These results are particularly interesting in light of current theories of deep-sea coral biology, which assume much cooler water conditions.įull size table Environment of the deep Red Sea Measurement of some basic biological characters provides some insight to how these corals function and survive in such a unique environment. We give some description of the distribution and habitat of various species of the observed deep-sea corals. The overall aim of this study is to present a report of opportunistic sampling of deep-sea corals in the Red Sea. Because the existing body of knowledge of deep-sea coral is based on studies of cold-water corals, the identification and study of deep-sea corals and their underlying biology in the Red Sea could open the door to new studies of the mechanisms used to adapt to these unique conditions. To date, however, no mechanism has been provided to explain the persistence of azooxanthellate corals at depths between 200 – 1000 m in the Red Sea under relatively warm water temperatures, nor has their physiology and metabolism been studied. Later work utilized extensive submersible deployments in the Gulf of Aqaba 21, 23, 24 to investigate extreme boundaries of the mesophotic reef system (to approximately 200 m depth). The presence of azooxanthellate corals in deep waters (between 400 – 1000 m) of the Red Sea was first documented in the late nineteenth century 22, but it was not possible to collect biological measurements at that time. Nonetheless, it is known for its extensive shallow water coral reefs of which some species are known to occur in depths outside the photic zone, in areas where available light is below 1% of that from the surface 21. Unfortunately, the ecology of the Red Sea is under-studied, particularly outside of the Gulf of Aqaba 20. It is unique in sustaining year-round temperatures exceeding 20☌ throughout the water column (>2000 m) 19. The Red Sea is one of the warmest, most saline and most oligotrophic marine ecosystems on Earth. A detailed understanding of the impacts of global climate change on the biology of slow-growing, long-living deep-sea corals is therefore critical. Although deep-sea corals can tolerate substantial fluctuations in temperature 17, a rise of 2☌ for only a few hours can cause significant increases in energy demands 18 with potentially serious consequences for organisms thriving in nutrient-deprived environments. Rising sea surface temperatures, a well-described threat to shallow-water coral reefs resulting in bleaching and mass mortalities 15, have been documented at great depths 16. By 2099 more than two thirds of the known deep-water coral habitats are predicted to be located in waters below the ASH potentially altering calcification abilities of corals and possibly impeding planktonic growth and hence affecting food availability for the deep-sea benthos 14. An excess of dissolved carbon dioxide in the oceans has been predicted to shoal the aragonite saturation horizon (ASH), limiting the availability of suitable habitat for deep-sea corals 13. While responses to local disturbances such as deep-sea trawling, seafloor drilling, mining, or oil spills have been investigated 12, the impacts of global climate change, such as ocean acidification and warming, remain less well understood, especially because they are difficult to measure in deep-water habitats. To date, most research in the area has focused on describing the diversity and distribution of deep-sea coral reefs. 2, 3, 4, 6, 7.ĭeep-sea coral reefs are largely valued for their importance as biodiversity hotspots 2, climate archives 9, habitats for commercial fish species 10 and promising sources of bioactive compounds 11. Aphotic deep-sea corals are thus synonymously referred to as ‘cold-water corals’ e.g. While the latter two are vital to maintaining calcification and aerobic metabolism in corals, the low temperature regimes decelerate food decay and reduce metabolic demands. In addition to nutrient availability, the main factors determining coral settlement include temperatures not exceeding 12☌ 2, 3, 6, aragonite saturation 7 and sufficient oxygen levels 8. Relatively strong currents in such areas maximize the food supply 4 and also facilitate sediment removal from either sessile organisms or the seafloor to provide suitable settlement substrata for coral larvae 5. Deep-sea corals primarily inhabit the dysphotic and aphotic zones of continental shelves, mainly in areas of distinct topography such as slopes, canyons and seamounts 3. Although first observed more than a century ago 1, coral ecosystems of the deeper aphotic zones of the oceans have only recently attracted broad interest 2.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |