Avaliação do nível trófico das águas do mar pequeno

resultados iniciais

Abstract

Trophic levei of waters from Mar Pequeno (São Paulo State, Brazil) - preliminary results. Since the 1800's, the Valo Grande Channel, 3 km long, conducted the waters from Ribeira de Iguape tiver to Mar Pequeno (a sea inlet). This channel was closed in 1978, to retum Mar Pequeno to its natural conditions. This attitude has lead to severa! problems, mostly flooding. ln order to give support to more specific studies concerning the reopening of the channel and its consequences, some algal assays to assess the trophic level of the waters were conducted. Toe test species was Skeletonema costa tum, and the EPA (1971, 1974) method was followed, with adaptations. Toe algae were inoculated in the water from Mar Pequeno, mixed with different proponions of Ribeira de lguape tiver water. The tiver water has shown algal growth potential. The maximum value was détected in a first sampling occasion, in a 1:9 river water/sea water proportion, in a second occasion in a 3:7, and for a third one, in 2:8, 4:6 and 1:1.Those relations were higher with higher salinities. The maximum growth in the first experiment was 1.84 x 10⁵ cells/ml; in the second, 1.65 x 10⁵ cells/ml and in the third one, 2.45 x 10⁵ cells/ml.