Diatoms (Bacillariophyta) from the southern lagoon complex of Santa Catarina, Brazil

Abstract

The southern lagoon complex of Santa Catarina is of great ecological and social importance because it is the reproduction site for fish and crustacean species that renew the marines stocks. The neighboring populations have used these stockes for surviv. This region has been impacted mostly by wastes from coaI mining and thermoeletric plants. As part ofan environmental diagnosis of the complex (Projeto Provida -1999), diatoms were surveyed and their horizontal distribution was analysed. The samples were collected from Mirim, Imaruí, Santo Antônio, Ribeirão Grande, Santa Marta, Camacho, Garopaba do Sul and Manteiga lagoons, in april / 1992 and november/1993. The samples were obtained with a phytoplankton net (25 µm mesh). There were 125 taxa identified, distributed among 66 genera: Coscinodiscophyceae (27), Fragillariophyceae (9) and Bacillariophyceae (30). Bacillariophyceae presented the greatest number of infrageneric taxa (64) followed by Coscinodiscophyceae (50) and Fragillariophyceae (10). Coscinodiscus and Diploneis had the greatest number (8) of species. Marine and estuarine taxa (96) dominate freshwater (24) and indiferent (5). Only 10 are planktic genera. The remainder are epipelic and occasionallyplanktic. The isolation degree of the lagoons was determinant for the species richness. Lesser richness occurred at Ribeirão Grande (10) and Manteiga lagoon (23), being the most isolated. Greatest richness occurred at Santo Antônio lagoon that received the greatest water flow from the complex and from the oceano.