Heterotrophic Nitrogen Fixation at the Hyper-Eutrophic Qishon River and Estuary System

Geisler, Eyal; Bogler, Anne; Bar‐Zeev, Edo; Rahav, Eyal

doi:10.3389/fmicb.2020.01370

Cited by 21 publications

(30 citation statements)

References 79 publications

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“…Moreover, diazotrophs were found associated to particles collected from sediment traps, which are often rich in TEP, in the North Pacific Subtropical Gyre (Farnelid et al 2019). Similarly, other studies demonstrated a direct association between TEP, as proxy for “marine/lake snow,” and viable (active) N 2 fixers (Geisler et al 2020).…”

Section: Discussionmentioning

confidence: 64%

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Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

Rahav

Herut

Spungin

et al. 2021

Limnology & Oceanography

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Unicellular photoautotrophic diazotrophs such as Crocosphaera spp. are ubiquitous in many oligotrophic and N‐limited oceans, as they can reduce N2 into bioavailable ammonia. The Mediterranean Sea is potentially an ideal environment for photoautotrophic diazotrophic activity, and yet N2‐fixation rates measured in the last two decades are typically very low and no diazotrophic blooms have been recorded in its offshore waters. Previous studies suggest that diazotrophs, as well as nondiazotrophic phytoplankton and heterotrophic bacteria, may be P‐limited, hence their low biomass and activity. Here, we amended surface seawater from six stations across a nutrient gradient in the Mediterranean Sea (east to west transect) with dissolved inorganic phosphorus (DIP), and with seawater‐acclimated inocula of Crocosphaera watsonii, a unicellular cyanobacterial diazotroph, to examine if DIP can stimulate diazotrophy. Our results demonstrate that C. watsonii are poor competitors for DIP relative to native nondiazotrophic heterotrophic microbial populations, especially in the ultraoligotrophic eastern Mediterranean basin, resulting in low N2‐fixation rates. Moreover, the results indicate that when the ambient DIP concentrations are < 35 nmol L−1, unicellular photoautotrophic diazotrophs such as C. watsonii will likely be outcompeted for this macronutrient in the Mediterranean Sea, whereas above 35 nmol L−1 diazotrophy can be stimulated. Our findings support the “bypass theory” stating that photoautotrophs may be outcompeted by heterotrophic bacteria for DIP in nutrient‐poor regions such as the Mediterranean Sea.

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Section: Discussionmentioning

confidence: 64%

“…Additionally, some Crocosphaera secrete high concentrations of transparent exopolymer particles (TEP) (Sohm et al 2011) surrounding the cells and aggregates (Bonnet et al 2018). TEP was hypothesized to facilitate nutrient recycling and N 2 fixation (Geisler et al 2020 and see the Discussion section). These characteristics may explain why Crocosphaera spp.…”

mentioning

confidence: 99%

Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

Rahav

Herut

Spungin

et al. 2021

Limnology & Oceanography

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“…2g), and a decrease in labile polysaccharide and polypeptide concentrations. The occurrence of such high growth rate 41 and bacterial abundance 25,42,43 is not seldom inside natural sinking particles. The increased community respiration ( Fig.…”

Section: Biochemical Dynamics Inside a Particle Under Static Environmmentioning

confidence: 99%

Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles

Chakraborty

Andersen

Visser³

et al. 2020

Preprint

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Nitrogen (N2) fixation by heterotrophic bacteria associated with sinking particles contributes to marine N cycling, but a mechanistic understanding of its regulation and significance are not available. Here we develop a mathematical model for unicellular heterotrophic bacteria growing on sinking marine particles and can fix N2 under suitable environmental conditions. We find that the interactive effects of polysaccharide and polypeptide concentrations, sinking speed of particles, and surrounding O2 and NO3- concentrations determine the N2 fixation rate inside particles. N2 fixation inside sinking particles is mainly fueled by SO42- respiration rather than NO3- respiration. Our model suggests that anaerobic processes, including heterotrophic N2 fixation, can take place in anoxic microenvironments inside sinking particles even in fully oxygenated marine waters. The modelled rates are similar to bulk rates measured in the aphotic ocean, and our study consequently suggests that particle-associated heterotrophic N2 fixation contributes significantly to oceanic N2 fixation.

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“…Therefore, eutrophic water will finally lose its original functionality, such as aquatic food production and safe-drinking water supply (Huisman et al 2018). Meanwhile, eutrophication is worldwide environmental problems and have been found in many countries, such as Israel (Geisler et al 2020), Mexico (Caballero and Vazquez 2020) and USA (Tomasko et al 2020). It is summarized that over 75% of the closed water bodies (e.g., lakes, ponds and reservoirs) in Africa, Asia and Latin America have deteriorated largely and encountered some extents of eutrophication since the 1990s (UN-Water 2018).…”

Section: Introductionmentioning

confidence: 99%

Purification effect evaluation of the designed new volcanic soil adsorption material containing bioreactor for eutrophic water treatment

Ding

Zhai³

et al. 2021

Environ Sci Pollut Res

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To investigate the purification effect of the new adsorption material containing bioreactor and the critical role of non-culture (VBNC) bacteria in eutrophication ecosystem, major water quality parameters and microbial community were determined and analyzed in prepared eutrophic water for 2 years monitoring. The results showed that removal rates of total phosphorus (TP), total nitrogen (TN), chlorophyll-a (Chl-a) and chemical oxygen demand (COD) ranged of 90.7% -95.9%, 84.5% -92.4%, 87.9% -95.8% and 68.3% -82.7%, respectively, indicating the designed bioreactor possessed high efficiency in eutrophic water treatment. Although the bioreactor had been operated for 2 years, water from treatment group was more clearer and odorless than control group, exhibiting the long service life of the bioreactor. Stopping operation in August caused the removal rates of major water quality parameters significantly decrease (p < 0.05), revealing stopping operation and high temperature in Summer exerted dual effect on the bioreactor, whereas the impact could be minimized when the bioreactor was running. According to most probable number (MPN) method, the total bacteria under +Rpf treatment were higher than under -Rpf treatment, implying Rpf could resuscitate VBNC bacteria in eutrophication ecosystem. Nine VBNC bacteria were isolated based on the BLAST results of 16S rRNA gene, and these bacteria might contribute to eutrophic water treatment based on their functions, such as phosphorus-collecting and denitrification. Those results provided new insights for engineering technology innovation and had benefit in eutrophic water treatment.

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Heterotrophic Nitrogen Fixation at the Hyper-Eutrophic Qishon River and Estuary System

Cited by 21 publications

References 79 publications

Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles

Purification effect evaluation of the designed new volcanic soil adsorption material containing bioreactor for eutrophic water treatment

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