Storage and decomposition of particulate organic matter along the longitudinal gradient of an agriculturally-impacted stream

An agriculturally-impacted stream in northern Idaho was examined over a two-year period to determine seasonal and longitudinal patterns of the storage and decomposition of particulate organic matter. Biomass of benthic organic matter (BOM) was considerably less than values reported in the literature for comparable, undisturbed streams. Coarse, fine, and total benthic particulate organic matter were not correlated with parameters pertaining to stream size (e.g., stream order), but were correlated with sample site and amount of litterfall. The association of BOM with site and litterfall suggests that storage of particulate organic matter is a function of local characteristics rather than stream size. Low biomass of stored organic matter is a response to the low input of terrestrially-derived organic matter resulting from removal of climax vegetation.Leaf packs of alder, Alnus sp., were placed in the stream seasonally for 30 and 60 d. While there were significant differences for months, there was no significant difference among sites for leaf packs exposed for 30 d. Significant differences were observed among both sites and months for leaf packs exposed for 60 d; however, differences among sites accounted for only 5% of the variance. The absence of differences in decomposition of organic matter along the gradient of Lapwai Creek, despite heterogeneity of the drainage basin and availability of organic matter, may be in response to the overall low biomass of stored benthic organic matter. This study demonstrates that agricultural activity can substantially influence instream heterotrophic processes through reduced availability of organic matter and can shape community structure and ecosystem dynamics of streams flowing through agricultural drainage basins.     

Significance of instream autotrophs in trophic dynamics of the Upper Mississippi River

Trophic dynamics of large river–floodplain ecosystems are still not well understood despite development of several conceptual models over the last 25 years. To help resolve questions about the relative contribution of algal and detrital organic matter to food webs in the Upper Mississippi River, we (1) separated living and detrital components of ultrafine and fine transported organic matter (UTOM and FTOM, respectively) by colloidal silica centrifugation; (2) identified stable isotope signatures (δ¹³C and δ¹⁵N) for these two portions of transported organic matter and other potential organic matter sources; and (3) employed a multiple source, dual-isotope mixing model to determine the relative contribution of major energy sources to primary consumers and the potential contribution of basal sources to the biomass of secondary consumers. The δ¹³C and δ¹⁵N of living and detrital fractions of UTOM and FTOM were distinct, indicating clear differences in isotopic composition of the algal and detrital fractions of transported organic matter. Living and detrital transported organic matter also differed from other potential organic matter sources by either δ¹³C or δ¹⁵N. A six-source mixing model using both δ¹³C and δ¹⁵N indicated that algal transported organic matter was the major resource assimilated by primary consumers. The contribution of detrital transported organic matter was small in most cases, but there were a small number of taxa for which it could potentially contribute to more than half the assimilated diet. Colloidal dissolved organic matter, which includes heterotrophic bacteria, accounted for only a small fraction of the organic matter assimilated by most primary consumers, indicating that coupling between microbial processes and metazoan production is minimal. Terrestrial C₃ litter from the floodplain forest floor and aquatic macrophytes were also relatively unimportant to the assimilated diet of primary consumers. Application of the mixing model to compare basal source isotopic ratios to secondary consumers revealed that most organic matter moving from primary to secondary consumers originated from algal TOM. Our findings indicate that autochthonous organic matter is the major energy source supporting metazoan production in the main channel of this large river, at least during the summer. This study joins a number of other investigations performed globally that indicate organic matter originating from instream production of sestonic and benthic microalgae is a major driver in the trophic dynamics of large river ecosystems.     

A study of dissolved oxygen flux across the water-bottom interface in the northeastern Black Sea (in the region of Dzhubga Village)

Oxygen exchange at the water-bottom interface in the northeastern Black Sea was studied using bottom tanks (fluxes and oxygen consumption for organic matter mineralization and for respiration of soil and water organisms). The relationship of biogenic fluxes and patterns of biochemical (enzyme) destruction of organic matter by the components of the bacterial and microproducer community was established. The prevalence of microbial oxidation of organic matter correlated with high proteolytic activity in near-bottom water. The principal significance of organic matter oxidation in near-bottom water for the phytoplankton and its respiratory expenditures was demonstrated both in the open system of the near-bottom layer and in the closed tank system. A similar trend was demonstrated for benthic organisms.     

Differing growth responses of major phylogenetic groups of marine bacteria to natural phytoplankton blooms in the western North Pacific Ocean

Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.     

Particulate organic carbon in the estuarine turbidity maxima of the Gironde,Loire and Seine estuaries: origin and lability

A study of the particulate organic carbon (POC) in the estuarine turbidity maxima (ETMs) of the three major French macrotidal estuaries shows that the average contents are 1.5, 3.3 and 3.1% (expressed in % of dry suspended sediment) in the Gironde, Loire and Seine Estuaries, respectively. There is no seasonal variation of POC contents in the Gironde Estuary, whereas, they often increase in the Loire and the Seine Estuaries in spring and summer. The lability of the estuarine particulate organic matter was estimated by two analyses: 1/labile organic matter was measured as the organic carbon loss during incubation tests over one month; 2/ the hydrolysable organic fraction was determined after 6N HCl digestion. The organic fractions of the ETMs are mainly refractory. Any increase in the amount of POC as compared to the background levels (cited above) is always correlated to an increase of organic matter lability. The yearly average fluvial contributions by various particulate organic pools (soil and litter organic matter; organic matter of phytoplanktonic and human origin) that enter the three estuaries were quantified. In the Garonne River, soil and litter are the major (90%) POC sources. In the Loire system, due to the eutrophication of the river water, phytoplankton contributes up to 50% of the total POC load. In the Seine river, soil and litter contribute 70% of the total POC input; POC of human origin is also significant (10%), due to the impact of the City of Paris (10 million inhabitants). The lability of the different types of organic matter ranks as follows: phytoplankton ∼litter > human-origin organic matter >> soil. By combining the POC budgets and the lability of each type of organic fraction, it was possible to explain why the POC of the three ETMs is different and characterizes its refractory vs. labile nature.     

Exoenzymatic activity and organic matter composition in sediments of the Northern Adriatic Sea: response to a river plume

Exoenzymatic activities (aminopeptidase and b-glucosidase) and organic matter composition were investigated in June 1996 and February 1997 in the sediment of two areas of the Adriatic Sea differently influenced by the Po river. Protein, carbohydrate, and lipid concentrations were comparable to those reported in most productive systems. Sediment chlorophyll a and biopolymeric carbon concentrations in June were twice as high as in February, but highest exoenzymatic activities and organic matter turnover rates were observed in February (with aminopeptidase activities 10 times higher than in June). The accumulation of organic matter and lower protein and carbohydrate turnover rates observed in June were the result of a different biochemical composition of organic matter in the two sampling periods. In June, organic matter was characterized by a more refractory composition. The consequent reduction of available organic substrate was associated with a decrease in the exoenzymatic substrate affinity. Lower organic matter turnover rates were also observed in deeper sediment layers. In February, the freshwater plume was almost completely confined to the northern area, whereas in June it was extended to the southern area. The results suggest that river inputs influence the biochemical composition and distribution of the sediment organic matter and exoenzymatic activities in coastal marine sediments.     

Changes of organic matter quality along the longitudinal axis of a large shallow lake (Lake Balaton)

Hydrobiologia - Dissolved organic matter (DOM) is quantitatively the most significant pool of organic matter in lakes. Within DOM, the pool of dissolved organic carbon (DOC) is dominated...     

Effect of fluoride pollution on the organic matter content of soil

In the present study effect of fluoride contamination of soil and litter by an aluminium factory on the organic matter content of soil is investigated. It was found that increase in fluoride content of litter and soil causes accumulation of organic matter content in the surface soil. It is suggested that the presence of fluoride in the litter and soil decreases the growth and activity of micro-organisms resulting in greater accumulation of organic matter in the soil.     

Oxygen isotope enrichment of organic matter in Ricinus communis during the diel course and as affected by assimilate transport

The oxygen isotope composition in leaf water and organic compounds in different plant tissues is useful for assessing the physiological performance of plants in their environment, but more information is needed on Delta(18)O variation during a diel course. Here, we assessed Delta(18)O of the organic matter in leaves, phloem and xylem in stem segments, and fine roots of Ricinus communis during a full diel cycle. Enrichment of newly assimilated organic matter in equilibrium with leaf water was calculated by applying a nonsteady-state evaporative enrichment model. During the light period, Delta(18)O of the water soluble organic matter pool in leaves and phloem could be explained by a 27 per thousand enrichment compared with leaf water enrichment. Leaf water enrichment influenced Delta(18)O of phloem organic matter during the night via daytime starch synthesis and night-time starch remobilization. Phloem transport did not affect Delta(18)O of phloem organic matter. Diel variation in Delta(18)O in organic matter pools can be modeled, and oxygen isotopic information is not biased during transport through the plant. These findings will aid field studies that characterize environmental influences on plant water balance using Delta(18)O in phloem organic matter or tree rings.     

The composition and distribution of the particulate matter in the Strait of Magellan (Chile) during the 1991 and 1995 Italian campaigns

During 1991 and 1995, the Italian National Program for Antarctic Research carried out two oceanographic campaigns in the framework of the International (Strait of) Magellan Project. In this paper, we describe the distribution, biochemical composition, and mineralogical characteristics of particulate matter and the characteristics of the water masses defining microbasins in the Strait of Magellan. The data analyses highlighted differences in quality and quantity of the suspended matter and its organic component in the basins that make up the Strait and the Pacific Ocean. The westernmost basin is subject to an eastward flow from the Pacific Ocean, and continental runoff in the surface layers, which are consequently rich in organic matter with a high C:N ratio. The central basin, Isla Carlos III–Segunda Angostura, is characterized by the mixing of Sub-Antarctic Pacific waters, continental runoff, and glacio-fluvial waters: The basin has the lowest particulate matter concentration, but at Paso Ancho showed high concentrations of organic matter with a lower C:N ratio. The easternmost basin, Segunda Angostura-Atlantic entrance, is characterized by the mixing of the water column due to strong Atlantic tides and showed high concentration of particulate matter with a high detritic component. Generally, the organic matter concentrations showed significant differences during the cruises, being higher in 1991. Using the multivariate discriminant factor analysis to determine whether statistically significant differences existed between defined sampling areas, we determined that temperature, particulate organic carbon, and total particulate matter were the variables most important for the difference between areas.     

Simulation of accumulated matter from human feces in the sawdust matrix of the composting toilet

A bio-kinetic model for aerobic biodegradation of human feces was applied to the practical operation of the composting toilet. The first aim of this study was to describe nitrogen transformation in the toilet as well as organic carbon. Second aim was to obtain the kinetic parameters for better prediction of accumulated matter for a long time of the practical operation. Six simple fractions of fecal carbon (slowly hydrolyzable matter, easily hydrolyzable matter, readily biodegradable matter, biologically inert type of matter etc.) were prepared in the model. Nitrogen factors were incorporated to each factor of fecal carbon. Modification of only one kinetic parameter for hydrolysis of slowly hydrolyzable carbon was required to obtain the best fitting curve of accumulation in the toilet. Model prediction for one-year operation of the toilet showed that temporal accumulation of biodegradable organic matter was significant in the first stage whereas main accumulation would be biologically inert type of organic matter at the end of the operation.     

Effects of organic matter on the growth of Thiobacillus intermedius

London, Jack (University of California, Los Angeles), and Sydney C. Rittenberg. Effects of organic matter on the growth of Thiobacillus intermedius. J. Bacteriol. 91:1062-1069. 1966.-Yeast extract, glucose, glutamate, and other organic materials stimulate the rate and extent of growth of Thiobacillus intermedius in thiosulfate broth. Growth did not occur in glucose or glutamate mineral salts medium in the absence of thiosulfate, although a stable variant was obtained which grows on yeast extract alone. Cells harvested from media supplemented with organic matter have a reduced rate of thiosulfate oxidation (20 to 30% of autotrophic), oxidize the organic supplement, and have an additive rate of oxidation in the presence of both the organic substrate and thiosulfate. Carboxydismutase synthesis is repressed, and the incorporation of bicarbonate carbon into cell material is almost completely eliminated by the presence of organic matter in the growth medium. It is concluded that the availability of organic matter eliminates the autotrophic assimilatory mechanisms of T. intermedius but not its autotrophic energy-generating system. The data are discussed in relation to the existence of "obligate" chemoautotrophic bacteria.     

Terrestrial dissolved organic matter inflow drives temporal dynamics of the bacterial community of a subarctic estuary (northern Baltic Sea)

Climate change is projected to cause increased inflow of terrestrial dissolved organic matter to coastal areas in northerly regions. Estuarine bacterial community will thereby receive larger loads of organic matter and inorganic nutrients available for microbial metabolism. The composition of the bacterial community and its ecological functions may thus be affected. We studied the responses of bacterial community to inflow of terrestrial dissolved organic matter in a subarctic estuary in the northern Baltic Sea, using a 16S rRNA gene metabarcoding approach. Betaproteobacteria dominated during the spring river flush, constituting ~ 60% of the bacterial community. Bacterial diversity increased as the runoff decreased during summer, when Verrucomicrobia, Betaproteobacteria, Bacteroidetes, Gammaproteobacteria and Planctomycetes dominated the community. Network analysis revealed that a larger number of associations between bacterial populations occurred during the summer than in spring. Betaproteobacteria and Bacteroidetes populations appeared to display similar correlations to environmental factors. In spring, freshly discharged organic matter favoured specialists, while in summer a mix of autochthonous and terrestrial organic matter promoted the development of generalists. Our study indicates that increased inflows of terrestrial organic matter-loaded freshwater to coastal areas would promote specialist bacteria, which in turn might enhance the transformation of terrestrial organic matter in estuarine environments.     

Estimation of export production in the coastal Baltic Sea: effect of resuspension and microbial decomposition on sedimentation measurements

Hydrography, nutrient concentrations, primary production and sedimentation of particulate matter were studied during spring, late summer and autumn in the coastal area of the northern Baltic Sea, SW Finland. Vernal phytoplankton productivity peak and biomass maximum in early May were followed by high sedimentation rates of organic matter at the end of May. In summer, sedimentation rates of organic material were generally low. The decay rates of organic carbon in the sediment traps, estimated by measuring oxygen uptake of settled organic matter, varied between 0.005 to 0.08 d^–1 and were on average 0.02 d^–1. Decomposition of organic matter inside the sediment traps was mainly controlled by temperature, while also organic contents of settled material were significant. Microbial decomposition decreased sedimentation rates of organic carbon and nitrogen on average by 11% and 15%, respectively, during the whole study period of ca. 6 months. Resuspension of organic matter from sediment surface was estimated to contribute ca. 17 and 24% of the total sedimentation of organic carbon during spring and summer, respectively. Export production (i.e. primary sedimentation of organic carbon corrected by decomposition) was estimated to be 32% of the net primary production during the whole productive season and 42% in spring when the flux of primary settling material was greatest. Sedimentation of the spring bloom was the major annual supply of organic matter to the benthos (>80% of the total primary sedimentation).     

Modeling the bacterial contribution to planktonic community respiration in the regulation of solar energy and nutrient availability

In planktonic ecosystems, algae and bacteria exhibit complex interrelationships, as algae provide an important organic matter source for microbial growth while microbial metabolism recycles limiting nutrients for algae in a loose commensalism. However, algae and bacteria can also compete for available nutrients if supplies of organic matter are sufficient to satisfy bacterial demand. We developed a stoichiometrically explicit model of bacteria–algae interactions that incorporated realistic assumptions about algal light and nutrient utilization, algal exudation of organic matter, and bacterial processing of organic matter and nutrients. The model makes specific predictions about how the relative balance of algae and bacteria should change in response to varied nutrient and light availability seen in lakes and oceans. The model successfully reproduces published empirical data and indicates that, under moderate nutrient supply, the bacterial percentage of total respiration should be maximal at intermediate light intensity.     

Improving the quality of municipal organic waste compost

The effects of different municipal organic waste (MOW) management practices (shredding, addition of carbon-rich materials and inoculation with earthworms) on organic matter stabilization and compost quality were studied. Four static piles were prepared with: (i) shredded MOW; (ii) shredded MOW+woodshavings; (iii) non-shredded MOW; and (iv) non-shredded MOW+woodshavings. After 50 days, a part of each pile was separated for vermistabilization, while the rest continued as traditional thermophilic composting piles. At different sampling dates, and in the finished products, the following parameters were measured: pH, electrical conductivity, carbon dioxide evolution, and concentrations of organic matter, total nitrogen, water-soluble carbon, nitrate nitrogen, ammonium nitrogen, and extractable phosphorus. Shredded treatments exhibited faster organic matter stabilization than non-shredded treatments, evidenced specially by earlier stabilization of carbon dioxide production and shorter thermophilic phases. Woodshavings addition greatly increased quality of final products in terms of organic matter concentration, and pH and electrical conductivity values, but decreased total nitrogen and available nutrient concentrations. Vermicomposting of previously composted material led to products richer in organic matter, total nitrogen, and available nutrient concentrations than composting only, probably due to the coupled effect of earthworm activity and a shorter thermophilic phase.     

A method for determining the cation-exchange capacity of organic materials

Summary A method for determining the cation-exchange capacity (CEC) of organic matter was developed by modifying the BaCl₂ triethanolamine, pH 8.1, method used in calcareous soils. Problems arising from the presence of sulphates and losses of water soluble organic matter were solved. The proposed method for organic matter is comparable to that of soil in terms of sensitivity, reproducibility and in the time necessary for each analysis. In the second part of the work the CEC's of diverse organic samples were determined and found to be reproducible with an average coefficient of variation of 3.56%.     

Organic matter fraction and pools of phosphorus as indicators of the impact of land use in the Amazonian periphery

The unsustainable use of the soil of the deforested area at the Amazonian border is one of the greatest threats to the rainforest. Among the causes of land degradation in the humid tropics are phosphorus depletion (P), the decrease of soil organic matter (SOM) and the loss of basic cations. The aim of this study was determine the effects of different land uses on the dynamics of soil organic matter and phosphorus, to determine whether and how changes in the P and SOM can be used to assess the degree of land degradation in the humid tropics and whether the use of ecological systems can lessen or mitigate this degradation. Five systems were chosen according to potential use in the region: pasture of 30 years; no-tillage with 5 years of rice–maize rotations; no-tillage in alley cropping systems of 10 years; a newly cleared area; and 20 years of undisturbed secondary forest. Each field was sampled in a “W” pattern, to collect the soil samples from the chosen systems, prior to the chemical analyses. The SOM was separated by physical soil fractionation. The soil P fractionation was performed. All of the soil samples showed a very low pH range. The potential acidity was high under the alley cropping system, with more intensive and continuous use. All of the more labile fractions of organic matter decreased with the continuous use of soil in the alley cropping system. Therefore under alley cropping, most of the P (approximately 95%) was found in an inorganic form, and approximately 60% was found in the less labile fractions. The pasture and secondary forest showed higher contents of the labile fractions of organic matter and organic P. Higher correlations of organic P were found with the silt and clay fractions of organic matter. The results indicate that the fractions of P and organic matter are important indicators to assess changes in the degree of land degradation in the humid tropics. These results indicate also that the intensive and continuous use of annual crops in the soils of the humid tropics must be considered as posing a high risk to the sustainability of the agrosystems, mainly because of the increase of the active and potential acidity, the decrease of the labile organic matter and the depletion of the pools of organic P, leading to land degradation.     

Specific features of soil organic matter in forest landscapes of Karelia

The organic matter reserves and the soil humus state are assessed in three types of landscapes of the middle taiga (Karelia). Peat soils are the main organic matter reservoir. Hence, the greater their area, the higher the organic matter reserves in a particular landscape. The organic matter stocks in the group of semihydromorphic and hydromorphic soils clearly correlate with the degree of their waterlogging. The distribution of organic matter reserves within these soils depends on the ratio between the areas of boggy forests and open mires. The forest supporting quality of the soil is related to the organic matter composition and parent rock (the properties of the soil mineral horizons) rather than to the organic matter stocks. The data obtained may be used for assessing the forest supporting qualities of the soils and the basis for estimating the carbon budget in the landscapes.     

Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River

Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside.