the effects of nutrient enrichment and herbivore abundance on the ability of turf algae to overgrow coral in the caribbean营养浓缩和食草动物丰度的影响的能力的地盘藻类生长过度珊瑚在加勒比海.pdf

The Effects of Nutrient Enrichment and Herbivore Abundance on the Ability of Turf Algae to Overgrow Coral in the Caribbean 1,2 2 2 ¨ 2 2 Mark J. A. Vermeij *, Imke van Moorselaar , Sarah Engelhard , Christine Hornlein , Sophie M. Vonk , Petra M. Visser1,2 1 Carmabi Foundation, Willemstad, Curac¸ao, 2 Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands Abstract Turf algae are multispecies communities of small marine macrophytes that are becoming a dominant component of coral reef communities around the world. To assess the impact of turf algae on corals, we investigated the effects of increased nutrients (eutrophication) on the interaction between the Caribbean coral Montastraea annularis and turf algae at their growth boundary. We also assessed whether herbivores are capable of reducing the abundance of turf algae at coral-algae boundaries. We found that turf algae cause visible (overgrowth) and invisible negative effects (reduced fitness) on neighbouring corals. Corals can overgrow neighbouring turf algae very slowly (at a rate of 0.12 mm 3 wk21) at ambient nutrient concentrations, but turf algae overgrew corals (at a rate of 0.34 mm 3 wk21) when nutrients were experimentally increased. Exclusion of herbivores had no measurable effect on the rate turf algae overgrew corals. We also used PAM fluorometry (a common approach for measuring of a colony’s ‘‘fitness’’) to detect the effects of turf algae on the photophysiology of neighboring corals. Turf algae always reduced the effective photochemical efficiency of neighbouring corals, r