CHLOROPHYLL DISTRIBUTION THROUGHOUT THE SOUTHEASTERN MEDITERRANEAN INRELATION TO THE PHYSICAL STRUCTURE OF THE WATER MASS

The spatial distribution of chlorophyll was recorded throughout the so uthern part of the Levantine Basin of the eastern Mediterranean and wa s related to patterns of the physical structure and nutrient concentra tions. Chlorophyll a concentration in the upper 200 m of the water col umn ranged from 9.2 to 423 ng l(-1), with an overall mean of 126+/-85. 6 (SD) ng l(-1). The pattern of vertical distribution of chlorophyll w as close to uniform throughout the basin, with a prominent deep chloro phyll maximum (DCM) of ca. 250 ng l(-1) at 90-110 m. The values we rep ort fall at the lower end of ranges reported from other oligotrophic s eas, in accordance with the ultra-oligotrophic nature of the eastern M editerranean. Throughout the basin more than 90% of the chlorophyll at the surface was confined to particles <10 mu in diameter and more tha n 60% was found in particles <2 mu. The proportion of chlorophyll in < 2 mu, particles increased with depth between the surface and the DCM, as was also confirmed by flow cytometric analysis. Discontinuities of physical and chemical features were mostly confined to depths greater than 200 m, and had little impact on the distribution of chlorophyll. An exception was an anti cyclonic eddy south of Crete, within which ch lorophyll (mostly > 100 mu g l(-1)) was more evenly distributed with d epth over the upper 200 m.