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Brokovich E.,Interuniversity Institute for Marine science at Eilat | Brokovich E.,Hebrew University of Jerusalem | Ayalon I.,Interuniversity Institute for Marine science at Eilat | Ayalon I.,Gulf | And 12 more authors.
Marine Ecology Progress Series | Year: 2010

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. © 2010 Inter-Research.

Polak O.,Ben - Gurion University of the Negev | Polak O.,Interuniversity Institute for Marine science at Eilat | Shashar N.,Ben - Gurion University of the Negev
Ocean and Coastal Management | Year: 2012

Part of the decline of coral reefs is attributed to the physical damage caused by divers. Consequently, active efforts are being invested to mitigate the diving pressure on and around natural reefs. We measured the effect of artificial reef (AR) placement on the diving behaviors of divers in training in the Red Sea's Gulf of Eilat on the southern tip of Israel. Dive groups were followed, and their diving times in an adjacent marine protected area (MPA) and surrounding natural coral outcrops were recorded. Time spent inside the MPA did not change. However, in-training divers reduced their times in the MPA and at two adjacent coral outcrops following AR deployment, but they did not alter other elements of their dives; coral transplantation did not affect diving behavior. A dive entry point located at least 90-m from the border of the MPA was sufficient to reduce dive time in the MPA. The AR had only a partial impact on diver behavior. Accordingly, future projects should take into account location, size, aesthetics, and the target visitors of the ARs. © 2011 Elsevier Ltd.

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