The potential of coastal ecosystems to mitigate the impact of sea-level rise in shallow tropical bays

L. M. Keyzer*, P. M.J. Herman, B. P. Smits, J. D. Pietrzak, R. K. James, A. S. Candy, R. E.M. Riva, T. J. Bouma, C. G. van der Boog, C. A. Katsman, D. C. Slobbe, M. Zijlema, R. M. van Westen, H. A. Dijkstra

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Shallow tropical bays in the Caribbean, like Orient Bay and Galion Bay in Saint Martin, are often sheltered by coral reefs. In the relatively calm environment behind the reefs, seagrass meadows grow. Together, these ecosystems provide valuable ecosystem services like coastal protection, biodiversity hotspots, nursery grounds for animals and enhancing tourism and fisheries. However, sea-level rise imperils these ecosystems and the services they provide because of changing hydrodynamic conditions, with potential effects on the interdependencies between these ecosystems. By means of a hydrodynamic model that accounts for the interaction with vegetation (Delft3D Flexible Mesh), the impact of sea-level rise (0.87 m in 2100) is investigated for three scenarios of future reef development (i.e. keep-up, give-up and catch-up). If coral reefs cannot keep up with sea-level rise, the wave height and flow velocity increase significantly within associated bays, with the wave height doubling locally in case of eroding reefs in our model simulations. Since the presence of seagrass strongly depends on the hydrodynamic conditions, the response of seagrass to the future hydrodynamic conditions is projected using a habitat suitability model that is based on a logistic regression. The spatial character of the bays determines the response of seagrass. In Orient Bay, which is deeper and partly exposed to higher waves, the seagrass will likely migrate from the deeper parts to shallow areas that become suitable for seagrass because of the surf zone moving landward. In contrast, the conditions for seagrass worsen in Galion Bay for the catch-up and give-up scenario; due to the shallowness of this bay, the seagrass cannot escape to more suitable areas, resulting in significant seagrass loss. It is shown that healthy coastal ecosystems are able to limit the change in hydrodynamic conditions due to sea-level rise. Therefore, preserving these ecosystems is key for ensuring the resilience of shallow tropical bays to sea-level rise and maintaining their ecosystem services.

Original languageEnglish
Article number107050
Number of pages11
JournalEstuarine, Coastal and Shelf Science
Volume246
DOIs
Publication statusPublished - 5 Nov 2020

Funding

LK and PH designed the study. LK and BS developed the hydrodynamic model and processed the data. PH developed the habitat suitability model. RJ collected field data. LK analysed the results and drafted the manuscript. PH, BS, JP, AC and RR supervised the work. All authors discussed the results and commented on the manuscript. This work is part of the research program ALW-Caribbean with project 858.14.061 (SCENES), which is financed by the Netherlands Organisation for Scientific Research (NWO) .

Keywords

  • Coral reefs
  • Habitat suitability model
  • Hydrodynamic modelling
  • Sea-level rise
  • Seagrass
  • Shallow tropical bays

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