Type: Large

SeyCCAT strategic objective: Support new and existing marine and coastal protected areas and sustainable use zones

Lead Project Partner: Seychelles Islands Foundation

Partners: Ministry of Environment, Energy and Climate Change and University of Oxford (UK)

Summary: Seychelles is a unique nation, with 115 islands stretching across an exclusive economic zone of 1.4 million km2. This marine area is one of the world’s richest biodiversity hotspots. The blue economy concept has been adopted by the Seychelles Government to implement and maintain sustainable management of these vast marine resources for present and future generations. Coral reefs form the base of the marine food web that is so paramount in securing biodiversity and safeguarding ecosystem health and food security in the region. Ensuring coral reef (and associated fisheries) persistence is, therefore, a top priority for Seychelles and one that will be hard to deliver, given the increasing frequency and severity of global bleaching events, e.g. the 2016 event that caused widespread mass coral mortality across Seychelles.

In this project, we will map connectivity among major reefs across Seychelles and use this map to determine keystone reefs – defined as highly connected sites that potentially supply larvae to many other reefs in the region. These sites are likely to be critical for recolonization following disturbance events like bleaching. Identifying these keystone reefs will be an important management tool for Seychelles: allowing conservation resources (time, money, legislation) to be better targeted. As ocean currents distribute coral larvae across marine ecosystems, we will also begin modelling ocean currents across a range of spatial scales using a nested numerical model. The connectivity mapping will also be useful to better understand dispersal routes of Seychelles’ major fisheries, a key factor in sustainable fisheries management. This project will start to fill a major gap in Seychelles ocean science allowing Seychelles to better meet the blue economy objective of sustainably managing the exclusive economic zone. This, in turn, will contribute to Seychelles fulfilling their contribution to achieving the sustainable development goals, particularly SD14: Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

We will determine the connectivity of coral populations across Seychelles using genetic techniques to identify the source and sink dynamics among coral populations. This will be done by sampling coral for up to three species from up to 24 reef sites across Seychelles. The output will be a connectivity map showing source and sink dynamics. We will use high-resolution numerical models and remote sensing data products to understand how ocean currents across a range of scales within Seychelles affect larval dispersal and therefore inter-island potential connectivity (the potential for a particle, e.g. a larva of fish or coral, to move from a source to a sink). The output will be freely accessible potential connectivity data, complimenting the genetic data to highlight locations which act as key larval sources and sinks to assist conservation efforts.

This project will be the first to address coral population connectivity and larval dispersal pathways across Seychelles. Previous connectivity studies in other regions have used either the genetic approach or have carried out particle-tracking experiments based on numerical models to predict potential connectivity. However, most modelling studies have either lacked the spatial resolution to resolve small-scale processes critical to predicting connectivity (e.g. Bode et al., 2018), or have not covered a sufficient time range to properly assess timescales of variability in potential connectivity (e.g. Thompson et al., 2018).

Furthermore, while ocean models have excellent potential to guide our understanding, potential connectivity (the potential of a larva to move from source to sink) is not equivalent to realized connectivity (how many larvae successfully settle at a sink). Similarly, ecological connectivity (connectivity of organisms) is not identical to genetic connectivity (connectivity of genotypes) (Watson et al., 2010). A combined approach fusing high-resolution numerical models with empirical estimates of genetic connectivity will, therefore, optimize our assessment of connectivity within Seychelles and will shed light on the spatially and temporally heterogeneous parameters that translate potential connectivity into ecological and genetic connectivity.

SeyCCAT funds:   SCR 1, 000, 000

Co-financing: SR 1,863,600

Duration: December 2019 – November 2021

ESMP: 12022020-ESMP_SIF

Project Application Form: SIF, MOE, Oxford- Mapping coral population connectivity and ocean currents to inform management & policy of the coral reef system

Knowledge Sharing

SeyCCAT and SIF co-hosted a webinar to share more on coral reef connectivity. Did you miss it? Here is a recording.