Coral Reef Seychelles

[Ermelindo Klatt]

Locatedabout 1600km east of the African Coast in the Indian Ocean is the Seychelles archipelago, consisting of 115 islands. Seychelles is dominated by numerous pristine beaches, nature reserves and coral reefs in addition to rare animal and bird species.

The Centre for Ocean Restoration Awareness and Learning (CORAL) has been launched under this project, to serve as a national and regional hub for knowledge sharing on coral reef conservation and restoration. Long term success of the project is currently being assessed, with initial data demonstrating an increase in both coral recruit and fish densities following intervention, highlighting the benefits of active reef restoration.

Additional support from the European Union (EU) through the Indian Ocean Commission resulted in a project with the 5-star resort Six Senses Zil Pasyon on Felicite Island. This 18-months project aimed at restoring the coral population within Coco Island National Park. The project conducted a feasibility assessment, built a coral-nursery and stocked it with 2000 coral fragments collected from donor sites.

Through an international training in 2015 and a regional training drawing participants from the Western Indian Ocean in 2019, the project has incubated similar projects by others elsewhere including smaller scale projects run by communities. Coral reef restorations efforts have also began in other countries such as Colombia.

As coral restoration efforts continue, Nature Seychelles is looking into ways of creating on land nurseries at its CORAL Centre on Praslin Island. This will help corals to be more resilient to warming and acidifying ocean conditions, as well enabling application of techniques such as micro-fragmentation for speedy growth.

Coral reef degradation and limited recovery may threaten the economy of Seychelles, including loss of revenue from tourism and recreational activities, negative impacts on fisheries, and exposure of the shoreline to erosion. Thus, restoration of coral reefs needs to be consistent and long-term to guarantee the recovery of ecological functions and benefits.

With the onset of a weak-to-moderately strong El Nio-Southern Oscillation (ENSO) event starting late summer to early fall 2014 and continuing through 2016, we had a unique opportunity to determine the effectiveness of the choice of coral reef species (initially chosen based on survival rates during the last seawater warming anomaly) and the restoration process itself in alleviating the impact of warmer ocean temperatures. We are using standardized protocols to monitor the survival, reproduction, recruitment and bleaching response of donor and transplanted colonies. We continue monitoring at the transplantation site and two control sites, representing a healthy and degraded coral reef. Such monitoring allows us to evaluate the effectiveness of the restoration effort. Additionally, we are assessing the costs of large-scale reef restoration via coral gardening and the life cycle of coral reef restoration technology.

In early 2022, RR outplanted more than 3,000 corals, belonging to 7 genera (Acropora, Pocillopora, Favites, Porites, Galaxea, Pavona and Stylophora), on the degraded reef around Cousin Island. Two different techniques were used, the cementing of colonies on the reef and the use of metal structures or coral frames. In this timespan, 9 volunteers, both Seychellois and foreigners, have been involved and trained in several aspects of ecology and restoration of coral reefs. Furthermore, educational activities have been carried out involving the local watersports center and primary and secondary schools (both students and teachers) at Praslin; additional training of staff at Raffles Seychelles will start in mid-2022.

The RR project aims to improve the scientific knowledge on coral restoration to increase efficiency, success, and awareness. Coral restoration is an active intervention to reduce the damage or loss of corals and associated organisms due to multiple natural and anthropogenic factors (e.g., anthropogenic-driven climate change, outbreaks of coral diseases and predators, and more). A multi-pronged scientific approach is needed to address the improvements and limitations through testing, experimenting, and involving researchers and organizations via solid collaborations.

Currently, the project involves a collaboration with a researcher from the University of Milano-Bicocca (Dr. Luca Fallati) and a student from Heriot-Watt University in Edinburgh (Ms. Charlotte Dale). Dr. Fallati is studying the efficiency of coral restoration by using underwater photogrammetry through the creation of 3D reef models. Ms. Dale as a part of her Master thesis, is researching the efficiency of different stocking methods to improve coral survival, reduce cleaning effort, and improve logistical management of mid-water floating nurseries.

Additionally, the Reef Rescuers are testing the effects of artificial reefs to increase coral cover and reef 3D structure to enhance biodiversity in areas with unstable substrata (e.g., sand and rubble) where outplanting using cement is not suitable. Artificial structures are constructed with iron rebar as spider-shaped coated modules (coral frames) which are deployed on the sea bottom and connected with cable ties to create a net where corals are attached, and space is created for fish and other reef-associated organisms. The future restoration strategy will include the expansion of the frame area and the application of 3D printed reefs in the context of the blue barrier concept.

The researchers collaborated with a wide range of coral reef management organisations and the Seychelles government to collect coral samples from 19 different reef sites. A comprehensive genetic analysis revealed recent gene flow between all sample sites - possibly within just a few generations - suggesting that coral larvae may be frequently transferred between different populations. The results also hinted at the existence of a new cryptic species of the common bouldering coral, Porites lutea.

The genetic analyses were then coupled with oceanographic modelling, simulating the process of larval dispersal. These simulations allowed researchers to visualise the pathways coral larvae take to travel between reefs across the wider region, and determine the relative importance of physical larval dispersal versus other biological processes in setting coral connectivity.

This revealed that dispersal of coral larvae directly between reefs across the Seychelles is highly plausible. For example, coral larvae spawned at the remote Aldabra atoll could disperse westwards towards the east coast of Africa via the East African Coastal Current. From here, they would then travel north along the coast, with some potentially even reaching the South Equatorial Counter Current, which could bring them eastwards again back towards the Inner Islands of Seychelles.

Map of the southwest Indian Ocean, with red lines connecting Aldabra Atoll, Seychelles, to simulated downstream coral larval destinations, primarily in East Africa. Solid white arrows show major current systems, dotted white arrows show minor or transient currents. The new study suggests that strong connectivity within Seychelles is established clockwise, potentially traveling between the Inner Islands and remote Aldabra Group via reefs in East Africa, and centrally located reefs within Seychelles. Credit: Dr Noam Vogt-Vincent.

The modelling data can be visualised in a new app: with just one click you can see how coral larvae from Seychelles potentially reach reefs across the whole region. The researchers suggest that this data could help identify major larval sources to be prioritised for inclusion in marine protected areas or active reef restoration efforts.

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Report Bleaching Seychelles

5 km Regional Bleaching Heat Stress Maps and Gauges (Version 3.1) NOTE: Alerts displayed on individual Regional Virtual Station (RVS) and Single-Pixel Virtual Station pages still use the heritage bleaching alert level system (which extended to Bleaching Alert Level 2). We are currently updating these systems to reflect the modified bleaching alert levels (now extending to Bleaching Alert Level 5). Until this update is complete, when a Station displays Alert Level 2, we suggest that users consult the Time Series data file that is linked directly below or to the right of the two-year time-series graph. This data file displays the underlying Coral Bleaching HotSpot and Degree Heating Week (DHW) values, from which a user can determine, on any day, what the new, corresponding Bleaching Alert Level should be, if higher than Alert Level 2.

The purpose of these Regional Coral Bleaching Heat Stress Gauges is to provide coral reef ecosystem managers with a comprehensive summary of current satellite-monitored and model-projected bleaching thermal stress conditions to help facilitate timely and effective management actions pertaining to mass coral bleaching.

NOAA Coral Reef Watch (CRW) has developed a set of Heat Stress Gauges to reflect the observed and forecasted bleaching alert level surrounding select islands or reefs. The areas chosen for monitoring are designed to match the 5 km Regional Virtual Station boundaries outlined in black. These gauges are based on CRW's Regional Virtual Station time series data, updated daily, and 0.5-degree Climate Forecast System (CFS)-based Four-Month Coral Bleaching Thermal Stress Outlook, updated weekly.

CRW provides four gauges per Virtual Station that include the current near-real-time coral bleaching thermal stress alert level and the projected alert level for three consecutive 4-week time periods (i.e., the upcoming 1-4 weeks, 5-8 weeks, and 9-12 weeks, hereafter referred to as 4, 8, and 12 weeks, respectively). A map of the region surrounding the island or coastline of interest accompanies the gauges. The image(s) show either the current 7-day maximum Bleaching Alert Area, the current Four-Month Coral Bleaching Outlook for 4, 8, or 12 weeks out, or a composite of the four depending on the user's selection. The gauge corresponding to the map is outlined in black.

Due to the regional nature of the virtual stations, the level displayed on each gauge is a derived value that is not taken from any one data point within the virtual station area. To derive alerts, the daily 90th percentile HotSpot values within the station boundary are used to calculate new Degree Heating Week Values unique to each Regional Virtual Station. From the 90th percentile HotSpot values and newly calculated DHW values, a new Bleaching Alert Area value can be calculated using the same heat stress level table as the standard 5 km Bleaching Alert Area product. The daily 90th percentile HotSpot value and unique DHW and BAA values are stored in the time series data files accessible on the all stations and products page. This methodology keeps the Heat Stress Gauges, Time Series Graphs and Bleaching Email Alerts internally consistent and prevents a few stray warm pixels from exaggerating bleaching risk while reflecting the greatest thermal stress impacting the reefs in the region.

The CFS-based Outlook product used is the 60% likelihood of bleaching thermal stress from the latest Four-Month Coral Bleaching Thermal Stress Outlook. Outlook values displayed are the maximum of a composite of each corresponding 4-week period (i.e., the maximum value from weeks 1-4, 5-8, or 9-12 of the Outlook). A small gray arrow is sometimes present on a gauge indicating a change from the previous gauge reading upon updating. If the arrow is not present then there has been no change since the last update. The current alert gauge and image updates daily while the outlook gauges and images update weekly.

For the current alert level, the area of interest is specified by a black outline surrounding the island(s) or known reef locations on the map. For the 4-, 8-, and 12-week Outlooks, the area of interest is the entire extent of the corresponding map. This increases the area used for the gauge level as one moves from the Bleaching Alert Area to the 4-, 8-, and 12-week Outlooks. The areas covered by the 8- and 12-week Outlooks increase by 2 degrees in every direction from the previous Outlook. The increase in area coverage as the outlook lead-time increases for the gauge calculation is designed to help coral reef managers understand the extent of potentially approaching offshore thermal stress, with increased projection uncertainty factored in over longer time scales. Incorporating an increase in the area at these predefined, projected, time-dependent spatial scales should capture thermal stress events that may contribute to bleaching risk at the depicted coral reefs. In some special cases (i.e, Central America) the extent of the outlook map may encompass two ocean basins that should not collectively be considered when determining the outlook alert. In these cases, a dark gray mask is drawn over the basin that is excluded when calculating the outlook alert to display on the gauges.

The time series graph provides a record of temperature, thermal stress, and bleaching potential and allows for comparisons between years. The SST trace shown depicts the SST value where the HotSpot value is equal to the 90th percentile HotSpot. The minimum and maximum SST range within the Regional Virtual Station boundary is shown as a light gray area behind the SST trace. Click here to access a more detailed description of the time series graphs and data. Search How to cite these products and methods

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