Toward Marine Environrnental Predictions in the Mediterranean Sea Coastal Areas
343
lation systems. Naturally we expect the primary production associated to mesoscale eddies to be very important, as already shown for the world ocean
(McGillicuddy et al., 1998) and for the case of deep water formation processes
(Levy et al., 2000). The evidence of important interactions between physical variability and biochemical cycles is evident from the satellite chlorophyll picture
shown in Fig. 17.2c where the surface chlorophyll pigments concentrate in patches
geographically correlated with vortices and gyres. However, more in situ work is
still required to quantitatively estimate the importance of mesoscale variability on
the primary productivity levels of the Mediterranean.
The absolute maximum in Chlorophyll concentration is achieved in the Adriatic
Sea. The winter average Sea WIFS Chlorophyll distribution is shown again in Fig.
17.3a together with the winter mean circulation resulting from the regional circulation model of the Adriatic Sea described later. In correspondence with the intense
Westem Adriatic Coastal Current (WACC) the largest chlorophyll values are
achieved along the Italian coastlines due to the advection of nutrients and chlorophyll (Zavatarelli et al., 2000, 2001). Here the interplay between general circulation transport and river sources is very clear showing how important are the
concepts of downscaling properly from the large to the shelf regions and then to the
coastal areas. The Italian side shelf slope is in fact relatively gentle but the high
chlorophyll band extends up to the 100 meters isobath in the Middle and Southem
Adriatic showing the effect ofthe coastal area in the deeper basin parts.
In Fig. 17.3b we show a single day picture of the surface chlorophyll which
shows another important mesoscale to sub-mesoscale phenomena due to the Po
river run-offplume (Kourafalou, 1999) in contrast with the average distribution of
ch10rophyll in the bas in. These high frequency events may have the same inf1uence
on the primary productivity ofthe she1fareas as the long-term trends due to general
circulation physical forcing.
The chlorophyll distributions shown above shou1d be interpreted also as the manifestation of complex food web interactions which have been described in the past
for the Mediterranean Sea by Legendre and Rassoulzadegan (1995). The schematic
shown in Fig. 17.4 represents two different pathways that may be taken either in
the open ocean or coasta1 areas ofthe Mediterranean Sea depending on the physical
water column conditions. In the Mediterranean, at the contrary of what happens in
other deep basin areas, these conditions can be present simultaneously in the she1f
areas and the deep ocean. Both the she1f and deep ocean areas loose a1most complete1y their stratification during winter thus produc ing a traditional herbivorous
food web. In summer both the coastal and open ocean water column is very well
stratified, thus favoring the set up of a microbial food web in competition with the
herbivorous one. This microbi al food web is common in shelf/coastal areas such as
the Northem Adriatic (Vichi et al., 1998) and in the deep ocean areas where a subsurface Chlorophyll maximum is formed during summer. The major difference in
the development of the food web between the open ocean and the shelf areas is
given by the light conditions that in the coastal areas are strongly affected by suspended inorganic sediments from rivers. Light limitation is a very efficient process
343
lation systems. Naturally we expect the primary production associated to mesoscale eddies to be very important, as already shown for the world ocean
(McGillicuddy et al., 1998) and for the case of deep water formation processes
(Levy et al., 2000). The evidence of important interactions between physical variability and biochemical cycles is evident from the satellite chlorophyll picture
shown in Fig. 17.2c where the surface chlorophyll pigments concentrate in patches
geographically correlated with vortices and gyres. However, more in situ work is
still required to quantitatively estimate the importance of mesoscale variability on
the primary productivity levels of the Mediterranean.
The absolute maximum in Chlorophyll concentration is achieved in the Adriatic
Sea. The winter average Sea WIFS Chlorophyll distribution is shown again in Fig.
17.3a together with the winter mean circulation resulting from the regional circulation model of the Adriatic Sea described later. In correspondence with the intense
Westem Adriatic Coastal Current (WACC) the largest chlorophyll values are
achieved along the Italian coastlines due to the advection of nutrients and chlorophyll (Zavatarelli et al., 2000, 2001). Here the interplay between general circulation transport and river sources is very clear showing how important are the
concepts of downscaling properly from the large to the shelf regions and then to the
coastal areas. The Italian side shelf slope is in fact relatively gentle but the high
chlorophyll band extends up to the 100 meters isobath in the Middle and Southem
Adriatic showing the effect ofthe coastal area in the deeper basin parts.
In Fig. 17.3b we show a single day picture of the surface chlorophyll which
shows another important mesoscale to sub-mesoscale phenomena due to the Po
river run-offplume (Kourafalou, 1999) in contrast with the average distribution of
ch10rophyll in the bas in. These high frequency events may have the same inf1uence
on the primary productivity ofthe she1fareas as the long-term trends due to general
circulation physical forcing.
The chlorophyll distributions shown above shou1d be interpreted also as the manifestation of complex food web interactions which have been described in the past
for the Mediterranean Sea by Legendre and Rassoulzadegan (1995). The schematic
shown in Fig. 17.4 represents two different pathways that may be taken either in
the open ocean or coasta1 areas ofthe Mediterranean Sea depending on the physical
water column conditions. In the Mediterranean, at the contrary of what happens in
other deep basin areas, these conditions can be present simultaneously in the she1f
areas and the deep ocean. Both the she1f and deep ocean areas loose a1most complete1y their stratification during winter thus produc ing a traditional herbivorous
food web. In summer both the coastal and open ocean water column is very well
stratified, thus favoring the set up of a microbial food web in competition with the
herbivorous one. This microbi al food web is common in shelf/coastal areas such as
the Northem Adriatic (Vichi et al., 1998) and in the deep ocean areas where a subsurface Chlorophyll maximum is formed during summer. The major difference in
the development of the food web between the open ocean and the shelf areas is
given by the light conditions that in the coastal areas are strongly affected by suspended inorganic sediments from rivers. Light limitation is a very efficient process