This project involves surveying the environs of all the islands within St Joseph Atoll for potential sites where mangroves could be re-introduced, planting mangroves at these sites and monitoring the success of the restoration attempts and the growth rates of the mangroves. Mangrove propagules are planted at the restoration sites and their growth is monitored over time. Important aspects of the study are to understand where in St Joseph Atoll mangroves occurred in the past and to identify the environmental conditions and habitat features that support their growth and success; this will help us to draft future plans for the habitat.
Since its inception in 2012, the SOSF-DRC has been managed and run by different people in various capacities. Lab managers, research officers and research assistants have been integral to the daily operations of the centre over these years and our long-term projects have been handed on from past to present management.
Currently the SOSF-DRC is run by Dr Robert Bullock and Henriette Grimmel in a joint-management capacity.
The following is a history of past management staff:
The key objective of the project is to study the distribution, abundance, ‘ecological use’ and growth rate of mangroves in St Joseph Atoll.
Understanding the past and current state of this ecosystem is essential for the preservation of the habitat, its associated species and the services the habitat provides now and in the future. Research into mangroves is complementary to other long-term SOSF-DRC projects, especially those concerned with sharks and rays, as mangroves are known to be a key habitat for these species. St Joseph Atoll also offers a template study site as an Indian Ocean coralline island where data on growth rates of mangroves can be acquired and will contribute to mangrove restoration science for the region.
Mangroves are important coastal features in tropical habitats, providing a multitude of ecosystem services and acting as nurseries and important feeding grounds for many species. Despite this, they are highly threatened and over the past 50 years mangrove habitat has declined rapidly around the world. Mangrove restoration projects like the one initiated at St Joseph aim to mitigate these losses and restore important mangrove habitat.
Mangrove ecosystems provide a variety of services to both people and animals. Science shows that mangroves provide important nurseries and habitats to many marine species, such as reef fish, rays and sharks. Mangroves act as buffers against strong wave energy during storms and protect coastlines, while at the same time preventing harmful terrestrial sediments from settling in the ocean. The benefits of mangroves are numerous and include their capacity to sequestrate carbon, the value of which is widely acknowledged. In addition, recent research suggests that corals adjacent to mangroves are at an advantage during bleaching events, as mangroves provide valuable nutrients that are taken up by corals as a secondary food source. Although the past extent of mangroves at St Joseph is poorly documented, we do know that the atoll is currently home to a great number of juvenile sharks and rays. Mangrove thickets are known to provide crucial habitat, especially for neonates and juveniles, as they can offer safety from larger predators and are rich in potential food sources.
The key objective of this project is met by several specific study objectives:
– To investigate the historical range of mangroves prior to the planting of coconut trees within St Joseph Atoll.
– To survey and map the current distribution and abundance of mangrove species occurring within St Joseph Atoll.
– To identify and establish restoration sites for red mangroves.
– To investigate correlations between success and growth rates of mangroves under differing environmental conditions at different restoration sites to inform future practice.
Understanding how different species of shark use St Joseph Atoll helps to define what they need from their environment and how we can best protect it. At least once a week the SOSF-DRC team visits the atoll to tag juvenile sharks at different locations in the lagoon. Juvenile Blacktip reef sharks (Carcharhinus melanopterus) and Sicklefin lemon sharks (Negaprion acutidens) are caught with a small gillnet. Small passive integrated transponder (PIT) tags are inserted under each animal’s skin and then act as a unique identifier for that animal. Tissue samples for genetic analysis and standard measurements of each animal are taken and their sex and weight are also recorded. These data help us to understand population dynamics, pupping success, growth and survival rates and tell us about the areas of the atoll used by the different species and how these change as the young sharks grow. This long-term project builds on the existing database of the longest mark-and-recapture study in the Indian Ocean region, which was set up by Dr Ornella Weideli for her PhD research.
The lagoon of St Joseph Atoll provides a home for three ray species. Juvenile mangrove whiptail (Urogymnus granulatus), porcupine (U. asperrimus) and feathertail (Pastinachus ater) rays all inhabit the shallow waters around the atoll’s various islands. We tag these rays with small electronic (PIT) tags that become their ID numbers. We also measure them and take a tissue sample. As time goes by and we recapture individuals, we can learn about how many of them use the lagoon, where they go and how quickly they grow. All this is important information that helps us to understand how these rays use the site. We collect data for this project every month.
To supplement much of the research conducted on site (e.g. coral monitoring and reef fish surveys) and to help better understand the lives of the animals using D’Arros Island and St Joseph Atoll, it is important to measure and monitor environmental conditions. One of the most important of these is sea temperature. A series of small loggers deployed at different areas and depths around the islands constantly record the water temperature. Additionally, via our on-site weather station, we collect meteorological data every day, including on wind, rainfall and air temperature.