Contaminação por metais em sedimentos superficiais e macroalgas em um complexo portuário da margem equatorial brasileira

Abstract

Mangroves have been impacted by various anthropic interventions, having their ecosystem functions compromised. The contamination of mangroves by heavy metals is an example of an anthropogenic impact that can cause several deleterious effects on the ecosystem and on organisms that depend on it. Macroalgae are the basis of the trophic chain in the mangrove. They are associated with pneumatophores, rhizophores, and mangrove tree trunks and are directly affected by the impacts suffered by this ecosystem. Macroalgae are excellent biomonitors and associated with the sediment study can show the state of contamination of the environment. Thus, this work aimed to evaluate the potential for biomonitoring of macroalgal species associated with mangroves in an estuarine complex on the Brazilian equatorial margin under the influence of port activity. Samples were collected between August 2020 and February 2021 at 09 sampling points, 07 in an estuarine complex under the influence of port activity and 02 in an estuarine complex without the port activity. The collections of macroalgae and superficial sediments (5 cm) were performed in all sampling points in the intertidal region. The measurement of abiotic parameters of the water was also at all points. The concentrations of metals Zn, Cu, PB, Cr, Mn, and Fe in macroalgae and sediments were determined by inductively coupled plasma optical emission spectrophotometry. The results of the analyzes showed that there was a significant difference between the parameters water temperature, salinity, dissolved oxygen (DO), and total dissolved solids (TSD) (p < 0.05), which did not occur for the variable pH (p > 0 .05). Metal concentrations in sediments were strongly correlated with temperature, while concentrations in macroalgae showed a correlation with OD. In the sampled points, 02 species of Rhodophyceae and 03 species of Chlorophyceae were found. The rhodophytes found were Bostrychia radicans and Catenella caespitosa. As for chlorophytes, Cladophoropsis membranacea, Rhizoclonium africanum and Rhizoclonium tortuosum. Bioaccumulation factor demonstrated that all macroalgal species bioaccumulate heavy metals. The bioaccumulation pattern followed different orders among the species. Mn and Zn were the most bioaccumulated elements in all the macroalgae. In general, the geochemical contamination indices indicated the estuarine complex under the influence of port activity as moderately contaminated by Pb, Cr, Mn, and Fe and considerably contaminated by Zn and Cu. The enrichment factor confirmed the significant mineral enrichment for Zn and Cu in this environment. The responses obtained through the different species of macroalgae proved to be complementary since each species proved to be a good indicator for a particular type of metal.