Proliferation of macro alga <i>Chaetomorpha linum</i> in shallow coral reef areas of Shingle Island, Gulf of Mannar, Southeastern India

Abstract

In May 2015, during summer, macro alga Chaetomorpha linum was seen entangled in high density on coral colonies at northern part of the Shingle Island (09°14’607”N 078°13’863”E) in Gulf of Mannar, Southeastern India. Underwater assessment revealed that C. linum bloom has proliferated on coral colonies of Acropora and non-acropora species. Filaments of C. linum formed larger mats and got entangled with coral colonies reducing light making hypoxia. The inter tidal zone of northern part of the Shingle Island has rich coral cover with about 23.5% at 0.5 to 3.0 meter depth (Patterson et al., 2007). Live coral cover decreased from 23.5% to 18.5% due to the sudden proliferation of C. linum. Maximum coral mortality was observed in branching corals such as Montipora divaricata, Acropora cytherea and Pocillopora damicornis. Other coral species under stress were Acropora intermedia, A. muricata, Montipora foliosa, Echinopora lamellosa, Porites solida and Favia pallida (Fig. 1 A to D).The present observation can be useful for further investigations regarding the spreading rate, algal biomass, nutrient level, and status of associated biodiversity from the bloom affected reef area.