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  • 1. Alexandre, Ana
    et al.
    Silva, Joao
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Botany.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Santos, Rui
    Effects of CO2 enrichment on photosynthesis, growth, and nitrogen metabolism of the seagrass Zostera noltii2012In: Ecology and Evolution, ISSN 2045-7758, Vol. 2, no 10, p. 2620-2630Article in journal (Refereed)
    Abstract [en]

    Seagrass ecosystems are expected to benefit from the global increase in CO2 in the ocean because the photosynthetic rate of these plants may be C-i-limited at the current CO2 level. As well, it is expected that lower external pH will facilitate the nitrate uptake of seagrasses if nitrate is cotransported with H+ across the membrane as in terrestrial plants. Here, we investigate the effects of CO2 enrichment on both carbon and nitrogen metabolism of the seagrass Zostera noltii in a mesocosm experiment where plants were exposed for 5 months to two experimental CO2 concentrations (360 and 700 ppm). Both the maximum photosynthetic rate (Pm) and photosynthetic efficiency (alpha) were higher (1.3- and 4.1-fold, respectively) in plants exposed to CO2-enriched conditions. On the other hand, no significant effects of CO2 enrichment on leaf growth rates were observed, probably due to nitrogen limitation as revealed by the low nitrogen content of leaves. The leaf ammonium uptake rate and glutamine synthetase activity were not significantly affected by increased CO2 concentrations. On the other hand, the leaf nitrate uptake rate of plants exposed to CO2-enriched conditions was fourfold lower than the uptake of plants exposed to current CO2 level, suggesting that in the seagrass Z. noltii nitrate is not cotransported with H+ as in terrestrial plants. In contrast, the activity of nitrate reductase was threefold higher in plant leaves grown at high-CO2 concentrations. Our results suggest that the global effects of CO2 on seagrass production may be spatially heterogeneous and depend on the specific nitrogen availability of each system. Under a CO2 increase scenario, the natural levels of nutrients will probably become limiting for Z. noltii. This potential limitation becomes more relevant because the expected positive effect of CO2 increase on nitrate uptake rate was not confirmed.

  • 2.
    Björk, Mats
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, Department of Botany. Fysiologi.
    Short, Fred
    Mcleod, Elisabeth
    Beer, Sven
    Managing Seagrasses for Resilience to Climate Change2008Book (Other (popular science, discussion, etc.))
    Abstract [en]

    There is growing evidence that seagrasses are experiencing

    declines globally due to anthropogenic

    threats (Short and Wyllie-Echeverria 1996, Duarte

    2002, Orth et al. 2006). Runoff of nutrients and

    sediments that affect water quality is the greatest

    anthropogenic threat to seagrass meadows,

    although other stressors include aquaculture, pollution,

    boating, construction, dredging and landfill

    activities, and destructive fishing practices. Natural

    disturbances such as storms and floods can

    also cause adverse effects. Potential threats from

    climate change include rising sea levels, changing

    tidal regimes, UV radiation damage, sediment

    hypoxia and anoxia, increases in sea temperatures

    and increased storm and flooding events.

    Thus, seagrass meadows, the ecosystems that

    they support and the ecosystem services that they

    provide are threatened by a multitude of environmental

    factors that are currently changing or will

    change in the future.

    Seagrasses are flowering plants that thrive in shallow

    oceanic and estuarine waters around the world.

    Descendants of terrestrial plants that re-entered

    the ocean between 100 and 65 million years ago,

    seagrasses have leaves, stems, rhizomes (horizontal

    underground runners) and roots. Although

    there are only about 60 species of seagrassesworldwide, these plants play an important role in

    many shallow, near-shore, marine ecosystems.

    Seagrass meadows provide ecosystem services

    that rank among the highest of all ecosystems on

    earth. The direct monetary outputs are substantial

    since highly valued commercial catches such

    as prawns and fish are dependent on these systems.

    Seagrasses provide protective shelter for

    many animals, including fish, and can also be a

    direct food source for manatees and dugongs,

    turtles, water fowl, some herbivorous fish and sea

    urchins. The roots and rhizomes of seagrasses

    also stabilise sediments and prevent erosion while

    the leaves filter suspended sediments and nutrients

    from the water column. Seagrass meadows

    are thus linked to other important marine habitats

    such as coral reefs, mangroves, salt marshes and

    oyster reefs.

    This paper presents an overview of seagrasses,

    the impacts of climate change and other threats to

    seagrass habitats, as well as tools and strategies

    for managers to help support seagrass resilience.

  • 3.
    Buapet, Pimchanok
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Does electron flow via photorespiration mitigate photoinhibition in the seagrass Zostera marina?Manuscript (preprint) (Other academic)
  • 4.
    Buapet, Pimchanok
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Roles of alternative electron flows to O2 and non-photochemical quenching during photosynthesis in the seagrass Zostera marinaManuscript (preprint) (Other academic)
  • 5. Buapet, Pimchanok
    et al.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    The role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L.2016In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 129, no 1, p. 59-69Article in journal (Refereed)
    Abstract [en]

    This study investigates the role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L. Electron transport rates (ETRs) and non-photochemical quenching (NPQ) of Z. marina were measured under saturating irradiance in synthetic seawater containing 2.2 mM DIC and no DIC with different O-2 levels (air-equilibrated levels, 3 % of air equilibrium and restored air-equilibrated levels). Lowering O-2 did not affect ETR when DIC was provided, while it caused a decrease in ETR and an increase in NPQ in DIC-free media, indicating that O-2 acted as an alternative electron acceptor under low DIC. The ETR and NPQ as a function of irradiance were subsequently assessed in synthetic seawater containing (1) 2.2 mM DIC, air-equilibrated O-2; (2) saturating CO2, no O-2; and (3) no DIC, air-equilibrated O-2. These treatments were combined with glycolaldehyde pre-incubation. Glycolaldehyde caused a marked decrease in ETR in DIC-free medium, indicating significant electron flow supported by photorespiration. Combining glycolaldehyde with O-2 depletion completely suppressed ETR suggesting the operation of the Mehler reaction, a possibility supported by the photosynthesis-dependent superoxide production. However, no notable effect of suppressing the Mehler reaction on NPQ was observed. It is concluded that during DIC-limiting conditions, such as those frequently occurring in the habitats of Z. marina, captured light energy exceeds what is utilised for the assimilation of available carbon, and photorespiration is a major alternative electron acceptor, while the contribution of the Mehler reaction is minor.

  • 6.
    Buapet, Pimchanok
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince Songkla University, Thailand.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Photosynthetic activity of seagrasses and macroalgae in temperate shallow waters can alter seawater pH and total inorganic carbon content at the scale of a coastal embayment2013In: Marine and Freshwater Research, ISSN 1323-1650, E-ISSN 1448-6059, Vol. 64, no 11, p. 1040-1048Article in journal (Refereed)
    Abstract [en]

    Many studies have reported fluctuations in pH and the concentration of dissolved inorganic carbon (DIC) in shallow coastal waters as a result of photosynthetic activity; however, little is known about how these fluctuations vary with degree of exposure among habitats, and at different scales. In the present study, diel variation in seawater pH was apparent in aquaria experiments with Zostera marina and Ruppia maritima. These pH variations were affected by light regime, biomass level and plant species. Subsequently, the natural variability in seawater pH and the concentration of DIC was assessed in six shallow embayments (three sheltered and three exposed) during sunny days. From the outer part towards the interior part of each bay, the following four habitats were identified and studied: the bay-mouth open water, seagrass beds, mixed macrophyte belts and unvegetated bottoms. The two vegetated habitats and unvegetated bottoms were characterised by higher pH and a lower concentration of DIC than in the bay-mouth water. The mixed macrophytes habitat showed slightly higher pH and a lower concentration of DIC than the seagrass and unvegetated habitats. No significant effect of exposure was detected. Our findings clearly showed that the photosynthetic activity of marine macrophytes can alter the coastal pH and the concentration of DIC and that the effects can be observed at the scale of a whole bay.

  • 7.
    Buapet, Pimchanok
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince Songkla University, Thailand.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Photorespiration and carbon limitation determine productivity in temperate seagrasses2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 12, article id e83804Article in journal (Refereed)
    Abstract [en]

    The gross primary productivity of two seagrasses, Zostera marina and Ruppia maritima, and one green macroalga, Ulva intestinalis, was assessed in laboratory and field experiments to determine whether the photorespiratory pathway operates at a substantial level in these macrophytes and to what extent it is enhanced by naturally occurring shifts in dissolved inorganic carbon (DIC) and O2 in dense vegetation. To achieve these conditions in laboratory experiments, seawater was incubated with U. intestinalis in light to obtain a range of higher pH and O2 levels and lower DIC levels. Gross photosynthetic O2 evolution was then measured in this pretreated seawater (pH, 7.8–9.8; high to low DIC:O2 ratio) at both natural and low O2concentrations (adjusted by N2 bubbling). The presence of photorespiration was indicated by a lower gross O2 evolution rate under natural O2 conditions than when O2 was reduced. In all three macrophytes, gross photosynthetic rates were negatively affected by higher pH and lower DIC. However, while both seagrasses exhibited significant photorespiratory activity at increasing pH values, the macroalga U. intestinalis exhibited no such activity. Rates of seagrass photosynthesis were then assessed in seawater collected from the natural habitats (i.e., shallow bays characterized by high macrophyte cover and by low DIC and high pH during daytime) and compared with open baymouth water conditions (where seawater DIC is in equilibrium with air, normal DIC, and pH). The gross photosynthetic rates of both seagrasses were significantly higher when incubated in the baymouth water, indicating that these grasses can be significantly carbon limited in shallow bays. Photorespiration was also detected in both seagrasses under shallow bay water conditions. Our findings indicate that natural carbon limitations caused by high community photosynthesis can enhance photorespiration and cause a significant decline in seagrass primary production in shallow waters.

  • 8.
    Carr, Herman
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, Department of Botany. Fysiologi.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, Department of Botany. Fysiologi.
    Parallel changes in non-photochemical quenching properties, photosynthesis and D1 levels at sudden, prolonged irradiance exposures in Ulva fasciata Delile.2007In: Journal of Photochemistry and Photobiology B: Biology, Vol. 87Article in journal (Refereed)
  • 9.
    Dahl, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Deyanova, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gütschow, Silvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Asplund, Maria E.
    Lyimo, Liberatus D.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Karamfilov, Ventzislav
    Santos, Rui
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sediment Properties as Important Predictors of Carbon Storage in Zostera marina Meadows: A Comparison of Four European Areas2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 12Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Dahl, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Deyanova, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Näslund, Johan
    Samuelsson, Göran S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mtolera, Marten S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of shading and simulated grazing on carbon sequestration in a tropical seagrass meadow2016In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 104, no 3, p. 654-664Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Dahl, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Infantes, Eduardo
    Clevesjö, Rosanna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Linderholm, Hans W.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Increased current flow enhances the risk of organic carbon loss from Zostera marina sediments: Insights from a flume experimentManuscript (preprint) (Other academic)
  • 12.
    Dahl, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Infantes, Eduardo
    Clevesjö, Rosanna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Linderholm, Hans W.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Increased current flow enhances the risk of organic carbon loss from Zostera marina sediments: Insights from a flume experiment2018In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, no 6, p. 2793-2805Article in journal (Refereed)
    Abstract [en]

    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 (C-org) in seagrass-vegetated sediments, we exposed patches (0.35 x 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 C-org in the suspended sediment resulting in a loss of up to 5.5% +/- 1.7% (mean +/- SE) C-org from the surface sediment. This was presumably due to increased surface erosion of larger, carbon-rich detritus particles. Resuspension of C-org in the seagrass plots correlated with sediment properties (i.e., bulk density, porosity, and sedimentary C-org) and seagrass plant structure (i.e., belowground biomass). However, shoot density had no influence on C-org 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.

  • 13.
    De La Torre-Castro, Maricela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Eklöf, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Rönnbäck, Patrik
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Seagrass importance in food provisioning services: fish stomach content as a link between seagrass meadows and local fisheries2008In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 7, no 1, p. 95-110Article in journal (Refereed)
    Abstract [en]

    The links between ecosystem processes and functions and ecosystem services (i.e. the humanbenefits from those) are elusive. In this paper, the food provisioning service of seagrass meadows isoperationalized through the study of the stomach contents of 13 important commercial fish species inChwaka Bay, Zanzibar. Using local fishers’ knowledge on bait, scientific knowledge about the structureof the meadows (associated flora and fauna), stomach content analysis and multivariate statistics, the foodprovisioning service associated with seagrasses and its importance for fish (as important diet component)and for humans (in small-scale artisanal fisheries) are described. The study presents the food items for 13commercial fish species identified at the lowest possible taxonomical level and compares with previousliterature findings. In addition, differences in stomach contents of Siganus sutor and Leptoscarus vaigiensiscaught with both drag-nets and dema basket traps are investigated in order to explore bait presence andindirectly evaluate fishers’ knowledge on bait preference. The results show that most of the items consumedby commercial fishes are associated with seagrass beds and that there are clear indicators that the baittraditionally used seems to be effective. The paper elaborates on the consideration of seagrass ecosystemsin a holistic perspective, the difficulties in valuation of ecosystem services and finally the crucial importanceof these aspects for human well-being and sustainability in coastal communities of the Western IndianOcean.

  • 14.
    Deyanova, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Asplund, Maria E.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Franco, Joao N.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Infantes, Eduardo
    Lundberg, Petter
    Engström, Pia
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Plant- and habitat productivity in a temperate seagrass systemManuscript (preprint) (Other academic)
    Abstract [en]

    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.

  • 15.
    Deyanova, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hamisi, Mariam I.
    Mtolera, Matern S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Contribution of seagrass plants to CO2 capture in a tropical seagrass meadow under experimental disturbance2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 7, article id e0181386Article in journal (Refereed)
    Abstract [en]

    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.

  • 16.
    Deyanova, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Sköld, Helen N.
    Bjök, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of ageing on the photosynthetic capacity of the seagrass Zostera marina LinnaeusManuscript (preprint) (Other academic)
    Abstract [en]

    The effect of tissue age and light stress on seagrass productivity was examined on three scale levels by comparisons among: (i) different parts of a leaf (i.e. the base middle and top), (ii) leaves of different ages, and (iii) shoots of different development stages on the same genet, in the temperate species Zostera marina L. Rapid light curves were performed to estimate chlorophyll fluorescence and to determine the maximal photosynthetic rate (ETRmax), the photosynthetic efficiency (the alpha slope) and the maximal quantum yield (both as Fv/Fm and as the more sensible Fv/F0). The plants were also exposed to inhibiting light stress with measurements performed during the following recovery and non-photochemical quenching (NPQ). The results suggest that seagrass tissue age has an effect on the photosynthetic performance of the plant and that the level of strength varies among different parts of a single shoot and also among shoots of different development stages along the same genet. Younger and senescing tissues generally had lower photosynthetic capacity than mature tissues. It appeared that very young tissues tolerate light stress better than mature and senescing tissues, as the NPQ values of the very young tissue were higher, and they also showed a lower recovery to initial Fv/F0 values. A clear difference was also found in photosynthetic performance and recovery capacity of the youngest shoot compared to the rest of the shoots belonging to the same genet. The leaves of young shoots appeared to better tolerate light stress than leaves of old shoots. These findings provide new insight on seagrass ageing and expand the understanding of ageing effects on photosynthesis on a population level.

  • 17.
    Deyanova, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus Dominick
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hamis, Mariam
    Mtolera, Marten SP
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Productivity of a tropical seagrass meadow under stress: effects of prolonged shading and simulated grazingManuscript (preprint) (Other academic)
  • 18.
    Eklöf, J.S.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gullström, Martin
    Department of Zoology. Ekologi.
    Björk, Mats
    Department of Botany.
    Asplund, M.E.
    Hammar, L.
    Dahlgren, A.
    Öhman, Marcus
    Department of Zoology. Ekologi.
    The importance of grazing intensity and frequency for physiological responses of the tropical seagrass Thalassia hemprichii2008In: Aquatic botany, Vol. 89, p. 337-340Article in journal (Refereed)
    Abstract [en]

    Seagrass grazing is an intrinsic disturbance in primarily tropical and subtropical areas. While there is a general parabolic response in seagrass growth to grazing intensity, there is less knowledge on the role of grazing frequency, as well as potential interactions between grazing intensity and frequency. This study experimentally investigated physiological responses in Thalassia hemprichii to simulated (leaf cutting) grazing regimes with different intensities (25% vs. 75%) and frequencies (I times vs. 3 times) over 35 days in Chwaka Bay (Zanzibar, Tanzania). The results showed that the two high-intensity treatments (75% removal) had 37-41% lower growth rate than the low-intensity/low-frequency treatment, and rhizome sugar and starch content were both affected in a similar way. A 36% lower starch content in the simulated low-intensity/high-frequency regime (25% x 3) compared to the one of low-intensity/low-frequency (25% x I) also shows an interaction between grazing intensity and frequency. This suggests that high-intensity (and to some extent frequency) grazing regimes, in comparison to low-intensity regimes, could negatively affect T. hemprichii growth, energy reserves, and thereby the ability to deal with additional stress like light limitation or grazing.

  • 19. Felisberto, Paulo
    et al.
    Jesus, Sergio M.
    Zabel, Friedrich
    Santos, Rui
    Silva, Joao
    Gobert, Sylvie
    Beer, Sven
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mazzuca, Silvia
    Procaccini, Gabriele
    Runcie, John W.
    Champenois, Willy
    Borges, Alberto V.
    Acoustic monitoring of O-2 production of a seagrass meadow2015In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 464, p. 75-87Article in journal (Refereed)
    Abstract [en]

    Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O-2) production of an entire seagrass meadow. In a shallow water area (<38 m), densely covered by P. oceanica, a sound source transmitted signals in 3 different bands (400-800 Hz, 1.5-3.5 kHz and 65-8.5 kHz) toward three self-recording hydrophones at a distance of 100 m, over the period of one week. The data show a high correlation between the diel cycle of the acoustic signals' energy received by the hydrophones and the temporal changes in water column O-2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O-2-based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O-2 as bubbles in seagrass ecosysterns suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O-2 measurements.

  • 20.
    George, Rushingisha
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania .
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mangora, Mwita M.
    Mtolera, Matern S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    High midday temperature stress has stronger effects on biomass than on photosynthesis: A mesocosm experiment on four tropical seagrass species2018In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 8, no 9, p. 4508-4517Article in journal (Refereed)
    Abstract [en]

    The effect of repeated midday temperature stress on the photosynthetic performance and biomass production of seagrass was studied in a mesocosm setup with four common tropical species, including Thalassia hemprichii, Cymodocea serrulata, Enhalus acoroides, and Thalassodendron ciliatum. To mimic natural conditions during low tides, the plants were exposed to temperature spikes of different maximal temperatures, that is, ambient (29-33 degrees C), 34, 36, 40, and 45 degrees C, during three midday hours for seven consecutive days. At temperatures of up to 36 degrees C, all species could maintain full photosynthetic rates (measured as the electron transport rate, ETR) throughout the experiment without displaying any obvious photosynthetic stress responses (measured as declining maximal quantum yield, Fv/Fm). All species except T.ciliatum could also withstand 40 degrees C, and only at 45 degrees C did all species display significantly lower photosynthetic rates and declining Fv/Fm. Biomass estimation, however, revealed a different pattern, where significant losses of both above- and belowground seagrass biomass occurred in all species at both 40 and 45 degrees C (except for C.serrulata in the 40 degrees C treatment). Biomass losses were clearly higher in the shoots than in the belowground root-rhizome complex. The findings indicate that, although tropical seagrasses presently can cope with high midday temperature stress, a few degrees increase in maximum daily temperature could cause significant losses in seagrass biomass and productivity.

  • 21.
    George, Rushingisha
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mtolera, Matern
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Seagrass cover reduces emissions of methane, nitrous oxide and sulphide levels in organic rich tropical seagrass sediments during daytimeManuscript (preprint) (Other academic)
  • 22.
    George, Rushingisha
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mtolera, Matern
    Lyimo, Thomas
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Methane emission and sulphide levels increase in tropical seagrass sediments during temperature stress: a mesocosm experimentManuscript (preprint) (Other academic)
  • 23. Gullström, Martin
    et al.
    Lundén, Bengt
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bodin, Maria
    Kangwe, Juma W.
    Stockholm University, Faculty of Science, Department of Botany.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mtolera, Matern S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Assessment of vegetation changes in seagrass communities of tropical Chwaka Bay (Zanzibar) using satellite remote sensing2006In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 67, no 3, p. 399-408Article in journal (Refereed)
    Abstract [en]

    Spatial and temporal dynamics of submerged aquatic vegetation (SAV) cover were studied in the relatively pristine and seagrass-dominated area of Chwaka Bay, Zanzibar (Tanzania) by using satellite remote sensing. Through complementary field work the potential of the technique for change detection was verified. The general changes in SAV cover were examined using Landsat images from 1986, 1987, 1998, 2001 and 2003. Two of these images, from 1987 (Landsat TM) and 2003 (Landsat ETM+), were specifically analysed to create a map of the change in SAV cover. Overall, the general distribution of SAV stayed fairly stable over the period investigated, but the result also showed regions where significant alterations, both losses and gains, had occurred between the two years. Based on our findings and anecdotal information from local fishermen and seaweed farmers potential causative factors are discussed. It was concluded that a repeated mapping with satellite remote sensing is a suitable tool to monitor changes of seagrass and seaweed distribution in shallow tropical environments.

  • 24.
    Gullström, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Samuelsson, Göran S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Anderberg, Elisabeth
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Linderholm, Hans W.
    Knudby, Anders
    Bandeira, Salomao
    Mtwana Nordlund, Lina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Blue Carbon Storage in Tropical Seagrass Meadows Relates to Carbonate Stock Dynamics, Plant–Sediment Processes, and Landscape Context: Insights from the Western Indian Ocean2018In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 3, p. 551-566Article in journal (Refereed)
    Abstract [en]

    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.

  • 25.
    Gullström, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus Dominick
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Samuelsson, Göran
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Anderberg, Elisabeth
    Rasmusson, Lina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Linderholm, Hans
    Bendeira, Salmão
    Nordlund, Lina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Knudby, Anders
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Carbon sequestration capacity in tropical and subtropical seagrass meadows of the Western Indian oceanManuscript (preprint) (Other academic)
  • 26.
    Gullström, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Thomas J.
    Eklöf, Johan S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Semesi, I. Sware
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Seagrass Meadows in Chwaka Bay: Socio-ecological and Management Aspects2012In: People, Nature and Research in Chwaka Bay, Zanzibar, Tanzania / [ed] Maricela de la Torre-Castro, Thomas J. Lyimo, Zanzibar: Western Indian Ocean Marine Science Associoation (WIOMSA) , 2012, p. 89-110Chapter in book (Refereed)
    Abstract [en]

    The shallow-water seascape of Chwaka Bay consists of diverse habitats including coral reefs, sand/mud flats, algal belts and mangrove forests, but the embayment is primarily characterized by its widespread and highly productive seagrass beds. The Bay is a unique seagrass diversity “hotspot”, with eleven species observed, from small, fast-growing and thin-leaved “pioneer” species like Halophila ovalis and H. stipulacea to large, slower-growing “climax species” with thick and long leaves like Thalassodendron ciliatum and Enhalus acoroides. Consequently, it is not surprising that the small-scale subsistence fishery of Chwaka Bay can be seen as a seagrass fishery, with catches consisting primarily of species intimately associated with the seagrass meadows (de la Torre-Castro and Rönnbäck 2004; de la Torre-Castro 2006).Seagrasses are a polyphyletic group of marine vascular, rhizomal plants (den Hartog 1970, 12-13), which form stands of varying sizes usually called “beds” or “meadows” in intertidal and subtidal coastal waters across the globe. Seagrass meadows typically occur on nearshore soft bottoms (although some species are found on rocky bottoms) in single- or mixed-species assemblages, with the typical wide range from tropical to boreal margins of coastal waters (Green and Short 2003, 21-22). They form one of the most productive aquatic ecosystems on Earth (Duarte and Chiscano 1999) and in most areas occur intermixed with other large primary producers like macroalgae. Seagrass ecosystems support multiple ecological functions, including nursery grounds, food and refuge for many benthic,

  • 27.
    Hamisi, Mariam I.
    et al.
    University of Dodoma, School of Natural Sciences and Mathematics.
    Mvungi, Esther F.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas J.
    University of Dar es Salaam, Department of Molecular Biology and Biotechnology.
    Mamboya, Florence A.
    Dar es Salaam Institute of Technology, Department of Sciences and Laboratory Technology.
    Österlund, Katrin
    Stockholm University, Faculty of Science, Department of Botany.
    Bergman, Birgitta
    Stockholm University, Faculty of Science, Department of Botany.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Díez, Beatriz
    Institut de Ciéncies del Mar (ICM), CMIMA-CSIC, Barcelona.
    Nutrient enrichment affects the seagrass Cymodocea serrulata and induces changes to its epiphytic cyanobacterial communityManuscript (preprint) (Other academic)
    Abstract [en]

    To better understand how elevated water column nutrient levels affect the performance of the seagrass Cymodocea serrulata as well as the composition and density of its associated epiphytes, two sets of experiments were carried out where nutrient concentration were manipulated in a flow though system containing seagrasses. The photosynthetic performance, growth characteristics and nutrient content (N:P) were followed for C. serrulata. Simultaneously the biomass, species composition for the epiphytic cyanobacteria, in particular diazotrophs was monitored. The photosynthetic capacity of seagrasses decreased with increase in nutrient concentrations and exposure time. Nutrient contents of seagrass leaves and epiphytes decreased after nutrient addition. A higher diversity of both heterocystous and non-heterocystous cyanobacteria was observed in the experimental seagrasses as compared with natural field samples. Many of the cyanobacterial sequences retrieved represented uncultured and potentially novel diazotrophic phylotypes. Diel nitrogenase activity measurements verified the presence of a distinct proportion of diazotrophs, which was negatively affected by moderate nutrient levels. These results demonstrate that seagrasses were physiologically stressed by the increased nutrient level as revealed by low maximum quantum yields, although the effect was not instant. In contrast the epiphytes whose response was apparent during the short term exposure to moderate nutrient concentration which also promoted rapid change in their composition.

  • 28.
    Hamisi, Mariam
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas
    University of Dar es Salaam.
    Díez, Beatriz
    Institut de Ciéncies del Mar (ICM), CMIMA-CSIC, Barcelona.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Mvungi, Esther
    Stockholm University, Faculty of Science, Department of Botany.
    Mamboya, Florence
    Dar es Salaam Institute of Technology.
    Changes in the epiphytic cyanobacterial community and diazotrophic activity on the tropical seagrasses induced by varying nutrient regimesManuscript (preprint) (Other academic)
    Abstract [en]

    Seagrasses were subject to different nitrogen (N) and phosphorus (P) regimes in a flow trough system (four weeks) to study the influence of moderate nutrient enrichments on the associated cyanobacterial diversity and diazotrophic activity. The seagrass Cymodocea serrulata (R. Brown) were collected outside an urbanized area, west of the Unguja Island, Zanzibar in the Indian Ocean. The epiphytic cyanobacterial community was characterized morphologically (light microscopy) and phylogenetically by DGGE fingerprinting using the 16S rRNA and nifH genes. A lower diversity of both heterocystous and non-heterocystous cyanobacteria was apparent in the natural seagrass stands, when compare to the pulsed nutrient additions that stimulated the growth of the cyanobacterial epiphytes. Non-heterocystous morpho- and genotypes (e.g. Lyngbya, Oscillatoria and Leptolyngbya) dominated and were intermixed with a few representatives of the heterocystous genus Calothrix. Many of the cyanobacterial sequences retrieved represented uncultured and potentially novel diazotrophic phylotypes. Diel nifH gene transcription levels and patterns, and the diel nitrogenase activity (acetylene reduction; max levels of 70.1 ±.19 nmol C2H4 g-1 h-1) verified the presence of a distinct proportion of diazotrophs, which however was negatively affected even by moderate nutrient additions. Although the seagrass host remained unaffected, the increased nutrients levels, mimicking anthropogenic eutrophication in these coastal regions, promoted a rapid change in the epiphytic community composition

  • 29.
    Ismail, Rashid
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Ulanga District Council, Tanzania.
    Asplund, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Buriyo, Amelia
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Calcifying algae modify the air-sea flux of CO2 in tropical seagrass meadowsManuscript (preprint) (Other academic)
  • 30. Kangwe,, Juma
    et al.
    Semesi, I. Sware
    Beer, Sven
    Mtolera, Matern
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Carbonate Production by Calcareous Algae in aSeagrass-Dominated System: The Example of Chwaka Bay. CHAPTER 8: CHAPTER 82012In: People, Nature and Research in Chwaka Bay, Zanzibar, Tanzania / [ed] de la Torre-Castro M. and Lyimo T.J., Zanzibar: WIOMSA , 2012Chapter in book (Refereed)
  • 31.
    Lyimo, Liberatus D.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Thomas J.
    Deyanova, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hamisi, Mariam
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Shading and simulated grazing increase the sulphide pool and methane emission in a tropical seagrass meadow2018In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 134, p. 89-93Article in journal (Refereed)
    Abstract [en]

    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.

  • 32.
    Lyimo, Liberatus Dominick
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hamis, Mariam
    Lyimo, Thomas J.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Emission of nitrous oxide and methane from tropical seagrass meadows: effects of gas transport through seagrass plant and eutrophicationManuscript (preprint) (Other academic)
  • 33.
    Lyimo, Liberatus Dominick
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Dodoma, Tanzania.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Thomas J.
    Deyanova, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hamis, Mariam
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Shading and simulated grazing of seagrass leaves increases sulphide production and methane emission in a tropical seagrass meadowManuscript (preprint) (Other academic)
  • 34.
    Mamboya, F.A
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, T.J.
    University of Dar es Salaam.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Influence of combined changes in salinity and copper modulation on growth and copper uptake in the tropical green macroalga Ulva reticulata.2009In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 84, no 3, p. 326-330Article in journal (Refereed)
    Abstract [en]

    The influence of salinity on growth and Cu uptake in the green macroalga Ulva reticulata collected from the intertidal area in the Western Indian Ocean was studied under controlled laboratory conditions. Exposure concentrations ranged from 5 to 500 μg Cu l−1 at five salinities (ranging 20–40). The accumulation of Cu increased with decreasing salinity, so that the uptake at 500 μg Cu l−1 was approximately 2.7, 2.4 and 2.0 times higher at salinities of 20, 25, and 30 respectively, than uptake at salinity of 35, and with uptake being lowest at salinity of 40. Ulva maintained a positive growth rate over the whole salinity range (20–40), with highest rates at salinity of 35. When exposing to Cu at low salinities (20 and 25), the growth rate of Ulva was strongly inhibited suggesting an increase in toxicity of Cu with decreasing salinity. EC50 and NOEC increased with increase in salinity, implying a reduced Cu toxicity at high salinities. It was concluded that salinity needs to be considered when using macroalgae, such as U. reticulata, as a bioindicator of heavy metals in areas with heavy rainfall, underground fresh water intrusion or in estuaries, as they might accumulate more metals and be more negatively affected.

  • 35.
    Mamboya, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Semesi, A
    Mtolera, Matern
    Pratab,
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Accumulation and physiological effects of copper and zinc on the brown macroalga Padina boergesenii.2007In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 6, no 1, p. 17-28Article in journal (Refereed)
  • 36. Mangora, M. M.
    et al.
    Mtolera, M. S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of waterlogging, salinity and light on the productivity of Bruguiera gymnorrhiza and Heritiera littoralis seedlings2017In: African Journal of Marine Science, ISSN 1814-232X, E-ISSN 1814-2338, Vol. 39, no 2, p. 167-174Article in journal (Refereed)
    Abstract [en]

    This study aimed to establish the effects of waterlogging, salinity and light on the early development of mangroves. Seedlings of Bruguiera gymnorrhiza (L.) Lamk. and Heritiera littoralis Dryand were exposed to 12 weeks of waterlogging, during which time growth and photosynthesis were measured every two weeks. The salinity of the water inundation ranged from fresh water to full-strength sea water (salinity 35). Seedlings were exposed to either full sunlight of 1 500 mu mol photon m(-2) s(-1) (SD 397) at midday or shade conditions of 325 mu mol photon m(-2) s(-1) (SD 40) of light at midday, to explore whether the plants would be differently affected by prolonged waterlogging in increased salinities and under different light conditions. Heritiera littoralis was more sensitive to waterlogging, salinity and light, displaying a least relative growth rate of 0.127 g g(-1) week(-1) (SE 0.032) under shade, and 0.025 g g(-1) week(-1) (SE 0.021) in full light; while under shade, photosynthesis continued only in fresh water, but photosynthetic yield decreased from 0.7 to 0.4 with increasing duration of waterlogging. By 12 weeks, all H. littoralis seedlings treated with any saltwater mixture had died. Bruguiera gymnorrhiza seedlings maintained a moderate rate of photosynthesis throughout inundation in both shade and full light, with yields of 0.7 and 0.3, respectively. Furthermore, B. gymnorrhiza survived waterlogging in up to 66% seawater, and maintained comparable relative growth rates of 0.164 g g(-1) week(-1) (SE 0.066) with 0.083 g g(-1) week(-1) (SE 0.065) and 0.074 g g(-1) week(-1) (SE 0.036) with 0.052 g g(-1) week(-1) (SE 0.037) under shade and in full light between fresh water and the highest salinity conditions, respectively. These results suggest that B. gymnorrhiza is broadly tolerant, making it a potential candidate species for restoring vulnerable mangrove forests.

  • 37. Mangora, Mwita M.
    et al.
    Mtolera, Matern S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Photosynthetic responses to submergence in mangrove seedlings2014In: Marine and Freshwater Research, ISSN 1323-1650, E-ISSN 1448-6059, Vol. 65, no 6, p. 497-504Article in journal (Refereed)
    Abstract [en]

    Flooding and salinity fluctuations are common in mangrove systems. Sometimes these events are long-lasting, persisting several months. With an increased frequency of heavy rainfalls and terrestrial run-off, subsequent floods have been associated with massive mangrove mortality and failure to regenerate in the region. Owing to climate change, these events are expected to be more common in the future. We investigated how three weeks of submergence in water of different salinities affected the photosynthetic rates in seedlings of three common mangroves: Bruguiera gymnorrhiza (L.) Lamk.; Avicennia marina (Forssk.) Vierh.; and Heritiera littoralis Dryand. We found that photosynthesis and survival rates declined with increasing salinity and submergence time for all species. Prolonged submergence caused a significant decline in photosynthetic rates (as electron transport rate - ETR) for B. gymnorrhiza (P = .021) and H. littoralis (P = 0.002), whereas significant effects of both salinity (P = 0.003) and submergence (P = 0.023) were observed between species. Maximum diurnal values of ETR declined in the order of A. marina > B. gymnorrhiza > H. littoralis. After submergence, survived seedlings were tended normally, watered twice a day with freshwater. Three seedlings of B. gymnorrhiza from freshwater and 33% seawater treatments and of A. marina from freshwater treatment displayed signs of recovery for the first 3-5 days, but after that they died. We conclude that submergence time and water salinity will affect the performance of mangrove areas, such that areas experiencing prolonged submergence with flooding dominated by saline water might be most severely impacted.

  • 38. Mazzuca, Silvia
    et al.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Beer, S.
    Felisberto, P.
    Gobert, S.
    Procaccini, G.
    Runcie, J.
    Silva, J.
    Borges, A. V.
    Brunet, C.
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Champenois, W.
    Costa, M. M.
    D'Esposito, D.
    Gullström, Martin
    Lejeune, P.
    Lepoint, G.
    Olive, I.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Richir, J.
    Ruocco, M.
    Serra, I. A.
    Spadafora, A.
    Santos, Rui
    Establishing research strategies, methodologies and technologies to link genomics and proteomics to seagrass productivity, community metabolism, and ecosystem carbon fluxes2013In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 4, article id 38Article in journal (Refereed)
    Abstract [en]

    A complete understanding of the mechanistic basis of marine ecosystem functioning is only possible through integrative and interdisciplinary research. This enables the prediction of change and possibly the mitigation of the consequences of anthropogenic impacts. One major aim of the European Cooperation in Science and Technology (COST) Action ES0609 Seagrasses productivity. From genes to ecosystem management, is the calibration and synthesis of various methods and the development of innovative techniques and protocols for studying seagrass ecosystems. During 10 days, 20 researchers representing a range of disciplines (molecular biology, physiology, botany, ecology, oceanography, and underwater acoustics) gathered at The Station de Recherches Sous-marines et Oceanographiques (STARESO, Corsica) to study together the nearby Posidonia oceanica meadow. STARESO is located in an oligotrophic area classified as pristine site where environmental disturbances caused by anthropogenic pressure are exceptionally low. The healthy P. oceanica meadow, which grows in front of the research station, colonizes the sea bottom from the surface to 37 m depth. During the study, genomic and proteomic approaches were integrated with ecophysiological and physical approaches with the aim of understanding changes in seagrass productivity and metabolism at different depths and along daily cycles. In this paper we report details on the approaches utilized and we forecast the potential of the data that will come from this synergistic approach not only for P. oceanica but for seagrasses in general.

  • 39. Mcleod, Elizabeth
    et al.
    Chmura, Gail L.
    Bouillon, Steven
    Salm, Rodney
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Duarte, Carlos M.
    Lovelock, Catherine E.
    Schlesinger, William H.
    Silliman, Brian R.
    A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO(2)2011In: Frontiers in Ecology and the Environment, ISSN 1540-9295, Vol. 9, no 10, p. 552-560Article, review/survey (Refereed)
    Abstract [en]

    Recent research has highlighted the valuable role that coastal and marine ecosystems play in sequestering carbon dioxide (CO(2)). The carbon (C) sequestered in vegetated coastal ecosystems, specifically mangrove forests, seagrass beds, and salt marshes, has been termed blue carbon. Although their global area is one to two orders of magnitude smaller than that of terrestrial forests, the contribution of vegetated coastal habitats per unit area to long-term C sequestration is much greater, in part because of their efficiency in trapping suspended matter and associated organic C during tidal inundation. Despite the value of mangrove forests, seagrass beds, and salt marshes in sequestering C, and the other goods and services they provide, these systems are being lost at critical rates and action is urgently needed to prevent further degradation and loss. Recognition of the C sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration; however, it is necessary to improve scientific understanding of the underlying mechanisms that control C sequestration in these ecosystems. Here, we identify key areas of uncertainty and specific actions needed to address them.

  • 40.
    Mvungi, Esther F.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas J.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    When Zostera marina is intermixed with Ulva, its photosynthesis is reduced by increased pH and lower light, but not by changes in light quality2012In: Aquatic Botany, ISSN 0304-3770, E-ISSN 1879-1522, Vol. 102, p. 44-49Article in journal (Refereed)
    Abstract [en]

    To evaluate the effects of Ulva on the photosynthetic capacities of the temperate seagrass Zostera marina, we compared it in the laboratory under normal light and light filtered through layers of Ulva intestinalis, and repeated the experiments with the addition of pH-induced changes in carbon speciation and availability. One thallus of Ulva reduced photosynthetically available irradiance to underlying seagrass by about 50% and shifted the quality of remaining light towards the green part of the spectrum (approximately 520–570 nm). There was no significant difference in photosynthetic performance between Z. marina under normal light and under Ulva-filtered light when adjusted to the same irradiance as for the control plants, indicating that the green spectrum transmitted through Ulva layers was being absorbed by the seagrass and was as efficient in driving photosynthesis as was the normal light. On the other hand, algae-generated pH shifts which could extend up to pH 10 had significant negative effects on photosynthesis of the seagrass, reducing the electron transport rates with up to 75%.

  • 41.
    Mvungi, Esther F.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas J.
    University of Dar es Salaam, Department of Molecular Biology and Biotechnology.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    When Zostera marina is intermixed with Ulva, its photosynthesis is reduced by increased pH and lower light, but not by changes in light qualityIn: Aquatic Botany, ISSN 0304-3770, E-ISSN 1879-1522Article in journal (Refereed)
    Abstract [en]

    In eutrophic coastal waters, seagrasses often become intermixed with opportunistic algae, such as different species of Ulva that grow on top of, or between shoots in Zostera marina beds. When this occurs, the algae can both reduce the amount of light reaching the seagrasses and also alter the quality of that light so that it becomes dominated by the green part of the spectrum. Since Ulva has an efficient photosynthetic carbon uptake, its photosynthesis can drastically increase the pH of the surrounding seawater, and thus create conditions where Zostera marina is unable to acquire inorganic carbon (Ci). To evaluate the effects of Ulva on the photosynthetic capacities of the temperate seagrass Zostera marina, we compared it in the laboratory under normal light and light filtered through layers of Ulva intestinalis, and repeated the experiments with the addition of pH-induced changes in carbon speciation and availability. One thallus of Ulva reduced photosynthetically available irradiance to underlying seagrass by about 50% and shifted the quality of remaining light towards the green part of the spectrum. Interestingly, there was no significant difference in photosynthetic performance between Zostera marina under normal light and under Ulva-filtered green light when adjusted to the same irradiance as for the control plants, indicating that the green spectrum transmitted through Ulva layers may be efficient in driving photosynthesis in the seagrass bed. On the other hand, algae-generated pH shifts had drastic negative effects on the photosynthesis of the seagrass.

  • 42.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Deyanoya, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Bik, Holly M.
    Schuelke, Taruna
    Pereira, Tiago José
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Creer, Simon
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure2019In: Communications biology, ISSN 2399-3642, Vol. 2, article id 362Article in journal (Refereed)
    Abstract [en]

    Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how sea- grass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high- throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.

  • 43. Procaccini, Gabriele
    et al.
    Beer, Sven
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Olsen, Jeanine
    Mazzuca, Silvia
    Santos, Rui
    Seagrass ecophysiology meets ecological genomics: are we ready?2012In: Marine Ecolocy, ISSN 0173-9565, E-ISSN 1439-0485, Vol. 33, no 4, p. 522-527Article in journal (Refereed)
    Abstract [en]

    In March 2011, the Ecophysiology and Genetics Working Groups of the European Science Foundation COST Action ES 0906, entitled Seagrass Productivity: From Genes to Ecosystem Management, organized an exploratory workshop entitled Linking Ecophysiology and Ecogenomics in Seagrass Systems. The goal of the workshop was to discuss how to integrate comparative gene expression studies with physiological processes such as photosynthetic performance, carbon and nitrogen utilization and environmental adaptation. The main questions discussed for integrative research related to mechanisms of carbon utilization, light requirements, temperature effects and natural variation in pH and ocean acidification. It was concluded that the seagrass research community is still in the nascent stages of linking ecophysiology with genomic responses, as carbon and nitrogen metabolism of seagrasses have not been sufficiently well studied. Likewise, genomic approaches have only been able to assign meaningful interpretations to a handful of differentially expressed genes. Nevertheless, the way forward has been established.

  • 44. Procaccini, Gabriele
    et al.
    Ruocco, Miriam
    Marin-Guirao, Lazaro
    Dattolo, Emanuela
    Brunet, Christophe
    D'Esposito, Daniela
    Lauritano, Chiara
    Mazzuca, Silvia
    Serra, Ilia Anna
    Bernardo, Letizia
    Piro, Amalia
    Beer, Sven
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince of Songkla University, Thailand.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Felisberto, Paulo
    Gobert, Sylvie
    Runcie, John W.
    Silva, Joao
    Olive, Irene
    Costa, Monya M.
    Barrote, Isabel
    Santos, Rui
    Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass Posidonia oceanica2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 42890Article in journal (Refereed)
    Abstract [en]

    Here we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong differences in the light environment. The photochemical pathway of energy use was more effective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic differentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-specific diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems.

  • 45.
    Rasmusson, Lina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Buapet, Pimchanok
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Gunnarsson, Pontus
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of temperature and hypoxia on respiration, photorespiration and photosynthesis of seagrassesManuscript (preprint) (Other academic)
  • 46.
    Rasmusson, Lina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gunnarsson, Pontus
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Seagrass productivity during temperature variations: estimation of a whole plant Q10 for respiration and photosynthesis in Zostera marinaManuscript (preprint) (Other academic)
  • 47.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Determining light suppression of mitochondrial respiration for three temperate marine macrophytes using the Kok method2014In: Botanica Marina, ISSN 0006-8055, E-ISSN 1437-4323, Vol. 57, no 6, p. 483-486Article in journal (Refereed)
    Abstract [en]

    To properly calculate the carbon budgets of coastal marine habitats, potential fluctuations in oxygen consumption due to mitochondrial respiration must be taken into account. As mitochondrial respiration is sometimes inhibited in light, we used the Kok method to estimate whether such suppression occurs in the seagrasses Zostera marina and Ruppia maritima as well as in the macroalga Ulva intestinalis. For Z. marina and U. intestinalis, the respiration rate was clearly downregulated in light, a finding that might be important when determining the impact of respiration on estimated net primary productivity in these marine habitats.

  • 48.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of increased temperature on respiration and photosynthesis differ among different leaf parts and with tissue age of the seagrass Zostera marinaManuscript (preprint) (Other academic)
  • 49.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gunnarsson, Pontus C. B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Estimation of a whole plant Q10 to assess seagrass productivity during temperature shifts2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 12667Article in journal (Refereed)
    Abstract [en]

    Through respiration and photosynthesis, seagrass meadows contribute greatly to carbon and oxygen fluxes in shallow coastal waters. There is increasing concern about how shallow-water primary producers will react to a near-future climate scenario with increased temperature variation. When modelling primary productivity under high temperature variability, Q10 values are commonly used to predict rate changes depending on biophysical factors. Q10 values are often assumed to be constant and around 2.0 (i.e. a doubling of the rate with a temperature increase of 10 degrees C). We aimed to establish how the gas exchange of seagrass (Zostera marina) tissues at various maturity stages would respond over a broad range of temperatures. Seagrass shoot maturity stage clearly affected respiration and apparent photosynthesis, and the Q10 results indicated a skewed balance between the two processes, with a higher photosynthetic Q10 during periods of elevated temperatures. When estimating whole-plant Q10 in a realistic maximal temperature range, we found that the overall response of a seagrass plant's net O-2 exchange balance can be as much as three to four times higher than under ambient temperatures. Our findings indicate that plant tissue age and temperature should be considered when assessing and modelling carbon and oxygen fluctuations in vegetated coastal areas.

  • 50.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lauritano, Chiara
    Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
    Procaccini, Gabriele
    Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Respiratory oxygen consumption in the seagrass Zostera marina is affected by light and varies on a diel basis: a combined gas exchange and gene expression studyManuscript (preprint) (Other academic)
12 1 - 50 of 57
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