Screening the toxicity and toxin content of blooms of the cyanobacterium Trichodesmium erythraeum (Ehrenberg) in northeast Brasil

Abstract

ABSTRACT:Blooms of the cyanobacterium Trichodesmium occur in massive colored patches over large areas of tropical and subtropical oceans. Recently, the interest in such events has increased given their role in major nitrogen and carbon dioxide oceanic fluxes. Trichodesmium occurs all along the Brazilian coast and patches frequently migrate towards the coast. In this paper we screen the toxicity and toxin content of Trichodesmium blooms off the coast of Bahia state. Four samples, collected from February to April 2007, were analyzed. Organisms were identified and assessed for toxicity by means of several methods. Analogues of microcystins, cylindrospermopsins and saxitoxins were analyzed using HPLC. Microcystins were also assayed through ELISA. Results showed dominance of T. erythraeum, which makes up as much as 99% of cell counts. Other organisms found in smaller quantities include the dinoflagellates Prorocentrum minimum and P. rhathymum. Extracts from all samples delayed or interrupted sea urchin larval development, but presented no acute toxicity during a mouse bioassay. Saxitoxin congeners and microcystins were present at low concentrations in all samples, occurrences that had not previously been reported in the literature. Despite our finding of saxitoxin analogues and microcystins in Trichodesmium blooms, these toxins do not represent a potential harm to human health by primary contact. We conclude, based on our results and those reported in the recent literature, which differ from results published in 1963, that although toxins are present, there is no evidence that T. erythraeum blooms represent a threat to humans.

Microplankton Community Composition Associated With Toxic Trichodesmium Aggregations in the Southwest Atlantic Ocean

“…In ecological tests performed with both species collected and isolated from Caribbean waters, T. thiebautii was highly toxic for Artemia salina and copepods, and was neurotoxic to mice and some non-grazing copepods . T. erythraeum toxicity was assessed in populations from the Northeast of Brazil through HPLC, Elisa and ecotoxicological tests, and was positive for STX and microcystins (Proença et al, 2009). In this same region, the specie was found in co-occurrence with toxic dinoflagellates; but analagous to our study, the organisms were present in small abundances.…”

The rise of harmful cyanobacteria blooms: The potential roles of eutrophication and climate change

“…In the last decade, MCY-LR (Ramos et al, 2005) and a MCY-like cyclic peptide have also been isolated from T. erythraeum. More recently, analogs of MCY, cylindrospermopsin, and saxitoxin produced by Trichodesmium have been reported off the coast of Brazil (Proença et al, 2009), which will require lab studies to confirm.…”

Emerging health issues of cyanobacterial blooms

“…Ramos et al [16] found 0.1-1 µg g -1 microcystins (MCs) in a bloom of Trichodesmium erythraeum, which was recorded for the first time in 2004 in the Canary Islands Archipelago, during the warmest period recorded since 1912. Samples from a Trichodesmium erythraeum bloom off the Brazilian coast were analyzed for MCs, saxitoxins analogues and cylindrospermopsin [17]. MCs and STX were found in the range 10-302 µg g -1 MC-LR equivalent and 2-10 µg g -1 STX equivalent, respectively; samples resulted toxic to sea-urchin larvae, but did not show any acute toxicity in the mouse bioassay.…”