title: Propensity to metal accumulation and oxidative stress responses of two benthic species (Cerastoderma edule and Nephtys hombergii): are tolerance processes limiting their responsiveness?
abstract: The chronic exposure of benthic organisms to metals in sediments can lead to the development of tolerance mechanisms, thus diminishing their responsiveness. This study aims to evaluate the accumulation profiles of V, Cr, Co, Ni, As, Cd, Pb and Hg and antioxidant system responses of two benthic organisms (Cerastoderma edule, Bivalvia; Nephtys hombergii, Polychaeta). This approach will provide clarifications about the ability of each species to signalise metal contamination. Organisms of both species were collected at the Tagus estuary, in two sites with distinct contamination degrees (ALC, slightly contaminated; BAR, highly contaminated). Accordingly, C. edule accumulated higher concentrations of As, Pb and Hg at BAR compared to ALC. However, antioxidant responses of C. edule were almost unaltered at BAR and no peroxidative damage occurred, suggesting adjustment mechanisms to the presence of metals. In contrast, N. hombergii showed a minor propensity to metal accumulation, only signalising spatial differences for As and Pb and accumulating lower concentrations of metals than C. edule. The differences in metal accumulation observed between species might be due to their distinctive foraging behaviour and/or the ability of N. hombergii to minimise the metal uptake. Despite that, the accumulation of As and Pb was on the basis of the polychaete antioxidant defences inhibition at BAR, including CAT, SOD, GR and GPx. The integrated biomarker response index (IBRv2) confirmed that N. hombergii was more affected by metal exposure than C. edule. In the light of current findings, in field-based studies, the information of C. edule as a bioindicator should be complemented by that provided by another benthic species, since tolerance mechanisms to metals can hinder a correct diagnosis of sediment contamination and of the system's health. Overall, the present study contributed to improve the lack of fundamental knowledge of two widespread and common estuarine species, providing insights of the metal accumulation profiles under a scenario of chronic contamination. Finally, this work provided useful information that can be applied in the interpretation of future environmental monitoring studies.
authors.affiliation: CESAM - Center for Environmental and Marine Studies and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal. anammarques@ua.pt.
authors.forename: Ana
authors.initials: A
authors.lastname: Marques
authors.affiliation: IPMA - The Portuguese Sea and Atmosphere Institute, Avenida 5 de Outubro, 8700-305, Olhão, Portugal.|Department of Biology, Faculty of Marine and Environmental Sciences, University of Cadiz, Campus de Excelencia Internacional del Mar (CEIMAR), Avenida República Saharaui S/N Puerto Real, 11510, Puerto Real, Cadiz, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Piló
authors.affiliation: IPMA - The Portuguese Sea and Atmosphere Institute, Avenida Brasília, 1449-006, Lisbon, Portugal.
authors.forename: Olinda
authors.initials: O
authors.lastname: Araújo
authors.affiliation: IPMA - The Portuguese Sea and Atmosphere Institute, Avenida 5 de Outubro, 8700-305, Olhão, Portugal.
authors.forename: Fábio
authors.initials: F
authors.lastname: Pereira
authors.affiliation: CESAM - Center for Environmental and Marine Studies and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Guilherme
authors.affiliation: IPMA - The Portuguese Sea and Atmosphere Institute, Avenida 5 de Outubro, 8700-305, Olhão, Portugal.|Biological and Environmental Sciences & Engineering Division, Red Sea Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Susana
authors.initials: S
authors.lastname: Carvalho
authors.affiliation: CESAM - Center for Environmental and Marine Studies and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Maria Ana
authors.initials: MA
authors.lastname: Santos
authors.affiliation: CESAM - Center for Environmental and Marine Studies and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Pacheco
authors.affiliation: CESAM - Center for Environmental and Marine Studies and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Pereira
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D049873:Cardiidae / Q000378:metabolism / Q000502:physiology*; D004784:Environmental Monitoring; D008668:Metallothionein / Q000378:metabolism; D008670:Metals / Q000378:metabolism / Q000633:toxicity*; D018384:Oxidative Stress; D011077:Polychaeta / Q000378:metabolism / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D015415:Biomarkers; D008670:Metals; D014874:Water Pollutants, Chemical; D008668:Metallothionein
keywords: Antioxidant defences; Benthic organisms; Estuary contamination; Integrated biomarker response; Metal accumulation; Tolerance mechanisms