Brownification affects phytoplankton community composition but not primary productivity in eutrophic coastal waters: A mesocosm experiment in the Baltic Sea

Spilling, Kristian; Asmala, Eero; Haraguchi, Lumi; Kraft, Kaisa; Lehto, Anne-Mari; Lewandowska, Aleksandra M.; Norkko, Joanna; Piiparinen, Jonna; Seppälä, Jukka; Vanharanta, Mari; Vehmaa, Anu; Ylöstalo, Pasi; Tamminen, Timo

doi:10.1016/j.scitotenv.2022.156510

Cited by 8 publications

(9 citation statements)

References 36 publications

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“…In lakes, this reduction in light availability has been linked to reduced dissolved oxygen concentrations (Couture et al, 2015), and reduced primary production (Thrane et al, 2014), as well as higher costs of drinking water purification (Hongve et al, 2004). Given that browning is associated with reduced acid deposition, increased precipitation and increased terrestrial primary production in catchment areas (Kritzberg et al, 2020), it is expected that climate change will further intensify ongoing brownification processes in surface waters (Björnerås et al, 2017; Kritzberg & Ekström, 2012; Spilling et al, 2022). In particular, the boreal zone could suffer more intense browning given the combination of increased precipitation (12%–20% expected increase; IPCC, 2013; Ruosteenoja et al, 2016) and the predominance of water bodies with peatland‐dominated catchments.…”

Section: Introductionmentioning

confidence: 99%

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

et al. 2022

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Light availability is the main regulator of primary production, shaping photosynthetic communities and their production of ecologically important biomolecules. In freshwater ecosystems, increasing dissolved organic carbon (DOC) concentrations, commonly known as browning, leads to lower light availability and the proliferation of mixotrophic phytoplankton. Here, a mixotrophic algal species (Cryptomonas sp.) was grown under five increasing DOC concentrations to uncover the plastic responses behind the success of mixotrophs in browning environments and their effect in the availability of nutritionally important biomolecules. In addition to the browning treatments, phototrophic, heterotrophic and mixotrophic growth conditions were used as controls. Despite reduced light availability, browning did not impair algal growth compared to phototrophic conditions. Comparative transcriptomics showed that genes related to photosynthesis were down‐regulated, whereas phagotrophy gene categories (phagosome, lysosome and endocytosis) were up‐regulated along the browning gradient. Stable isotope analysis of phospholipid fractions validated these results, highlighting that the studied mixotroph increases its reliance on heterotrophic processes with browning. Metabolic pathway reconstruction using transcriptomic data suggests that organic carbon is acquired through phagotrophy and used to provide energy in conjunction with photosynthesis. Although metabolic responses to browning were observed, essential fatty acid content was similar between treatments while sterol content was slightly higher upon browning. Together, our results provide a mechanistic model of how a mixotrophic alga responds to browning and how such responses affect the availability of nutritionally essential biomolecules for higher trophic levels.

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Section: Introductionmentioning

confidence: 99%

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

et al. 2022

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“…For instance, a recent study by Spilling et al . (2022) found that the interaction between browning and nutrients stimulated Chl a production fivefold and gross primary production threefold with respect to ambient conditions over the short term. However, such stimulatory effects disappeared after 6 d when inorganic N was depleted.…”

Section: Discussionmentioning

confidence: 99%

“…High terrestrial inputs promote changes toward communities dominated by microphytoplankton (Villafañe et al, 2018); reductions in primary and bacterial production (Paczkowska et al, 2020); respiration and Chla (Soulié et al, 2022); species richness and photosynthetic efficiency (Rasconi et al, 2015), as well as in the trophic transfer efficiency toward consumers (Hébert et al, 2022). By contrast, recent results obtained by Spilling et al (2022) evidenced that neither browning nor nutrient inputs, or their interaction, altered the primary production, but actually slightly stimulated bacterial and picoeukaryotes biomass, once inorganic nutrients were depleted.…”

Section: Introductionmentioning

confidence: 94%

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Browning, nutrient inputs, and fast vertical mixing from simulated extreme rainfall and wind stress alter estuarine phytoplankton productivity

et al. 2023

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Summary Browning and nutrient inputs from extreme rainfall, together with increased vertical mixing due to strong winds, are more frequent in coastal ecosystems; however, their interactive effects on phytoplankton are poorly understood. We conducted experiments to quantify how browning, together with different mixing speeds (fluctuating radiation), and a nutrient pulse alter primary productivity and photosynthetic efficiency in estuarine phytoplankton communities. Phytoplankton communities (grazers excluded) were exposed simultaneously to these drivers, and key photosynthetic targets were quantified: oxygen production, electron transport rates (ETRs), and carbon fixation immediately following collection and after a 2‐d acclimation/adaptation period. Increasing mixing speeds in a turbid water column (e.g. browning) significantly decreased ETRs and carbon fixation in the short term. Acclimation/adaptation to this condition for 2 d resulted in an increase in nanoplanktonic diatoms and a community that was photosynthetically more efficient; however, this did not revert the decreasing trend in carbon fixation with increased mixing speed. The observed interactive effects (resulting from extreme rainfall and strong winds) may have profound implications in the trophodynamics of highly productive system such as the Southwest Atlantic Ocean due to changes in the size structure of the community and reduced productivity.

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“…Empty cells indicate no data. The primary data is discussed in [ 15 ], and additional results on photochemical degradation of dissolved organic matter is presented in [ 16 ].…”

Section: Data Descriptionmentioning

confidence: 99%

Dataset from a mesocosm experiment on brownification in the Baltic Sea

et al. 2022

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Brownification affects phytoplankton community composition but not primary productivity in eutrophic coastal waters: A mesocosm experiment in the Baltic Sea

Cited by 8 publications

References 36 publications

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

Browning, nutrient inputs, and fast vertical mixing from simulated extreme rainfall and wind stress alter estuarine phytoplankton productivity

Dataset from a mesocosm experiment on brownification in the Baltic Sea

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