Page 3 - Zaccone_al_2001

SPATIAL AND TEMPORAL VARIATIONS IN MICROBIAL ACTIVITY 201

In the area around the Egadi Islands, Atlantic waters flow in the picnocline layer and

carry out trophic resources towards the southern part where a greater protease
activity can be observed in the surface layers (0.048 µg C h-1 dm-3). Moving from the

South to the North, protease activity levels shift to the deeper layers in relation to the
sinking of picnocline (0.013 µg C h-1 dm-3 in the photic zone and in bottom layer
0.055 µg C h-1 dm-3), following a trend which is related to the distribution of

particulate organic nitrogen content (PON) (Caruso et al., 1998).

Fig. 2 Distribution of the CO2 production rates along the water column (from 100 to 3000 m) in the
Western Mediterranean (Christensen et al., 1989), in the Ionian Sea and in the Eastern Mediterranean
(Azzaro, 1997).

A general picture of the Mediterranean Sea deriving from mean respiration data
has revealed a different scenario for the euphotic and aphotic zone. Infact, in the
surface layer (0-200m) a decreasing respiratory activity from the West to the East has
been observed, as in the Northern Adriatic towards the Otranto Channel (Fig. 1). In
opposite the respiratory rates and than the CO2 production rates, in layers below 200