Evaluation of Paralytic Shellfish Toxins in Marine Oyster Farming and Microalgae in the Atlantic Amazon Evidences Safety but Highlights Potential Risks of Shellfish Poisoning.

Marine phycotoxins are organic compounds synthesized by some species of microalgae, which accumulate in the tissues of filter-feeder organisms such as bivalve mollusks. These toxins can cause acute intoxication episodes in humans, a severe threat to aquaculture and fisheries. In the State of Pará, Brazil, oyster farming has community, artisanal and sustainable bases, using mangroves as cultivation environment and seed banks. In small-scale production, there are often no established methods of safeguarding the health of consumers elevating the potential risks of shellfish poisoning outbreaks. Our study evaluated the presence of phycotoxins in oysters cultivated in five municipalities in the region of the Atlantic Amazon (Pará, Brazil) assessing the quality of the final product. We further evaluated the microalgae, water quality, and the spatio-temporal variation of physicochemical factors in the same area. Diatoms dominated the microalgae composition, followed by dinoflagellates, some of which are reported to be potentially toxic and producers of paralytic shellfish toxins. For the first time, we describe the occurrence of the potentially toxic dinoflagellate Ostreopsis sp. in the Amazon region. Furthermore, for the first time, toxins were detected in oyster farming in the northeast of the State of Pará, namely GTX2,3, STX, and dc-STX nevertheless, with nontoxic values. The identified toxins represent a potential threat to shellfish consumers.

Largest baleen whale mass mortality during strong El Niño event is likely related to harmful toxic algal bloom.

While large mass mortality events (MMEs) are well known for toothed whales, they have been rare in baleen whales due to their less gregarious behavior. Although in most cases the cause of mortality has not been conclusively identified, some baleen whale mortality events have been linked to bio-oceanographic conditions, such as harmful algal blooms (HABs). In Southern Chile, HABs can be triggered by the ocean-atmosphere phenomenon El Niño. The frequency of the strongest El Niño events is increasing due to climate change. In March 2015, by far the largest reported mass mortality of baleen whales took place in a gulf in Southern Chile. Here, we show that the synchronous death of at least 343, primarily sei whales can be attributed to HABs during a building El Niño. Although considered an oceanic species, the sei whales died while feeding near to shore in previously unknown large aggregations. This provides evidence of new feeding grounds for the species. The combination of older and newer remains of whales in the same area indicate that MMEs have occurred more than once in recent years. Large HABs and reports of marine mammal MMEs along the Northeast Pacific coast may indicate similar processes in both hemispheres. Increasing MMEs through HABs may become a serious concern in the conservation of endangered whale species.

Purification and characterization of saxitoxin from Mytilus chilensis of southern Chile.

In the current communication we describe an innovative method to purify saxitoxin (STX), a toxin presents in contaminated muscle of Mylitus chilensis extracted in the southern part of Chile, using a liquid chromatographic methodology based on ionic pairs. The STX was extracted using HCl and treated with ammonium sulfate following a treatment with trichloroacetic acid and hexane/diethyl ether (97/3). The samples were analyzed by a semi-preparative HPLC in order to collect pure fractions of STX and these fractions were eluted in solid-phase cationic interchange SCX extraction columns. The purified STX was stable and homogeneous and its identity was confirmed by LC-MS-MS, which demonstrated a high quality purification of STX, without presence of analogs such as neosaxitoxin (Neo) and decarbamoyl saxitoxin (dcSTX). The STX biological activity was analyzed in a bioassay in mice model and compared to the standard STX produced by the FDA and no significant differences were observed.

Facile and Cost-Effective Detection of Saxitoxin Exploiting Aptamer Structural Switching.

A simple method to detect saxitoxin (STX), one of the main components of the paralytic shellfish poison from red tide, has been developed. By using a next generation dye for double-stranded DNA we were able to differentiate fluorescence from STX-binding aptamers when exposed to different concentrations of STX, suggesting a change in aptamer folding upon target binding. The developed method is extremely rapid, only requiring small sample volumes, with quantitative results in the concentration range of 15 ng/mL to 3 µg/mL of STX, with a detection limit of 7.5 ng/mL.