scholarly journals Particle-associated and free-living microbial assemblages are distinct in a permanently redox-stratified freshwater lake

2021 ◽  
Author(s):  
Ashley B. Cohen ◽  
Vanja Klepac-Ceraj ◽  
Kristen Butler ◽  
Felix Weber ◽  
Arkadiy I. Garber ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Seasonal Variability ◽  
Inorganic Nitrogen ◽  
Niche Partitioning ◽  
Green Sulfur Bacteria ◽  
Redox Conditions ◽  
Substrate Availability ◽  
Free Living ◽  
Sulfate Reducing ◽  
Green Lake

Microbial assemblages associated with biogenic particles are phylogenetically distinct from free-living counterparts, yet biogeochemically coupled. Compositions may vary with organic carbon and inorganic substrate availability and with redox conditions, which determine reductant and oxidant availability. To explore microbial assemblage compositional responses to steep oxygen and redox gradients and seasonal variability in particle and substrate availability, we analyzed taxonomic compositions of particle-associated (PA) and free-living (FL) bacteria and archaea in permanently redox-stratified Fayetteville Green Lake. PA and FL assemblages (> 2.7 μm and 0.2-2.7 μm) were surveyed at the peak (July) and end (October) of concurrent cyanobacteria, purple and green sulfur bacteria blooms that result in substantial vertical fluxes of particulate organic carbon. Assemblage compositions varied significantly among redox conditions and size fractions (PA or FL). Temporal differences were only apparent among samples from the mixolimnion and oxycline, coinciding with seasonal hydrographic changes. PA assemblages of the mixolimnion and oxycline shifted from aerobic heterotrophs in July to fermenters, iron-reducers, and denitrifiers in October, likely reflecting seasonal variability in photoautotroph biomass and inorganic nitrogen. Within a light-scattering layer spanning the lower oxycline and upper monimolimnion, photoautotrophs were more abundant in July than in October, when Desulfocapsa, a sulfate-reducing and sulfur-disproportionating bacterium, and Chlorophyte chloroplasts were abundant in PA assemblages. In this layer, microbial activity and cell concentrations were also highest. Below, the most abundant resident taxa were sulfate-reducing bacteria and anaerobic respirers. Results suggest PA and FL assemblage niche partitioning interconnects multiple elemental cycles that involve particulate and dissolved phases.

scholarly journals Biodegradability of dissolved organic carbon in the Yukon River and its tributaries: Seasonality and importance of inorganic nitrogen

2012 ◽  
Vol 26 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
K. P. Wickland ◽  
G. R. Aiken ◽  
K. Butler ◽  
M. M. Dornblaser ◽  
R. G. M. Spencer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Inorganic Nitrogen ◽  
Yukon River

scholarly journals Forest defoliator outbreaks alter nutrient cycling in northern waters

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Samuel G. Woodman ◽  
Sacha Khoury ◽  
Ronald E. Fournier ◽  
Erik J. S. Emilson ◽  
John M. Gunn ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Chemistry ◽  
Inorganic Nitrogen ◽  
Biogeochemical Cycles ◽  
Dissolved Inorganic Nitrogen ◽  
Insect Outbreaks ◽  
Receiving Waters ◽  
North Temperate Lakes ◽  
Lake Waters ◽  
Terrestrial Biomass

AbstractInsect defoliators alter biogeochemical cycles from land into receiving waters by consuming terrestrial biomass and releasing biolabile frass. Here, we related insect outbreaks to water chemistry across 12 boreal lake catchments over 32-years. We report, on average, 27% lower dissolved organic carbon (DOC) and 112% higher dissolved inorganic nitrogen (DIN) concentrations in lake waters when defoliators covered entire catchments and reduced leaf area. DOC reductions reached 32% when deciduous stands dominated. Within-year changes in DOC from insect outbreaks exceeded 86% of between-year trends across a larger dataset of 266 boreal and north temperate lakes from 1990 to 2016. Similarly, within-year increases in DIN from insect outbreaks exceeded local, between-year changes in DIN by 12-times, on average. As insect defoliator outbreaks occur at least every 5 years across a wider 439,661 km2 boreal ecozone of Ontario, we suggest they are an underappreciated driver of biogeochemical cycles in forest catchments of this region.

Column experiments show that cycling of both nitrogen and phosphorus is altered by dissolved organic carbon in river sediments

2021 ◽  
Author(s):  
Marc Stutter ◽  
Daniel Graeber ◽  
Gabriele Weigelhofer
Keyword(s):  
Organic Carbon ◽  
Nutrient Uptake ◽  
Inorganic Nitrogen ◽  
River Sediments ◽  
P Uptake ◽  
Controlled Study ◽  
Column Experiments ◽  
Nitrogen And Phosphorus ◽  
Organic C ◽  
Riparian Trees

<p>Since agriculture and wider development have altered simultaneously runoff, pollution and natural structures in catchments (e.g. wetlands, floodplains, soil drainage, riparian trees) aquatic ecosystems deviate from background concentrations of N and P, but also organic C (OC). Hence mechanistic studies coupling OC, N and P are needed and whilst data coupling OC:N is becoming more available and interpreted this is not yet the case for aquatic OC:P.  Column flow experiments (excluding light) allow preliminary controlled study of microbial biogeochemical processes in benthic sediments exposed to factorial nutrients (here +C, +NP, +CNP using simple dissolved substrates glucose, nitrate, and phosphate).</p><p>Based on the stoichiometric theory, we tested the hypothesis that bioavailable DOC will stimulate the heterotrophic uptake of soluble reactive P (SRP) and dissolved inorganic nitrogen in stream sediments. Glucose-C additions increased nutrient uptake, but also NP additions enhanced consumption of native and added OC. The effects of C addition were stronger on N than P uptake, presumably because labile C stimulated both assimilation and denitrification, while adsorption (unaffected by the presence or not of OC) formed a part of P uptake. Internal biogeochemical cycling lessened net nutrient uptake due to N and P recycling into dissolved organically-complexed forms (DOP and DON).</p><p>Simple column experiments point to mechanisms whereby availability of organic carbon can stimulate N and P sequestration in the bed of nutrient-polluted streams. This should promote further studies coupling OC with N and, especially P, towards better knowledge and ability to incorporate coupled macronutrient cycles into nutrient models and, potentially, ecosystem management.</p>

scholarly journals Estimation of the Particulate Organic Carbon to Chlorophyll-a Ratio Using MODIS-Aqua in the East/Japan Sea, South Korea

2020 ◽  
Vol 12 (5) ◽  
pp. 840 ◽  
Author(s):  
Dabin Lee ◽  
SeungHyun Son ◽  
HuiTae Joo ◽  
Kwanwoo Kim ◽  
Myung Joon Kim ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Chlorophyll A ◽  
Primary Productivity ◽  
Seasonal Variability ◽  
Japan Sea ◽  
Global Ocean ◽  
Phytoplankton Communities

In recent years, the change of marine environment due to climate change and declining primary productivity have been big concerns in the East/Japan Sea, Korea. However, the main causes for the recent changes are still not revealed clearly. The particulate organic carbon (POC) to chlorophyll-a (chl-a) ratio (POC:chl-a) could be a useful indicator for ecological and physiological conditions of phytoplankton communities and thus help us to understand the recent reduction of primary productivity in the East/Japan Sea. To derive the POC in the East/Japan Sea from a satellite dataset, the new regional POC algorithm was empirically derived with in-situ measured POC concentrations. A strong positive linear relationship (R2 = 0.6579) was observed between the estimated and in-situ measured POC concentrations. Our new POC algorithm proved a better performance in the East/Japan Sea compared to the previous one for the global ocean. Based on the new algorithm, long-term POC:chl-a ratios were obtained in the entire East/Japan Sea from 2003 to 2018. The POC:chl-a showed a strong seasonal variability in the East/Japan Sea. The spring and fall blooms of phytoplankton mainly driven by the growth of large diatoms seem to be a major factor for the seasonal variability in the POC:chl-a. Our new regional POC algorithm modified for the East/Japan Sea could potentially contribute to long-term monitoring for the climate-associated ecosystem changes in the East/Japan Sea. Although the new regional POC algorithm shows a good correspondence with in-situ observed POC concentrations, the algorithm should be further improved with continuous field surveys.

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