scholarly journals Summertime Amino Acid and Carbohydrate Patterns in Particulate and Dissolved Organic Carbon Across Fram Strait

2021 ◽  
Vol 8 ◽  
Author(s):  
Julia Grosse ◽  
Eva-Maria Nöthig ◽  
Sinhué Torres-Valdés ◽  
Anja Engel
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Arctic Ocean ◽  
Size Fraction ◽  
Water Masses ◽  
Fram Strait ◽  
Central Arctic Ocean ◽  
Size Fractions ◽  
Food Web Interactions ◽  
Relative Differences

Amino acids (AA) and carbohydrates (CHO) are important components of the marine organic carbon cycle. Produced mainly by phytoplankton as part of the particulate organic carbon (POC) fraction, these compounds can be released into the outer medium where they become part of the dissolved organic carbon (DOC) pool and are rapidly taken up by heterotrophs (e.g., bacteria). We investigated the quantity and quality of POC and DOC, AA and CHO composition in both pools in three different water masses in the Fram Strait (Arctic Ocean) in summer 2017. Polar Waters and Atlantic Waters showed similar concentrations of particulate and dissolved AA and CHO, despite Polar Waters showing the highest DOC concentrations. In Mixed Waters, where the two water masses mix with each other and with melting sea ice, the concentrations of particulate and dissolved AA and CHO were highest. AA and CHO composition differed substantially between the particulate and dissolved fractions. The particulate fraction (>0.7 μm) was enriched in essential AA and the CHO galactose, xylose/mannose, and muramic acid. In the dissolved fraction non-essential AA, several neutral CHO, and acidic and amino CHO were enriched. We further investigated different size fractions of the particulate matter using a separate size fractionation approach (0.2–0.7 μm, 0.7–10 μm and >10 μm). The chemical composition of the 0.2–0.7 μm size-fraction had a higher contribution of non-essential AA and acidic and amino sugars, setting them apart from the 0.7–10 μm and >10 μm fractions, which showed the same composition. We suggest that the relative differences observed between different size fractions and DOC with regards to AA and CHO composition can be used to evaluate the state of organic matter processing and evaluate the contribution of autotrophic phytoplankton or more heterotrophic biomass. In the future, changing conditions in the Central Arctic Ocean (Atlantification, warming, decreasing ice concentrations) may increase primary production and consequently degradation. The AA and CHO signatures left behind after production and/or degradation processes occurred, could be used as tracers after the fact to infer changes in microbial loop processes and food web interactions.

scholarly journals Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. III. Distribution and kinetics of soil organic carbon in particle size fractions

Soil Research ◽  
1986 ◽  
Vol 24 (2) ◽  
pp. 293 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Size Fraction ◽  
Organic C ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Clay Size Fraction ◽  
Sand Size

Distribution of soil organic carbon in sand-, silt- and clay-size fractions during cultivation for periods ranging from 20 to 70 years was studied in six major soils used for cereal cropping in southern Queensland. Particle-size fractions were obtained by dispersion in water using cation exchange resin, sieving and sedimentation. In the soils' virgin state no single particle-size fraction was found to be consistently enriched as compared to the whole soil in organic C in all six soils, although the largest proportion (48%) of organic C was in the clay-size fraction; silt and sand-size fractions contained remaining organic C in equal amounts. Upon cultivation, the amounts of organic C declined from all particle-size fractions in most soils, although the loss rates differed considerably among different fractions and from the whole soil. The proportion of the sand-size fraction declined rapidly (from 26% to 12% overall), whereas that of the clay-size fraction increased from 48% to 61% overall. The proportion of silt-size organic C was least affected by cultivation in most soils. It was inferred, therefore, that the sand-size organic matter is rapidly lost from soil, through mineralization as well as disintegration into silt-size and clay-size fractions, and that the clay fraction provides protection for the soil organic matter against microbial and enzymic degradation.

scholarly journals Low export flux of particulate organic carbon in the central Arctic Ocean as revealed by234Th:238U disequilibrium

2010 ◽  
Vol 115 (C10) ◽  
Author(s):  
P. Cai ◽  
M. Rutgers van der Loeff ◽  
I. Stimac ◽  
E.-M. Nöthig ◽  
K. Lepore ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Arctic Ocean ◽  
Particulate Organic Carbon ◽  
Central Arctic Ocean ◽  
Export Flux

Free soil colloids and colloidal building units of soil aggregates

2020 ◽  
Author(s):  
Ni Tang ◽  
Nina Siebers ◽  
Erwin Klumpp
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Organic Carbon ◽  
Inductively Coupled Plasma ◽  
Soil Aggregates ◽  
Size Fraction ◽  
Ionization Mass ◽  
Soil Matrix ◽  
Size Fractions ◽  
20 Nm

<p>Nanosized mineral particles and organic matter (<100 nm) ,as well as their associations, belong to the most important ingredients for the formation of the soil aggregate structure being a hierarchically organized system. Colloids (< 220 nm) including nanoparticles can be occluded as primary building units of soil aggregates. Nevertheless, a large proportion of these colloids is mobile and presents in the solution phase (as “free”) within the soil matrix. However, the differences between “free” and occluded colloids remain unclear.</p><p>Here, both occluded and free colloids were isolated from soil samples of an arable field with different clay contents (19% and 34%) using wet sieving and centrifugation. The release of occluded colloids from soil macroaggregates (>250 µm) was carried out with ultrasonic treatment at 1000 J mL<sup>-1</sup>. The free and occluded colloidal fractions were then characterized for their size-resolved elemental composition using flow field-flow fractionation inductively coupled plasma mass spectrometry and organic carbon detector (FFF-ICP-MS/OCD). In addition, selected samples were also subjected to transmission electron microscopy as well as pyrolysis field ionization mass spectrometry (Py-FIMS).</p><p>Both, free and occluded colloids were composed of three size fractions: nanoparticles <20 nm, medium-sized nanoparticles (20 nm–60 nm), and, fine colloids (60 nm–220 nm). The fine colloid fraction was the dominant size fraction in both free and occluded colloids, which mainly consist of organic carbon, Al, Si, and Fe, probably present as phyllosilicates and associations of Fe- and Al- (hydr)oxides and organic matter. However, the organic matter contents for all three size fractions were higher for the occluded colloids than for the free ones. The role of OM concentration and composition in these colloids will be discussed in the paper.</p>

Sign in / Sign up

Export Citation Format

Share Document