The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean

Primary production, pigment concentrations and spectral measurements of downwelling irradiance were made at four stations in four seasons (spring, summer, autumn, winter) during 1994 in the waters of the South Aegean Sea (Cretan Sea), Eastern Mediterranean. sates of production were determined using in situ incubation techniques and included measurements st the surface microlayer. Depth-integrated values averaged over season were 5.66 mg C m(-2) h(-1) for primary production and the corresponding chlorophyll (Chl) a and phaeophytin (Phaeo) a values had means of 4.87 and 1.21 mg m(-3), respectively. The assimilation ratio remained very low (mean over season: 1.19 mg C mg(-1) Chl a h(-1)), as did the Phaeo a/Chl a ratio (mean over season: 0.24). The annual production for the;area was estimated to yield 24.79 g C m(-2) year(-1). Primary production and Chi a estimates showed statistically significant seasonal, spatial and depth variations. The spectral values of :he attenuation coefficient K-d (lambda) at 480 nm in the water column 0-50 m varied seasonally with higher values in spring (average 0.043 m(-1)) and winter (average 0.056 m(-1)), and lower values in summer (average 0.035 m(-1)) and autumn (average 0.026 m(-1)). The overall mean of this coefficient was 0.040 m(-1), thus classifying the waters of the South Aegean Sea as Jerlov's Optical Type I. The results of the present investigation based on the productivity and light attenuation data demonstrate clearly that the South Aegean can be considered as one of the most oligotrophic areas of the Mediterranean Sea.