| 1. |
- Fransner, Filippa, et al.
(författare)
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Non-Redfieldian Dynamics Explain Seasonal pCO2 Drawdown in the Gulf of Bothnia
- 2018
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 123:1, s. 166-188
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Tidskriftsartikel (refereegranskat)abstract
- High inputs of nutrients and organic matter make coastal seas places of intense air-sea CO2 exchange. Due to their complexity, the role of coastal seas in the global air-sea CO2 exchange is, however, still uncertain. Here, we investigate the role of phytoplankton stoichiometric flexibility and extracellular DOC production for the seasonal nutrient and CO2 partial pressure (pCO2) dynamics in the Gulf of Bothnia, Northern Baltic Sea. A 3-D ocean biogeochemical-physical model with variable phytoplankton stoichiometry is for the first time implemented in the area and validated against observations. By simulating non-Redfieldian internal phytoplankton stoichiometry, and a relatively large production of extracellular dissolved organic carbon (DOC), the model adequately reproduces observed seasonal cycles in macronutrients and pCO2. The uptake of atmospheric CO2 is underestimated by 50% if instead using the Redfield ratio to determine the carbon assimilation, as in other Baltic Sea models currently in use. The model further suggests, based on the observed drawdown of pCO2, that observational estimates of organic carbon production in the Gulf of Bothnia, derived with the method, may be heavily underestimated. We conclude that stoichiometric variability and uncoupling of carbon and nutrient assimilation have to be considered in order to better understand the carbon cycle in coastal seas.
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| 2. |
- Klais, Riina, et al.
(författare)
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Spring phytoplankton communities shaped by interannual weather variability and dispersal limitation : Mechanisms of climate change effects on key coastal primary producers
- 2013
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 58:2, s. 753-762
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Tidskriftsartikel (refereegranskat)abstract
- Spring bloom composition in the Baltic Sea, a partially ice-covered brackish coastal waterbody, is shaped by winter-spring weather conditions affecting the relative dominance of diatoms and a heterogeneous assemblage of cold-water dinoflagellates, dominated by the chain-forming Peridiniella catenata and a complex of at least three medium-sized, single-celled species: Biecheleria baltica, Gymnodinium corollarium, and Scrippsiella hangoei. During the last decades, the bloom community has dramatically changed in several basins. We analyze here a 30 yr time series of quantitative phytoplankton data, as predicted by hindcast modeled ice thickness and storminess for three distinct Baltic Sea localities, to verify climate-driven mechanisms affecting the spring bloom composition. Thick (> 30 cm) and long-lasting ice cover favored diatom-dominated spring blooms, and mild winters, with storms and thin ice cover (10 to 20 cm), supported blooms of the B. baltica complex. Dispersal limitation plays an important role in the spatial extent of blooms of the B. baltica complex, caused by intricate interplay of local hydrodynamics and the dinoflagellate life cycle. Proportion peaks of key phytoplankton groups have shifted about 10 d earlier in the northwestern Baltic Sea (P. catenata and diatoms) and in the Gulf of Riga (P. catenata). The significant weather effects imply future shifts in spring bloom composition and consequent biogeochemical cycles, driven by the predicted changes in winter storminess and decrease in ice cover extent and duration in climate change models.
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| 3. |
- Mattsson, Lina, 1992-
(författare)
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Microalgal solutions in Nordic conditions : industries transition toward resource recovery?
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microalgal solutions can through photosynthesis recover greenhouse gas (CO2) and nutrients from industrial waste, reducing climate footprint and eutrophication. An added value to the process is algal biomass containing lipids, proteins, and carbohydrates with commercial potential for biofuel, feed, and fertilizer. Microalgal cultivation in Nordic conditions is challenged by strong seasonality in light and temperature that can compromise biomass stability. To make microalgal cultivation sustainable and competitive with conventional feedstock, large-scale outdoor cultivation using waste streams is necessary but limits control over seasonal fluctuations in environmental conditions. In this thesis, I used a polyculture approach in outdoor large-scale cultivations with industrial waste resources, to study biomass production and quality in an annual, seasonal, and diurnal perspective. Research focused on the biomass potential for nutrient recovery and carbon capture from industries, year around stability and quality. Production was tested in the South Baltic Region using a brackish water polyculture grown for five years in a green wall panel (GWP) fed with cement industry flue gas (CO2 source). In a second setup, a freshwater polyculture was cultivated seasonally in raceway ponds (RWP), with an additional waste resource from landfill leachate water (nitrogen source). Stable biomass performance and CO2 recovery up to 10 g m-2 d-1 was achieved for five years over seasons in the GWP with high protein in autumn and winter, whereas lipids remained stable throughout the annual cycle. Laboratory experiments confirmed naturally occurring diurnal shifts in temperature as superior lipid boosters compared to conventional nitrogen limitation. Stability of overall performance could be explained by flue gas recirculation mode, lack of contamination and polyculture complementarity of the two green algal strains that dominated throughout the five years. The use of multiple waste streams in the RWP added complexity to the cultivation as leachate water composition varied, resulting in a diverse green algal polyculture. Seasonality in nitrogen recovery rate was explained by total nitrogen and light. Results indicate stability of biomass and resource recovery in Nordic conditions using local polycultures in large-scale outdoor cultivation and periods of lower biomass production can be compensated by high quality metabolites such as proteins and lipids.
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| 4. |
- Tamelander, Tobias, et al.
(författare)
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Organic matter export to the seafloor in the Baltic Sea : Drivers of change and future projections
- 2017
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 46:8, s. 842-851
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Tidskriftsartikel (refereegranskat)abstract
- The impact of environmental change and anthropogenic stressors on coastal marine systems will strongly depend on changes in the magnitude and composition of organic matter exported from the water column to the seafloor. Knowledge of vertical export in the Baltic Sea is synthesised to illustrate how organic matter deposition will respond to climate warming, climate-related changes in freshwater runoff, and ocean acidification. Pelagic heterotrophic processes are suggested to become more important in a future warmer climate, with negative feedbacks to organic matter deposition to the seafloor. This is an important step towards improved oxygen conditions in the near-bottom layer that will reduce the release of inorganic nutrients from the sediment and hence counteract further eutrophication. The evaluation of these processes in ecosystem models, validated by field observations, will significantly advance the understanding of the system's response to environmental change and will improve the use of such models in management of coastal areas.
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| 5. |
- Vehmaa, Anu, et al.
(författare)
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Copepod reproductive success in spring-bloom communities with modified diatom and dinoflagellate dominance
- 2012
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 69:3, s. 351-357
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Tidskriftsartikel (refereegranskat)abstract
- Dinoflagellates have increased and diatoms decreased in the Baltic Sea in recent decades, possibly because of changes in the climate and altered patterns of stratification. The hypothesis that grazing copepods would benefit from the change in species composition was tested experimentally by studying the reproductive output of the crustacean copepod Eurytemora affinis in five Baltic Sea phytoplankton spring communities dominated by different dinoflagellates (Biecheleria baltica, Gymnodinium corollarium) and diatoms (Chaetoceros cf. wighamii, Skeletonema marinoi, and Thalassiosira baltica). After a 5-d acclimation and a 4-d incubation, egg production, egg hatching success, and the RNA: DNA ratio of E. affinis were measured. Egg production was highest on a G. corollarium-dominated diet and lowest on a S. marinoi-dominated diet and on a B. baltica-dominated natural spring bloom, but there were no differences in hatching success. The results demonstrate strong species-specific effects unconstrained by the dominating group. Hence, the hypothesis of specific effects derived from a diatom or dinoflagellate diet is too simplistic, and there is a need to explore phytoplankton taxa at a species level to reveal the reasons for copepod reproductive success.
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