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11 pages, 5 figures, 2 tables ; Bottom trawling in submarine canyons can affect their natural sedimentation rates, but studies addressing this issue are still scarce. In the Gulf of Palermo (SW Mediterranean), bottom trawling occurs on the slope around Oreto, Arenella and Eleuterio canyons. Analyses of excess 210Pb concentrations and grain size fractions in sediment cores from their canyon axes revealed that sedimentation rates and silt contents increased in all canyons in the 1980s, due to the expansion of more powerful trawlers (>500 HP) to deeper fishing grounds. In Eleuterio and Arenella canyons, sedimentation rates increased by an order of magnitude (0.1-1.4 cm·yr-1), whereas they increased less (0.1-0.7 cm·yr-1) in Oreto Canyon, since the enhanced trawling-derived sediment fluxes into this canyon are affected by sediment resuspension from trawling along its axis. Considering the global expansion of bottom trawling, we anticipate similar alterations in other trawled canyons, with ecological consequences that should be addressed by management strategies ; The results presented in this study were obtained within the Exploring SiciLian CAnyoN Dynamics (ISLAND) project, supported by the European Commission, Seventh Framework Programme (EUROFLEETS2 (grant no. 312762)). The analyses were funded by the "Assessment of Bottom-trawling Impacts in Deep-sea Sediments" (ABIDES) Spanish Research Project (CTM2015-65142-R). Additional funds were provided by the Generalitat de Catalunya (2017 SGR-863 and SGR-1588), by the Australian Research Council LIEF Project (LE170100219) and by the Spanish Research Project ABRIC (RTI2018-096434-B-I00). This work is contributing to the ICTA's "Unit of Excellence" Maria de Maetzu (CEX2019-000940-M), and ICM's "Center of Excellence" Severo Ochoa (CEX2019-000928-S). The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco. CLI was supported by the H2020 MSC Action HABISS (GA 890815) ; Peer reviewed

© 2014 American Chemical Society. Submarine groundwater discharge (SGD) and derived nutrient (NO2 -, NO3 -, NH4 +, PO4 3-, and SiO2) and trace element (Cd, Co, Cu, Fe, Mo, Ni, Pb, V and Zn) loadings to the coastal sea were systematically assessed along the coast of Majorca Island, Spain, in a general survey around the island and in three representative coves during 2010. We estimated that brackish water discharges through the shoreline are important contributors to the DIN, SiO2, Fe, and Zn budgets of the nearshore waters. Furthermore, our results showed that SGD-derived elements are conditioned by the hydrogeological formations of the aquifer and discharge type. Thus, while rapid discharges through karstic conduits are enriched in SiO2 and Zn, the large detrital aquifers of the island typically present enhanced concentrations of Fe. The estimated total annual inputs of chemicals constituents discharged by SGD to the coastal waters were as follows: DIN: 610 × 103 kg yr-1, SiO2: 1400 × 103 kg yr-1, Fe: 3.2 × 103 kg yr-1, and Zn: 2.0 × 103 kg yr-1. Our results provide evidence that SGD is a major contributor to the dissolved pool of inorganic nutrients and trace metals in the nearshore waters of Majorca. ; This research has been funded by the Spanish Government projects EDASE (ref CGL2008-00047/BTE) and GRADIENTS (CTM2012-39476-C02-01). D.S.-Q. was supported by the JAE-predoc program of the Spanish National Research Council (CSIC). V.R. was supported through a Ph.D. fellowship (AP2008-03044) from MICINN (Spain). P.M. was partially supported by the ICREA Academia prize, funded by the Generalitat de Catalunya. Authors want to thank the support of the Generalitat de Catalunya to MERS (2014 SGR − 1356) ; Peer Reviewed

Este artículo contiene 12 páginas, 4 figuras, 3 tablas. ; Seagrass ecosystems rank amongst the most efficient natural carbon sinks on earth, sequestering CO2 through photosynthesis and storing organic carbon ( Corg) underneath their soils for millennia and thereby, mitigating climate change. However, estimates of Corg stocks and accumulation rates in seagrass meadows (blue carbon) are restricted to few regions, and further information on spatial variability is required to derive robust global estimates. Here we studied soil Corg stocks and accumulation rates in seagrass meadows across the Colombian Caribbean. We estimated that Thalassia testudinum meadows store 241 ± 118 Mg Corg ha− 1 (mean ± SD) in the top 1 m-thick soils, accumulated at rates of 122 ± 62 and 15 ± 7 g Corg m− 2 year− 1 over the last ~ 70 years and up to 2000 years, respectively. The tropical climate of the Caribbean Sea and associated sediment runoff, together with the relatively high primary production of T. testudinum, influencing biotic and abiotic drivers of Corg storage linked to seagrass and soil respiration rates, explains their relatively high Corg stocks and accumulation rates when compared to other meadows globally. Differences in soil Corg storage among Colombian Caribbean regions are largely linked to differences in the relative contribution of Corg sources to the soil Corg pool (seagrass, algae Halimeda tuna, mangrove and seston) and the content of soil particles < 0.016 mm binding Corg and enhancing its preservation. Despite the moderate areal extent of T. testudinum in the Colombian Caribbean (661 km2), it sequesters around 0.3 Tg CO2 year− 1, which is equivalent to ~ 0.4% of CO2 emissions from fossil fuels in Colombia. This study adds data from a new region to a growing dataset on seagrass blue carbon and further explores differences in meadow Corg storage based on biotic and abiotic environmental factors, while providing the basis for the implementation of seagrass blue carbon strategies in Colombia. ; external actions ENV/2016/380-526 cofounded by INVEMAR and Fundación Natura (Colombia,) with the support of ECU (Australia) and CSIC (project COOPB20366, I-COOP+ program, Spain). Its contents are the sole responsibility of the authors and do not necessarily reflect the views of the European Union. O.S. was supported by an ARC DECRA (DE170101524). C.S. was supported by ECU Higher Degree by Research Scholarship. P.M. was supported by the Australian Research Council LIEF Project (LE170100219). The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco. This is the Contribution #1306 from INVEMAR. ; Peer reviewed

Sequestration of plastics in sediments is considered the ultimate sink of marine plastic pollution that would justify unexpectedly low loads found in surface waters. Here, we demonstrate that mangroves, generally supporting high sediment accretion rates, efficiently sequester plastics in their sediments. To this end, we extracted microplastics from dated sediment cores of the Red Sea and Arabian Gulf mangrove (Avicennia marina) forests along the Saudi Arabian coast. We found that microplastics <0.5 mm dominated in mangrove sediments, helping explain their scarcity, in surface waters. We estimate that 50 ± 30 and 110 ± 80 metric tons of plastic may have been buried since the 1930s in mangrove sediments across the Red Sea and the Arabian Gulf, respectively. We observed an exponential increase in the plastic burial rate (8.5 ± 1.2% year$^{−1}$) since the 1950s in line with the global plastic production increase, confirming mangrove sediments as long-term sinks for plastics. ; We thank A. Qasem and P. Priahartato, from Saudi Aramco, for support and advice on sampling design; R. Lindo, R. Magalles, P. Bacquiran, S. Ibrahim, and M. Lopez, at the Marine Studies section of the Center for Environment and Water of King Fahd University of Petroleum and Minerals, for contribution in fieldwork sampling in the Arabian Gulf; and Z. Batang and staff from the Coastal and Marine Resources core laboratory at King Abdullah University of Science and Technology (KAUST) for help with sampling in the Red Sea. We thank I. Schulz, N. Geraldi, K. Rowe, S. Roth, M. Ennasri, and D. Prabowo for helping with processing of the cores. We thank the KAUST Workshop for manufacturing the SMI unit. We thank R. al Nahdi for help during plastic extraction. The International Atomic Energy Agency (IAEA) is grateful for the support provided to its Environment Laboratories by the government of the Principality of Monaco. ; This work was supported and funded by KAUST through the baseline funding of C.M.D. and by the Australian Research Council LIEF Project (LE170100219) and the Generalitat de Catalunya (grant 2017 SGR-1588) through the funding provided to P.M. This work is contributing to the ICTA "Unit of Excellence" (MinECo, MDM2015-0552).

An amendment to this paper has been published and can be accessed via a link at the top of the paper. ; P.I.M. and C.E.L. were supported by an Australian Research Council Linkage Project (LP160100242). C.M.D. was supported by baseline funding from King Abdullah University of Science and Technology. T.K. and K.W. were supported by JSPS KAKENHI (18H04156) and the Environment Research and Technology Development Fund (S-14) of the Ministry of the Environment, Japan. B.D.E. was supported by Australian Research Council grants DP160100248 and LP150100519. D.A.S. was supported by the UK Natural Environment Research Council (NE/K008439/1), and D.K.J. was supported by the CARMA project (8021-00222B), funded by the Independent Research Fund Denmark. Funding was provided to P.M. by the Generalitat de Catalunya (MERS, 2017SGR 1588) and an Australian Research Council LIEF Project (LE170100219). This work is contributing to the ICTA 'Unit of Excellence' (MinECo, MDM2015-0552). O.S. was supported by an ARC DECRA (DE170101524). N.M. was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MedShift project). N.B. was supported by the UK Research Councils under Natural Environment Research Council award NE/N013573/1. J.W.F. was supported by the US National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Grant No. DEB-1237517. R.S. had the support of FCT, project FCT UID/MAR/00350/2018. I.E.H. was supported by Ramon y Cajal Fellowship RYC2014-14970, co-funded by the Conselleria d'Innovació, Recerca i Turisme of the Balearic Government and the Spanish Ministry of Economy, Industry and Competitiveness. The University of Dundee is a registered Scottish charity, no. 015096. J.P.M. was supported by the Smithsonian Institution and the National Science Foundation Long-Term Research in Environmental Biology Program (DEB-0950080, DEB-1457100, DEB-1557009).

Policies aiming to preserve vegetated coastal ecosystems (VCE; tidal marshes, mangroves and seagrasses) to mitigate greenhouse gas emissions require national assessments of blue carbon resources. Here, we present organic carbon (C) storage in VCE across Australian climate regions and estimate potential annual CO2 emission benefits of VCE conservation and restoration. Australia contributes 5-11% of the C stored in VCE globally (70-185 Tg C in aboveground biomass, and 1,055-1,540 Tg C in the upper 1 m of soils). Potential CO2 emissions from current VCE losses are estimated at 2.1-3.1 Tg CO2-e yr-1, increasing annual CO2 emissions from land use change in Australia by 12-21%. This assessment, the most comprehensive for any nation to-date, demonstrates the potential of conservation and restoration of VCE to underpin national policy development for reducing greenhouse gas emissions. ; This project was supported by the CSIRO Marine and Coastal Carbon Biogeochemical Cluster, CSIRO Oceans and Atmosphere, the ECU Faculty Research Grant Scheme and Early Career Research Grant Schemes, UTS Plant Functional Biology and Climate Change Cluster, NSW Southeast Local Land Services, Department of Environment, Land, Water and Planning (DELWP), Parks Victoria, Victorian Coastal Catchment Management Authorities (GHCMA, CCMA, PPWCMA, WGCMA, EGCMA), University of Queensland Centennial Scholarship, Hodgkin Trust Scholarship, Australian Institute of Nuclear Science and Engineering, Northern Territory Government Innovation Grant, Australian Research Council (DE130101084, DE140101733, DE150100581, DE160100443, DE170101524, DP150103286, DP150102092, DP160100248, DP160100248, DP180101285, LE140100083, LE170100219, LP150100519, LP160100242 and LP110200975), the Generalitat de Catalunya (MERS 2014 SGR-1356), the ICTA 'Unit of Excellence' (MinECo, MDM2015-0552), Obra Social "LaCaixa", SUMILEN, CTM 2013-47728-R, Ministry of Economy and Competitiveness and UKM-DIP-2017-005. The authors are grateful to G. Bastyan, D. Kyrwood, G. Davis, J. Bongiovanni, A. Jesse, Q. Hua, A. Zawadzki, J. Gudiño, P. Bray, H. Markham, M. Lepore, K-le Gómez-Cabrera, and J. Pandolfi for their help in field and/or laboratory tasks.

Este artículo contiene 10 páginas, 3 tablas, 2 figuras. ; Policies aiming to preserve vegetated coastal ecosystems (VCE; tidal marshes, mangroves and seagrasses) to mitigate greenhouse gas emissions require national assessments of blue carbon resources. Here, we present organic carbon (C) storage in VCE across Australian climate regions and estimate potential annual CO2 emission benefits of VCE conservation and restoration. Australia contributes 5–11% of the C stored in VCE globally (70–185 Tg C in aboveground biomass, and 1,055–1,540 Tg C in the upper 1m of soils). Potential CO2 emissions from current VCE losses are estimated at 2.1–3.1 Tg CO2-e yr-1, increasing annual CO2 emissions from land use change in Australia by 12–21%. This assessment, the most comprehensive for any nation to-date, demonstrates the potential of conservation and restoration of VCE to underpin national policy development for reducing greenhouse gas emissions. ; This project was supported by the CSIRO Marine and Coastal Carbon Biogeochemical Cluster, CSIRO Oceans and Atmosphere, the ECU Faculty Research Grant Scheme and Early Career Research Grant Schemes, UTS Plant Functional Biology and Climate Change Cluster, NSW Southeast Local Land Services, Department of Environment, Land, Water and Planning (DELWP), Parks Victoria, Victorian Coastal Catchment Management Authorities (GHCMA, CCMA, PPWCMA, WGCMA, EGCMA), University of Queensland Centennial Scholarship, Hodgkin Trust Scholarship, Australian Institute of Nuclear Science and Engineering, Northern Territory Government Innovation Grant, Australian Research Council (DE130101084, DE140101733, DE150100581, DE160100443, DE170101524, DP150103286, DP150102092, DP160100248, DP160100248, DP180101285, LE140100083, LE170100219, LP150100519, LP160100242 and LP110200975), the Generalitat de Catalunya (MERS 2014 SGR-1356), the ICTA 'Unit of Excellence' (MinECo, MDM2015-0552), Obra Social "LaCaixa", SUMILEN, CTM 2013-47728-R, Ministry of Economy and Competitiveness and UKM-DIP-2017- 005. ; Peer reviewed