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- 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
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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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- Dahl, Martin, et al.
(författare)
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Impacts of land-use change and urban development on tropical seagrass carbon sinks
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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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- 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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