The euphotic realm of the ocean is defined as the zone that receives enough light to allow photosynthesis. The bottom of the euphotic zone is often set as the depth at which 1 % of the incident sunlight is still available, which is in the open oligotrophic ocean approximately 200 m below the surface. In more turbid coastal waters, the euphotic zone ends at much shallower waters. Whether or not photosynthesis occurs at 1 % of the incident light intensity depends first on the actual value of the latter, on the sun angle, and not in the last place on the organism considered. Even among the same species low and high-light adapted ecotypes exist. The euphotic realm is important because it provides the primary production for the food web of the whole ocean. The microbiome of this realm is therefore characterized by microorganisms that use light. The composition of the microbiome and the ecology is intimately associated with the physicochemical characteristics of the euphotic realm.
KeywordsExtracellular Polymeric Substance Fecal Pellet Euphotic Zone Compensation Point Microbial Loop
The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 311975. This publication reflects the views only of the author, and the European Union cannot be held responsible for any use which may be made of the information contained therein.
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