Environmental heterogeneity of a tropical river-to-sea continuum and its relationship with structure and phytoplankton dynamics - Lençóis Maranhenses National Park.

ß-diversity and functional traits of phytoplankton indicators associated with environmental heterogeneity were investigated as environmental quality descriptors in coastal (CS), estuarine (ES), and limnetic (LS) sectors in a tropical river-to-sea ecosystem. Results showed that environmental heterogeneity was marked by spatial differences, contributing to biological heterogeneity. Sporadic and recurrent blooms were associated with environmental spatiotemporal variations and reflected a reduction in ES α-diversity. Salinity acted as an environmental filter that governed the structure and dynamics of the community. The spatial heterogeneity and high turnover of phytoplankton resulted in reliable bioindicators selection. Colonial, bloom-forming and harmful species were associated with highly suspended particulate matter (SPM) because these species are better adapted to these conditions. Species small in size were associated with high concentrations of silicate and chlorophyll-a in the ES because of the occurrence of diatom recurrent blooms. Most flagellates indicators genera have bloom-forming potential. Integrating morphofunctional with taxonomic approaches enabled detailed observations of environmental filters, supporting the selection of priority species and areas for introducing biodiversity monitoring programs and conservation in tropical ecosystems.

Evaluation of metal contamination in surface sediments and macroalgae in mangrove and port complex ecosystems on the Brazilian equatorial margin.

This study evaluated metal contamination in surface sediments and macroalgae of mangroves and port complexes on the Brazilian equatorial margin. Samples were collected between August 2020 and February 2021 at seven points in a mangrove swamp under the influence of port activity and at two points without port activity. Metal concentrations in the macroalgae and sediments were determined using inductively coupled plasma‒optical emission spectrometry. All macroalgal species bioaccumulated metals, as demonstrated by their bioaccumulation factors. The geochemical contamination indices indicated that the estuarine complex was influenced by port activity as moderately contaminated by Pb, Cr, Mn, and Fe and considerably contaminated by Zn and Cu. The enrichment factor confirmed significant mineral enrichment of Zn and Cu in this environment. The concentrations of the metals in the sediment followed the order Fe > Mn > Cr > Zn > Cu > Pb at most sampling points. Cladophoropsis membranacea recorded the highest bioaccumulation values for Pb (0.44), Rhizoclonium africanum for Zn (1.08), Cr (0.55), and Fe (0.30), and Bostrychia radicans for Mn (2.22). The bioaccumulation pattern of metals in the most abundant macroalgal species followed the order Bostrychia radicans (Mn > Zn > Cu > Cr > Pb > Fe) and Rhizoclonium africanum (Zn > Mn > Cr > Cu > Pb > Fe).

Using a toxicity test with Ruppia maritima (Linnaeus) to assess the effects of Roundup.

Glyphosate, the active ingredient in Monsanto's broad-spectrum herbicide Roundup, consists of one of the most used pesticides worldwide, but its effects on the marine flora are still not well understood. Were examined Roundup toxic effects on Ruppia maritima specimens collected from Jansen Lagoon (São Luís, MA, Brazil) and acclimatized under laboratory conditions. The numbers of new and dead leaves, the root and leaf length, the chlorophyll a content, and the weight of R. maritima branches were determined before and after exposure to different Roundup concentrations for seven days. High concentrations caused a significant lethal effect. In addition, significant changes were observed in the wet and dry weights, the number and length of the leaves, and the chlorophyll a content. Leaf elongation was observed in the branches exposed to low concentrations, and this change was likely activated as a compensatory mechanism. The results indicate that high concentrations of this herbicide may compromise estuarine flora.