Seasonal changes in phytoplankton biomass as detected by remote sensing

8 Seasonal changes in phytoplankton biomass as detected by remote sensing 

By March the seasonal thermocline would have reappeared and the characteristic summer conditions begin to reestablish themselves initially in the southern Levantine Basin. With the initiation of the bloom, mesoscale features control the details of the re-establishment of summer conditions. Eddies can still be clearly seen as areas of higher biomass in the southern Levantine, particularly in March. Summer conditions with extremely low productivity in the surface layers, and a DCM is fully established by May and reach their peak between June and August, when all of the southern Levantine has extremely low chlorophyll levels in the surface layers. It is important to remember that the satellite only sees the phytoplankton in the uppermost layers of the system. Once the seasonal thermocline is developed, the system is characterised by a deep chlorophyll maximum. Thus the drastic changes in chlorophyll shown by these images are in reality less marked. 

The major terrestrial input into the basin is the river Po which discharges into the northern Adriatic. The plume from the river flows to the south along the east coast of Italy. There seems to be a seasonality to the discharge with the highest chlorophyll presumably caused by nutrient and/or particulate input occurring in October and November. 

The Black Sea shows up as an area of very high chlorophyll throughout the year. This is expected since it is dominated by river inputs and estuarine circulation. The sea of Marmara also has high chlorophyll throughout the entire year. While there is a higher chlorophyll plume from the Black Sea into the northern Aegean, the amount seems to be relatively small and certainly smaller than the plumes observed from the Po and the Nile. Qualitative observations on the biomass produced by these extra-basin inputs are entirely compatible with recent estimates for the amount of nutrients fluxed into the basin from the sources (Krom etal., in preparation). In addition to these natural increases in biomass there is a major increase in colour off the Tunisian coast. This corresponds to an area of shallow water where there is both an increase in chlorophyll and particulates in the water column. 

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