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

Eran Brokovich, Inbal Ayalon, Shai Einbinder, Nitzan Segev, Yonathan Shaked, Amatzia Genin, Salit Kark, Moshe Kiflawi

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)69-80
Number of pages12
JournalMarine Ecology - Progress Series
StatePublished - 2010
Externally publishedYes


  • Benthic algae
  • Deep reefs
  • Depth gradient
  • Gulf of aqaba
  • Herbivore fish
  • Technical diving

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology


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