photo: Erik Meesters

What makes MaCoBioS unique? According to Meesters, in the past the factors associated with climate change were almost always studied in isolation. “This project will show us how the various factors influence one another and what their impact is on biodiversity.”

Longest time series

The scientific data on Bonaire’s coral reef goes back to 1974, the year in which this research started. The data collected over the past 48 years is the longest time series in the world for living coral, making it unique. The time series is a key source in international studies of the condition and health of coral reefs throughout the Caribbean.

End to underwater fieldwork

Research on coral reefs involves fieldwork conducted underwater. However, Meesters fears for the future of this kind of fieldwork and hence for the future of the world’s longest time series. He has been told by WUR that he is no longer allowed to dive under pressure — with air tanks — for scientific purposes. In the MaCoBioS project too, Meesters and his Dutch co-workers are not allowed to dive with air tanks so they rely on their French colleagues to install the research equipment. The reason is that the Dutch government is monitoring compliance with the legislation on professional diving more strictly. The legislation was drawn up for the offshore industry in the North Sea and is largely irrelevant for diving in the tropics in warm, clear water only ten metres deep. Meesters says it is “crazy” to require research divers to be able to perform welding at depths of fifty metres. For years, universities and research centres have unofficially allowed scientists to dive but that is now coming to an end. Meesters sees this legislation as an obstacle to his work and that of many of his colleagues. He is calling for an exemption for research divers. “Nearly all European counties have a special ‘research diver’ category, but not the Netherlands. We are really behind the times. You can’t do this work with just a diving mask and a snorkel.”

European research context

Marine Coastal Ecosystems Biodiversity and Services in a Changing World (MaCoBioS) addresses the following European policy challenge: Acquiring and disseminating knowledge about the relationship between climate change, biodiversity and marine ecosystem services

Wageningen University & Research groups involved: Wageningen Marine Research European countries involved: The Caribbean area, France, Germany, Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden and United Kingdom

Duration: 2020 – 2024

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