The Ecology of the Tropical Compound Ascidian Trididemnum solidum. II. Abundance, Growth and Survival

The distribution of Trididemnum solidum (Van Name) was investigated in 42 transects over the coral reef on the leeward coast of C u r a ~a o .Ascidian colonies were abundantly present at depths from 1.5 to 34 m along the central part of this coast, but absent towards the tips of the island.This reflects characteristics of the lift, history of T. solidum, such as short pelagic life, and the local current regime.Another factor influencing the distribution is the ambient light level.For 9 mo, July 1978 to April 1979, w e measured the monthly in sjtu growth of a population varying between 38-50 colonies.Each fortnight these colonies were checked for presence/absence.The constancy in population size masks a highly dynamic system.During our study period 85 novel colonies appeared through division.43 colonies disappeared through f u s ~o n with other colonies and 33 colonles ceased to exist (dead) or were lost.Growth rates were extremely r a p ~d , u p to 13 cm mo-' i n linear direction, compared with the most common s p a t ~a l competitors (Sclel-actinia).Although T solidum overgrows corals, growth rates are reduced over I~ving coral tissue Hornogenates of the ascldlan had variant but adverse effects on different coral spccles and, apart from s ~n i p l c overgrowth, allelochem~cals could be involved in spatial competition.There I S I~ttle e v ~d e n c e of predation on Trididemnum solidum and drtificial lesions were rapidly rrgenpl-ated.Our ohservat~ons show I t i < ~t T solidum had a life span largely exceeding our study p e r ~o d crnd we suspect that clones !nay survive indefinitely.