(Ecology of Ribeira de Iguape River : I í Ionic content and chlorophyll a..)

Abstract

This paper is part of a project that, since 1978, investigates physical and chemical characteristcs of Ribeira de Iguape River to complement the study of autoecology of Anchoviella ("manjuba") and Macrobrachium ("pitu"), usualy found there. The research was undertaken at monthly intervals, from April 1981 to March 1984 to determine the content of chlorophyll a and the major ions (Na, K, Ca, Mg, HC0₃, S0₄ and Cl) at surface waters. The samples were collected at 14 sampling stations distributed in 4 river segments located along 160 km of the river. The studied stretch included the City of Registro (24°29'14"S and 47°50'17"W, 10 m of altitude) and stend to Iguape (24°43'S and 47°33'W) where the river reaches the sea. The salinity (the sum of the median values of dominant ions) showed low values, with the exception of the station near the estuary; the median values was 58 mg/L, with the following proportions: Ca > Mg > Na > K and HCO₃ > Cl > SO₄.·At the estuary the salinity median value was 1140 mg/L, with the following proportions: Na > Mg > Ca > K, and Cl > SO₄ > HC0₃. The relation of the monovalent (M) and divalent (D) cation as well M/M and D/D did not present any relation with chlorophyll a concentration. This shows the highest median values at Jacupiranga River (6.55 µg /L) and Ribeira de Iguape River near VaIo Grande (6,22 µg /L) and the lowest near Registro City (1.58 and 2.89 µg/L).