Demographic approaches to community dynamics: a coral reef example

Hughes, Terence P.

Abstract

Understanding how changes occur in the species composition of an assemblage is a major goal of ecology. Such alterations are typically caused by a variety of interacting physical, biological, and anthropogenic processes that vary in intensity, frequency, and spatial scale (e.g., Connell and Keough 1985, Levin 1992, Karlson and Hurd 1993). A recent example of large-scale changes in community structure has been reported for coral reefs around Jamaica, where a complex sequence of interacting events has resulted in a phase shift from a coral- to an algal-dominated system (Hughes et al. 1985, 1987, Liddell and Ohlhorst 1986, 1992, Hughes 1989, 1994a, Knowlton 1992, Steneck 1993). The transition was partly caused by two hurricanes (Hurricane Allen in 1980 and Gilbert in 1988), which sharply reduced the abundance of corals, sponges, and gorgonians in shallow water <25 m deep (Knowlton et al. 1981, Porter et al. 1981, Woodley et al. 1981, Hughes 1994a). In addition, levels of herbivory have declined on Jamaican reefs in recent decades due first to chronic overfishing (Munro 1983) and secondly to a sustained reduction in abundance of the major grazing echinoid, Diadema antillarum, caused by mass mortality from disease (Hughes et al. 1987, Ste-neck 1993). This marked reduction in macroherbivores has coincided with a protracted bloom of benthic macroalgae along >300 km of Jamaica's coastline (Hughes 1994a). More-localized inputs of nutrients from rivers and ground water may also have affected algal growth (Goreau 1992). However, there has been no systematic attempt to quantify long-term changes in water quality or inputs of nutrients to the reefs, which has led to conflicting opinions on the causes of the widespread algal bloom (Hodgson 1994, Hughes 1994a, Ogden 1994).

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Ecology

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1939-9170

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Ecological Society of America

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DOI

10.2307/2265718