Changes in benthic community composition following the mass mortality of Diadema at Jamaica

Document Type

Article

Journal/Book Title/Conference

J. Exp. Mar. Biol. Ecol.

Volume

95

Publication Date

1986

First Page

1

Last Page

8

Abstract

The urchin, Diadema antillarum Philippi, is normally ubiquitous on Caribbean reefs and exerts an important control on benthic algal populations through its grazing activity. At Discovery Bay, Jamaica, the urchin was essentially eliminated from fore reef sites during August, 1983 by disease. Four 100-m2 sites located between 5 and 22 m on the fore reef were censused prior to and after the urchin mortality. At 15 m, the urchin density declined from 6.6 to 0.0 · m −2 while bottom cover by noncrustose algae (mainly Dictyota species and filamentous red and green algal turf species) increased from 30.7 to 49.7% within 2 wk of the urchins′ death and by 4 months had increased to 72.3%, finally declining to 64.7% after 1 yr. This sharp increase in algal cover was achieved at the expense of other reef benthos, such as crustose coralline algae and clionid sponges. A similar pattern was found at the other depths. Depending upon the urchins' ability to re-establish itself, this trend may have serious implications for the shallower (< 30 m) Jamaican reefs, which are still undergoing a succession with recruitment of many coral species following Hurricane Alien, in 1980.

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