Abstract
Sri Lanka, an island nation located off the southeast coast of the Indian sub-continent, has an unappreciated diversity of corals and other reef organisms. In particular, knowledge of the status of coral reefs in its northern region has been limited due to 30 years of civil war. From March 2017 to August 2018, we carried out baseline surveys at selected sites on the northern coastline of the Jaffna Peninsula and around the four largest islands in Palk Bay. The mean percentage cover of live coral was 49 ± 7.25% along the northern coast and 27 ± 5.3% on the islands. Bleaching events and intense fishing activities have most likely resulted in the occurrence of dead corals at most sites (coral mortality index > 0.33). However, all sites were characterised by high values of diversity (H’ ≥ 2.3) and evenness (E ≥ 0.8). The diversity index increased significantly with increasing coral cover on the northern coast but showed the opposite trend on the island sites. One hundred and thirteen species of scleractinian corals, representing 16 families and 39 genera, were recorded, as well as seven soft coral genera. Thirty-six of the scleractinian coral species were identified for the first time on the island of Sri Lanka. DNA barcoding using the mitochondrial cytochrome oxidase subunit I gene (COI) was employed to secure genetic confirmation of a few difficult-to-distinguish new records: Acropora aspera, Acropora digitifera, Acropora gemmifera, Montipora flabellata, and Echinopora gemmacea.
Highlights
Corals are foundational species that appeared 425 million years ago and are responsible for creating the structural complexity and high productivity of coral reef ecosystems [1].They have radiated into more than 1500 species and nearly 900 scleractinian corals
50% of the substrate at the reef sites on the northern coast was composed of hard corals, while the remaining part was mostly composed of dead corals (RC and nutrient indicating algae (NIA))
The substrate cover at the island sites was composed principally of dead coral rocks covered with turf algae, with the rest mostly consisting of hard corals, rubbles, and fleshy macroalgae
Summary
Corals are foundational species that appeared 425 million years ago and are responsible for creating the structural complexity and high productivity of coral reef ecosystems [1]. They have radiated into more than 1500 species and nearly 900 scleractinian corals. The high species diversity of coral reefs has led to their designation as oceanic “rain forests” [5]. The most recent widespread degradation of coral reefs, involving coral bleaching and the consequent death and loss of corals, is mostly due to climate change and ocean acidification [6,7]. Averting the effects of climate change will be a considerable challenge if we are to secure the ecological, economic, and social values of coral reefs in the marine biome
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