| 1. |
- Röhr, Maria Emilia, et al.
(författare)
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Blue Carbon Storage Capacity of Temperate Eelgrass (Zostera marina) Meadows
- 2018
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 32:10, s. 1457-1475
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Tidskriftsartikel (refereegranskat)abstract
- Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their carbon storage capacity and the factors driving variability in storage capacity is still limited. Here we provide an estimate on the magnitude and variability of carbon stocks within a widely distributed marine foundation species throughout its distribution area in temperate Northern Hemisphere. We sampled 54 eelgrass (Zostera marina) meadows, spread across eight ocean margins and 36° of latitude, to determine abiotic and biotic factors influencing organic carbon (Corg) stocks in Zostera marina sediments. The Corg stocks (integrated over 25-cm depth) showed a large variability and ranged from 318 to 26,523gC/m2 with an average of 2,721gC/m2. The projected Corg stocks obtained by extrapolating over the top 1m of sediment ranged between 23.1 and 351.7MgC/ha, which is in line with estimates for other seagrasses and other blue carbon ecosystems. Most of the variation in Corg stocks was explained by five environmental variables (sediment mud content, dry density and degree of sorting, and salinity and water depth), while plant attributes such as biomass and shoot density were less important to Corg stocks. Carbon isotopic signatures indicated that at most sites <50% of the sediment carbon is derived from seagrass, which is lower than reported previously for seagrass meadows. The high spatial carbon storage variability urges caution in extrapolating carbon storage capacity between geographical areas as well as within and between seagrass species.
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| 2. |
- Deyanova, Diana, 1984-
(författare)
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Seagrass productivity : from plant to system
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Seagrasses form one of the most productive habitats on earth and are recognized as very efficient carbon sinks. The levels and patterns of productivity within and across different seagrass systems vary widely due to natural or human-induced factors. Seagrass plants, being the foundation species of seagrass meadows, have a substitutional role as primary producers to the overall productivity of their habitat. Clarifying the variation in the carbon capture potential of these plants on physiological and ecological levels is essential to understand of the whole system’s carbon balance. In this thesis, the photosynthetic performance and productivity of seagrass plants were studied in relation to factors that have large impact on productivity, such as tissues age, season and water depth. Furthermore, the seagrass response, in terms of capacity to capture and sequester carbon, to human-induced stress factors such as shading and simulated grazing was evaluated in a tropical seagrass meadow. The research has included a multitude of seagrass productivity assessments from plant- to system level.The results showed that age has a significant effect on the photosynthetic performance of the temperate seagrass Zostera marina L., both within a single shoot and between shoots. When comparing leaves among the same shoot, the photosynthetic capacity and efficiency were highest in mature tissues and significantly reduced in very young tissues as well as in tissues undergoing senescence. In response to high light stress, very young tissues seemed to cope better with dissipating excess light energy, which was demonstrated by the higher values of non-photochemical quenching (NPQ) observed compared to mature and senescent tissues. Such an effect was also observed when comparing the oldest and youngest shoots from the same genet; the youngest shoot showed higher ability to dissipate excess light energy compared to the oldest one, and might thus be able to better withstand light stress.On a larger spatiotemporal scale, the areal productivity of seagrass plants was significantly affected by light availability and temperature, leading to a strong seasonal variation. In addition, depth had a strong site-specific effect on plant productivity in terms of biomass. On a yearly basis, productivity rates varied substantially, reaching up to 20 g C m-2 24h-1 in the summer months. This high carbon capture potential was, however, outbalanced by the high respiration rates of the benthic community. Overall, the whole system had a low but positive yearly carbon balance.Both shading and simulated grazing negatively affected seagrass plants and the whole habitat after five months of experimental disturbance. On the plant level, photosynthesis, productivity and growth were all reduced. On the system level, a reduction in community productivity was recorded. The long-term refractory carbon was, however, not affected although erosion was observed in treatments subjected to simulated grazing.In summary, this thesis has established that age, season, depth and exposure are factors highly responsible for natural variation in seagrass plant- and habitat productivity, and that seagrasses respond to human-induced stress by significantly reducing their productivity. Even though seagrass plants are generally capable of surviving stress periods, these results suggest that prolonged deteriorating stress conditions will lead to serious harm on the plants as well as the entire habitat, and thereby compromising the carbon burial capacity of the seagrass system.
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| 3. |
- Leinikki, Jouni, et al.
(författare)
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Marin basinventering av Natura 2000 områden i Blekinge län 2018
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För att förbättra kunskapen om naturvärden i Blekinges befintliga marina Natura 2000 områden, har Alleco AB fått i uppdrag att genomföra en marin inventering i tre Natura 2000 områden längs Blekinges kust. Inventeringen genomfördes den 22–28 juli, 2018 och de tre områdena som studerades var Elleholm, Fölsö och Blötö-Kidö. Inventeringen utfördes genom dyk- och snorklingstransekter, samt videopunkter.Rådata innefattar position, djup, bottensubstrat och täckningsgrad av samtliga observerade arter. Dessa har lagrats i databasen SHARK, som tillhandahålls av SMHI. För att tydligare illustrera naturvärdena och mångfalden i de tre lokalerna, klassificerade vi in rådata till HUB-systemets biotoper, som etablerades 2013 av HELCOM. Våra resultat visar på att: (1) öarna i Elleholms södra delar stämmer in på Naturtyp 1620 Skär i Östersjön, och (2) den norra och östra sidan av Fölsö bör klassas till Naturtyp 1170 Rev, och Blötö-Kidö hör i sin helhet till naturtyp 1160 Stora vikar och sund (NNK 2018).Det största hotet vi identifierade för de olika växtsamhällena är övergödning. Även båttrafik kan ses som ett potentiellt problem, framförallt i de grunda skyddade områdena såsom Marsund i Elleholm, den västra sidan av Fölsö och de nordligaste delarna av Blötö-Kidö området. Här rekommenderar vi att begränsa ankringsmöjligheterna och hastigheterna, åtminstone i de mest känsliga delarna. Vi föreslår även att helt begränsa tillgängligheten till det mindre området i nordvästra delen av Blötö-Kidö området, då området karakteriseras av ett rikt och varierat kransalgsbestånd som inte borde utsättas för trampning och/eller starka strömmar.Slutligen föreslår vi studier av infauna, epifauna och fisk för att få en bättre helhetsbild av naturvärdena i de studerade områdena.
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| 4. |
- Lyimo, Liberatus D., et al.
(författare)
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Shading and simulated grazing increase the sulphide pool and methane emission in a tropical seagrass meadow
- 2018
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Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 134, s. 89-93
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Tidskriftsartikel (refereegranskat)abstract
- Though seagrass meadows are among the most productive habitats in the world, contributing substantially to long-term carbon storage, studies of the effects of critical disturbances on the fate of carbon sequestered in the sediment and biomass of these meadows are scarce. In a manipulative in situ experiment, we studied the effects of successive loss of seagrass biomass as a result of shading and simulated grazing at two intensity levels on sulphide (H2S) content and methane (CH4) emission in a tropical seagrass meadow in Zanzibar (Tanzania). In all disturbed treatments, we found a several-fold increase in both the sulphide concentration of the sediment pore-water and the methane emissions from the sediment surface (except for CH4 emissions in the low-shading treatment). This could be due to the ongoing degradation of belowground biomass shed by the seagrass plants, supporting the production of both sulphate-reducing bacteria and methanogens, possibly exacerbated by the loss of downwards oxygen transport via seagrass plants. The worldwide rapid loss of seagrass areas due to anthropogenic activities may therefore have significant effects on carbon sink-source relationships within coastal seas.
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