Composición y ciclo de pigmentos clorofílicos en las poblaciones del fitobentos del rio Ter durante un período de nueve meses.

Resum

Composition and seasonal variations of the chlorophyllic pigments in phytobcnthos assemblages of the Ter river along a nine-month period. Dynamics of pigments were studied in eighteen sites in the Ter river basin during a túne-month period. Clorophyll a has been revealed as the most abundant form of ehlorophyllic pigmenls throurih an HPLC analysis. Highest chl a concentrations were observed downstream the reservoirs (around 300 mg/mí and in sorne calcareous tributaries. Minimal values were recorded in the headwaters (20-50 mg/m2 ) and in somne siliceous mountain tributaires. Spring and summer were the periods when the chl a concentration reached the highest values in the basin, with lower ones in winter. The phaeopigment concentration was imponant during summer and winter, but was near to zero during spring, suggesting chl a was completely active at this time. The D43()/D66.5 ratio was around 2 always. Correlation analysis and PCA carried out between physico-chemical variables and ch! a values suggested a clear arrangement with salinity and nutriem concentralion. In fact, an stepwise regression analysis carried out with the five first principal components of PCA, pointed out that the pigment concentration is a result of the linear combination of river salinity (space) and water flow (time). The sites of the middle stretch in the axis of the river, seem to be the most favoured by this combination, mainly during spring and summer.