Bioinvasion of Kappaphycus alvarezii on corals in the Gulf of Mannar, India

Kappaphycus alvarezii (Doty) Doty (Rhodophyta: Solieriaceae) is a Philippine-derived macroalga introduced into the Gulf of Mannar Marine Biosphere Reserve, South India for mariculture in 2000. Here we report its bioinvasion on branching corals (Acropora sp.) in the Kurusadai Island. Qualitative data collected using underwater photography clearly indicated its invasion and establishment on live and dead corals as well as coral rubbles and pavements. It specifically invaded Acropora sp. as monospecific beds with extraordinary phenotypic plasticity in the form of thallus, thickness of its major axis and lateral branching. It shows remarkable shadowing and smothering effects over the coral colonies.