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Publications (10 of 17) Show all publications
Figueroa, D., Capo, E., Lindh, M. V., Rowe, O. F., Paczkowska, J., Pinhassi, J. & Andersson, A. (2021). Terrestrial dissolved organic matter inflow drives temporal dynamics of the bacterial community of a subarctic estuary (northern Baltic Sea). Environmental Microbiology, 23(8), 4200-4213
Open this publication in new window or tab >>Terrestrial dissolved organic matter inflow drives temporal dynamics of the bacterial community of a subarctic estuary (northern Baltic Sea)
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2021 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 23, no 8, p. 4200-4213Article in journal (Refereed) Published
Abstract [en]

Climate change is projected to cause increased inflow of terrestrial dissolved organic matter to coastal areas in northerly regions. Estuarine bacterial community will thereby receive larger loads of organic matter and inorganic nutrients available for microbial metabolism. The composition of the bacterial community and its ecological functions may thus be affected. We studied the responses of bacterial community to inflow of terrestrial dissolved organic matter in a subarctic estuary in the northern Baltic Sea, using a 16S rRNA gene metabarcoding approach. Betaproteobacteria dominated during the spring river flush, constituting ~ 60% of the bacterial community. Bacterial diversity increased as the runoff decreased during summer, when Verrucomicrobia, Betaproteobacteria, Bacteroidetes, Gammaproteobacteria and Planctomycetes dominated the community. Network analysis revealed that a larger number of associations between bacterial populations occurred during the summer than in spring. Betaproteobacteria and Bacteroidetes populations appeared to display similar correlations to environmental factors. In spring, freshly discharged organic matter favoured specialists, while in summer a mix of autochthonous and terrestrial organic matter promoted the development of generalists. Our study indicates that increased inflows of terrestrial organic matter-loaded freshwater to coastal areas would promote specialist bacteria, which in turn might enhance the transformation of terrestrial organic matter in estuarine environments.

Place, publisher, year, edition, pages
John Wiley & Sons, 2021
National Category
Ecology Microbiology
Identifiers
urn:nbn:se:umu:diva-184471 (URN)10.1111/1462-2920.15597 (DOI)000656706300001 ()33998121 (PubMedID)2-s2.0-85107376018 (Scopus ID)
Available from: 2021-06-14 Created: 2021-06-14 Last updated: 2024-02-13Bibliographically approved
Paczkowska, J., Brugel, S., Rowe, O., Lefèbure, R., Brutemark, A. & Andersson, A. (2020). Response of Coastal Phytoplankton to High Inflows of Terrestrial Matter. Frontiers in Marine Science, 7, Article ID 80.
Open this publication in new window or tab >>Response of Coastal Phytoplankton to High Inflows of Terrestrial Matter
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2020 (English)In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 7, article id 80Article in journal (Refereed) Published
Abstract [en]

Climate change scenarios project that precipitation will increase in northern Europe, causing amplified inflows of terrestrial matter (tM) and inorganic nutrients to coastal areas. How this will affect the plankton community is poorly understood. A mesocosm experiment was carried out to investigate the influence of two levels of tM inputs on the composition, size-structure and productivity of a natural coastal phytoplankton community from the northern Baltic Sea. The tM addition caused browning of the water and decreased underwater light levels, while the concentrations of dissolved organic carbon (DOC) and inorganic nutrients increased. Microphytoplankton were promoted by tM addition, while in the controls picophytoplankton dominated the phytoplankton community. Inorganic nutrient availability was instrumental in defining the phytoplankton community composition and size-structure. As a response to tM addition, the phytoplankton increased their chlorophyll a content. This physiological adaptation helped to maintain high primary production rates at the low tM enrichment, but at the high tM load the primary production decreased as did the biomass of mesozooplankton. The ciliate biomass was high when the mesozooplankton biomass was low, indicating that a trophic cascade occurred in the system. Structural equation modeling showed that tM borne DOC promoted ciliates, while primary and bacterial production were disfavored. Thus, DOC originating from soils had an indirect negative effect on the mesozooplankton by reducing their food availability. Although, a positive correlation between heterotrophic bacteria and phytoplankton suggested coupling between phytoplankton produced carbon and heterotrophs growth. The results from our study indicate that river-borne DOC and inorganic nutrients have a large impact on the phytoplankton community, driving the system to the dominance of large diatoms. However, since river-borne humic substances cause browning of the water, phytoplankton increase their light harvesting pigments. At moderate inflow this helps to support the primary production, but at high inflows of terrestrial material the primary production will decrease. As high river inflows have been projected to be a consequence of climate change, we foresee that primary production will decrease in coastal areas in the future, and the impacts of such changes on the food web could be significant.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2020
Keywords
coastal phytoplankton, terrestrial organic matter, climate change, primary production, chlorophyll a
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-169083 (URN)10.3389/fmars.2020.00080 (DOI)000517578000001 ()2-s2.0-85082550038 (Scopus ID)
Available from: 2020-03-23 Created: 2020-03-23 Last updated: 2023-03-23Bibliographically approved
Paczkowska, J., Rowe, O. F., Figueroa, D. & Andersson, A. (2019). Drivers of phytoplankton production and community structure in nutrient-poor estuaries receiving terrestrial organic inflow. Marine Environmental Research, 151, Article ID 104778.
Open this publication in new window or tab >>Drivers of phytoplankton production and community structure in nutrient-poor estuaries receiving terrestrial organic inflow
2019 (English)In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 151, article id 104778Article in journal (Refereed) Published
Abstract [en]

The influence of nutrient availability and light conditions on phytoplankton size-structure, nutritional strategy and production was studied in a phosphorus-poor estuary in the northern Baltic Sea receiving humic-rich river water. The relative biomass of mixotrophic nanophytoplankton peaked in spring when heterotrophic bacterial production was high, while autotrophic microphytoplankton had their maximum in summer when primary production displayed highest values. Limiting substance (phosphorus) only showed small temporal variations, and the day light was at saturating levels all through the study period. We also investigated if the phytoplankton taxonomic richness influences the production. Structural equation modelling indicated that an increase of the taxonomic richness during the warm summer combined with slightly higher phosphorus concentration lead to increased resource use efficiency, which in turn caused higher phytoplankton biomass and primary production. Our results suggest that climate warming would lead to higher primary production in northerly shallow coastal areas, which are influenced by humic-rich river run-off from un-disturbed terrestrial systems.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Phytoplankton, Size-structure, Primary production, Autotrophy, Mixotrophy, Taxonomic richness, Resource use efficiency, Coastal waters, Phosphorus-poor estuaries
National Category
Oceanography, Hydrology and Water Resources Ecology Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-166459 (URN)10.1016/j.marenvres.2019.104778 (DOI)000497258600017 ()31488340 (PubMedID)2-s2.0-85071595027 (Scopus ID)
Funder
Swedish Research Council FormasSwedish Agency for Marine and Water ManagementSwedish Environmental Protection Agency
Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2023-03-23Bibliographically approved
Villafane, V. E., Paczkowska, J., Andersson, A., Duran Romero, C., Valinas, M. S. & Walter Helbling, E. (2018). Dual role of DOM in a scenario of global change on photosynthesis and structure of coastal phytoplankton from the South Atlantic Ocean. Science of the Total Environment, 634, 1352-1361
Open this publication in new window or tab >>Dual role of DOM in a scenario of global change on photosynthesis and structure of coastal phytoplankton from the South Atlantic Ocean
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2018 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 634, p. 1352-1361Article in journal (Refereed) Published
Abstract [en]

We evaluated the dual role of DOM (i.e., as a source of inorganic nutrients and as an absorber of solar radiation) on a phytoplankton community of the western South Atlantic Ocean. Using a combination of microcosms and a cluster approach, we simulated the future conditions of some variables that are highly influenced by global change in the region. We increased nutrients (i.e., anthropogenic input) and dissolved organic matter (DOM), and we decreased the pH, to assess their combined impact on growth rates (mu), species composition/abundance and size structure, and photosynthesis (considering in this later also the effects of light quality i.e., with andwithout ultraviolet radiation). We simulated two Future conditions (Fut) where nutrients and pHwere similarly manipulated, but in one the physical role of DOM (Fut(out)) was assessed whereas in the other (Fut(in)) the physicochemical role was evaluated; these conditions were compared with a control (Present condition, Pres). The mu significantly increased in both Fut conditions as compared to the Pres, probably due to the nutrient addition and acidification in the former. The highest mu were observed in the Fut(out), due to the growth of nanoplanktonic flagellates and diatoms. Cells in the Fut(in) were photosynthetically less efficient as compared to those of the Fut(out) and Pres, but these physiological differences, also between samples with or without solar UVR observed at the beginning of the experiment, decreased with time hinting for an acclimation process. The knowledge of the relative importance of both roles of DOM is especially important for coastal areas that are expected to receive higher inputs and will be more acidified in the future.

Keywords
Acidification, Dissolved organic matter, Nutrients, Oxygen evolution, Photosynthesis, Ultraviolet diation
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-150166 (URN)10.1016/j.scitotenv.2018.04.121 (DOI)000433153600139 ()29710635 (PubMedID)2-s2.0-85045386293 (Scopus ID)
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE
Available from: 2018-07-18 Created: 2018-07-18 Last updated: 2023-03-24Bibliographically approved
Andersson, A., Brugel, S., Paczkowska, J., Rowe, O. F., Figueroa, D., Kratzer, S. & Legrand, C. (2018). Influence of allochthonous dissolved organic matter on pelagic basal production in a northerly estuary. Estuarine, Coastal and Shelf Science, 204, 225-235
Open this publication in new window or tab >>Influence of allochthonous dissolved organic matter on pelagic basal production in a northerly estuary
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2018 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 204, p. 225-235Article in journal (Refereed) Published
Abstract [en]

Phytoplankton and heterotrophic bacteria are key groups at the base of aquatic food webs. In estuaries receiving riverine water with a high content of coloured allochthonous dissolved organic matter (ADOM), phytoplankton primary production may be reduced, while bacterial production is favoured. We tested this hypothesis by performing a field study in a northerly estuary receiving nutrient-poor, ADOM-rich riverine water, and analyzing results using multivariate statistics. Throughout the productive season, and especially during the spring river flush, the production and growth rate of heterotrophic bacteria were stimulated by the riverine inflow of dissolved organic carbon (DOC). In contrast, primary production and photosynthetic efficiency (i.e. phytoplankton growth rate) were negatively affected by DOC. Primary production related positively to phosphorus, which is the limiting nutrient in the area. In the upper estuary where DOC concentrations were the highest, the heterotrophic bacterial production constituted almost 100% of the basal production (sum of primary and bacterial production) during spring, while during summer the primary and bacterial production were approximately equal. Our study shows that riverine DOC had a strong negative influence on coastal phytoplankton production, likely due to light attenuation. On the other hand DOC showed a positive influence on bacterial production since it represents a supplementary food source. Thus, in boreal regions where climate change will cause increased river inflow to coastal waters, the balance between phytoplankton and bacterial production is likely to be changed, favouring bacteria. The pelagic food web structure and overall productivity will in turn be altered.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Primary and bacterial production, Coastal areas, Estuary, Allochthonous dissolved organic matter, Northern Baltic Sea
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-147287 (URN)10.1016/j.ecss.2018.02.032 (DOI)000429757300020 ()2-s2.0-85043270673 (Scopus ID)
Available from: 2018-05-28 Created: 2018-05-28 Last updated: 2023-03-24Bibliographically approved
Rowe, O. F., Dinasquet, J., Paczkowska, J., Figueroa, D., Riemann, L. & Andersson, A. (2018). Major differences in dissolved organic matter characteristics and bacterial processing over an extensive brackish water gradient, the Baltic Sea. Marine Chemistry, 202, 27-36
Open this publication in new window or tab >>Major differences in dissolved organic matter characteristics and bacterial processing over an extensive brackish water gradient, the Baltic Sea
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2018 (English)In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 202, p. 27-36Article in journal (Refereed) Published
Abstract [en]

Dissolved organic matter (DOM) in marine waters is a complex mixture of compounds and elements that contribute substantially to the global carbon cycle. The large reservoir of dissolved organic carbon (DOC) represents a vital resource for heterotrophic bacteria. Bacteria can utilise, produce, recycle and transform components of the DOM pool, and the physicochemical characteristics of this pool can directly influence bacterial activity; with consequences for nutrient cycling and primary productivity. In the present study we explored bacterial transformation of naturally occurring DOM across an extensive brackish water gradient in the Baltic Sea. Highest DOC utilisation (indicated by decreased DOC concentration) was recorded in the more saline southerly region where waters are characterised by more autochthonous DOM. These sites expressed the lowest bacterial growth efficiency (BGE), whereas in northerly regions, characterised by higher terrestrial and allochthonous DOM, the DOC utilisation was low and BGE was highest. Bacterial processing of the DOM pool in the south resulted in larger molecular weight compounds and compounds associated with secondary terrestrial humic matter being degraded, and a processed DOM pool that was more aromatic in nature and contributed more strongly to water colour; while the opposite was true in the north. Nutrient concentration and stoichiometry and DOM characteristics affected bacterial activity, including metabolic status (BGE), which influenced DOM transformations. Our study highlights dramatic differences in DOM characteristics and microbial carbon cycling in sub-basins of the Baltic Sea. These findings are critical for our understanding of carbon and nutrient biogeochemistry, particularly in light of climate change scenarios.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Dissolved organic matter, DOC utilisation, DOM fluorescence, Bacterial growth efficiency, Bacterial oduction, Baltic Sea
National Category
Ecology Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-148733 (URN)10.1016/j.marchem.2018.01.010 (DOI)000432764600003 ()2-s2.0-85043466446 (Scopus ID)
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2018-06-20Bibliographically approved
Meunier, C. L., Liess, A., Andersson, A., Brugel, S., Paczkowska, J., Rahman, H., . . . Rowe, O. F. (2017). Allochthonous carbon is a major driver of the microbial food web: a mesocosm study simulating elevated terrestrial matter runoff. Marine Environmental Research, 129, 236-244
Open this publication in new window or tab >>Allochthonous carbon is a major driver of the microbial food web: a mesocosm study simulating elevated terrestrial matter runoff
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2017 (English)In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 129, p. 236-244Article in journal (Refereed) Published
Abstract [en]

Climate change predictions indicate that coastal and estuarine environments will receive increased terrestrial runoff via increased river discharge. This discharge transports allochthonous material, containing bioavailable nutrients and light attenuating matter. Since light and nutrients are important drivers of basal production, their relative and absolute availability have important consequences for the base of the aquatic food web, with potential ramifications for higher trophic levels. Here, we investigated the effects of shifts in terrestrial organic matter and light availability on basal producers and their grazers. In twelve Baltic Sea mesocosms, we simulated the effects of increased river runoff alone and in combination. We manipulated light (clear/shade) and carbon (added/not added) in a fully factorial design, with three replicates. We assessed microzooplankton grazing preferences in each treatment to assess whether increased terrestrial organic matter input would: (1) decrease the phytoplankton to bacterial biomass ratio, (2) shift microzooplanlcton diet from phytoplankton to bacteria, and (3) affect microzooplankton biomass. We found that carbon addition, but not reduced light levels per se resulted in lower phytoplanlcton to bacteria biomass ratios. Microzooplankton generally showed a strong feeding preference for phytoplanlcton over bacteria, but, in carbon-amended mesocosms which favored bacteria, microzooplankton shifted their diet towards bacteria. Furthermore, low total prey availability corresponded with low microzooplankton biomass and the highest bacteria/phytoplankton ratio. Overall our results suggest that in shallow coastal waters, modified with allochthonous matter from river discharge, light attenuation may be inconsequential for the basal producer balance, whereas increased allochthonous carbon, especially if readily bioavailable, favors bacteria over phytoplankton. We conclude that climate change induced shifts at the base of the food web may alter energy mobilization to and the biomass of microzooplankton grazers.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Trophic interactions, Food quality, Phytoplankton, Bacteria, Competition, Microzooplankton
National Category
Environmental Sciences Oceanography, Hydrology and Water Resources Ecology
Identifiers
urn:nbn:se:umu:diva-139152 (URN)10.1016/j.marenvres.2017.06.008 (DOI)000407981500021 ()28645656 (PubMedID)2-s2.0-85021065789 (Scopus ID)
Available from: 2017-09-15 Created: 2017-09-15 Last updated: 2023-03-24Bibliographically approved
Paczkowska, J., Rowe, O., Schlüter, L., Legrand, C., Karlson, B. & Andersson, A. (2017). Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea. Journal of Plankton Research, 39(1), 23-34
Open this publication in new window or tab >>Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea
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2017 (English)In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 39, no 1, p. 23-34Article in journal (Refereed) Published
Abstract [en]

It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south-north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes. The opposite trend was observed for autotrophs. The chlorophyll a (Chl a): carbon (C) ratio increased while the levels of photoprotective pigments decreased from south to north, indicating adaptation to the darker humic-rich water in the north. Picocyanobacteria dominated in phosphorusrich areas while nanoplankton increased in ADOM- rich areas. During the winter-spring the phytoplankton biomass and concentrations of photoprotective pigments were low, and no trends with respect to autotrophs and mixotrophs were observed. Microplankton was the dominant size group in the entire study area. We conclude that changes in the size structure of the phytoplankton community, the Chl a: C ratio and the concentrations of photoprotective pigments are indicative of changes in ADOM, a factor of particular importance in a changing climate.

Place, publisher, year, edition, pages
Oxford University Press, 2017
Keywords
phytoplankton, allochthonous dissolved organic matter, humic substances, nitrogen, phosphorus, structuring factors
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-126382 (URN)10.1093/plankt/fbw081 (DOI)000397101400004 ()2-s2.0-85014726588 (Scopus ID)
Note

Originally published in manuscript form.

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2023-03-24Bibliographically approved
Figueroa, D., Rowe, O., Paczkowska, J., Legrand, C. & Andersson, A. (2016). Allochthonous Carbon - a major driver of bacterioplankton production in the subarctic Northern Baltic Sea. Microbial Ecology, 71(4), 789-801
Open this publication in new window or tab >>Allochthonous Carbon - a major driver of bacterioplankton production in the subarctic Northern Baltic Sea
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2016 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 71, no 4, p. 789-801Article in journal (Refereed) Published
Abstract [en]

Heterotrophic bacteria are, in many aquatic systems, reliant on autochthonous organic carbon as their energy source. One exception is low-productive humic lakes, where allochthonous dissolved organic matter (ADOM) is the major driver. We hypothesized that bacterial production (BP) is similarly regulated in subarctic estuaries that receive large amounts of riverine material. BP and potential explanatory factors were measured during May–August 2011 in the subarctic Råne Estuary, northern Sweden. The highest BP was observed in spring, concomitant with the spring river-flush and the lowest rates occurred during summer when primary production (PP) peaked. PLS correlations showed that ∼60 % of the BP variation was explained by different ADOM components, measured as humic substances, dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM). On average, BP was threefold higher than PP. The bioavailability of allochthonous dissolved organic carbon (ADOC) exhibited large spatial and temporal variation; however, the average value was low, ∼2 %. Bioassay analysis showed that BP in the near-shore area was potentially carbon limited early in the season, while BP at seaward stations was more commonly limited by nitrogen-phosphorus. Nevertheless, the bioassay indicated that ADOC could contribute significantly to the in situ BP, ∼60 %. We conclude that ADOM is a regulator of BP in the studied estuary. Thus, projected climate-induced increases in river discharge suggest that BP will increase in subarctic coastal areas during the coming century.

Place, publisher, year, edition, pages
Springer, 2016
Keywords
Allochthonous organic matter, carbon utilization, bacterioplankton production, Sub-arctic estuary, Baltic Sea
National Category
Ecology
Research subject
Earth Sciences with Specialization Environmental Analysis
Identifiers
urn:nbn:se:umu:diva-117966 (URN)10.1007/s00248-015-0714-4 (DOI)000373683000001 ()2-s2.0-84949972178 (Scopus ID)
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE
Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2023-03-23Bibliographically approved
Paczkowska, J. (2016). Phytoplankton drivers in a marine system influenced by allochthonous organic matter – the Baltic Sea. (Doctoral dissertation). Umeå: Umeå University
Open this publication in new window or tab >>Phytoplankton drivers in a marine system influenced by allochthonous organic matter – the Baltic Sea
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Climate change scenarios predict that seawater temperature and precipitation will increase in the Baltic Sea region during the next century. In the northern part of the Baltic Sea, increasing inflows of the terrestrial allochthonous dissolved organic matter (ADOM) are expected to be a major consequence of elevated rainfall, which can alter light and nutrient availability for phytoplankton. The aim of my thesis was to elucidate effects of ADOM on phytoplankton production, community, size-structure and nutritional strategy along offshore south-north gradients in the Baltic Sea, as well as in estuarine systems exposed to seasonal variation in river discharge. Field studies, a mesocosm experiment and a modeling study were used to explore these issues.

Results from the field studies and mesocosm experiment illustrated that the nutritional strategy, size-structure and cellular pigment content of the phytoplankton were governed by changes in ADOM, and thus in light and nutrient availability. A summer study along an offshore south-north gradient showed that the proportion of mixotrophic phytoplankton increased towards the north. In this area the concentrations humic substances (proxy for ADOM) were high, while the light availability and phosphorus concentrations were relatively low. The phytoplankton cells responded to reduced light availability by increasing their chlorophyll a: carbon ratio. Additionally, the levels of photoprotective pigments decreased from south to north, as a result of acclimation to a low-light environment and reduced exposure to ultraviolet radiation. According to ecological assumptions picophytoplankton should be favored in light- and nutrient-limited environments. However, the results did not follow that pattern, the proportion of picophytoplankton being highest in the relatively nutrient rich Baltic Proper. The study was performed during the decline of an extensive bloom of filamentous cyanobacteria, a successional phase in which picophytoplankton often dominate the phytoplankton community.

The estuarine studies performed in the Bothnian Bay (Råne estuary) and in the Bothnian Sea (Öre estuary) showed different successions. In the Råne estuary no spring phytoplankton bloom occurred and highest primary production was observed during the summer. This absence of a spring bloom was explained by low phosphorus and high ADOM concentrations, while the summer maximum could be explained by higher temperature and nutrient concentrations. In the Öre estuary a marked phytoplankton spring bloom was observed as well as an ADOM sustained bacterial production phase. The later secondary peak of bacterial production observed in summer, concomitant with an extended secondary primary production peak, suggests that autochthonous dissolved organic matter supported the bacterial growth Furthermore, the photosynthetic efficiency (i.e. phytoplankton growth rates) was lower during spring, indicating that high ADOM, and thus lower light and phosphorus availability, disfavored phytoplankton growth.

Our modeling study showed that climate change can impact the food web; however effects will be different between basins. In the southern Baltic Sea elevated temperature and nutrient discharge may promote nutrient recycling and oxygen consumption, potentially extending anoxic areas, sediment nutrient release and cyanobacteria blooms. In the north, increased inflow of ADOM may promote heterotrophic bacterial production and decrease primary production due to light attenuation and lower phosphorus availability. This will favor the heterotrophic microbial food web and consequently lead to lower food web efficiency of the ecosystem.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. p. 31
Keywords
phytoplankton, nutrients, allochthonous organic matter, humic substances, structuring factors
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-126389 (URN)978-91-7601-571-1 (ISBN)
Public defence
2016-10-28, Lilla Hörsalen (KB3A9), KBC-huset, Umeå, 09:30 (English)
Opponent
Supervisors
Available from: 2016-10-07 Created: 2016-10-03 Last updated: 2018-06-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3568-7968

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