The Mediterranean in general and the Eastern Mediterranean in particular is a unique ocean. It is situated immediately south of industrialised Europe with a population of approximately 120 million people living close to its shoreline (Turley, 1999) and is subjected to an annual invasion of a further 120–200 million tourists. Despite the natural inputs of nutrients to the system and the considerable additional anthropogenic pressures which this population subjects the basin to, it is a marine desert. It is as much of a desert as the Sahara which is located immediately to the south of the basin. Many studies have shown that the Eastern Mediterranean is ultra-oligotrophic and probably the most oligotrophic sea known. The deep blue colour of the pelagic water is an expression of this extreme desert nature. The world record Secchi depth, of 53 m, has been reported from the southern Levantine Basin (Berman et al., 1985). Other lines of evidence which demonstrate the ultra-oligotrophic nature of the system include the low depth-integrated chlorophyll values (Yacobi et al., 1995), the high contribution of pico- and nano-phytoplankton to this total chlorophyll (Li et al., 1993; Vidussi et al., 2001), and the deeper deep chlorophyll maximum (DCM) ranging seasonally between 90–110 m in summer-fall and 130–140 m in winter-spring. These and related issues will be discussed in more detail below.