Deep water populations of Lobophora variegata (Phaeophyceae) on the coral reef of Curagao: influence of grazing and dispersal on distribution patterns

Abstract

On the coral reef of Curacao (Netherlands Antilles) the foliose brown macroalga Lobophora variegata (Lamouroux) Womersley displays a discontinuous depth distribution, with distinct belts in the deep algal community (below 30 m) and in the eulittoral community. This distribution pattern is attributed to high grazing pressure in the areas devoid of L. variegata, where the alga will sumve and grow year-long if protected from sea urchins and herbivorous fish. There was a distinct gradient in grazing pressure decreasing with depth. After the occurrence of mass mortality in the sea urchin Diadema antillarum Philippi, which took place in the course of this study, overall grazing pressure on the alga was reduced. However, this 'natural experiment' did not result in a very marked increase of the depth range of L. variegata, probably because the dispersal range of propagules is very limited. Recruitment only occurred within meters of the nearest L. variegata stand.