Active DNRA and denitrification in oxic hypereutrophic waters

Broman, Elias; Žilius, Mindaugas; Samuilovienė, Aurelija; Vybernaitė-Lubienė, Irma; Politi, Tobia; Klawonn, Isabell; Voß, Maren; Nascimento, Francisco J. A.; Bonaglia, Stefano

doi:10.1016/j.watres.2021.116954

Cited by 74 publications

(29 citation statements)

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“…Our prior work also showed enhanced PN export to the Baltic Sea during periods when the lagoon was dominated by cyanobacteria. Positive buoyancy allows A. flos-aquae and other cyanobacteria to remain suspended in the water column, which favors export in lagoon outflow rather than retention via sedimentation (Bukaveckas et al, 2019). Overall, these findings suggest that the occurrence of heterocystous cyanobacteria blooms has substantially diminished the potential for the lagoon to attenuate N fluxes to the Baltic Sea.…”

Section: Discussionmentioning

confidence: 87%

Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

et al. 2021

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Abstract. Coastal lagoons are important sites for nitrogen (N) removal via sediment burial and denitrification. Blooms of heterocystous cyanobacteria may diminish N retention as dinitrogen (N2) fixation offsets atmospheric losses via denitrification. We measured N2 fixation in the Curonian Lagoon, Europe's largest coastal lagoon, to better understand the factors controlling N2 fixation in the context of seasonal changes in phytoplankton community composition and external N inputs. Temporal patterns in N2 fixation were primarily determined by the abundance of heterocystous cyanobacteria, mainly Aphanizomenon flos-aquae, which became abundant after the decline in riverine nitrate inputs associated with snowmelt. Heterocystous cyanobacteria dominated the summer phytoplankton community resulting in strong correlations between chlorophyll a (Chl a) and N2 fixation. We used regression models relating N2 fixation to Chl a, along with remote-sensing-based estimates of Chl a to derive lagoon-scale estimates of N2 fixation. N2 fixation by pelagic cyanobacteria was found to be a significant component of the lagoon's N budget based on comparisons to previously derived fluxes associated with riverine inputs, sediment–water exchange, and losses via denitrification. To our knowledge, this is the first study to derive ecosystem-scale estimates of N2 fixation by combining remote sensing of Chl a with empirical models relating N2 fixation rates to Chl a.

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Section: Discussionmentioning

confidence: 87%

Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

et al. 2021

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“…In contrast, dissimilatory nitrate reduction is not repressed by the increase in ammonia and was observed to increase throughout the experiment with KO IDs related to this pathway observed to be differentially abundant in the continuous nutrient treatments and especially the NPS.cont treatment. This process reduces nitrate to ammonia, recycling the fixed N in the system and is in competition with denitrification for free nitrate (van den Berg et al 2015;Broman et al 2021). Dissimilatory nitrate reduction requires anoxic conditions and has previously been described to happen in cyanobacterial aggregates (Klawonn et al 2015).…”

Section: Temporal Changes In Functional Potentialmentioning

confidence: 99%

“…This could explain the increase of this process towards the end of the current experiment as the breakdown of the bloom creates anoxic micro-niches where dissimilatory nitrate reduction can occur and recycle the N within the system. Broman et al (2021) suggested that approximately a fifth of the nitrate pool is recycled by dissimilatory nitrate reduction and has the potential to sustain algal proliferation and enhance eutrophication.…”

Section: Temporal Changes In Functional Potentialmentioning

confidence: 99%

Comparative metagenomics of phytoplankton blooms after nutrient enrichment of oligotrophic marine waters

Pearman¹,

Casas²,

Michell³

et al. 2022

MBMG

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Increasing anthropogenic pressures on the coastal marine environments impact these ecosystems via a variety of mechanisms including nutrient loading, leading to eutrophication and increases in algal blooms. Here, we use a metagenomics approach to assess the taxonomic and functional changes of the microbial community throughout a nutrient enriched mesocosm phytoplankton bloom. We tested four different nutrient treatments consisting of either nitrate and phosphate or nitrate, phosphate and silicate, administered on the first day or continuously for the first two weeks of the experiment. Our results show a shift in the taxonomic composition of the community over time that is dependent on the nutrient addition regime. Significant differences in the functional potential of the communities were detected, with an interaction between bloom period (pre-bloom, bloom and post-bloom) and nutrient treatment (p = 0.004). A sharp drop in functional similarity was observed in the first week in all treatments and after 20 days had not returned to pre-bloom levels. Changes within energy metabolism pathways showed a remarkable enrichment of the dissimilatory nitrate reduction pathway in the post-bloom period. Eukaryotic oxidative phosphorylation and photosynthetic antenna proteins were more abundant during the bloom, especially in the continuous treatment with silicate. Our results suggest that continuous (i.e. chronic) nutrient enrichment has a larger effect on the functioning of marine systems compared to a single (i.e acute) addition. A deep understanding of the functional and taxonomic shifts in the community during blooms is essential to reverse or mitigate human impacts on coastal environments.

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“…The DO concentrations of the bulk seawater at the Pingtan Sea sites, including the PIN4 site with the highest Prorocentrum population and algal biomass, indicated that the bulk seawater was oxic at the time of sampling, which, due to logistical reasons, took place during the daytime. Under oxic conditions, DNRA is not likely to occur, as it is known as a strictly anaerobic process; however considering the high populations of the fast-metabolizing Vibrio and Prorocentrum that may be potent O 2 sinks at dark hours, it is plausible that periodic oxic-anoxic shifts may occur in the region, especially at highly eutrophicated locales such as the PIN4 and PIN5 sites [52,53]. Spatial microaerobic or anoxic niches may also exist, such as in bio lms attached to particle surfaces, microbial aggregates, and intracellular spaces within zooplankton or phytoplankton where Vibrio spp.…”

Section: Ecological Association Of Vibrio Spp With Dino Agellate Algal Bloommentioning

confidence: 99%

“…Spatial microaerobic or anoxic niches may also exist, such as in bio lms attached to particle surfaces, microbial aggregates, and intracellular spaces within zooplankton or phytoplankton where Vibrio spp. may be able to colonize [52,[54][55][56]. Rapid decay of algal carcass, and/or upwelling of hypoxic bottom water may also cause temporal anoxia that may not be captured by snapshots of DO measurement [57,58].…”

Section: Ecological Association Of Vibrio Spp With Dino Agellate Algal Bloommentioning

confidence: 99%

Metagenomic Insights Into Co-Proliferation of Vibrio Spp. and Dinoflagellates Prorocentrum During A Spring Algal Bloom in the Coastal East China Sea Near Xiamen

Kim

Wan

Cao

et al. 2021

Preprint

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BackgroundCoastal harmful algal blooms (HAB), commonly termed ‘Red tides’, have severe undesirable consequences to the marine ecosystems and local fishery and tourism industries. Increase in nitrogen and/or phosphate loading is often attributed as the major culprits of increasing frequency and intensity of the coastal HAB; however, fundamental understanding is lacking as to the causes and mechanism of bloom formation despite decades of intensive investigation.ResultsIn this study, we interrogated the prokaryotic microbiomes of surface water samples collected at two neighboring segments of East China Sea that contrast greatly in terms of the intensity and frequency of Prorocentrum-dominated HAB. Mantel tests identified significant correlations between the structural and functional composition of the microbiomes and the physicochemical state and the algal biomass density of the surface seawater, implying the possibility that prokaryotic microbiota may play key roles in coastal HAB. A conspicuous feature of the microbiomes at the sites characterized with high trophic state index and eukaryotic algal cell counts was disproportionate proliferation of Vibrio spp., and their complete domination of the functional genes attributable to the dissimilatory nitrate reduction to ammonia (DNRA) pathway significantly enriched at these sites. The genes attributed to phosphorus uptake function were also significantly enriched at these sites, presumably due to the Pi-deficiency induced by algal growth; however, the profiles of the phosphorus mineralization genes lacked consistency, barring any conclusive evidence with regard to contribution of prokaryotic microbiota to phosphorous bioavailability. The results of the co-occurrence network analysis performed with the core prokaryotic microbiome also supported that the observed proliferation of Vibrio and HAB may be causally associated.ConclusionsThe findings of this study suggest a previously unidentified association between Vibrio proliferation and the Prorocentrum-dominated HAB in the subtropical East China Sea, and opens a discussion regarding an unlikely, but still possible, involvement of Vibrio-mediated DNRA in Vibrio-Prorocentrum symbiosis. Further substantiation of this interaction with culture-based experiments may prove crucial for understanding of the dynamics of explosive local algal growth during HAB events endemic to the region.

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Active DNRA and denitrification in oxic hypereutrophic waters

Cited by 74 publications

References 78 publications

Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

Comparative metagenomics of phytoplankton blooms after nutrient enrichment of oligotrophic marine waters

Metagenomic Insights Into Co-Proliferation of Vibrio Spp. and Dinoflagellates Prorocentrum During A Spring Algal Bloom in the Coastal East China Sea Near Xiamen

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Active DNRA and denitrification in oxic hypereutrophic waters

Cited by 74 publications

References 78 publications

Spatiotemporal patterns of N&lt;sub&gt;2&lt;/sub&gt; fixation in coastal waters derived from rate measurements and remote sensing

Spatiotemporal patterns of N&lt;sub&gt;2&lt;/sub&gt; fixation in coastal waters derived from rate measurements and remote sensing

﻿Comparative metagenomics of phytoplankton blooms after nutrient enrichment of oligotrophic marine waters

Metagenomic Insights Into Co-Proliferation of Vibrio Spp. and Dinoflagellates Prorocentrum During A Spring Algal Bloom in the Coastal East China Sea Near Xiamen

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Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

Spatiotemporal patterns of N<sub>2</sub> fixation in coastal waters derived from rate measurements and remote sensing

Comparative metagenomics of phytoplankton blooms after nutrient enrichment of oligotrophic marine waters