Freitas, A.S.; Aguiar, V.M.C., and Baptista Neto, J.A., 2021. Modern dinoflagellate cyst abundance and trace metals as biomonitoring tools in a tropical bay in Brazil. Journal of Coastal Research, 37(6), 1247–1259. Coconut Creek (Florida), ISSN 0749-0208.
The spatial distribution of the dinoflagellate cyst assemblages in 11 surface sediment samples collected in Guanabara Bay embayments and associated trace metals revealed the applicability of dinocysts as bioindicators of environmental conditions in estuarine systems. The surface sediment samples presented coarse to fine granulometry. The dinoflagellate cyst analysis followed the standard methodology through the elimination of carbonates and silica. Trace metals were extracted by the evaluation of 1 g of sediment plus a mixture of HNO3 and HCl in a microwave digestion system. Dinoflagellate cyst assemblages were dominated by Operculodinium centrocarpum, Spiniferites spp., and Lingulodinium machaerophorum. Trace metals (Cu, Zn, Pb, Cr, and Ni) showed variations at the different sampling points. The values obtained were Cu (6.7–82.8 mg kg–1), Zn (29.5–355.4 mg kg–1), Pb (18.3–86.2 mg kg–1), Cr (5.1–196.2 mg kg–1), and Ni (19.6–286.0 mg kg–1). Several samples showed high pseudototal concentrations of trace metals, which were above the natural concentrations found in nature. Statistical analysis showed a strong correlation between dinocysts species and some trace metals. Lingulodinium machaerophorum showed a high correlation with 4/5 analysed trace metals and is a eutrophication-sensitive species. However, Brigantedinium sp. presented a positive correlation with all trace metals analysed. The high frequency of L. machaerophorum cysts in all analysed samples associated with several trace metals is indicative of environmental eutrophication. The high availability of trace metals in the surface sediments of Guanabara Bay may be related to the untreated industrial wastes that are dumped directly into the bay.
