Browsing by Author "Caetano, Miguel"
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- An artificial reef at the edge of the deep: An interdisciplinary case studyPublication . Ramos, Jorge; Tuaty-Guerra, Miriam; Almeida, Mariana; Raposo, Ana C.; Gaudêncio, Maria J.; Silva, Alexandra D.; Rodrigues, Nuno; Leandro, Sérgio M.; Caetano, MiguelJust nearby the largest submarine canyon in Europe - off the western coast of Portugal - is located the Nazare acute accent artificial reef (NAR) deployed in 2010 and the first of its kind in this coast. NAR aimed to improve social and economic resilience of the local communities, mainly by creating a safer and closer area for fishing and to enhance commercially exploitable marine resources. The innovative part of this research lies on the fact that for the first time was developed a multidisciplinary approach for NAR. Scientific evidence from fieldwork shows that in 2015 the reef was already mature and colonized by abundant and diversified macrobenthic assemblages. No evidence of negative impacts of NAR on the soft bottom macrofauna was observed, as assemblage composition in the NAR area and in the vicinity areas is similar. In relation to the primary producers that support the subsequent food chain, there also seems to be a balance between NAR and the surrounding area since phytoplankton was equally abundant throughout the area. Experimental fisheries and underwater visual census results on ichthyofaunal communities in the reef revealed high abundance and low levels of species richness, pouting, Trisopterus luscus Linnaeus, 1758 being the most common fish species found. Concerning NAR socio-economic impact, results from direct site observations (DSOs) showed that only some small-scale fishing vessels were eligible to operate on the NAR area. Thus, comparatively to non-AR areas nearby reef use by fishing vessels differs according to spatial and temporal strata. In what perception was concerned, the NAR has contributed to fish aggregation, though being populated mostly by small fish. Fishers have stated that some factors seemed to have changed after reef deployment. Notwithstanding, the NAR may have been a valuable contribution to an apparently overall socio-economic positive impact on the local fishing community that can be corroborated by the presence of good biological indicators.
- Footprint of roman and modern mining activities in a sediment core from the southwestern Iberian Atlantic shelfPublication . Mil-Homens, Mário; Vale, Carlos; Naughton, Filipa; Brito, Pedro; Drago, Teresa; Anes, Bárbara; Raimundo, Joana; Schmidt, Sabine; Caetano, MiguelA 5-m long sediment core (VC2B), retrieved in the Southwestem Iberian Atlantic shelf, at 96 m water depth, was used to assess major changes in climate and human activities during the last 9.7 kyrs. Analytical measurements included sedimentological (mean grain size, and the contents of sand, silt and day), geochemical (major, minor, trace and rare earth elements; REEs) and chronological (Pb-210 and C-14) parameters. Two episodes of increment of fine-grained particles, occurring at 3050 BCE and 1350 CE, suggest the retreat of the coast line to the present level and the beginning of a wetter phase associated with the "Little Ice Age". The North American Shale Composite (NASC)-normalized REE-pattern detected in the shelf is similar to that found in the Guadiana estuarine sediments. The possibility of this estuary as a contributor to the sediment load deposited in the adjacent coastal zone was indicated. Trace elements were significantly correlated with Al until 1850 CE, pointing that grain-size rules its distribution in sediments. The depth variation of As, Cu and Pb enrichment factors relative to background values shows two periods of intense human activity that can be mainly linked to mining: (i) across the Roman Period, marked by low enrichments; and (ii) starting on the second half of the 19th century until nowadays with significantly increased enrichments, especially of Pb and Cu. In addition to As, Cu and Pb, this period is also marked by high enrichments of Hg and Zn. Despite the decrease/closure of sulphide massive deposits mining exploitation (e.g., Sao Domingos, Las Herrerias) during the second half of the 20th century, results showed ongoing input of Pb,Cu, As, Hg and Zn to coastal sediments. Thus, the legacy of contamination by these elements, mainly from leaching of slags and tailings, and remobilization/reworking of contaminated estuarine sediments, is still recorded in marine sediments. (C) 2016 Elsevier B.V. All rights reserved.
- Insights of Pb isotopic signature into the historical evolution and sources of Pb contamination in a sediment core of the southwestern Iberian Atlantic shelfPublication . Mil-Homens, Mario; Vale, Carlos; Brito, Pedro; Naughton, Filipa; Drago, Teresa; Raimundo, Joana; Anes, Barbara; Schmidt, Sabine; Caetano, MiguelStable Pb isotopic ratios and concentrations of Al, Cu and Pb were measured in a 5 m long sediment core (VC2B) retrieved at 96 m water depth in the southwestern Iberian Atlantic shelf. Five phases during the last 9.5 kyrs were identified, two of them (Roman Period and modern mining) marked by a decrease of Pb-206/Pb-207 ratios reflecting additional inputs of Pb derived from mining activities. The Roman Period was also characterized by high Pb-208/Pb-206 ratios suggesting the exploitation of the outcropping portion of the orebody intensely weathered when compared with the other formations later mined. The shift of Pb-208/Pb-206 ratios towards linearity took approximately 1.0 kyrs, which may mirror the time of environmental recovery from the impact of Roman mining activities. The application of a mixing model allowed the quantification of the contribution associated with anthropogenic mining activities to the shelf sediments. The maximum values of Pb contamination occurred in the 20th century. This study gives direct evidence of Pb and Cu exploitation over the last 2000 years. The stable Pb isotopic signatures point to legacy of mining activities that are still the prevailing metal source recorded in the southwestern Iberian Atlantic shelf sediments. (C) 2017 Elsevier B.V. All rights reserved.
- Sources and distribution of organic matter and polycyclic aromatic hydrocarbons in sediments of the southwestern Portuguese shelfPublication . Mil-Homens, Mário; Gonçalves, Sofia; Cortés, Alejandro; van Drooge, Barend L.; Stigter, Henko de; Grimalt, Joan O.; Cordeiro, Lívia; Santos, Miguel M.; Almeida, C. Marisa R.; Caetano, MiguelTotal organic carbon (Corg), total nitrogen (Ntot), Corg/Ntot, δ13Corg, δ15N, calcium carbonate (CaCO3), and grain size were analyzed in 70 surface samples and 19 short cores from the southwestern Portuguese shelf. Perylene and USEPA-16 PAHs were quantified in a subset of these samples. The findings suggest that organic matter derives from a mix of terrestrial and marine sources, outlined by Corg, Ntot, and isotopic signatures. Perylene combined with δ13Corg was used to identify the main PAH sources in these environments. Diagnostic perylene ratios revealed contributions from natural sources in the Tagus region and contaminated materials from the Sado Dredged Disposal Site, with additional perylene in Sines linked to atmospheric deposition of pyrogenic sources. A significant correlation between perylene and USEPA-16 PAHs indicates natural and anthropogenic inputs from the Tagus. This multiproxy approach—combining USEPA-16ΣPAHs, perylene, and δ13Corg—offers insights for assessing environmental risks and guiding marine environmental management according to the MSFD.
- Spatial distribution and temporal trends of butyltin compounds (TBT, DBT & MBT) in short sediment cores of the SW Portuguese Shelf (western Iberian Margin, NE Atlantic)Publication . Mil-Homens, Mário; Almeida, C. Marisa R.; Dias, Sofia; Soares, Warley; van Gaever, Piet; de Stigter, Henko; Santos, Miguel M.; Santana, André; Freitas, Mafalda; Abrantes, Fatima; Caetano, MiguelSpatial patterns and temporal trends of the butyltin compounds tributyltin (TBT), dibutyltin (DBT), and mon-obutyltin (MBT) were investigated in a set of sediment samples collected along the SW Portuguese continental shelf. This region did not reach the Good Environmental Status (GES) in accordance with the Marine Strategy Framework Directive (MSFD) during a first evaluation carried out in 2012. Overall, MBT and DBT were the predominant organotin species detected, but high concentrations of TBT were found in and around disposal sites for dredge sludge derived from the dredging in navigation channels, harbours, and shipyard facilities of the Tagus and Sado estuaries. Although Portuguese regulations for monitoring sediment quality in relation to dredging activities consider only PAH, PCB and HCB, they also dictate that other organic contaminants such as butyltin compounds (BTs) should be monitored if suspicion of high values exists, but no action limits are defined for these (MAOTDR, 2007). Without action limits, the monitoring recommendation given in the regulations is not put into practice. Considering their toxicity, BT derivates should be integrated in the legislation, because they represent an environmental threat in the relocation of dredged material, especially when derived from harbour and shipyards areas. Based on this study, we recommend giving more attention to the amounts and impacts of BTs in sediments at dredged material disposal sites (DMDS) and their surroundings. Or even better, in order to be more efficient, monitoring should be done at the source of the dredged materials and not at the sink. In case it is not done, the monitoring of concentrations of TBT (and other BTs) in sediments and organisms, including imposex studies, at all Portuguese sites for disposal of dredged material receiving slightly to strongly contami-nated dredged material must be developed.
- Stakeholders' conceptualization of offshore aquaculture and small-scale fisheries interactions using a Bayesian approachPublication . Ramos, Jorge; Caetano, Miguel; Himes-Cornell, Amber; Santos, Miguel Neves dosRecent coastal planning measures in south-east Portugal (Algarve), where offshore aquaculture developments were set up in fishing areas aiming to maximize expected utility of seafood production activities, raised some discontentment. Public policies created to safeguard offshore aquaculture (OSA) producers and limit small-scale fishing (SSF) activities must be adjusted accordingly in order to maximize income and keep discontentment at a minimum. We collected primary data from stakeholders, fishers (n = 18) and offshore aquaculture operators (n = 3) through participatory workshops and interviews by eliciting problematic issues derived from the offshore area creation and their relative relevance. We used these data to populate conditional probability tables and construct a related influence diagram (Bayesian belief networks) to model the affected system. We selected nine scenarios based on navigability and aquaculture area size with the aim of finding the best expected utility combinations for the OSA SSF system. The inferred results show that maximizing employment and keep pollution at low levels were the most influential factors to keep the system at a satisfactory level. The best decision was not to enlarge the aquaculture area, but to condition the access to other operational stakeholders, namely SSF operators from nearby areas. The overall results of the Bayesian belief network can be used to recommend coastal planners and decision-makers to deal with the interaction between OSA and SSF activities.(c) 2017 Elsevier Ltd. All rights reserved.