Chemoprotection mediated by açaí berry (Euterpe oleracea) in white shrimp Litopenaeus vannamei exposed to the cyanotoxin saxitoxin analyzed by in vivo assays and docking modeling.

Saxitoxin (STX) is a neurotoxic cyanotoxin that also generate reactive oxygen species, leading to a situation of oxidative stress and altered metabolism. The Amazonian fruit açaí Euterpe oleracea possesses a high concentration of antioxidant molecules, a fact that prompted us to evaluate its chemoprotection activity against STX toxicity (obtained from samples of Trichodesmium sp. collected in the environment) in the shrimp Litopenaeus vannamei. For 30 days, shrimps were maintained in 16 aquaria containing 10 shrimps (15% salinity, pH 8.0, 24 °C, 12C/12D photoperiod) and fed twice daily with a diet supplemented with lyophilized açaí pulp (10%), in addition to the control diet. After, shrimps (7.21 ± 0.04 g) were exposed to the toxin added to the feed for 96 h. Four treatments were defined: CTR (control diet), T (lyophilized powder of Trichodesmium sp. 0.8 µg/g), A (10% of açaí) and the combination T + A. HPLC analysis showed predominance of gonyautoxin-1 concentrations (GTX-1) and gonyautoxin-4 concentrations (GTX-4). The results of molecular docking simulations indicated that all variants of STX, including GTX-1, can be a substrate of isoform mu of the glutathione-S-transferase (GST) enzyme since these molecules obtained similar values of estimated Free Energy of Binding (FEB), as well as similar final positions on the binding site. GSH levels were reduced in muscle tissues of shrimp in the T, A, and T + A treatments. Increased GST activity was observed in shrimp hepatopancreas of the T treatment and the gills of the A and T + A treatments. A decrease of protein sulfhydryl groups (P-SH) was observed in gills of shrimps from T + A treatment. A reduction in malondialdehyde (MDA) levels was registered in the hepatopancreas of the T + A treatment in respect to the Control, T, and A treatments. The use of açaí supplements in L. vannamei feed was able to partially mitigate the toxic effects caused by Trichodesmium sp. extracts, and points to mu GST isoform as a key enzyme for saxitoxin detoxification in L. vannamei, an issue that deserves further investigation.

Saxitoxins from the freshwater cyanobacterium Raphidiopsis raciborskii can contaminate marine mussels.

Raphidiopsis raciborskii (formerly Cylindrospermopsis raciborskii) is a freshwater cyanobacterium potentially producing saxitoxins (STX) and cylindrospermopsin. Its ecophysiological versatility enables it to form blooms in the most diverse types of environments, from tropical to temperate, and from relatively pristine to polluted. In Peri Lake, located in the subtropical south of Brazil, growing populations of STX-producing R. raciborskii have been detected since 1994, posing risks to the use of its waters that supply a population of about 100,000 inhabitants. Despite the existence of a monitoring system for the presence and toxicity of cyanobacteria in Peri Lake water, no assessment has been made in the coastal region, downstream of outflowing lake water, thereby potentially making available a toxic biomass to natural and cultivated shellfish populations in the salt water ecosystem. To address this problem, the present study evaluated environmental variables and STX concentration by profiling the outflowing waters between Peri Lake and the adjacent coastal zone. Laboratory experiments were carried out with three strains of R. raciborskii in order to confirm the effect of salinity on STX production and verify if Perna Perna mussels fed with R. raciborskii cultures would absorb and accumulate STX. Results showed that environmental concentrations of STX reach high levels (up to 6.31 µg L-1 STX eq.), especially in the warmer months, reaching the coastal zone. In laboratory tests, it was found that the strains tolerate salinities between 4 and 6 and that salinity influences the production of STX. In addition, mussels fed with R. raciborskii effectively absorb and accumulate STX, even in typically marine salinities (22 to 30), suggesting that R. raciborskii biomass remains available and toxic despite salinity shock. These results draw attention to the ecological and health risk associated with R. raciborskii blooms, both in the lake environment and in the adjacent marine environment, calling attention to the need to improve the monitoring and management systems for water and shellfish toxicity in the region of interest, as well as other places where toxic cyanobacteria of limnic origin can reach the coastal zone.

Nickel, vanadium, and lead as indicators of sediment contamination of marina, refinery, and shipyard areas.

Metallic elements found in the aquatic environment may originate in areas where petroleum is refined and vessels are maintained and repaired. This study aims to assess contamination caused by nickel (Ni), lead (Pb), and vanadium (V) in sediment of the Lagoa dos Patos estuary (RS, Brazil) and to evaluate them as indicators of areas under the influence of petroleum products and antifouling paints. Surface sediments were collected in summer and in winter in areas of marinas, shipyards, refinery, and a control station. High Pb and V concentrations in shipyards and at the Yacht Club showed that some organisms may be affected by toxicity. High Pb results of the index of geoaccumulation (Igeo) were found at the Yacht Club and shipyards. Al, Ni, and V had similar distribution in the sediment in both seasons. Ni and V had high relation in winter at the Yacht Club and at the Santos Shipyard, thus suggesting that these elements come mainly from petroleum products. The same happened to the relations between Pb and V, as well as Pb and Ni at the Santos Shipyard. These elements are employed as useful tools as indicators to identify places with moderate to high localized anthropogenic inputs of petroleum derivatives and antifouling paints.

Toxic Trichodesmium bloom occurrence in the southwestern South Atlantic Ocean.

Harmful Trichodesmium blooms have been reported on the continental slope of the southwestern South Atlantic Ocean; we sampled six such blooms. The highest saxitoxin concentration was observed where the number of colonies was proportionally greater relative to the total density of trichomes. Trichodesmium blooms are harmful to shrimp larvae and may lead to plankton community mortality. This study is the first record of neurotoxic blooms in the open waters of the South Atlantic.

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil.

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT-Cu concentrations was only significant (p < 0.05) at one shipyard area, while DGT-Zn was significant (p < 0.05) in every locations. The LPF of Cu and Zn concentrations demonstrated seasonal and spatial variability in all locations, mainly at shipyard areas during high salinity conditions. In general, except the control location, the sampling locations showed mean variations of 0.11-0.45 µg L(-1) for DGT-Cu, 0.89-9.96 µg L(-1) for DGT-Zn, 0.65-3.69 µg g(-1) for LPF-Cu, and 1.35-10.87 µg g(-1) for LPF-Zn. Shipyard areas demonstrated the most expressive values of labile Cu and Zn in both fractions. Strong relationship between DGT-Zn and LPF-Zn was found suggesting that the DGT-Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries.