| 1. |
- Asplund, Maria. E., 1970, et al.
(författare)
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Dynamics and fate of blue carbon in a mangrove-seagrass seascape : influence of landscape configuration and land-use change
- 2021
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Ingår i: Landscape Ecology. - : Springer. - 0921-2973 .- 1572-9761. ; 36, s. 1489-1509
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Tidskriftsartikel (refereegranskat)abstract
- Context Seagrass meadows act as efficient natural carbon sinks by sequestering atmospheric CO2 and through trapping of allochthonous organic material, thereby preserving organic carbon (C-org) in their sediments. Less understood is the influence of landscape configuration and transformation (land-use change) on carbon sequestration dynamics in coastal seascapes across the land-sea interface. Objectives We explored the influence of landscape configuration and degradation of adjacent mangroves on the dynamics and fate of C-org in seagrass habitats. Methods Through predictive modelling, we assessed sedimentary C-org content, stocks and source composition in multiple seascapes (km-wide buffer zones) dominated by different seagrass communities in northwest Madagascar. The study area encompassed seagrass meadows adjacent to intact and deforested mangroves. Results The sedimentary C-org content was influenced by a combination of landscape metrics and inherent habitat plant- and sediment-properties. We found a strong land-to-sea gradient, likely driven by hydrodynamic forces, generating distinct patterns in sedimentary C-org levels in seagrass seascapes. There was higher C-org content and a mangrove signal in seagrass surface sediments closer to the deforested mangrove area, possibly due to an escalated export of C-org from deforested mangrove soils. Seascapes comprising large continuous seagrass meadows had higher sedimentary C-org levels in comparison to more diverse and patchy seascapes. Conclusion Our results emphasize the benefit to consider the influence of seascape configuration and connectivity to accurately assess C-org content in coastal habitats. Understanding spatial patterns of variability and what is driving the observed patterns is useful for identifying carbon sink hotspots and develop management prioritizations.
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| 2. |
- Asplund, Maria. E., 1970, et al.
(författare)
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Methane Emissions From Nordic Seagrass Meadow Sediments
- 2022
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Dahl, Martin, 1984-, et al.
(författare)
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A 2,000-Year Record of Eelgrass (Zostera marina L.) : Colonization Shows Substantial Gains in Blue Carbon Storage and Nutrient Retention
- 2024
-
Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 38:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Dahl, Martin, et al.
(författare)
-
A temporal record of microplastic pollution in Mediterranean seagrass soils
- 2021
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- Plastic pollution is emerging as a potential threat to the marine environment. In the current study, we selected seagrass meadows, known to efficiently trap organic and inorganic particles, to investigate the concentrations and dynamics of microplastics in their soil. We assessed microplastic contamination and accumulation in 210Pb dated soil cores collected in Posidonia oceanica meadows at three locations along the Spanish Mediterranean coast, with two sites located in the Almería region (Agua Amarga and Roquetas) and one at Cabrera Island (Santa Maria). Almería is known for its intense agricultural industry with 30 000 ha of plastic-covered greenhouses, while the Cabrera Island is situated far from urban areas. Microplastics were extracted using enzymatic digestion and density separation. The particles were characterized by visual identification and with Fourier-transformed infrared (FTIR) spectroscopy, and related to soil age-depth chronologies. Our findings showed that the microplastic contamination and accumulation was negligible until the mid-1970s, after which plastic particles increased dramatically, with the highest concentrations of microplastic particles (MPP) found in the recent (since 2012) surface soil of Agua Amarga (3819 MPP kg-1), followed by the top-most layers of the soil of the meadows in Roquetas (2173 kg-1) and Santa Maria (68-362 kg-1). The highest accumulation rate was seen in the Roquetas site (8832 MPP m-2 yr-1). The increase in microplastics in the seagrass soil was associated to land-use change following the intensification of the agricultural industry in the area, with a clear relationship between the development of the greenhouse industry in Almería and the concentration of microplastics in the historical soil record. This study shows a direct linkage between intense anthropogenic activity, an extensive use of plastics and high plastic contamination in coastal marine ecosystems such as seagrass meadows. We highlight the need of proper waste management to protect the coastal environment from continuous pollution.
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| 5. |
- Dahl, Martin, et al.
(författare)
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Effects of seagrass overgrazing on sediment erosion and carbon sink capacity : Current understanding and future priorities
- 2021
-
Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 6:6, s. 309-319
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Tidskriftsartikel (refereegranskat)abstract
- We searched the literature for experimental and observational studies assessing the effects of seagrass overgrazing on erosion of sediment and sedimentary organic carbon (SOC) and found that most studies reported a significant impact, likely caused by a cascading effect (i.e., seagrass shoot loss -> belowground biomass degradation -> sediment destabilization or SOC erosion). However, there appears to be a clear lack of knowledge on the extent and mechanisms behind SOC erosion in seagrass meadows and we highlight the need for research to (1) define spatial and temporal scales of occurrence; (2) assess the influence of belowground biomass degradation, sediment characteristics, and hydrodynamic exposure on sediment stabilization; and (3) estimate the greenhouse gas emission after a disturbance. Such information would help coastal resource managers to address the causes and effects of SOC loss and sediment erosion when evaluating impacts of global change on coastal ecosystems.
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| 6. |
- Dahl, Martin, et al.
(författare)
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Effects of shading and simulated grazing on carbon sequestration in a tropical seagrass meadow
- 2016
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 104:3, s. 654-664
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Tidskriftsartikel (refereegranskat)abstract
- 1. There is an ongoing world-wide decline of seagrass ecosystems, one of the world's most efficient carbon sink habitats. In spite of this, there is a clear lack of studies experimentally testing the effects of anthropogenic disturbances on carbon sequestration of seagrass systems. 2. We assessed the effects of two disturbances of global concern on the carbon sink function in a five-month in situ experiment within a tropical seagrass (Thalassia hemprichii) meadow by testing the impacts of shading and simulated grazing at two levels of intensity using shading cloths and clipping of shoot tissue. We measured the effects of these disturbances on the carbon sequestration process by assessing the net community production (NCP), carbon and nitrogen content in tissue biomass, and organic matter and THAA (total hydrolysable amino acids) in the sediment down to 40 cm depth. 3. Treatments of high-intensity shading and high-intensity clipping were similarly impacted and showed a significantly lower NCP and carbon content in the below-ground biomass compared to the seagrass control. No significant effects were seen in organic carbon, total nitrogen, C:N ratio and THAA in the sediment for the seagrass treatments. However, both clipping treatments showed different depth profiles of carbon and THAA compared to the seagrass control, with lower organic carbon and THAA content in the surface sediment. This can be explained by the clipping of shoot tissue causing a less efficient trapping of allochthonous carbon and reduced input of shredded seagrass leaves to the detritus sediment layer. In the clipping plots, erosion of the surface sediment occurred, which was also most likely caused by the removal of above-ground plant biomass. 4. Synthesis. Our findings show that during the course of this experiment, there were no impacts on the sedimentary carbon while the high-intensity disturbances caused a clear depletion of carbon biomass and reduced the seagrass meadow's capacity to sequester carbon. From a long-term perspective, the observed effect on the carbon biomass pool in the high-intensity treatments and the sediment erosion in the clipping plots may lead to loss in sedimentary carbon.
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| 7. |
- Dahl, Martin, 1984-, et al.
(författare)
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First assessment of seagrass carbon accumulation rates in Sweden: A field study from a fjord system at the Skagerrak coast
- 2023
-
Ingår i: PLoS Climate. - : Public Library of Science (PLoS). - 2767-3200. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Dahl, Martin, et al.
(författare)
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High Seasonal Variability in Sediment Carbon Stocks of Cold-Temperate Seagrass Meadows
- 2020
-
Ingår i: Journal of Geophysical Research: Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:1
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Tidskriftsartikel (refereegranskat)abstract
- ©2020. American Geophysical Union. All Rights Reserved. Seagrass meadows have a high ability to capture and store atmospheric CO2 in the plant biomass and underlying sediment and thereby function as efficient carbon sinks. The seagrass Zostera marina is a common species in the temperate Northern Hemisphere, a region with strong seasonal variations in climate. How seasonality affects carbon storage capacity in seagrass meadows is largely unknown, and therefore, in this study, we aimed to assess variations in sedimentary total organic carbon (TOC) content over a 1-year cycle in seagrass meadows on the Swedish west coast. The TOC was measured in two Z. marina sites, one wave exposed and one sheltered, and at two depths (1.5 and 4 m) within each site, every second month from August 2015 to June 2016. We found a strong seasonal variation in carbon density, with a peak in early summer (June), and that the TOC was negatively correlated to the net community production of the meadows, presumably related to organic matter degradation. There was seasonal variation in TOC content at all sediment sections, indicating that the carbon content down to 30 cm is unstable on a seasonal scale and therefore likely not a long-term carbon sink. The yearly mean carbon stocks were substantially higher in the sheltered meadow (3,965 and 3,465 g m−2) compared to the exposed one (2,712 and 1,054 g m−2) with similar seasonal variation. Due to the large intra-annual variability in TOC content, seasonal variation should be considered in carbon stock assessments and management for cold-temperate seagrass meadows.
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| 9. |
- Dahl, Martin, 1984-, et al.
(författare)
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Impacts of land-use change and urban development on carbon sequestration in tropical seagrass meadow sediments
- 2022
-
Ingår i: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- 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. |
- Dahl, Martin, et al.
(författare)
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Impacts of land-use change and urban development on tropical seagrass carbon sinks
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Seagrass meadows store significant carbon stocks at a global scale, but land-use change and 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 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 sediment Corg in the Mbweni meadow since the early 2010s was likely linked to Corg transport from mangrove/terrestrial material run-off following the 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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| 11. |
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| 12. |
- Dahl, Martin, et al.
(författare)
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Increased current flow enhances the risk of organic carbon loss from Zostera marina sediments: Insights from a flume experiment
- 2018
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 63:6, s. 2793-2805
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic processes are important for carbon storage dynamics in seagrass meadows, where periods of increased hydrodynamic activity could result in erosion and the loss of buried carbon. To estimate hydrodynamic impacts on the resuspension of organic carbon (Corg) in seagrass-vegetated sediments, we exposed patches (0.35 × 0.35 cm) of Zostera marina (with different biomass, shoot densities, and sediment properties) to gradually increased unidirectional (current) flow velocities ranging from low (5 cm s−1) to high (26 cm s−1) in a hydraulic flume with a standardized water column height of 0.12 m. We found that higher flow velocities substantially increased (by more than threefold) the proportion of Corg in the suspended sediment resulting in a loss of up to 5.5% ± 1.7% (mean ± SE) Corg from the surface sediment. This was presumably due to increased surface erosion of larger, carbon-rich detritus particles. Resuspension of Corg in the seagrass plots correlated with sediment properties (i.e., bulk density, porosity, and sedimentary Corg) and seagrass plant structure (i.e., belowground biomass). However, shoot density had no influence on Corg resuspension (comparing unvegetated sediments with sparse, moderate, and dense seagrass bed types), which could be due to the relatively low shoot density in the experimental setup (with a maximum of 253 shoots m−2) reflecting natural conditions of the Swedish west coast. The projected increase in the frequency and intensity of hydrodynamic forces due to climate change could thus negatively affect the function of seagrass meadows as natural carbon sinks. © 2018 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography
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| 13. |
- Dahl, Martin, 1984-
(författare)
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Natural and human-induced carbon storage variability in seagrass meadows
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Seagrasses are considered highly important CO2 sinks, with the capacity to store substantial quantities of organic carbon in the living biomass and sediments, and thereby acting as a buffer against climate change. In this thesis, I have studied carbon storage variability in temperate and tropical seagrass habitats and identified factors influencing this variation. In addition, as seagrass areas are decreasing worldwide, I have assessed effects of different anthropogenic disturbances on carbon sequestration processes. The result from this thesis showed that there was a large variation in carbon storage within and among temperate, tropical and subtropical regions. The highest organic carbon stocks were found in temperate Zostera marina meadows, which also showed a larger carbon storage variability than the subtropical and tropical seagrass habitats. The tropical and subtropical seagrass meadows had inorganic carbon pools exceeding the organic carbon accumulation, which could potentially weakens the carbon sink function. The variability in organic carbon stocks was generally strongly related to the sediment characteristics of the seagrass habitats. In Z. marina meadows, the strength of the carbon sink function was mainly driven by the settings of the local environment, which in turn indicates that depositional areas will likely have higher organic carbon stocks than more exposed meadows, while in the tropics seagrass biomass was also influencing sedimentary carbon levels. Furthermore, locations with large areas of seagrass were associated with higher carbon storage in tropical and subtropical regions, which could be related to increased accumulation of both autochthonous and allochthonous carbon. In an in situ experiment, impacts on carbon sequestration processes from two types of disturbances (with two levels of intensity) were tested by simulating reduced water quality (by shading) and high grazing pressure (through removal of shoot biomass). At high disturbance intensity, reductions in the net community production and seagrass biomass carbon were observed, which negatively affected carbon sequestration and could impact the sedimentary organic carbon stocks over time. In the treatments with simulated grazing, erosion was also seen, likely due to an increase in near-bed hydrodynamics. When experimentally testing effects of increased current flow on organic carbon suspension in Z. marina sediment, a ten-fold release of organic carbon with higher current flow velocities was measured, which resulted in an increase in the proportion of suspended organic carbon by three times in relation to other sediment particles. Therefore, periods with enhanced hydrodynamic activity could result in a removal of organic carbon and thereby likely reduce the seagrass meadows’ capacity to store carbon. The findings of this thesis add to the emerging picture that there is a large natural variability in seagrasses’ capacity to store carbon, and highlight how human-induced disturbances could negatively affect the carbon sink function in seagrass meadows.
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| 14. |
- Dahl, Martin, et al.
(författare)
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Sediment Properties as Important Predictors of Carbon Storage in Zostera marina Meadows : A Comparison of Four European Areas
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Seagrass ecosystems are important natural carbon sinks but their efficiency varies greatly depending on species composition and environmental conditions. What causes this variation is not fully known and could have important implications for management and protection of the seagrass habitat to continue to act as a natural carbon sink. Here, we assessed sedimentary organic carbon in Zostera marina meadows (and adjacent unvegetated sediment) in four distinct areas of Europe (Gullmar Fjord on the Swedish Skagerrak coast, Asko in the Baltic Sea, Sozopol in the Black Sea and Ria Formosa in southern Portugal) down to similar to 35 cm depth. We also tested how sedimentary organic carbon in Z. marina meadows relates to different sediment characteristics, a range of seagrass-associated variables and water depth. The seagrass carbon storage varied greatly among areas, with an average organic carbon content ranging from 2.79 +/- 0.50% in the Gullmar Fjord to 0.17 +/- 0.02% in the area of Sozopol. We found that a high proportion of fine grain size, high porosity and low density of the sediment is strongly related to high carbon content in Z. marina sediment. We suggest that sediment properties should be included as an important factor when evaluating high priority areas in management of Z. marina generated carbon sinks.
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| 15. |
- Dahl, Martin, et al.
(författare)
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The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Cold-temperate seagrass (Zostera marina) meadows provide several important ecosystem services, including trapping and storage of sedimentary organic carbon and nutrients. However, seagrass meadows are rapidly decreasing worldwide and there is a pressing need for protective management of the meadows and the organic matter sinks they create. Their carbon and nutrient storage potential must be properly evaluated, both at present situation and under future climate change impacts. In this study, we assessed the effect of wave exposure on sedimentary carbon and nitrogen accumulation using existing data from 53 Z. marina meadows at the Swedish west coast. We found that meadows with higher hydrodynamic exposure had larger absolute organic carbon and nitrogen stocks (at 0-25 cm depth). This can be explained by a hydrodynamically induced sediment compaction in more exposed sites, resulting in increased sediment density and higher accumulation (per unit volume) of sedimentary organic carbon and nitrogen. With higher sediment density, the erosion threshold is assumed to increase, and as climate change-induced storms are predicted to be more common, we suggest that wave exposed meadows can be more resilient toward storms and might therefore be even more important as carbon- and nutrient sinks in the future.
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| 16. |
- Deyanova, Diana, et al.
(författare)
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Contribution of seagrass plants to CO2 capture in a tropical seagrass meadow under experimental disturbance
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:7
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Tidskriftsartikel (refereegranskat)abstract
- Coastal vegetative habitats are known to be highly productive environments with a high ability to capture and store carbon. During disturbance this important function could be compromised as plant photosynthetic capacity, biomass, and/or growth are reduced. To evaluate effects of disturbance on CO2 capture in plants we performed a five-month manipulative experiment in a tropical seagrass (Thalassia hemprichii) meadow exposed to two intensity levels of shading and simulated grazing. We assessed CO2 capture potential (as net CO2 fixation) using areal productivity calculated from continuous measurements of diel photosynthetic rates, and estimates of plant morphology, biomass and productivity/respiration (P/R) ratios (from the literature). To better understand the plant capacity to coping with level of disturbance we also measured plant growth and resource allocation. We observed substantial reductions in seagrass areal productivity, biomass, and leaf area that together resulted in a negative daily carbon balance in the two shading treatments as well as in the high-intensity simulated grazing treatment. Additionally, based on the concentrations of soluble carbohydrates and starch in the rhizomes, we found that the main reserve sources for plant growth were reduced in all treatments except for the low-intensity simulated grazing treatment. If permanent, these combined adverse effects will reduce the plants' resilience and capacity to recover after disturbance. This might in turn have long-lasting and devastating effects on important ecosystem functions, including the carbon sequestration capacity of the seagrass system.
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| 17. |
- Deyanova, Diana, et al.
(författare)
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Plant- and habitat productivity in a temperate seagrass system
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Seagrass meadows are highly productive coastal habitats. Yet, little is known about the contribution of seagrass plants to the total seagrass habitat. To clarify the particular role of the seagrass plants for carbon capture in temperate environments, a one-year study was performed in seagrass meadows on the Swedish west coast. We aimed to assess the link between the net primary productivity of seagrass plants per se, the net production of the seagrass community and the net production of the entire system. To be able to predict effects of environmental changes on seagrass productivity, results were related to changes in water temperature, oxygen levels, light conditions and ice cover. Results showed large variations in net plant productivity across seasons, generally following light- and temperature variability, and ranging from very high (20.03 g C m-2 24h-1 ) in the summer to negative rates (-1.60 g C m-2 24h-1 ) in the least productive winter month. The patterns of variability in seagrass productivity were also influenced by depth- and site-specific dynamics in biomass. The high respiration of the benthic community did largely outbalance the productivity of the seagrass plants, probably as an effect of fast turnover rates. This resulted in an overall yearly low positive carbon balance of the entire seagrass system. Overall, the findings show that seagrass plants contribute substantially to the carbon capture in temperate seagrass habitats, but also that the rate of community respiration appears to be highly dependent on the degree of how much detritus material that is retained within the system. Thus, even though these seagrass systems are highly productive and may contain a large carbon stock, seagrass productivity per se seems not to be the most important determining factor for their carbon sink function.
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| 18. |
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| 19. |
- Gullström, Martin, et al.
(författare)
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Blue Carbon Storage in Tropical Seagrass Meadows Relates to Carbonate Stock Dynamics, Plant–Sediment Processes, and Landscape Context : Insights from the Western Indian Ocean
- 2018
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 21:3, s. 551-566
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Tidskriftsartikel (refereegranskat)abstract
- Globally, seagrass ecosystems are considered major blue carbon sinks and thus indirect contributors to climate change mitigation. Quantitative estimates and multi-scale appraisals of sources that underlie long-term storage of sedimentary carbon are vital for understanding coastal carbon dynamics. Across a tropical–subtropical coastal continuum in the Western Indian Ocean, we estimated organic (Corg) and inorganic (Ccarb) carbon stocks in seagrass sediment. Quantified levels and variability of the two carbon stocks were evaluated with regard to the relative importance of environmental attributes in terms of plant–sediment properties and landscape configuration. The explored seagrass habitats encompassed low to moderate levels of sedimentary Corg (ranging from 0.20 to 1.44% on average depending on species- and site-specific variability) but higher than unvegetated areas (ranging from 0.09 to 0.33% depending on site-specific variability), suggesting that some of the seagrass areas (at tropical Zanzibar in particular) are potentially important as carbon sinks. The amount of sedimentary inorganic carbon as carbonate (Ccarb) clearly corresponded to Corg levels, and as carbonates may represent a carbon source, this could diminish the strength of seagrass sediments as carbon sinks in the region. Partial least squares modelling indicated that variations in sedimentary Corg and Ccarb stocks in seagrass habitats were primarily predicted by sediment density (indicating a negative relationship with the content of carbon stocks) and landscape configuration (indicating a positive effect of seagrass meadow area, relative to the area of other major coastal habitats, on carbon stocks), while seagrass structural complexity also contributed, though to a lesser extent, to model performance. The findings suggest that accurate carbon sink assessments require an understanding of plant–sediment processes as well as better knowledge of how sedimentary carbon dynamics are driven by cross-habitat links and sink–source relationships in a scale-dependent landscape context, which should be a priority for carbon sink conservation.
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| 22. |
- Gullström, Martin, et al.
(författare)
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Övervakning av makrovegetation i Bottniska viken– en vägledning
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- SammanfattningVi rekommenderar att dyktransekter enligt den nationella undersökningstypenförVegetationsklädda bottnar, ostkust (Naturvårdsverket 2004) används vidövervakning av makrovegetation. Metoden ger möjlighet till hög taxonomisknoggrannhet och kan svara upp mot i stort sett alla förvaltningsuppdrag. Denfungerar bra för att beskriva djuputbredning och täckningsgrad av arter.Skattningarna kan även omräknas till täckningsindex. Tyvärr finns det ingenfullständig metodbeskrivning. För att säkerställa kvalitén i nationella databaseroch underlätta upphandling av inventeringsuppdrag för myndigheterna bör entydlig metodbeskrivning omgående tas fram. Av samma orsaker behövs ävenmetodikkurser anordnas och i kombination med kontinuerlig interkalibrering avtäckningsgradsskattning och artbestämning kan en ackreditering av utföraregenomföras.När det gäller att designa ett miljöövervakningsprogram så bör syftet medövervakningen först definieras. Att övervaka klimatförändringen, övergödningeneller följa upp ekologisk status i vattenförekomster styr hur programmet sättsupp. Ett brett program med transekter spridda från inner till ytter skärgård dvs. iskärgårdsgradienten och en metod som har bra taxonomisk (och rumslig)upplösning ger möjlighet att nyttja data för fler syften.Vår rekommendation när det gäller att designa ett övervakningsprogram för attfölja upp storskaliga förändringar är att inte lägga stationerna alltför nära lokalautsläppskällor. Om stationerna ska användas som referens till recipienter ska dedock inte placeras för långt ut, så att de enbart beskriver förhållanden längst ut iskärgårdsgradienten.Vi rekommenderar att programmet bör följa upp flera responsvariabler t.ex.djuputbredning av arter, täckningsgrad, och diversitet. På detta sätt ökar chansenatt programmet fångar upp framtida, okända förändringar. Det är också enförutsättning för att nyttja transekterna för fler förvaltningssyften.Bottensubstrat är en av de faktorer som har störst betydelse förmakrovegetationens sammansättning och täckningsgrad. Det är viktigt att tahänsyn till detta när framtida analyser av data görs. Det är troligtvis en mycketviktig faktor när det gäller att stratifiera placering och bestämma antalet stationervid uppbyggnad av ett övervakningsprogram. I Bottniska viken är det mycketvanligt med transekter med blandade substrat eller att transekterna relativt snabbtövergår från hårdbotten till mjukbotten eftersom kusten är på många ställenflack. Detta är probelmatiskt för övervakning av ekologisk status kopplat tilldjuputbredning av arter.Våra analyser av djuputbredning och täckningsindex inom fyra skärgårdsområdenvisar att man med fördel kan stratifiera sina provpunkter utifrånvågexponering. Syftet med undersökningen bestämmer dock var i skärgårdendessa lokaler bör ligga.
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| 23. |
- Ismail, Rashid O., 1986-, et al.
(författare)
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Effects of calcification on air-water CO2 fluxes in tropical seagrass meadows : A mesocosm experiment
- 2023
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 561
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
- Ismail, Rashid O., 1986-, et al.
(författare)
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Plant productivity, community composition and carbon import are key drivers of air-water CO2 fluxes in a tropical seagrass meadow : implications for blue carbon science
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Seagrass meadows are considered efficient sinks of Blue Carbon. They capture CO2 by an effective photosynthetic uptake as well as by trapping large amounts of carbon originating from adjacent systems, which in turn can be stored in the sediments. Such import of allochthonous carbon will be partly degraded in the system, increasing the overall community respiration and thus CO2 production and at the same time add to sediment carbon accumulation. Additionally, tropical seagrass meadows can contain a high proportion of calcareous organisms, which (by the pH suppressing the effect of calcification) can further increase the CO2 partial pressure of the seawater if resulting CO2 is not internally used. The scarce literature on actual CO2 fluxes over submerged vegetation in coastal marine areas is reporting partly contrasting data over how coastal areas in general shall be counted in carbon budgets. To better understand the CO2 cycle within a tropical seagrass system, we constructed a simple carbon flux simulation model in which we evaluated the possible fluxes of carbon within the meadow and with regards to the surrounding seascape. We measured air-water CO2 fluxes in seagrass meadows with different plant community compositions (i.e. mixtures of seagrass and calcifying macroalgae) using field measurements, estimated water column productivity, and extracted data for primary productivity, plant composition, and calcification from previous studies in the same area and, traced organic carbon (Corg) sources in seagrass sediment by measuring bulk stable isotope signals of carbon (δ13C) in order to feed the model with the best available data. When needed we supplemented with published data from other regions. The measured fluxes indicated a net efflux of CO2 over the meadows, from sea to air. The fluxes changed both in rate and direction over the day, and were significantly related to plant community composition and environmental conditions, where pH had the strongest influence on CO2 fluxes. Downward fluxes were found only over vegetation in the afternoon. The isotope signals of carbon revealed a strong input of carbon from other habitats. The outcome of the simulation model suggests that highly productive seagrass meadows can generate a net CO2 flux from the water column to the atmosphere since the plants’ demand for CO2 to a large extent is covered by a major internal cycling of CO2, which is from degradation of autochthonous and allochthonous material as well as from CO2 released from calcification. The calculated accumulation3of sedimentary carbon is however larger than the flow to the atmosphere, indicating that these systems can still be carbon sinks.
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| 25. |
- Krause-Jensen, D, et al.
(författare)
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Nordic Blue Carbon Ecosystems: Status and Outlook
- 2022
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
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Forskningsöversikt (refereegranskat)abstract
- 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 km2 salt marshes, 1,861 (potentially 2,735) km2 seagrass meadows, and 16,532 km2 (potentially 130,735 km2, including coarse Greenland estimates) brown macroalgae, yielding a total of 19,833 (potentially 134,910) km2. 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 Corg m-2 (top 40-100 cm) and sequestration rates average 142 g Corg m-2 yr-1. Eelgrass C-stocks average 2,414 g Corg m-2 (top 25 cm) and initial data for sequestration rates range 5-33 g Corg 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.
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