Phytoplankton of the shipping sector of São Marcos Bay (Amazon Coast): A potential risk area for the establishment of non-indigenous species

Abstract

The coastal zone of the Brazilian state of Maranhão is an area characterized by diverse human activities and services, in particular in the “Ponta da Madeira” shipping terminal. The present study evaluated the structure and spatiotemporal dynamics of the phytoplankton community of the shipping sector of São Marcos Bay. Additionally, the study also investigates the evidence of the presence of allochthonous phytoplankton species. Data were collected at three sampling stations during four months in the dry season and four months in the rainy season. The phytoplankton community structure and abiotic variables varied between seasons. Mean salinity was significantly higher in the dry season (33.6 ± 3.6), while water temperature (29.0±0.3°C) and turbidity (274.2 ± 11.9 NTU) were significantly higher during the rainy season. A total of 179 phytoplankton taxa were recorded, with the highest phytoplankton biomass (chlorophyll-a) observed during the rainy months (11.6±7.8μg L−1) reflecting the availability of dissolved nutrients, as well as the intense local hydrodynamics, which contribute to the re-suspension of benthic microalgae. The occurrence of species such as Chaetoceros danicus, Coscinodiscus cf. wailesii and Planctonema lauterbornii reported for the first time on the coast of Maranhão, as well as a number of potentially harmful species of microalgae reinforces the need for the continuous monitoring of the phytoplankton community of this shipping sector, in addition to the adoption of new approaches, such as toxicological studies, which may contribute to the prediction and prevention of the proliferation of harmful algae in the region.