Vol.: (0123456789) 1 3 Environ Monit Assess (2023) 195:261 https://doi.org/10.1007/s10661-022-10867-2 Effects of dredging activities and seasonal variation on coastal plankton assemblages: results from 10 years of environmental monitoring Lohengrin D. A. Fernandes  · Guilherme N. Corte · Laura Moura · Carolina Reis · Thiago Matos · Danubia Moreno · Pedro Sant’ Anna Cortez · Wanderson Fernandes de Carvalho · Wanda Monteiro‑Ribas · José Eduardo A. Gonçalves · Fernando Ribeiro · Fernanda Thomazelli · Nafisa Rizzini‑Ansari · Eduardo Barros Fagundes Neto · Luiz Ricardo Gaelzer · Elizabeth de Souza Martins · Márcio Martins Lobão · Maria Helena Baeta‑Neves · Ricardo Coutinho Received: 23 August 2022 / Accepted: 19 December 2022 © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2023 the abundance of both groups increased during dredg- ing due to the resuspension of nutrients and benthic organisms. This increase was particularly evident in the dinoflagellate Scrippsiellaa cuminata, the diatoms Thalassiosira rotula and Nitzschia longissima, and the herbivorous zooplankton Acartia clausii and Pseude- vadne tergestina. Moreover, season and dredging activ- ities synergistically influenced plankton assemblages, resulting in larger seasonal variations during dredging activities. After the end of the harbor construction, plankton abundance decreased and remained low until the end of the monitoring, which may indicate persis- tent changes in the biodiversity and ecosystem func- tioning of impacted areas. Abstract Coastal zones support the most productive marine ecosystems, yet they are increasingly threat- ened by anthropogenic stressors such as dredging. In this study, we investigated how seasonal variation and dredging activities conducted during the construc- tion of a harbor and submarine base (Sepetiba Bay, RJ, Brazil) affected the phytoplankton and zooplank- ton assemblages. The observed temporal variability at five different sites over 10 years revealed that dredging exceeds the expected influence of dry and rainy sea- sons on plankton abundance and diversity. In general, Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s10661-022-10867-2. L. D. A. Fernandes (*) · G. N. Corte · L. Moura · J. E. A. Gonçalves · M. H. Baeta-Neves · R. Coutinho  Division of Applied Biotechnology, Department of Marine Biotechnology, Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM), Brazilian Navy, Kioto St, 253, Arraial do Cabo, Rio de Janeiro 28930-000, Brazil e-mail: lohengrin.fernandes@gmail.com; lohengrin@ marinha.mil.br L. D. A. Fernandes · C. Reis · T. Matos · M. H. Baeta-Neves · R. Coutinho  Marine Biotechnology Post-Graduation Program (PPGBM), Rio de Janeiro, Brazil G. N. Corte  College of Science and Mathematics, University of Virgin Islands, Charlotte Amalie West, Saint Thomas, USVI, USA D. Moreno · P. S. A. Cortez · W. Monteiro-Ribas · E. B. F. Neto · L. R. Gaelzer · E. de Souza Martins  Division of Biological Oceanography, Department of Oceanography, IEAPM, Brazilian Navy, Kioto St, 253, Rio de Janeiro, Arraial Do Cabo, Brazil W. F. de Carvalho  Department of Marine Ecology and Resources, Federal University of the State of Rio de Janeiro, DERM/UNIRIO, Rio de Janeiro, Brazil F. Ribeiro  Division of Physical Oceanography, Department of Oceanography, IEAPM, Brazilian Navy, Kioto St, 253, Rio de Janeiro, Arraial Do Cabo, Brazil