Trichodesmium Erythraeum Bloom on the Continental Shelf off Santos, Southeast Brazil

The Trichodesmium erythraeum is a common colonial marine cyanobacterium in tropical and subtropical oceans. Several authors have reported its importance for the fixation of both atmospheric C and N (CAPONE; CARPENTER, 1982; ZEHR et al., 2001; LUGOMELA et al., 2002; CAPONE et al., 2005). According to Carpenter and Romans (1991), nitrogen fixation by Trichodesmium cells represents an important input of new nitrogen into the euphotic zone, with daily fixation rates of approximately 30 mg 1 N m d. This exceeds the estimated flux of nitrate across the thermocline. Capone and Carpenter (1982) reported the total annual nitrogen fixation by Trichodesmium sp as 4.8 10 g N y in the world’s oceans, corresponding to 1/5 of the N fixation in all terrestrial environments. Besides fixing nitrogen, Trichodesmium cells are able to maintain their phosphorus requirement through the production of alkaline phosphatases, enzymes which enable the organism to remove the inorganic phosphate radical from organically bound phosphate (YENTSCH et al., 1972). Hahn and Capra (1992) have demonstrated the ability of T. erythraeum (Oscillatoria erythraea) to synthesize a ciguatoxin-like compound. Other studies (FONSECA et al., 2002, unpublished; NEGRI et al., 2004) report the presence of T. erythraeum in the environment with harmful effects on the components of the marine biota. Here we report the occurrence of a T. erythraeum bloom off the southeastern Brazilian coast (Fig. 1). A superficial brownish patch was detected visually (Fig. 2) during an oceanographic cruise from March 23-26, 2006 on the continental shelf off Santos.