Coral Reefs

, Volume 19, Issue 4, pp 358–366 | Cite as

Large-scale associations between macroalgal cover and grazer biomass on mid-depth reefs in the Caribbean

  • I. Williams
  • N. Polunin
Reports

Abstract.

Since the 1970s, macroalgae have become considerably more abundant on many Caribbean reefs and overfishing of grazing fishes has been implicated as a contributory factor. We explored relationships between algal cover and grazers (biomass of herbivorous fishes and abundance of the sea-urchin Diadema antillarum) on mid-depth reefs (12–15 m) in 19 areas at seven locations in Jamaica, Barbados, Belize, Grand Cayman and Cuba, between April 1997 and April 1998. Diadema antillarum density was never >0.01 m–2, while herbivorous fish biomass (acanthurids and scarids ≥12 cm total length) varied from 2–5 g m–2 in Jamaica to 17.1 g m–2 in Barbados, and was strongly correlated, negatively with macroalgal cover and positively with 'cropped' substratum (sum of 'bare', turf and crustose-coralline substrata) cover. However, overfishing of herbivorous fishes alone cannot explain the widespread abundance of macroalgae, as even on lightly fished reefs, macroalgal cover was mostly >20%. Herbivorous fish populations on those reefs were apparently only able to maintain approximately 40–60% of reef substratum in cropped states, but due to low space-occupation by coral and other invertebrates, 70–90% of substratum was available to algae. The abundance of macroalgae on lightly fished reefs may therefore be a symptom of low coral cover in combination with the continuing absence of Diadema antillarum.

Coral reef Grazing Macroalgal overgrowth Caribbean Herbivorous fish Diadema antillarum Phase shifts 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • I. Williams
    • 1
  • N. Polunin
    • 1
  1. 1.Department of Marine Sciences and Coastal Management, University of Newcastle upon TyneNewcastle upon TyneUK

Personalised recommendations