Growth inhibition of Lobophora variegata (Lamouroux) Womersley by scleractinian corals

Abstract

Growth rate, blade size, cover, and longevity of the foliose brown macroalga Lobophora variegata (Lamouroux) Womersley were recorded at various distances from the periphery of living coral colonies at ≈ 30 m depth on the coral reef of Curaçao, Netherlands Antilles. Five coral species were studied: Agaricia agaricites (Linnaeus), Agaricia lamarcki Milne Edwards et Haime, Meandrina meandrites (Linnaeus), Mycetophyllia aliciae Wells, and Stephanocoenia michelinii Milne Edwards et Haime. Growth rates of Lobophora variegata blades close to corals (< 1 cm distance) were significantly lower than at a greater distance, which was accompanied by a higher proportion of blades having damaged margins. These effects were not due to differences in longevity of the blades, as half-lives were not significantly different at various distances from corals (≈15 days). Reduced growth rates resulted in smaller blade size and lower cover close to corals. All coral species reduced the growth rates of L. variegata blades by ≈ 35 % when in contact with the alga. In addition, Agaricia lamarcki and Meandrina meandrites reduced growth rates of Lobophora variegata at distances up to 1 cm. For Meandrina meandrites and Mycetophyllia aliciae, the reduction in growth rate was not accompanied by an increased proportion of damaged blades close to the colonies. These interspecific differences among corals suggest that there are various defence mechanisms against being overgrown by Lobophora variegata. Although L. variegata was observed to overgrow living coral tissues, it is concluded that high turnover rates of L. variegata blades (a result of intense herbivory), together with defence mechanisms of the corals themselves, generally prevent L. variegata from overgrowing coral colonies.