There are several terms used to describe depth zones in the literature, although not with a consistently defined depth range (reviewed by Costello 2009 ). Terms like neritic and oceanic, epipelagic, abyssal, and bathyal are concepts rather than strict depth zones. For example, the epipelagic is the zone with enough light for photosynthesis, and light penetration will vary with water clarity. Thus photosynthesis occurs at greater depths in offshore waters than in more turbid coastal waters. Classifying species to such concepts is unnecessary if actual depth ranges are known. If a species would have its deepest and shallowest known records reported it could then be placed within any depth zone classification. The WoRMS deep-sea database has chosen 500m as the boundary for the ‘deep-sea’ because below that temperature and light generally show little variation (Rex 1981). A minimal depth zone classification could thus distinguish intertidal (or littoral, i.e. seabed exposed at low tide), subtidal (or sublittoral) and deep-sea (> 500 m depth) zones. Beyond that it would be preferable to assign actual depth ranges from known data (e.g. from OBIS and literature).
 Costello M.J. 2009. Distinguishing marine habitat classification concepts for ecological data management. Marine Ecology Progress Series 397, 253-268.