title: Metal accumulation and oxidative stress responses in Ulva spp. in the presence of nocturnal pulses of metals from sediment: a field transplantation experiment under eutrophic conditions.
abstract: In aquatic systems under eutrophic conditions, remobilization of metals from sediment to the overlying water may occur. Consequently, adaptive responses of local organisms could result from the accumulation of metals intermittently released from the sediment. In summer 2007, a field transplantation experiment was performed in the Óbidos lagoon (Portugal) with Ulva spp. comprising three short-term exposures (between 15:30-23:30; 23:30-07:30; 07:30-15:30) during a 24-h period. In each period, Ulva spp. was collected at a reference site located in the lower lagoon (LL) and transplanted to a eutrophic site located at the Barrosa branch (BB), characterized by moderate metal contamination. For comparison purposes, macroalgae samples were simultaneously exposed at LL under the same conditions. Both sites were surveyed in short-time scales (2-4 h) for the analysis of the variability of physical-chemical parameters in the water and metal levels in suspended particulate matter. The ratios to Al of particulate Mn, Fe, Cu and Pb increased during the period of lower water oxygenation at the eutrophic site, reaching 751 × 10⁻⁴, 0.67, 12 × 10⁻⁴, 9.9 × 10⁻⁴, respectively, confirming the release of metals from the sediment to water during the night. At the reference site, dissolved oxygen oscillated around 100%, Mn/Al ratios were considerably lower (81 × 10⁻⁴-301 × 10⁻⁴) compared to BB (234 × 10⁻⁴-790 × 10⁻⁴), and no increases of metal/Al ratios were found during the night. In general, algae uptake of Mn, Cu, Fe, Pb and Cd was significantly higher at the eutrophic site compared to the reference site. The results confirmed the potential of Ulva spp. as bioindicator of metal contamination and its capability to respond within short periods. An induction of SOD, an inhibition of CAT and the increase of LPO were recorded in Ulva spp. exposed at BB (between 23:30 and 7:30) probably as a response to the higher incorporation of Mn, Fe and Pb in combination with the lack of dissolved oxygen in the water. Current findings emphasize the importance of assessing, in eutrophic systems, the relationship between the variability of chemical conditions and its repercussions on autochthonous organisms over day-night cycles.
authors.affiliation: IPMA - Portuguese Institute for the Sea and Atmosphere, Av. Brasília, 1449-006 Lisbon, Portugal; Department of Biology and CESAM, Aveiro University, 3810-193 Aveiro, Portugal. Electronic address: ppereira@ipma.pt.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Pereira
authors.affiliation: IPMA - Portuguese Institute for the Sea and Atmosphere, Av. Brasília, 1449-006 Lisbon, Portugal.
authors.forename: Hilda
authors.initials: H
authors.lastname: de Pablo
authors.affiliation: Department of Biology and CESAM, Aveiro University, 3810-193 Aveiro, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Guilherme
authors.affiliation: KAUST - King Abdullah University of Science and Technology, Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Susana
authors.initials: S
authors.lastname: Carvalho
authors.affiliation: Department of Biology and CESAM, Aveiro University, 3810-193 Aveiro, Portugal.
authors.forename: Maria Ana
authors.initials: MA
authors.lastname: Santos
authors.affiliation: IPMA - Portuguese Institute for the Sea and Atmosphere, Av. Brasília, 1449-006 Lisbon, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Vale
authors.affiliation: Department of Biology and CESAM, Aveiro University, 3810-193 Aveiro, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Pacheco
mesh_terms: D017753:Ecosystem; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry*; D008670:Metals / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000032:analysis / Q000378:metabolism; D044445:Ulva / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical; D010088:Oxidoreductases; D010100:Oxygen
keywords: Day–night cycles; Eutrophication; Metals; Oxidative stress; Ulva spp.