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Katz T.,Israel Oceanographic And Limnological Research | Katz T.,Interuniversity Institute for Marine science Eilat | Ginat H.,The Dead Sea and Arava Science Center | Eyal G.,Interuniversity Institute for Marine science Eilat | And 6 more authors.
Earth and Planetary Science Letters | Year: 2015

Running rivers are very scarce in globally distributed hyperarid and arid coastlines (~28,000 km worldwide), and it is ephemeral rivers that carry most terrestrial sediment into the sea in these regions. However, there is very little information regarding the contribution of terrestrial sediment and dynamics of transport of sediment that enter marine basins from these rivers. One hyperarid region, the Gulf of Aqaba received an exceptional number of flashflood events during the winter of 2012-2013. The results illustrate, for the first time, how the high volume of flashflood sediment influences the distribution of coral reefs; dwarfs the contribution of airborne dust; elevates floodwater densities to produce hyperpycnal flows, despite highest ocean salinities; and is subsequently transported to the deep basin where it may be preserved as a climate archive. © 2015 Elsevier B.V.

Dishon G.,Bar - Ilan University | Dishon G.,Interuniversity Institute for Marine science Eilat | Dubinsky Z.,Bar - Ilan University | Fine M.,Bar - Ilan University | And 2 more authors.
Israel Journal of Plant Sciences | Year: 2012

In this study, we describe the seasonal patterns and the depth dependence of the underwater distribution of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR) in the Gulf of Eilat (Aqaba). Our data show a remarkable seasonal variation in the daily irradiance dose that reaches the benthos, including seaweeds, turf algae, seagrasses, and the endosymbiotic algae of corals. Corals experience 7 times less light in the winter than in summer, which is equivalent to an almost 30 m deeper location. This seasonal variation in irradiance to which high-latitude benthic phototrophs are exposed, is due to a synergetic effect of changes in solar elevation and in water transparency. Unlike the major seasonal difference in insolation in subtropical regions, low-latitude coral reefs and benthic macrophytes are exposed to only much subtler differences in irradiance. One of the northernmost coral reefs in the world, yet a very highly diverse one, is found at the northern tip of the Gulf of Eilat (Aqaba) at 29 N. Together with its geographical marginality, this reef is also characterized by low cloud cover, making it an appropriate model for demonstrating the dynamics of a "clean" seasonal light field, in contrast to coral reefs at high latitudes with much higher cloud cover. Based on these data, we present a model allowing calculation of the seasonal variation of a light field as a function of depth and latitude under clear-sky conditions, and variable water transparency. © 2012 Science From Israel / LPPltd., Jerusalem.

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