scholarly journals Hydrological contingency: drying history affects aquatic microbial decomposition

2018 ◽  
Vol 80 (3) ◽  
Author(s):  
Maite Arroita ◽  
Lorea Flores ◽  
Aitor Larrañaga ◽  
Eric Chauvet ◽  
Arturo Elosegi
1996 ◽  
Vol 34 (9) ◽  
pp. 157-164 ◽  
Author(s):  
Kim C.-H. ◽  
M. Hosomi ◽  
A. Murakami ◽  
M. Okada

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.


1975 ◽  
Vol 72 (7) ◽  
pp. 2515-2519 ◽  
Author(s):  
T. K. Kirk ◽  
W. J. Connors ◽  
R. D. Bleam ◽  
W. F. Hackett ◽  
J. G. Zeikus

2019 ◽  
Vol 12 (9) ◽  
pp. 1428-1433
Author(s):  
Niranjan Kumar ◽  
Jayesh B. Solanki ◽  
Prabhakar Shil ◽  
Dharmesh C. Patel ◽  
Ramasamy Meneka ◽  
...  

Background and Aim: The most widely adopted technique to preserve the gross specimen of the parasite is immersions and storage in liquid preservatives. The present study aimed to describe the dry method of the preservation of Toxocara vitulorum using plastination technique. Materials and Methods: Acetone dehydrated parasites were incubated at –20°C for 1 month in five different plastination solutions, prepared by mixing melamine and turpentine oil with clove oil (MTCl)/chloroform (MTC)/isopropanol (MTI)/benzene (MTB)/xylene (MTX) in 1:1:1 ratio to infiltrate the polymer. Technical personnel was asked to assign weekly score for dryness, stickiness, shrinkage, glossiness, flexibility, and odor of the prepared model on a 5-point scale. Results: Overall, the plastinated parasites were dry, non-sticky, glossy, odorless, chemical-free, harmless, to some extent flexible, with detectable morphological structure including natural form but lost their natural color, and cuticle became translucent. A varying level of shrinkage was noted in all types of plastinated model, but it was least in MTCl model. One month post-plastination, the mean evaluation score for glossiness was maximum in the parasite plastinated in MTCl solution (4.50±0.17), followed by MTC (3.72±0.32), MTX (3.56±0.38), MTB (2.83±0.37), and MTI (2.31±0.33). Likewise, for flexibility, the score was maximum in the parasite plastinated in MTCl solution (4.36±0.16), followed by MTB (3.11±0.14), MTC (2.94±0.41), MTX (2.75±0.41), and MTI (1.97±0.28). The degree of dryness, stickiness, and odor of the prepared model varies non-significantly (p>0.05) with the polymer mixtures. Maximum shrinkage percentage in terms of length and width was 4.24% and 50%, respectively, in the parasites plastinated in MTB solution. Shrinkage percentage was minimal (1.81% in length and 25% in width) in the MTCl plastinated parasites. Shrinkage percentage in terms of dimension was statistically non-significant among the different polymer solutions. Plastinated models withstand the process of microbial decomposition. There were 5 and 11 odd points in favor of plastination and formalin preservation technique, respectively. Conclusion: The prepared T. vitulorum model in MTCl can be used as an adjunct to the parasite preserve in 10% formalin solution. The plastination technique can be used as an alternative method of liquid preservation.


2013 ◽  
Vol 10 (6) ◽  
pp. 10229-10269
Author(s):  
J.-F. Exbrayat ◽  
A. J. Pitman ◽  
Q. Zhang ◽  
G. Abramowitz ◽  
Y.-P. Wang

Abstract. Reliable projections of future climate require land–atmosphere carbon (C) fluxes to be represented realistically in Earth System Models. There are several sources of uncertainty in how carbon is parameterized in these models. First, while interactions between the C, nitrogen (N) and phosphorus (P) cycles have been implemented in some models, these lead to diverse changes in land–atmosphere fluxes. Second, while the parameterization of soil organic matter decomposition is similar between models, formulations of the control of the soil physical state on microbial activity vary widely. We address these sources uncertainty by implementing three soil moisture (SMRF) and three soil temperature (STRF) respiration functions in an Earth System Model that can be run with three degrees of biogeochemical nutrient limitation (C-only, C and N, and C and N and P). All 27 possible combinations of a SMRF with a STRF and a biogeochemical mode are equilibrated before transient historical (1850–2005) simulations are performed. As expected, implementing N and P limitation reduces the land carbon sink, transforming some regions from net sinks to net sources over the historical period (1850–2005). Differences in the soil C balance implied by the various SMRFs and STRFs also change the sign of some regional sinks. Further, although the absolute uncertainty in global carbon uptake is reduced, the uncertainty due to the SMRFs and STRFs grows relative to the inter-annual variability in net uptake when N and P limitations are added. We also demonstrate that the equilibrated soil C also depend on the shape of the SMRF and STRF. Equilibration using different STRFs and SMRFs and nutrient limitation generates a six-fold range of global soil C that largely mirrors the range in available (17) CMIP5 models. Simulating the historical change in soil carbon therefore critically depends on the choice of STRF, SMRF and nutrient limitation, as it controls the equilibrated state to which transient conditions are applied. This direct effect of the representation of microbial decomposition in Earth System Models adds to recent concerns on the adequacy of these simple representations of very complex soil carbon processes.


Author(s):  
D. Bangieva ◽  
D. Stratev ◽  
T. Stoyanchev

Background: Histamine is an essential biogenic amine produced as a result of microbial decomposition of histidine during seafood processing and storage. The objective of this study was to evaluate histamine concentration in freshwater and marine fish marketed in Stara Zagora region, Bulgaria. Methods: Forty fish samples were purchased from local fish farms and retail stores in Stara Zagora, Bulgaria. Enzyme-Linked Immunosorbent Assay was used to determine histamine levels. The data were processed using GraphPad Software InStat 3. Results: Histamine was detected in 26 out of 40 (65%) samples, and none of them exceeded the regulatory limit of 200 mg/kg. The average histamine content in marine fish (6.965±3.187 mg/kg) was insignificantly (p>0.05) higher than that in freshwater fish (4.503±1.133 mg/kg). Conclusion: The results reveal low levels of histamine in freshwater and marine fish indicating their good quality. However, its presence in seafoods remains a major food safety problem that requires permanent regulation of histamine concentration in fish.  


2015 ◽  
Vol 12 (15) ◽  
pp. 12761-12782
Author(s):  
N. Geeraert ◽  
F. O. Omengo ◽  
G. Govers ◽  
S. Bouillon

Abstract. A significant amount of carbon is transported to the ocean as dissolved organic carbon (DOC) in rivers. During transport, it can be transformed through microbial consumption and photochemical oxidation. In dark incubation experiments with water from the Tana River, Kenya, we examined the consumption of DOC through microbial decomposition and the associated change in its carbon stable isotope composition (δ13C). In 15 of the 18 incubations, DOC concentrations decreased significantly by 10 to 60 %, with most of the decomposition taking place within the first 24–48 h. After 8 days, the remaining DOC was up to 3 ‰ more depleted in 13C compared with the initial pool, and the change in δ13C correlated strongly with the fraction of DOC remaining. We propose that the shift in δ13C is consistent with greater microbial lability of DOC originating from herbaceous C4 vegetation than DOC derived from woody C3 vegetation in the semi-arid lower Tana. The findings complement earlier data that riverine C sources do not necessarily reflect their proportion in the catchment: besides spatial distribution, also processing within the river can further influence the riverine δ13C.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Daniel N. Schillereff ◽  
Richard C. Chiverrell ◽  
Jenny K. Sjöström ◽  
Malin E. Kylander ◽  
John F. Boyle ◽  
...  

AbstractOmbrotrophic peatlands are a globally important carbon store and depend on atmospheric nutrient deposition to balance ecosystem productivity and microbial decomposition. Human activities have increased atmospheric nutrient fluxes, but the impacts of variability in phosphorus supply on carbon sequestration in ombrotrophic peatlands are unclear. Here, we synthesise phosphorus, nitrogen and carbon stoichiometric data in the surface and deeper layers of mid-latitude Sphagnum-dominated peatlands across Europe, North America and Chile. We find that long-term elevated phosphorus deposition and accumulation strongly correlate with increased organic matter decomposition and lower carbon accumulation in the catotelm. This contrasts with literature that finds short-term increases in phosphorus supply stimulates rapid carbon accumulation, suggesting phosphorus deposition imposes a threshold effect on net ecosystem productivity and carbon burial. We suggest phosphorus supply is an important, but overlooked, factor governing long-term carbon storage in ombrotrophic peatlands, raising the prospect that post-industrial phosphorus deposition may degrade this carbon sink.


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