MEPS 399:69-80 (2010)  -  doi:10.3354/meps08354

Grazing pressure on coral reefs decreases across a wide depth gradient in the Gulf of Aqaba, Red Sea

Eran Brokovich1,2,3,* Inbal Ayalon1,4, Shai Einbinder1,3, Nitzan Segev1,4, Yonathan Shaked1,4 Amatzia Genin1,3,4, Salit Kark2, Moshe Kiflawi1,5

1The Interuniversity Institute for Marine Sciences at Eilat (IUI), PO Box 469, Eilat 88103, Israel
2The Biodiversity Research Group, Department of Evolution, Systematics and Ecology, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 91904, Israel
3Department of Evolution, Systematics and Ecology, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 91904, Israel
4The Israel National Monitoring Program at the Gulf of Eilat, at the IUI
5Department of Life Sciences, Ben Gurion University, PO Box 653, Beer-Sheva, 84105, Israel

ABSTRACT: Algae are an essential component of healthy coral reefs and serve as the base of the food chain and as a living habitat for numerous organisms. Herbivorous fish play an important role in coral reef ecology by mediating competition between fast-growing algae and relatively slow-growing corals. However, because of diving-related difficulties, the importance of herbivory in deep mesophotic coral reefs (30 to 150 m) remains largely unknown. We examined the relationship between herbivores and algae along a depth gradient down to 65 m, and evaluated grazing pressure along the depth gradient. We visually assessed the abundance of herbivorous fish along the depth gradient and estimated fish biomass. We measured in situ turf algae growth rates and performed experimental assessments of grazing pressure using settlement plates and bioassays. We discovered that, while both algal growth and fish density decrease with depth, the decrease in grazing pressure is steeper, with a consumption of <20% of turf-algae production at 65 m versus 40 to 60% at depths of 5 to 20 m. Concomitantly, a decrease in fish biomass and density along the depth gradient reduced potential grazing pressure on macroalgae. Our findings suggest a less important role for herbivorous fish in maintaining algal-free substrate for coral recruitment and growth in deep zones compared with the shallow reef.


KEY WORDS: Depth gradient · Deep reefs · Gulf of Aqaba · Herbivore fish · Benthic algae · Technical diving


Full text in pdf format 
Cite this article as: Brokovich E, Ayalon I, Einbinder S, Segev N and others (2010) Grazing pressure on coral reefs decreases across a wide depth gradient in the Gulf of Aqaba, Red Sea. Mar Ecol Prog Ser 399:69-80

Export citation: Endnote - Reference Manager
Mail this link - Contents Mailing Lists - RSS
- -