Properties Of Particulate Organic Matter Research Articles

Seasonal variations in biochemical and stable isotope compositions of particulate organic matter in two contrasting temperate coastal lagoons of Korea

The geomorphology of coastal lagoons has an important effect on the hydrological balance between fresh water and seawater, which exhibit a wide range of salinity from nearly fresh water to hypersaline water. The present study aimed to characterize seasonal biogeochemical properties of suspended particulate organic matter (POM) in response to environmental variability driven by hydrological dynamics in contrasting coastal lagoon systems. We selected two lagoons distinguished by their geomorphological features, a permanently open artificial lagoon (Gyeongpoho) and an intermittently open natural lagoon (Hyangho), analyzed environmental characteristics, and compared the seasonal differences in the biochemical compositions of POM. Variations in temperature and precipitation in both lagoons showed the characteristics of a typical monsoon climate but variation in salinity differed 6.5−35.0 in Gyeongpoho and 1.1−10.8 in Hyangho. A self-organizing map analysis using the environmental data revealed that the spatiotemporal variations in salinity and nutrient concentrations differed significantly between the two lagoon systems, indicating a difference in hydrologic connectivity between lagoons and marine systems. Furthermore, a canonical correlation analysis highlighted that the POM properties differed according to physicochemical factors. The differing environmental conditions may affect the spatial and temporal variations in organic matter composition, resulting in significant differences in the biochemical composition of POM between two lagoon systems. Overall, this information provides insight into the origin and transport process of POM under changing coastal lagoon environments caused by climatic and human activities.

Testing the effects of coastal culture on particulate organic matter using absorption and fluorescence spectroscopy

Aquaculture is a major type of human activity that disturbs the biogeochemistry and ecosystem in coastal environments, yet its influence on the optical properties of particulate organic matter remains largely unknown. This was studied for the Aojiang Estuary-cultural zone-adjacent seawater continuum in SE China in July and October 2019, and in January 2020, using absorption spectroscopy and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). The POM absorption, three humic-like components (C1, C2, and C5), and humification index (HIX) generally decreased from the river to the seawater and were higher in October than in January. The humic substances were mainly derived from terrestrial sources and sediment resuspension, which were dependent largely on the level of total suspended matter (r: 0.823–0.888). The intensity of shoulder peak in the absorption spectra and the tryptophan-like C4 were lower in the river than in seawater in July, which was in contrast to the spatial distribution in other months. They correlated positively with Chl a (r: 0.779–0.912), indicating they were mainly related to the algal production. Principal component analysis (PCA) revealed notable seasonal variations of POM with an elevated autochthonous contribution in July, indicating stronger algal production than the removal by shellfish. The low autochthonous POM in October and January identified with PCA suggested limited addition from the laver culture after the shellfish harvest. The mooring monitoring in July and October further demonstrated that the POM in the cultural zone and adjacent seawater was influenced by the active material exchange across the continuum, strong tides, sediment resuspension, algal production, and microbial transformation. Our results have implications for assessing the influences of aquaculture activities on the water quality and ecosystem in the coastal environments.

Hydro-biogeochemical alterations to optical properties of particulate organic matter in the Changjiang Estuary and adjacent shelf area

Base-extracted particulate organic matter (BEPOM) collected in low (spring) and high (summer) runoff seasons in the Changjiang Estuary and adjacent nearshore/offshore shelf areas was examined using absorption and fluorescence spectroscopy. Parallel factor analysis (PARAFAC) identified two humic-like (C1p and C2p) biologically-refractory components and two protein-like (C3p and C4p) bioreactive components. Absorption coefficient a350p, C1p and C2p of BEPOM showed strong positive correlations with particulate organic carbon (POC), and were generally higher in spring than in summer. C4p correlated positively with Chl a, and was higher in summer than in spring. In the inner estuary, an anthropogenic POM signal from the highly polluted Huangpu River was effectively identified by the fluorescent component ratio (IT:IC)P. In the nearshore area during spring, resuspension within the well-developed turbidity maximum zone (TMZ) supplied large amounts of refractory POM into the water column. POM fractions from an autochthonous source (i.e., algal bloom) were dominant in the offshore area during the summer. A multivariate regression model inferred that POM export fluxes from the Changjiang River during spring had a higher percentage of labile POM fractions, which were subsequently retained by the TMZ. However, these labile fractions were discharged into the offshore shelf area contributing to hypoxia in the summer. The summer high runoff season also transported large amounts of refractory POM that was subsequently buried in the sediment. This study highlights the utilization of optical analyses to trace pollution sources and reveal POM fate and transport dynamics allowing better assessment of its ecological consequences in estuaries.

Effects of fish culture on particulate organic matter in a reservoir-type river as revealed by absorption spectroscopy and fluorescence EEM-PARAFAC

Dam construction and fish culture can change the biogeochemical processes in river, yet their impact on the spectral properties of particulate organic matter (POM) remains to be studied. This was investigated in a reservoir-type river (Minjiang river, SE China) using absorption spectroscopy and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Five fluorescent components were identified from POM with PARAFAC. Four components C1–C4 were affected by the seasonal variations of rainfall and runoff, indicating the influences of hydrological condition and terrestrial inputs. The Chlorophyll a concentration (Chl a) correlated significantly with the humic-like C3 (p < 0.05) and the protein-like C4 (p < 0.01), indicating phytoplankton was an important source of C3 and C4. The Chl a and fluorescence intensities of C3–C4 were higher in the fish culture zones than in other areas, and the absorption coefficient a300 and C1–C4 were lower downstream the dam. These results indicated that fish farming in the reservoir probably promoted the production of POM. The a300 and C1 per unit mass of suspended particulate matter (a300/TSM and C1/TSM) correlated significantly with the median particle size (p < 0.01), which might be related to the contribution of micro-phytoplankton. The absorption spectra of POM showed a shoulder peak at ∼280 nm, and its intensity correlated significantly and positively with Chl a (p < 0.01). These results indicated that the peak was probably derived from phytoplankton production. Our results have implications for better understanding the influences of human activities on the dynamics of river POM.

Molecular characterization of particulate organic matter in full scale anaerobic digesters: An NMR spectroscopy study

This study assesses the molecular characteristics of particulate organic matter (POM) in agricultural and food waste digesters and elucidates the molecular properties of the recalcitrant POM fraction, which remains in the digestate after AD process. Molecular properties of POM in influent (substrate) and effluent (digestate) of seven full-scale AD plants (three agricultural waste and four food waste digesters) were characterized and compared using solid-state 13C cross-polarization magic angle spinning (CP-MAS) and solution-state 1H,13C heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy. Comparison of the POM structural compositions of substrate and digestate from each AD plant revealed an enrichment of protein structures relative to the carbohydrates in most cases, implying a preferential degradation of the carbohydrates over proteins and/or increase of microbial biomass upon AD of agricultural and food wastes. Distinctive molecular structures of labile and recalcitrant fractions of POM, subjected to AD, were identified by comparing the NMR spectra of all substrate and digestate POM. Accordingly, the labile POM fraction in food and agricultural solid wastes is characterized by structural entities of lipids and starch-like carbohydrates, whereas recalcitrant POM structures resemble alkyl and aromatic subunits of amino acids, lignin, and polysaccharides with β-glycosidic linkages. This information serves as a basis to further explore optimization approaches for improving AD of the underutilized POM and the fate of organic matter in digestate-amended arable lands.

Seasonal changes in particulate organic matter (POM) concentrations and properties measured from deep areas of the Baltic Sea

Summary In seawater particulate organic matter (POM) serves as a food source for heterotrophic bacteria and zooplankton and is a source of dissolved organic compounds and nutrients. POM plays a critical role in transporting carbon to marine sediments where a fraction of it is buried in subsurface sediments and thus avoids conversion to carbon dioxide on shorter time scales. Distribution and properties of POM were investigated in the Baltic Proper from 2013 to 2015. Particulate organic carbon (POC) was used to investigate POM sources and dynamics. Stable carbon isotopes (δ13C), elemental composition (C, N), chlorophyll a and POM contribution to suspended particulate matter (SPM) were also measured and interpreted. The water column exhibited concentrations ranging from 0.2 mg POC/l (deep water layer – DWL, cold season – CS) to 1.7 mg POC/l (surface water layer – SWL, warm season – WS). POM represented 0.15 to 0.45 of SPM during respective cold and warm seasons. Stable carbon isotopes (δ13CPOC) ranged from −22.5‰ (WS) to −28.0‰ (CS), while the POC/Chl a ratio ranged from 180 g/g (SWL-WS) to 300 g/g (DWL-CS). Seasonal changes were attributed to high primary production in the SWL during the WS, which represented a major POM source. Continuous mineralization/sedimentation throughout the water column constituted a major POM sink.

Buffer capacity and Cu affinity of soil particulate organic matter (POM) size fractions

SummaryParticulate organic matter fractions (POM), defined as sand‐sized organic separates in soils, are known to be labile organic components with a rapid turnover. Recently, POM fractions were identified to be metal‐enriched in both metal‐contaminated and uncontaminated soils. However, mechanisms for such metal‐enrichment are poorly understood, because of the paucity of information on the chemical properties of POM. The aim of this study was to quantify the reactivity of POM towards Cu and to show a POM‐size effect on this reactivity. POM was isolated from soils with different organic amendment managements: straw (S), conifer compost (CC), and non‐amended (NA). Two POM size fractions were isolated by density‐fractionation in water: 50–200 μm and 200–2000 μm. These fractions were studied for their metal contents, acid‐base properties and affinity toward Cu. The buffer capacity and Cu affinity were modeled by FITEQL 4.0 software and compared between the two POM size fractions. Each POM size fraction provided a buffer capacity due to the presence of reactive sites, the greatest being for the 50–200 μm POM fractions. A signature of organic inputs as seen by the buffer capacities was observed for the 50–200 μm but not for the 200–2000 μm POM fractions. But Cu affinity was comparable between the coarse and fine POM fractions and no significant differences were found between NA, S and CC samples. We checked the hypothesis that decreasing POM size due to degradation processes generates more reactive surface sites. Results confirmed that soil POM plays a key role as a metal sink, due to its chemical properties.

Crayfish effects on fine particulate organic matter quality and quantity

Coarse particulate organic matter (CPOM), especially leaves, plays a key role in food webs of many streams and can be converted to fine particulate organic matter (FPOM) by specific macroinvertebrate functional groups (i.e., shredders). In this study, we examined crayfish [Orconectes obscurus (Hagen)] effects on FPOM generation from two leaf types, red maple and white oak, that differ in recalcitrance and decomposition rates. Further, we examined potential quality differences between FPOM generated by crayfish via fragmentation and defecation. Crayfish were fed stream-conditioned maple or oak leaves in hanging 1-mm mesh-bottom baskets in aquaria. After 12 h, C:N ratios and dry/ash-free dry weights of remaining CPOM, FPOM fragments that fell through the mesh, and crayfish feces (collected using finger cots that encased the crayfish abdomens) were determined. Loss of CPOM attributable to crayfish feeding was higher for maple than oak; fragment FPOM and crayfish feces generation were also higher for maple. Maple CPOM percent organic matter was lower than oak CPOM but feces and fragment FPOM percent organic matter did not differ among leaf species suggesting that crayfish actions homogenize the properties of particulate organic matter. Both C:N ratios and bacterial abundance were also altered by crayfish processing and digestion underscoring potential crayfish effects on FPOM bioavailability. Overall, crayfish altered the ontogeny of the detritus, which may, in turn, affect stream FPOM dynamics.

Seston particles along a eutrophication gradient in coastal waters of the Southern Baltic Sea: Significance of detritus and transparent mucoid material

Exposed to over 30 yr of continuous eutrophication, the Dars-Zingst bodden chain, a shallow tideless estuary accumulated large amounts of particulate organic matter (POM). We sam- pled along the eutrophication gradient throughout the vegetation period 1996, in order to assess POM properties. Besides parameters describing the chemical composition, such as C/N ratio, protein content and protein:carbohydrate ratio, particles were microscopically analysed. From the volumes of non-transparent, nucleic acid-containing (fluorescently labelled by propidium iodide) and organic particles (stained with DTAF), the percentages of detrital and transparent mucoid material were derived. Ten to 63% of particulate organic carbon (POC) in the bodden system consisted of carbon from bacteria, phytoplankton and protozoans. Of the total organic particle volume, up to 46% were microorganisms. Although detritus volume averaged 14%, maximum values of 68% could be deter- mined. Most of the organic particle volume consisted to 64% of transparent mucoid matter, which is an important carbon compartment in material cycling (e.g. settling substrate). At higher POC con- centrations the chemically unidentified material as well as the mucoid matter were quantitatively more important compared to the mesotrophic Baltic Sea station, where the portion of detritus (62% on average) was much higher. The microscopically derived quantification of detrital and mucoid mat- ter provides additional information on the suitability of seston as settling substrate, its age, origin and physical properties. Since the riverine water input into the bodden system is small and its POC con- centration lower compared to the bodden itself, most of the estuarine POM was obviously produced locally. Detritus from submersed macrophytes did not occur before the end of the vegetation period in October and thus cannot contribute significantly to the POM analysed in this study. The high amounts of POM in the bodden system probably originate mainly from pelagic primary production. The sedimentation of POM, its processing in and frequent resuspension from the several mm-thick flocculent sediment layers, seems to be the main source for the high amount of mucoid particles.

Staining particulate organic matter with DTAF--a fluorescence dye for carbohydrates and protein:a new approach and application of a 2D image analysis system

Aggregates consist in many cases of microorganisms attached to an organic matrix. Several attempts have been made to visualise the mucoid components of the matrix by staining (e.g. alcian blue for carbohydrates and coomassie brilliant blue for proteins). Modern equipment, such as epfluorescence microscopes, flow cytometers and confocal laser scanning n?icroscopes, requires or works best with fluorescently marked objects. Therefore, there is a great need for a fluorescent dye to visualise polysaccharides associated with aggregates. Like proteins, polysaccharides are very heterogeneous in their 3-dunensional structure. Depending on the types of interglycosidic bonds and the orders of monosaccharide building blocks, various conformations are possible (i.e. helices or molecule layers). Moreover, saccharides are very hard to modify covalently in water at natural pH levels. To date, the only available fluorescence marker is 5-(4,6-dichlorotriazinyl)aminofluorescein (DTAF), which binds covalently to polysaccharides at room temperature when the pH is above 9 This paper compares the results of staining particulate organic matter (POM) with DTAF with the results of staining with the DNA-specific stain propidium iodide, which has been recently introduced to visualise detritus. Results are related to other POM properties, e.g. particle volume measured by coultere Counter and particulate organic carbon (POC). When plankton and floccular sediment layer samples were stained with DTAF, the total particle volume was, in 13 out of 17 samples, 11 to 393% greater than that revealed by propidium iodide. The mucoid matrix of large particles (>50 pm charneter) stained well with DTAF, whereas this material was only weakly detected w t h propidium iodide. In contrast, very small particles such as bacteria were seen better with propidium iohde. The total parbcle volume of a DTAF-stained sample calculated from 2-dimensional image analysis data correlated significantly with POC, total particulate polysaccharides, Coultera-counter-derived total particle volume, and light-microscope-derived summed volumes of bacteria, phytoplankton and protozooplankton. The total biovolumes contributed on average 62% of the Coultera Counter volume and 45% of propidium-iodide-stainable and 50% of DTAF-stainable volume in plankton samples from the Kirr Bucht and 58,59 and 61 % from the Rassower Strom, respectively. The remaining volume must be interpreted as the volume of amorphous detritus and, particularly in the case of the fluorescently stained particles, also as amorphous organic material.