Diaz-Pulido, G., McCook, L. J.

Relative roles of herbivory and nutrients in the recruitment of coral-reef seaweeds

2003

Australian Institute of Marine Science and Cooperative Research Centre for the Great Barrier Reef World Heritage Area

Ecology

84

8

2026-2033

"The relative effects of and interactions between, bottom-up and top-down processes are fundamental to population and community structure in both terrestrial and marine systems. These issues are especially critical for seaweed populations on coral reefs, since both bottom-up and top-down factors are suggested as causes of algal invasions during reef degradation. Although algal invasions require the establishment of new recruits, most previous studies of tropical marine algae have focused on mature stages. We simultaneously manipulated nutrient supply to and herbivory on recruits of two ecologically different species of seaweed on the Great Barrier Reef. We found that herbivory strongly reduced both density and growth of recruits for both species, whereas nutrient supply had minor effects on growth of Lobophora variegata recruits and no detectable effects on Sargassum fissifolium recruits. Notwithstanding the dominance of herbivory over nutrient effects, herbivory was not uniform, but varied both between species and among response variables (density and size), and was apparently stronger for nutrient-enriched plants. Our data demonstrate that the relative importance of bottom-up and top-down processes may depend on the species, circumstances, and life-history processes under consideration. These results also emphasize the importance of herbivores to the protection of coral reefs against algal overgrowth."

algal recruitment; coral-reef algae; coral-reef degradation; coral reefs; Great Barrier Reef; Australia; herbivory; Lobophora variegata; nutrient enhancement; nutrient supply and herbivory; Sargassum fissifolium; seaweeds; top down versus bottom-up effects

10.1890/01-3127

Supported by the Australian Institute of Marine Science, CRC Reef, School of Tropical Biology, James Cook University, and the Instituto Colombiano para el Desarrollo de la Ciencia y Tecnologia (COLCIENCIAS)

James Cook University

Instituto Colombiano para el Desarrollo de la Ciencia y Tecnologia