How coral reefs are affected by pollution

We know that coral reefs worldwide are in decline, but remarkably little is known about how exactly this happens. That is why a multidisciplinary team of Dutch and Caribbean researchers, including TU Delft’s Boris van Breukelen, will investigate this in the coming years. The project ‘SEALINK’ was recently awarded 3,5 million euros of funding as part of  NWO's Caribbean Research programme.

For the first time, Dutch and Caribbean scientists are looking at how the coral reefs are affected by pollution such as sewage water and chemicals that flow from land into the sea. The team will focus on Curaçao and St. Eustatius. Little is known on how exactly pollutants reach the sea from these islands, how subsequently water motion and marine organisms move and change these substances, and the overall impact that land based pollution has on the coral reef ecosystem. This knowledge is crucial for the preservation of coral reefs and biodiversity as well as for tourism and local communities in the Caribbean part of the Kingdom of the Netherlands.

Boris van Breukelen (Department of Water Management) will lead the work package on the hydro(geo)logy to understand precisely how pollutants (including nutrients, sediments, organic compounds, pathogens) are transported into the sea (overland or underground, or both, and to what extent) to ultimately support effective land and water (including sanitary) management. Van Breukelen and Victor Bense (WUR) will together supervise two PhD students who will combine extensive field work, novel water tracing methods, and numerical water and pollutant transport modelling.

Currently, it is unknown what the magnitude and seasonal variation is of the water and associated pollutant fluxes from land towards the sea. Of particular relevance is to establish the importance of the two markedly different transport pathways. On the one hand, pollution can reach coral reefs via surface water flows as is the dominant transport route affecting for example the Great Barrier Reef; this pathway is often clearly visible by plumes of sediments floating on sea water. On the other hand, underground transport of pollution via groundwater flow is more important at islands like Hawaii consisting of porous rocks and receiving ample rainfall; this usually invisible pathway often goes unnoticed. We suspect that in the Dutch Caribbean both pathways are relevant. Therefore, we will investigate how water and pollution are transported via both incidental overland run-off events in the wet season and year-round via underground groundwater flow gradually entering the sea as mostly diffuse submarine groundwater discharge. Specific pollutants are linked to different extents to these transport pathways. For example, sediments and plastics are associated with overland flow, while nutrients from leaking pit latrines are transported by groundwater flow. Establishing such mechanistic insights is essential for building a knowledge base for effective land and water management including selecting cost-effective sanitary engineering solutions in the Dutch Caribbean.

The consortium
The consortium consists of hydro(geo)logists, oceanographers, marine ecologists and social scientists of the following universities: University of Amsterdam, NIOZ, TU Delft, Wageningen University, VU University, and Utrecht University. Programme Chair: Prof dr Mark Vermeij (University of Amsterdam, CARMABI Curaçao)

More information
The objective of NWO’s Caribbean Research programmes is to structurally strengthen  the knowledge system and the embedding of scientific research in the Caribbean part of the Kingdom of the Netherlands. The programme focusses on issues that are of great societal and scientific importance for the Caribbean region, and facilitate the transfer of knowledge via education and outreach. This is the first time that NWO has funded programmes of this size in the Dutch Caribbean.

More information is available on the website of NWO or https://www.sealinkcaribbean.net/

The project is a follow-up of the NWO NICO expedition to the ABC islands (Aruba, Bonaire, Curaçao) that Boris van Breukelen joined in 2018, see the following NTR NPO 2 documentary.