Harmful algal blooms (HABs) constitute a worldwide problem, affecting aquatic ecosystems, public health and local economies. Supported by the International Atomic Energy Agency since 2009, Latin America and the Caribbean (LAC) countries, including Brazil, Chile, Colombia, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Haiti, Mexico, Nicaragua, Panama, Uruguay and Venezuela, have integrated a regional network for early warning of HABs and biotoxins in seafood. Technical capacities have been developed at regional level to identify toxic species, evaluate biota toxicity, and to perform retrospective analysis of HAB occurrence. This network involves 58% of the coastal LAC countries, two regional reference centers (in El Salvador and Cuba), 14 well equipped institutions, and 177 professionals trained to contribute to the operation of HAB and biotoxin monitoring programs. All countries from the network have reported planktonic and benthic toxic species, and in selected cases, associated with toxin in biota. Dinocyst abundance analysis in ²¹⁰Pb-dated sediment cores have shown that some harmful species have been present in the region for at least 100 years ago, and that both coastal water pollution and climate change are important drivers for HAB occurrence. Efforts must be made to enrich the data base records on HAB events occurred in LAC, better understand key environmental variables that control HABs and expand coverage of HAB monitoring to all coastal countries in LAC to promote sustainable development of the region.

Coastal vegetated ecosystems constitute very productive habitats, characterized by efficient Corg sequestration and long-term preservation in sediments, so they play an important role in climate change mitigation. The temporal evolution of Corg content, stocks and burial rates were evaluated in seagrass and salt marsh habitats in San Quintin Bay (northeast Pacific, Mexico) by using 210Pb-dated sediment cores. Salt marsh cores were characterized by fine-grained sediments, higher salinities, lower terrigenous input and lower mass accumulation rates (MAR: 0.01-0.03 g cm-2 yr-1) than seagrass cores (MAR: 0.02-3.21 g cm-2 yr-1). Accumulation rates in both habitats steadily increased throughout the past century most likely because of soil erosion promoted by land use changes in the surroundings. The Corg stocks were highest in salt marsh cores (12.2-53.6 Mg ha-1 at 10 cm depth; 259-320 Mg ha-1 at 1 m depth) than in seagrass cores (5.7-14.4 Mg ha-1, and 80-98, Mg ha-1, respectively), whereas Corg burial rates were considerably lower in salt marsh (13-60 g m-2 yr-1) than in seagrass (9-144 g m-2 yr-1) habitats, and the temporal variations observed in Corg burial rates were mostly driven by changes in the accumulation rates. The overall Corg stock (485 ± 51 Gg C) for both habitats together was comparable to the carbon emissions of a major city nearby. Our results highlight the need to protect these environments as relevant carbon reservoirs.

The use of dinoflagellate cyst assemblages as a tool for palaeo-environmental reconstructions strongly relies on the robustness of cyst identification and existing information on the distribution of the different species. To this purpose, we propose a functional key for the identification of Pliocene and Quaternary Spiniferites bearing intergonal processes and depict the range of morphological variation of the different species on the basis of new observations from estuarine and coastal regions. Accordingly, the description of Spiniferites mirabilis is emended to include the new subspecies Spiniferites mirabilis subsp. serratus. We also report the occasional presence of intergonal processes in Spiniferites bentorii and Spiniferites belerius. This key aims to facilitate identification of this group of Spiniferites bearing intergonal processes and standardize cyst identification among researchers.