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  • 1.
    Vinogradova, Olena
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Gaillard, Marie-José
    Linnaeus University, Sweden.
    Andrén, Elinor
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Palm, Veronica
    Södertörns högskola, Institutionen för historia och samtidsstudier, MARIS (Marinarkeologiska forskningsinstitutet).
    Rönnby, Johan
    Södertörns högskola, Institutionen för historia och samtidsstudier, MARIS (Marinarkeologiska forskningsinstitutet). Södertörns högskola, Institutionen för historia och samtidsstudier, Arkeologi.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Almgren, Elisabeth
    Uppsala University, Sweden.
    Karlsson, Jon
    Umeå University, Sweden.
    Nielsen, Anne Birgitte
    Lund University, Sweden.
    Åkesson, Christine
    Lund University, Sweden; St Andrews University, UK.
    Andrén, Thomas
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    3000 Years of past regional and local land-use and land-cover change in the southeastern Swedish coastal area: Early human-induced increases in landscape openness as a potential nutrient source to the Baltic Sea coastal waters2024Ingår i: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 34, nr 1, s. 56-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reconstructions of past land use and related land-cover changes at local and regional scales are needed to evaluate the potential long-term impacts of land use on the coastal waters of the Baltic Sea. In this purpose, we selected the Gamleby area at the Swedish Baltic Sea coast for a case study. We use a new, high resolution pollen record from a small lake (Lillsjön) located 3.6 km NNW of the bay Gamlebyviken and detailed analysis of the available archeological data to reconstruct local land-use changes over the last 3000 years. To estimate land-cover change at local (2–3 km radius area) and regional (50 km radius area) scales we use four additional, published pollen records from two small and two large lakes (25–70 km S of Lillsjön) and the Landscape Reconstruction Algorithm, a pollen-vegetation modeling scheme. Results show that regional and local (small lakes Lillsjön and Hyttegöl) land-cover changes are comparable over the last 1500 years (Late Iron Age to present), and that landscape openness was much larger locally than regionally (difference of 20–40% cover over the last 500 years). The periods of largest potential impacts on the Gamlebyviken Bay from regional and local land use are 200–950 CE (Late Iron Age) and 1450 CE to present, and of lowest potential impacts 950–1450 CE. The question on whether the large landscape openness 1150–50 BCE and significant afforestation 50 BCE–200 CE reconstructed for Lillsjön’s area are characteristic of the Gamlebyviken region will require additional pollen records in the catchment area. 

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  • 2.
    Dahl, Martin
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Bernabeu, I.
    Consejo Superior de Investigaciones Científicas (CEAB‐CSIC), Spain.
    Serrano, O.
    Consejo Superior de Investigaciones Científicas (CEAB‐CSIC),Spain, Edith Cowan University, Australia.
    Leiva-Dueñas, C.
    Aarhus University, Denmark.
    Linderholm, H. W.
    University of Gothenburg, Sweden.
    Asplund, M. E.
    University of Gothenburg, Sweden.
    Björk, M.
    Stockholm University, Sweden.
    Ou, T.
    University of Gothenburg, Sweden.
    Svensson, J. R.
    University of Gothenburg, Sweden.
    Andrén, Elinor
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Andrén, Thomas
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Bergman, S.
    UiT—The Arctic University of Norway, Norway.
    Braun, Sara
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Eklöf, A.
    Stockholm University, Sweden.
    Ežerinskis, Z.
    Center for Physical Sciences and Technology, Lithuania.
    Garbaras, A.
    Center for Physical Sciences and Technology, Lithuania.
    Hällberg, P.
    Stockholm University, Sweden.
    Löfgren, E.
    Stockholm University, Sweden.
    Kylander, M. E.
    Stockholm University, Sweden.
    Masqué, P.
    Edith Cowan University, Australia, PrincipalityofMonaco,Monaco.
    Šapolaitė, J.
    Center for Physical Sciences and Technology, Lithuania.
    Smittenberg, R.
    Stockholm University, Sweden, Principality of Monaco, Monaco.
    Mateo, M. A.
    Consejo Superior de Investigaciones Científicas (CEAB‐CSIC), Spain, Edith Cowan University, Australia.
    A 2,000-Year Record of Eelgrass (Zostera marina L.): Colonization Shows Substantial Gains in Blue Carbon Storage and Nutrient Retention2024Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 38, nr 3, artikel-id e2023GB008039Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Assessing historical environmental conditions linked to habitat colonization is important for understanding long-term resilience and improving conservation and restoration efforts. Such information is lacking for the seagrass Zostera marina, an important foundation species across cold-temperate coastal areas of the Northern Hemisphere. Here, we reconstructed environmental conditions during the last 14,000 years from sediment cores in two eelgrass (Z. marina) meadows along the Swedish west coast, with the main aims to identify the time frame of seagrass colonization and describe subsequent biogeochemical changes following establishment. Based on vegetation proxies (lipid biomarkers), eelgrass colonization occurred about 2,000 years ago after geomorphological changes that resulted in a shallow, sheltered environment favoring seagrass growth. Seagrass establishment led to up to 20- and 24-fold increases in sedimentary carbon and nitrogen accumulation rates, respectively. This demonstrates the capacity of seagrasses as efficient ecosystem engineers and their role in global change mitigation and adaptation through CO2 removal, and nutrient and sediment retention. By combining regional climate projections and landscape models, we assessed potential climate change effects on seagrass growth, productivity and distribution until 2100. These predictions showed that seagrass meadows are mostly at risk from increased sedimentation and hydrodynamic changes, while the impact from sea level rise alone might be of less importance in the studied area. This study showcases the positive feedback between seagrass colonization and environmental conditions, which holds promise for successful conservation and restoration efforts aimed at supporting climate change mitigation and adaptation, and the provision of several other crucial ecosystem services. © 2024. The Authors.

  • 3.
    Ismail, R. O.
    et al.
    Stockholm University, Sweden; University of Dar es Salaam, Tanzania.
    Asplund, M. E.
    University of Gothenburg, Sweden.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    George, R.
    Stockholm University, Sweden; Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Buriyo, A. S.
    University of Dar es Salaam, Tanzania.
    Mtolera, M. S. P.
    University of Dar es Salaam, Tanzania.
    Björk, M.
    Stockholm University, Sweden.
    Effects of calcification on air-water CO2 fluxes in tropical seagrass meadows: A mesocosm experiment2023Ingår i: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 561, artikel-id 151864Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seagrass meadows deliver a range of ecosystem services, where one of the more important is the capacity to store carbon and serve as sinks for atmospheric carbon dioxide. The capacity of seagrass meadows for carbon storage might, however, be modified and complicated by several factors; one important factor is the possible effects of calcification within the meadows. In tropical areas, seagrass meadows can contain high proportions of calcareous organisms, which through their calcification may cause release of CO2. To study this aspect of the CO2 balance within tropical seagrass systems, we investigated the air-water CO2 flux in seagrass mesocosms with different plant community compositions, i.e. mixtures of seagrass and calcifying macroalgae, having similar overall photosynthetic oxygen evolution rates. The measured CO2 fluxes changed both in rate and direction over the day and were significantly related to plant community composition. Downward fluxes of CO2 were found only over vegetation with high proportion of seagrass and in the afternoon, whereas occurrence of calcifying algae appeared to reverse the flow. A partial least squares (PLS) regression model indicated that pH, pCO2 and dissolved inorganic carbon (DIC) were the primary environmental variables predicting the CO2 fluxes. Our findings show that algal calcification might partly counteract the carbon sequestration in seagrass meadows.

  • 4.
    Dahl, Martin
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap. Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, Spain.
    Asplund, Maria E.
    University of Gothenburg, Sweden.
    Bergman, Sanne
    Stockholm University, Sweden.
    Björk, Mats
    Stockholm University, Sweden.
    Braun, Sara
    Stockholm University, Sweden.
    Löfgren, Elin
    Stockholm University, Sweden.
    Martí, Elisa
    University of Cadiz, Spain.
    Masque, Pere
    Edith Cowan University, Australia; IAEA Marine Environment Laboratories, Principality of Monaco, Monaco.
    Svensson, Robin
    University of Gothenburg, Sweden.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    First assessment of seagrass carbon accumulation rates in Sweden: A field study from a fjord system at the Skagerrak coast2023Ingår i: PLOS Climate, E-ISSN 2767-3200, Vol. 2, nr 1, artikel-id e0000099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seagrass meadows are globally important blue carbon sinks. In northern cold-temperate regions, eelgrass (Zostera marina) is the dominant seagrass species, and although their sedimentary carbon stocks have been quantified across regions, information regarding the CO2 withdrawal capacity as carbon sinks remains scarce. Here we assessed the carbon (Corg) accumulation rates (CARs) and stocks as well as the organic matter sources in five seagrass meadows in the Gullmar Fjord area on the Swedish Skagerrak coast. We found that the mean (±SD) CAR was 14 ± 3 g Corg m-2 yr-1 over the last ~120–140 years (corresponding to a yearly uptake of 52.4 ± 12.6 g CO2 m-2). The carbon sink capacity is in line with other Z. marina areas but relatively low compared to other seagrass species and regions globally. About half of the sedimentary carbon accumulation (7.1 ± 3.3 g Corg m-2 yr-1) originated from macroalgae biomass, which highlights the importance of non-seagrass derived material for the carbon sink function of seagrass meadows in the area. The Corg stocks were similar among sites when comparing at a standardized depth of 50 cm (4.6–5.9 kg Corg m-2), but showed large variation when assessed for the total extent of the cores (ranging from 0.7 to 20.6 kg Corg m-2 for sediment depths of 11 to at least 149 cm). The low sediment accretion rates (1.18–1.86 mm yr-1) and the relatively thick sediment deposits (with a maximum of >150 cm of sediment depth) suggests that the carbon stocks have likely been accumulated for an extended period of time, and that the documented loss of seagrass meadows in the Swedish Skagerrak region and associated erosion of the sediment could potentially have offset centuries of carbon sequestration.

  • 5.
    Katrantsiotis, Christos
    et al.
    Umeå University, Sweden.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Palm, Veronica
    Södertörns högskola, Institutionen för historia och samtidsstudier, MARIS (Marinarkeologiska forskningsinstitutet). Västerviks Museum, Sweden.
    Rönnby, Johan
    Södertörns högskola, Institutionen för historia och samtidsstudier, Arkeologi. Södertörns högskola, Institutionen för historia och samtidsstudier, MARIS (Marinarkeologiska forskningsinstitutet).
    Andrén, Thomas
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Andrén, Elinor
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Holocene relative sea level changes in the Vastervik-Gamlebyviken region on the southeast coast of Sweden, southern Baltic Sea2023Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 52, nr 2, s. 206-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We reconstruct the Holocene shore displacement of the Vastervik-Gamlebyviken area on the southeast coast of Sweden, characterised by a maritime cultural landscape and archaeological significance since the Mesolithic. Sediment cores were retrieved from four lake basins that have been raised above sea level due to the postglacial land uplift and eustatic sea level changes after the melting of the Fennoscandian Ice Sheet. The cores were radiocarbon dated and analysed for loss on ignition and diatoms. The isolation thresholds of the basins were determined using LiDAR data. The results provide evidence for the initiation of the first Littorina Sea transgression in this area at 8.5 thousand calibrated years before present (cal. ka BP). A relative sea level rise by similar to 7 m a.s.l. is recorded between 8.0 and 7.5 cal. ka BP with a highstand at similar to 22 m a.s.l. between 7.5 and 6.2 cal. ka BP. These phases coincide with the second and third Littorina Sea transgressions, respectively, in the Blekinge area, southern Sweden and are consistent with the final deglaciation of North America. After 6.2 cal. ka BP, the relative sea level dropped below 22 m a.s.l., and remained at similar to 20 m a.s.l. until 4.6 cal. ka BP coinciding with the fourth Littorina Sea transgression in Blekinge. From 4.6 to 4.2 cal. ka BP, the shore displacement shows a regression rate of 10 mm a(-1) followed by a slowdown with a mean value of 4.6 mm a(-1) until 1.6 cal. ka BP, when the relative sea level dropped below 3.3 m a.s.l. The Middle to Late Holocene highstand and other periods of minor sea level transgressions and/or higher salinity between 6.2 and 1.7 cal. ka BP are attributed to a combination of warmer climate and higher inflow of saline waters in the southern Baltic Sea due to stronger westerlies, caused by variations in the North Atlantic atmospheric patterns.

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  • 6.
    Yau, Y. Y. Y.
    et al.
    University of Gothenburg, Sweden.
    Reithmaier, G.
    University of Gothenburg, Sweden.
    Majtenyi-Hill, C.
    University of Gothenburg, Sweden.
    Serrano, O.
    Ctr Estudios Avanzados Blanes, Spain; Edith Cowan Univ, Australia.
    Pineiro-Juncal, N.
    Ctr Estudios Avanzados Blanes, Spain.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap. Ctr Estudios Avanzados Blanes, Spain.
    Mateo, M. A.
    Ctr Estudios Avanzados Blanes, Spain; Edith Cowan Univ, Australia; Universidade de Aveiro, Spain; Universidade de Santiago de Compostela, Spain.
    Bonaglia, S.
    University of Gothenburg, Sweden.
    Santos, I. R.
    University of Gothenburg, Sweden.
    Methane Emissions in Seagrass Meadows as a Small Offset to Carbon Sequestration2023Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 128, nr 6, artikel-id e2022JG007295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seagrass meadows are effective carbon sinks due to high primary production and sequestration in sediments. However, methane (CH4) emissions can partially counteract their carbon sink capacity. Here, we measured diffusive sediment-water and sea-air CO2 and CH4 fluxes in a coastal embayment dominated by Posidonia oceanica in the Mediterranean Sea. High-resolution timeseries observations revealed large spatial and temporal variability in CH4 concentrations (2-36 nM). Lower sea-air CH4 emissions were observed in an area with dense seagrass meadows compared to patchy seagrass. A 6%-40% decrease of CH4 concentration in the surface water around noon indicates that photosynthesis likely limits CH4 fluxes. Sediments were the major CH4 source as implied from radon (a natural porewater tracer) observations and evidence for methanogenesis in deeper sediments. CH4 sediment-water fluxes (0.1 +/- 0.1-0.4 +/- 0.1 mu mol m(-2) d(-1)) were higher than average sea-air CH4 emissions (0.12 +/- 0.10 mu mol m(-2) d(-1)), suggesting that dilution and CH4 oxidation in the water column could reduce net CH4 fluxes into the atmosphere. Overall, relatively low sea-air CH4 fluxes likely represent the net emissions from subtidal seagrass habitat not influenced by allochthonous CH4 sources. The local CH4 emissions in P. oceanica can offset less than 1% of the carbon burial in sediments (142 +/- 69 g CO2eq m(-2) yr(-1)). Combining our results with earlier observations in other seagrass meadows worldwide reveals that global CH4 emissions only offset a small fraction (<2%) of carbon sequestration in sediments from seagrass meadows. Plain Language Summary Seagrass meadows are hotspots for marine carbon storage in sediments. Part of the sediment carbon can be released as carbon dioxide and methane (CH4). Methane has 45-96 times more powerful global warming effect than carbon dioxide. If seagrass meadows release CH4, the emissions counteract their climate mitigation potential. We measured greenhouse gas concentrations and fluxes in a seagrass-dominated Mediterranean embayment. Low CH4 coincided with oxygen produced from seagrass photosynthesis. Areas with dense seagrass meadows had lower CH4 emissions. Overall, seagrass-dominated coasts were a small source of CH4 that offset only <2% of carbon buried in sediments on local and global scales. Hence, seagrass meadows remain an effective carbon sink.

  • 7.
    Dahl, Martin
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap. Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Cientificas (CEAB-CISC), Blanes, Spain.
    McMahon, K.
    Edith Cowan University, Australia.
    Lavery, P. S.
    Edith Cowan University, Australia.
    Hamilton, S. H.
    Australian National University, Australia.
    Lovelock, C. E.
    The University of Queensland, Australia.
    Serrano, O.
    Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Cientificas (CEAB-CISC), Blanes, Spain; Edith Cowan University, Australia.
    Ranking the risk of CO2 emissions from seagrass soil carbon stocks under global change threats2023Ingår i: Global Environmental Change, ISSN 0959-3780, E-ISSN 1872-9495, Vol. 78, artikel-id 102632Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seagrass meadows are natural carbon storage hotspots at risk from global change threats, and their loss can result in the remineralization of soil carbon stocks and CO2 emissions fueling climate change. Here we used expert elicitation and empirical evidence to assess the risk of CO2 emissions from seagrass soils caused by multiple human-induced, biological and climate change threats. Judgments from 41 experts were synthesized into a seagrass CO2 emission risk score based on vulnerability factors (i.e., spatial scale, frequency, magnitude, resistance and recovery) to seagrass soil organic carbon stocks. Experts perceived that climate change threats (e.g., gradual ocean warming and increased storminess) have the highest risk for CO2 emissions at global spatial scales, while direct threats (i.e., dredging and building of a marina or jetty) have the largest CO2 emission risks at local spatial scales. A review of existing peer-reviewed literature showed a scarcity of studies assessing CO2 emissions following seagrass disturbance, but the limited empirical evidence partly confirmed the opinion of experts. The literature review indicated that direct and long-term disturbances have the greatest negative impact on soil carbon stocks per unit area, highlighting that immediate management actions after disturbances to recover the seagrass canopy can significantly reduce soil CO2 emissions. We conclude that further empirical evidence assessing global change threats on the seagrass carbon sink capacity is required to aid broader uptake of seagrass into blue carbon policy frameworks. The preliminary findings from this study can be used to estimate the potential risk of CO2 emissions from seagrass habitats under threat and guide nature-based solutions for climate change mitigation.

  • 8.
    Silas, Mathew O.
    et al.
    Fisheries Research Institute (TAFIRI), Dar es Salaam, Tanzania.
    Kishe, Mary A.
    Fisheries Research Institute (TAFIRI), Dar es Salaam, Tanzania.
    Semba, Masumbuko R.
    Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania.
    Kuboja, Bigeyo N.
    Fisheries Research Institute (TAFIRI), Dar es Salaam, Tanzania.
    Ngatunga, Benjamin
    Tanzania Tuna Fishery National Alliance, Dar es Salaam, Tanzania.
    Mgeleka, Said S.
    Fisheries Research Institute (TAFIRI), Dar es Salaam, Tanzania; Stockholm University, Sweden.
    Linderholm, Hans W.
    University of Gothenburg, Sweden.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Seascape configuration influences big blue octopus (Octopus cyanea) catches: Implications for a sustainable fishery2023Ingår i: Fisheries Research, ISSN 0165-7836, E-ISSN 1872-6763, Vol. 264, artikel-id 106716Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seascape configuration is known to influence fish distribution and abundance in coastal waters. However, there is little information regarding how the shape of the coastal seascape influences catches of landed fisheries species, particularly so in the understudied western Indian Ocean (WIO). With focus on big blue octopus (Octopus cyanea), which is a widely found cephalopod species in the WIO, we compared landed catches (biomass, catch rate, and density) in submerged and exposed reefs, and explored the influence of proximity to fishing villages and reef habitat size on octopus landings. We used fishery-dependent data collected between 2018 and 2020 from eight landing sites spread across the Tanzanian coast. We found a strong relationship between biomass of octopus catch and distance from fished reefs to fishing villages, with higher fished biomass on reefs farther away. Octopus densities were higher, while catch rates were lower, on reefs very close to (within one km distance from) fishing villages compared to more distant reefs. In general, submerged reefs provided higher catches than exposed reefs. The low octopus catches on the exposed reefs were attributed to high fishing pressure, while submerged reefs that are only accessible through diving provide optimal areas for octopuses to grow. Octopus catches were, however, not significantly affected by reef size. The findings suggest that management policies should proportionate fishing efforts to ensure sustainable exploitation of reefs and associated fishery resources.

  • 9.
    Dahl, Martin
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap. Stockholm University, Sweden.
    Ismail, Rashid
    Stockholm University, Sweden; University of Dar es Salaam, Tanzania.
    Braun, Sara
    Stockholm University, Sweden.
    Masqué, Pere
    Edith Cowan University, Australia; International Atomic Energy, Monaco.
    Lavery, Paul S
    Edith Cowan University, Australia.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Arias-Ortiz, Ariane
    University of California, USA.
    Asplund, Maria E
    University of Gothenburg, Sweden.
    Garbaras, Andrius
    Center for Physical Sciences and Technology, Lithuania.
    Lyimo, Liberatus D
    Sokoine University of Agriculture, Tanzania.
    Mtolera, Matern S P
    University of Dar es Salaam, Tanzania.
    Serrano, Oscar
    Edith Cowan University, Australia; Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, Spain.
    Webster, Chanelle
    Edith Cowan University, Australia.
    Björk, Mats
    Stockholm University, Sweden.
    Impacts of land-use change and urban development on carbon sequestration in tropical seagrass meadow sediments2022Ingår i: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 176, artikel-id 105608Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seagrass meadows store significant carbon stocks at a global scale, but land-use change and other anthropogenic activities can alter the natural process of organic carbon (Corg) accumulation. Here, we assessed the carbon accumulation history of two seagrass meadows in Zanzibar (Tanzania) that have experienced different degrees of disturbance. The meadow at Stone Town has been highly exposed to urban development during the 20th century, while the Mbweni meadow is located in an area with relatively low impacts but historical clearing of adjacent mangroves. The results showed that the two sites had similar sedimentary Corg accumulation rates (22-25 g m-2 yr-1) since the 1940s, while during the last two decades (∼1998 until 2018) they exhibited 24-30% higher accumulation of Corg, which was linked to shifts in Corg sources. The increase in the δ13C isotopic signature of sedimentary Corg (towards a higher seagrass contribution) at the Stone Town site since 1998 points to improved seagrass meadow conditions and Corg accumulation capacity of the meadow after the relocation of a major sewage outlet in the mid-1990s. In contrast, the decrease in the δ13C signatures of sedimentary Corg in the Mbweni meadow since the early 2010s was likely linked to increased Corg run-off of mangrove/terrestrial material following mangrove deforestation. This study exemplifies two different pathways by which land-based human activities can alter the carbon storage capacity of seagrass meadows (i.e. sewage waste management and mangrove deforestation) and showcases opportunities for management of vegetated coastal Corg sinks.

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  • 10.
    Asplund, Maria E.
    et al.
    Department of Biological and Environmental Sciences, University of Gothenburg, Fiskebäckskil, Sweden.
    Bonaglia, Stefano
    Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden.
    Boström, Christoffer
    Faculty of Science and Engineering, Environmental and Marine Biology, Åbo Akademi University, Åbo, Finland.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Deyanova, Diana
    Department of Biological and Environmental Sciences, University of Gothenburg, Fiskebäckskil, Sweden.
    Gagnon, Karine
    Faculty of Science and Engineering, Environmental and Marine Biology, Åbo Akademi University, Åbo, Finland.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Holmer, Marianne
    Department of Biology, Danish Institute for Advanced Study, University of Southern Denmark, Odense, Denmark.
    Björk, Mats
    Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
    Methane Emissions From Nordic Seagrass Meadow Sediments2022Ingår i: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 8, artikel-id 811533Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shallow coastal soft bottoms are important carbon sinks. Submerged vegetation has been shown to sequester carbon, increase sedimentary organic carbon (C-org) and thus suppress greenhouse gas (GHG) emissions. The ongoing regression of seagrass cover in many areas of the world can therefore lead to accelerated emission of GHGs. In Nordic waters, seagrass meadows have a high capacity for carbon storage, with some areas being recognized as blue carbon hotspots. To what extent these carbon stocks lead to emission of methane (CH4) is not yet known. We investigated benthic CH4 emission (i.e., net release from the sediment) in relation to seagrass (i.e. Zostera marina) cover and sedimentary C-org content (%) during the warm summer period (when emissions are likely to be highest). Methane exchange was measured in situ with benthic chambers at nine sites distributed in three regions along a salinity gradient from similar to 6 in the Baltic Sea (Finland) to similar to 20 in Kattegat (Denmark) and similar to 26 in Skagerrak (Sweden). The net release of CH4 from seagrass sediments and adjacent unvegetated areas was generally low compared to other coastal habitats in the region (such as mussel banks and wetlands) and to other seagrass areas worldwide. The lowest net release was found in Finland. We found a positive relationship between CH4 net release and sedimentary C-org content in both seagrass meadows and unvegetated areas, whereas no clear relationship between seagrass cover and CH4 net release was observed. Overall, the data suggest that Nordic Zostera marina meadows release average levels of CH4 ranging from 0.3 to 3.0 mu g CH4 m(-2) h(-1), which is at least 12-78 times lower (CO2 equivalents) than their carbon accumulation rates previously estimated from seagrass meadows in the region, thereby not hampering their role as carbon sinks. Thus, the relatively weak CH4 emissions from Nordic Z. marina meadows will not outweigh their importance as carbon sinks under present environmental conditions.

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  • 11.
    Krause-Jensen, Dorte
    et al.
    Aarhus University, Denmark.
    Gundersen, Hege
    Norwegian Institute for Water Research (NIVA), Norway.
    Björk, Mats
    Stockholm University, Sweden.
    Gullström, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Asplund, Maria E.
    University of Gothenburg, Sweden.
    Boström, Christoffer
    Åbo Akademi University, Finland.
    Holmer, Marianne
    University of Southern Denmark, Denmark.
    Banta, Gary T.
    University of Southern Denmark, Denmark.
    Graversen, Anna Elizabeth Lovgren
    Aarhus University, Denmark.
    Pedersen, Morten Foldager
    Roskilde University, Denmark.
    Bekkby, Trine
    Norwegian Institute for Water Research (NIVA), Norway.
    Frigstad, Helene
    Norwegian Institute for Water Research (NIVA), Norway.
    Skjellum, Solrun Figenschau
    Norwegian Institute for Water Research (NIVA), Norway.
    Thormar, Jonas
    Institute of Marine Research, Norway.
    Gyldenkærne, Steen
    Aarhus University, Denmark.
    Howard, Jennifer
    Conservation International, Arlington, USA.
    Pidgeon, Emily
    Conservation International, Arlington, USA.
    Ragnarsdottir, Sunna Björk
    Icelandic Institute of Natural History, Iceland.
    Mols-Mortensen, Agnes
    TARI Faroe Seaweed, Faroe Islands; Fiskaaling, Faroe Islands.
    Hancke, Kasper
    Norwegian Institute for Water Research (NIVA), Norway.
    Nordic Blue Carbon Ecosystems: Status and Outlook2022Ingår i: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 9, artikel-id 847544Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Vegetated coastal and marine habitats in the Nordic region include salt marshes, eelgrass meadows and, in particular, brown macroalgae (kelp forests and rockweed beds). Such habitats contribute to storage of organic carbon (Blue Carbon - BC) and support coastal protection, biodiversity and water quality. Protection and restoration of these habitats therefore have the potential to deliver climate change mitigation and co-benefits. Here we present the existing knowledge on Nordic BC habitats in terms of habitat area, C-stocks and sequestration rates, co-benefits, policies and management status to inspire a coherent Nordic BC roadmap. The area extent of BC habitats in the region is incompletely assessed, but available information sums up to 1,440 km(2) salt marshes, 1,861 (potentially 2,735) km(2) seagrass meadows, and 16,532 km(2) (potentially 130,735 km(2), including coarse Greenland estimates) brown macroalgae, yielding a total of 19,833 (potentially 134,910) km(2). Saltmarshes and seagrass meadows have experienced major declines over the past century, while macroalgal trends are more diverse. Based on limited salt marsh data, sediment C-stocks average 3,311 g C-org m(-2) (top 40-100 cm) and sequestration rates average 142 g C-org m(-2) yr(-1). Eelgrass C-stocks average 2,414 g C-org m(-2) (top 25 cm) and initial data for sequestration rates range 5-33 g C-org m(-2), quantified for one Greenland site and one short term restoration. For Nordic brown macroalgae, peer-reviewed estimates of sediment C-stock and sequestration are lacking. Overall, the review reveals substantial Nordic BC-stocks, but highlights that evidence is still insufficient to provide a robust estimate of all Nordic BC-stocks and sequestration rates. Needed are better quantification of habitat area, C-stocks and fluxes, particularly for macroalgae, as well as identification of target areas for BC management. The review also points to directives and regulations protecting Nordic marine vegetation, and local restoration initiatives with potential to increase C-sequestration but underlines that increased coordination at national and Nordic scales and across sectors is needed. We propose a Nordic BC roadmap for science and management to maximize the potential of BC habitats to mitigate climate change and support coastal protection, biodiversity and additional ecosystem functions.

  • 12.
    Gullström, Martin
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Dahl, Martin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Miljövetenskap.
    Lindén, Olof
    Vorhies, Francis
    Forsberg, Sara
    Stockholm University, Sweden .
    Ismail, Rashid O.
    Stockholm University, Sweden; University of Dar es Salaam, Tanzania.
    Björk, Mats
    Stockholm University, Sweden.
    Coastal blue carbon stocks in Tanzania and Mozambique: Support for climate adaptation and mitigation actions2021Rapport (Övrigt vetenskapligt)
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