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

Marine Ecology Progress Series

Yonathan Shaked¹  Salit Kark¹  Amatzia Genin¹  Nitzan Segev¹  Inbal Ayalon¹  Moshe Kiflawi¹  Eran Brokovich¹  Shai Einbinder¹ 

关键词: Depth gradient;    Deep reefs;    Gulf of Aqaba;    Herbivore fish;    Benthic algae;    Technical diving;   

DOI  :  10.3354/meps08354

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

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.

【 授权许可】

Unknown