Sargassum-associated gastropod and amphipod assemblages in relation to metal pollution in a semi-enclosed bay

Species diversity, trophic structure, and taxonomic distinctness of molluscan assemblages associated with Sargassum beds in a historically impacted bay

“…However, another major micrograzer species, Eulithidium afine , presented a pattern more similar to what was expected, with higher densities in Santa Rita and lower densities in Lamberto. CETESB annual reports have already registered high levels of heavy metals in sediment; Longo et al (2021) similarly registered higher concentrations of Cu, Zn, and Fe in Sargassum tissue from Lamberto beach than from the remaining sites studied herein, while Santa Rita levels were constantly lower. Many studies have demonstrated that different gastropod species accumulate heavy metals in their tissues, with potential effects on their physiology and population biology (Cunha et al, 2007; Gammon et al, 2009; Krupnova et al, 2018; Maher et al, 2016); this could potentially be affecting E. affine populations in Flamengo Bay, although further manipulative studies are fundamental to test this hypothesis.…”

“…In a previous study in Flamengo Bay that simultaneously evaluated heavy metal concentrations in Sargassum tissues and associated gastropod diversity, Longo et al (2021) found lower diversity levels in Ribeira and Lamberto than in Flamengo and Santa Rita, where lower diversity levels were associated with higher levels of metal contamination. In the present more extensive study, considering the whole molluscan assemblages throughout the year, the same diversity pattern was observed, which could be associated with differences in contamination levels, such as heavy metal concentrations, as indicated by the strong correlation we found between beta diversity among assemblages from different localities and their respective differences in heavy metal concentrations.…”

“…For the estimation of community distances, we calculated de Sorensen index of beta diversity among molluscan assemblages from all pair of sites. To estimate the environmental distances, we used the information on heavy metal concentrations in Sargassum tissues from the same sites in the Flamengo Bay considered in this study, available in Longo et al (2021), and with those data we first performed a principal components analysis (PCA, Data S2), and then with the mean of the scores for the first three principal components (which retain the total variation of environmental data), we calculated the Euclidean distances between pairs of localities. The association between beta diversity and environmental distances was investigated through a Mantel test.…”

Variation in population and reproductive parameters of the amphipods, Cymadusa filosa Savigny, 1816 and Sunamphitoe pelagica (H. Milne Edwards, 1830), associated with Sargassum beds in an historically impacted bay

“…Also, in a previous study conducted by P.A.S. Longo et al (2021) in Flamengo Bay, it was shown that Sargassum fronds located in sites within Saco da Ribeira had high concentrations of heavy metals (Cu, Zn, and Fe) in their tissues.…”

“…Therefore, we hypothesize that differences in the patterns of variation in population parameters of S. pelagica and C. filosa are related to differences in contaminant concentrations between sites, associated with the ecological niche of each species. Flamengo Bay is considered a polluted area, however, with intermediate values of metal concentration compared to other sites (Longo et al, 2021). Therefore, metal concentrations found in the areas closer to the pollution source allow amphipod survival.…”