Citation: Delgado, J.d.F.; Amorim, R.M.; Lima, L.d.S.; Gaylarde, C.C.; Neto, J.A.B.; Pinto, S.C.d.S.; Gonçalves, B.F.d.S.; Fonseca, E.M.d. Negative Impacts of Trace Metal Contamination on the Macrobenthic Communities along the Santos Port Complex—Brazil. Eng 2023, 4, 1210–1224. https://doi.org/ 10.3390/eng4020071 Academic Editors: George Z. Papageorgiou, Maria Founti and George N. Nikolaidis Received: 31 March 2023 Revised: 16 April 2023 Accepted: 18 April 2023 Published: 20 April 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Negative Impacts of Trace Metal Contamination on the Macrobenthic Communities along the Santos Port Complex—Brazil Jéssica de F. Delgado 1,2 , Renan M. Amorim 1,2 , Leonardo da S. Lima 1,2 , Christine C. Gaylarde 1,3 , José Antônio Baptista Neto 1,2,4 , Samira C. de S. Pinto 1 , Beatriz F. dos S. Gonçalves 1 and Estefan M. da Fonseca 1,2,5, * 1 AEQUOR-Laboratório de Inteligência Ambiental, R. Joaquim Eugênio dos Santos, 408-Eldorado, Maricá 24901-040, RJ, Brazil 2 Programa de Pós-Graduação em Dinâmica dos Oceanos e da Terra, Universidade Federal Fluminense, Niterói 24210-346, RJ, Brazil 3 Department of Microbiology and Plant Biology, Oklahoma University, Norman, OK 73019, USA 4 Laboratório de Geologia Marinha, Department of Geology and Geophysics, Instituto de Geociências, Universidade Federal Fluminense, Niterói 24210-340, RJ, Brazil 5 Programa de Pós-Graduação em Administração, Universidade Federal Fluminense, Niterói 24210-340, RJ, Brazil * Correspondence: oceano25@hotmail.com Abstract: Port sites represent one of the most impacted coastal areas; this impact is due to intensive anthropogenic pressures. In addition to the port complex itself, associated activities, such as indis- criminate disposal of pollutants, including trace metals, affect the local ecosystem. Macroinvertebrate benthic communities are one of the most effective bioindicators of environmental health because of their importance as a primary food source for many fish, birds, and mammals, as well as their influence on sediment stability and geochemical composition. This article evaluates the benthic macrofauna in the Santos Estuarine System (SES), the location of the Santos Port Complex (SPC), linking trace metal levels to differences in microbenthic community structure and pollutant bioavail- ability. The distribution of Cd, Ni, and Pb was directly related to organic matter deposits, while Cu and Zn appeared to result from port activities. The SES contained a poor benthic macroinvertebrate community, resulting from the contaminated muddy sediments. A significant negative correlation was found between the macrobenthic diversity and concentrations of Cu in the soluble phase; this implied the pollution-induced degradation of the macrobenthos in SES. Keywords: macrobenthos; heavy metals; sediments; bioindicators 1. Introduction Harbors significantly impact the surrounding environments, including their biota and the pre-established ecosystem balance. They are generally located in geomorphologically protected water bodies, such as bays or estuaries, with low hydrodynamic conditions and restricted water exchange with the adjacent sea; they also frequently present lower oxygen levels in the water column, accumulating highly contaminated sediments [1]. As a result, many harbors are classified as critically contaminated spots, with low pollutant removal in the sediments resulting in high bioavailability and toxicity to the local trophic net [2,3]. The low hydrodynamic flow conditions result in the accumulation of fine-grained sediments, turning these sites into potential sinks for pollutants, especially trace metals. This may result in negative impacts on the marine ecosystem and environmental health [4]. Trace metals usually enter aquatic environments as a result of human activities linked to agriculture, fuel burning, metal corrosion, industrial plant residues, domestic sewage, and vehicular transit [5]. The bioavailability of metal to the trophic net may result in Eng 2023, 4, 1210–1224. https://doi.org/10.3390/eng4020071 https://www.mdpi.com/journal/eng