Further insights into brevetoxin metabolism by de novo radiolabeling

Precipitation, submarine groundwater discharge of nitrogen, and red tides along the southwest Florida Gulf coast

Blooms of the dinoflagellate Karenia brevis occur almost every year along the southwest Florida Gulf coast. Long-duration blooms with especially high concentrations of K. brevis, known as red tides, destroy marine life through production of neurotoxins. Current hypotheses are that red tides originate in oligotrophic waters far offshore using nitrogen (N) from upwelling bottom water or, alternatively, from blooms of Trichodesmium, followed by advection to nearshore waters. But the amount of N available from terrestrial sources does not appear to be adequate to maintain a nearshore red tide. To explain this discrepancy, we hypothesize that contemporary red tides are associated with release of N from offshore submarine groundwater discharge (SGD) that has accumulated in benthic sediment biomass by dissimilatory nitrate reduction to ammonium (DNRA). The release occurs when sediment labile organic carbon (LOC), used as the electron donor in DNRA, is exhausted. Detritus from the resulting destruction of marine life restores the sediment LOC to continue the cycle of red tides. The severity of individual red tides increases with increased bloom-year precipitation in the geographic region where the SGD originates, while the severity of ordinary blooms is relatively unaffected.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Gambierone, a Ladder-Shaped Polyether from the Dinoflagellate Gambierdiscus belizeanus

A new natural product named gambierone (1) was isolated from the cultured dinoflagellate Gambierdiscus belizeanus. The structure of this compound features an unprecedented polyether skeleton and an unusual right-hand side chain. Its relative configuration was fully determined by interpretation of ROESY experiment and comparison between experimental and theoretical NMR data. Although the succession of cycles has no chemical similarity with ciguatoxins, 1 has a molecular formula and biological activity similar to those of CTX-3C, although much lower in intensity.