Occurrence of potentially toxic microalgae and diarrhetic shellfish toxins in the digestive tracts of green sea turtles (Chelonia mydas) from southern Brazil.

Algal toxins are involved in the mortality and/or illness of marine organisms via consumption of contaminated prey, or upon direct exposure to toxic cells. In this study, the presence of potentially toxic microalgal cells was investigated within the digestive tract contents of a threatened species of green turtle (Chelonia mydas). Additionally, lipophilic toxins were determined by LC-MS/MS in tissue samples (liver, stomach and/or intestine) of selected animals (n = 39 individuals) found dead-stranded in southern Brazil, from winter/2015 to autumn/2016. Thirteen potentially toxic species of microalgae (both benthic and planktonic), including seven dinoflagellates, six cyanobacteria and one diatom, were found in the digestive tract contents of green turtles. Among them, dinoflagellates belonging to the Dinophysis acuminata species complex were the most frequent (36%) and abundant (maximum average abundance of 566 cells g-1 in spring/2015). Moreover, 23% of the examined sea turtles exhibited detectable levels of the diarrhetic shellfish toxin okadaic acid (OA) in washed digestive tissues. Seven individuals accumulated OA in their intestines (max. 24.1 ng g-1) and two in the stomachs (max. 7.4 ng g-1). Toxin levels in the tissues were directly and significantly (r = 0.70, p < 0.025) associated with the cell abundance of OA-producing D. acuminata and Prorocentrum lima species complexes within the digestive contents of green turtles. Although OA concentrations were relatively low, possible chronic exposure might deteriorate general health conditions of exposed sea turtles, increasing the risk for diseases. Okadaic acid has been regarded as a tumor-promoting compound and an environmental co-factor in the incidence of fibropapillomatosis, a frequent disease in juvenile green turtles inhabiting this geographic region. Even though, only one green turtle containing OA in the digestive tissues (out of six examined) also presented fibropapillomatosis in this study. Notwithstanding, sea turtles are sentinels of ocean health. Monitoring the accumulation of algal toxins and their negative effects on these organisms contributes to conserving biodiversity and marine habitats.

Prevalence of okadaic acid in benthic organisms associated Prorocentrum lima complex in a sub-tropical estuary.

Lipophilic toxins were investigated in different benthic compartments of Paranaguá Bay, southern Brazil. Relatively low concentrations of okadaic acid (OA) were frequently reported in macrophyte extracts (maximum 0.64 ng g-1), mainly in sheltered estuarine areas, correlated with the cell abundance of toxigenic benthic dinoflagellates, Prorocentrum lima. Non-conjugated OA was also detected in benthic marine animals, mostly during summer-autumn 2016. Higher OA concentrations were found in the viscera of Genidens genidens fish (24.3 ± 3.7 ng g-1) and in soft tissues of Mytella guyanensis bivalves (21.3 ± 2.13 ng g-1), whereas lower levels were less frequently reported in many other benthic feeders, including cephalopods, gastropods, crustaceans and fishes. Although OA concentrations were below the levels associated with acute human intoxication, possible chronic effects to benthic animals and their consumers cannot be disregarded due to the frequent presence of this biotoxin in various fishery resources. Human health risks are substantially enhanced for small-scale fishing communities and other socioeconomically vulnerable populations.

Summer bloom of Vulcanodinium rugosum in Cienfuegos Bay (Cuba) associated to dermatitis in swimmers.

The marine dinoflagellate Vulcanodinium rugosum produces powerful paralyzing and cytotoxic compounds named pinnatoxins (PnTX) and portimines. Even though, no related human intoxication episodes following direct exposure in seawater or the ingestion of contaminated seafood have been documented so far. This study aimed at investigating a dinoflagellate bloom linked to acute dermatitis cases in two recreational beaches in Cienfuegos Bay, Cuba. We used epidemiological and clinical data from 60 dermatitis cases consisting of individuals in close contact with the bloom. Seawater physical-chemical properties were described, and the microorganism causing the bloom was identified by means of light and scanning electron microscopy. Morphological identification was confirmed genetically by sequencing the internal transcribed spacers ITS1 and ITS2, and the 5.8S rDNA region. Toxic compounds were identified from a bloom extract using liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS), and their concentrations were estimated based on low-resolution tandem mass spectrometry (LC-MS/MS). Sixty people who had prolonged contact with the dinoflagellate bloom suffered acute dermal irritation. Most patients (79.2%) were children and had to be treated with antibiotics; some required >5-day hospitalization. Combined morphological and genetic characters indicated V. rugosum as the causative agent of the bloom. rDNA sequences of the V. rugosum genotype found in the bloom aligned with others from Asia, including material found in the ballast tank of a ship in Florida. The predominant toxins in the bloom were portimine, PnTX-F and PnTX-E, similar to strains originating from the Pacific Ocean. This bloom was associated with unusual weather conditions such as frequent and prolonged droughts. Our findings indicate a close link between the V. rugosum bloom and a dermatitis outbreak among swimmers in Cienfuegos Bay. Phylogenetic evidence suggests a recent introduction of V. rugosum from the Pacific Ocean into Caribbean waters, possibly via ballast water.

Morphology, toxicity and molecular characterization of Gambierdiscus spp. towards risk assessment of ciguatera in south central Cuba.

Ciguatera poisoning is caused by the consumption of reef fish or shellfish that have accumulated ciguatoxins, neurotoxins produced by benthic dinoflagellates of the genera Gambierdiscus or Fukuyoa. Although ciguatera constitutes the primary cause of seafood intoxication in Cuba, very little information is available on the occurrence of ciguatoxins in the marine food web and the causative benthic dinoflagellate species. This study conducted on the south-central coast of Cuba reports the occurrence of Gambierdiscus and Fukuyoa genera and the associated benthic genera Ostreopsis and Prorocentrum. Gambierdiscus/Fukuyoa cells were present at low to moderate abundances depending on the site and month of sampling. This genus was notably higher on Dictyotaceae than on other macrophytes. PCR analysis of field-collected samples revealed the presence of six different Gambierdiscus and one Fukuyoa species, including G. caribaeus, G. carolinianus, G. carpenteri, G. belizeanus, F. ruetzleri, G. silvae, and Gambierdiscus sp. ribotype 2. Only Gambierdiscus excentricus was absent from the eight Gambierdiscus/Fukuyoa species known in the wider Caribbean region. Eleven clonal cultures were established and confirmed by PCR and SEM as being either G. carolinianus or G. caribaeus. Toxin production in each isolate was assessed by a radioligand receptor binding assay and found to be below the assay quantification limit. These novel findings augment the knowledge of the ciguatoxin-source dinoflagellates that are present in Cuba, however further studies are needed to better understand the correlation between their abundance, species-specific toxin production in the environment, and the risk for fish contamination, in order to develop better informed ciguatera risk management strategies.