Distribution Of Sedimentary Organic Matter Research Articles

Sedimentary organic matter applied to paleoenvironmental reconstruction of the Devonian of the Paraná Basin, SW Gondwana

The study of sedimentary organic matter (SOM) is essential for understanding paleoenvironmental conditions and depositional settings of geological formations. This paper explores the Devonian strata of the Paraná Basin, utilizing SOM analysis to reconstruct paleoenvironments and identify global events. The Devonian period is notable for significant geological and biological changes, including mass extinctions and extensive organic-rich sediment deposition. By examining the composition, distribution, and diagenesis of SOM in this region, we aim to elucidate the paleoenvironmental dynamics and depositional history. The Devonian outcrops in the state of Mato Grosso do Sul, Brazil rocks reveal distinct depositional characteristics, when compared to those found on the eastern border of the basin. The palynofacies analysis was conducted on 59 samples from four outcrops (MS-26, MS-29, MS-30 and MS-70), which age spans from Pragian to Givetian. The main groups and subgroups of the SOM were identified: amorphous organic matter (AOM) (“amorphous organic matter” and pseudoamorphous), phytoclasts (opaques, non-opaque-non biostructured, cuticles, membranes and Spongiophyton) and palynomorphs (spores, freshwater algae, scolecodonts, chitinozoan and acritarchs). The SOM was grouped into three palynofacies associations: opaques, land-derived and marine+AOM. In the Pragian—Emsian interval (MS-26, MS-29 and MS-30), a prevalent occurrence of phytoclasts and marine microphytoplankton is noted, with their distribution exhibiting distinct alternations in each section suggesting a deposition in the marine environment ranging from onshore to offshore. In the Givetian (MS-70 outcrop), we detected a progressive increase and diversification of marine elements (e.g., acritarchs), indicating a transgressive phase probably related with the Kačák event.

Composition and distribution of sedimentary organic matter in nearshore Berriasian strata (‘German Wealden’) of the eastern Lower Saxony Basin, NW Germany

Abstract In the Lower Saxony Basin of Northern Germany, the Earliest Cretaceous (Berriasian, ‘German Wealden’) is represented by organic-rich shales assigned to the Isterberg Formation, which have been deposited under brackish-lacustrine conditions in a partially restricted basin. Towards the southern basin margin, these shales interfinger with nearshore sandstones sourced from the Deister-Hils delta. In order to better understand the environmental conditions and depositional dynamics of the Isterberg Fm, the sedimentary organic matter has been studied with a combined approach including bulk rock organic geochemistry and palynofacies analysis. The lower part (W 1 to W 3) is interpreted to reflect very shallow-water conditions and episodic emergence, indicated by multiple occurrences of palaeosol horizons, rhizoliths and intercalated coal beds formed within a mud-dominated and protected domain of the delta plain. The overlying sand-rich interval represents a nearshore deltaic setting. A distinct change is observed in the upper part (W 4), indicating more distal conditions characterized by clay-dominated sedimentation, abundant lumachelle interbeds and a predominance of aquatic-derived organic matter. The newly acquired data fill a gap in the record between the proximal and distal strata of the Berriasian Lower Saxony Basin and provide new insights into the accumulation and preservation of organic matter within this exceptional depositional setting.

Paleoenvironmental changes recorded in the Santa Marta Formation (Santonian–Campanian, Upper Cretaceous), James Ross Island, Antarctica, inferred from palynofacies analyses

The Santa Marta Formation (Santonian–Campanian; James Ross Island, Antarctic Peninsula) is part of one of the most complete sedimentary sequences in the Southern Hemisphere. Paleoenvironmental changes recorded in the formation are reflected in the stratigraphic distribution of sedimentary organic matter in the Lachman Crags and Herbert Sound members. Fifty-three samples from the Lachman Crags section and ten samples from the Herbert Sound section were prepared using standard non-oxidative methods for palynofacies. Analyses were performed using transmitted white light and fluorescence microscopy to identify the groups and subgroups of sedimentary organic matter: non-opaque non-biostructured and biostructured opaque particles, membrane fragments, degraded and non-degraded cuticles, spores, pollen grains, fungal spores, Botryococcus, Palambages, dinoflagellates cysts, amorphous organic matter, pseudoamorphous (product of disintegration of macrophyte tissues) and resins. Three palynofacies associations are distinguished: terrestrial, opaque, and marine palynomorphs. Based on stratigraphically restricted cluster analysis (CONISS), three intervals have been identified: Interval 1, at the base of the Lachman Crags section, conspicuously dominated by the terrestrial palynofacies association. Interval 2, the middle portion of the Lachman Crags section, is marked by alternating terrestrial and opaque palynofacies associations. Interval 3, which coincides with the Herbert Sound section, is distinguished by an abrupt increase in marine elements. The composite section shows progressive transgression, accompanied by a decrease in continental elements, culminating in an open marine environment towards the top of the section.

Deciphering the source contribution of organic matter accumulation in an urban wetland ecosystem

AbstractA better understanding of the organic matter (OM) dynamics is a key to successful wetland management. We established the radiocarbon chronology (14C) and vertical distribution of nitrogen (N), phosphorus (P), OM, and carbon to nitrogen ratio (C/N) in the sediment core retrieved from the Anchar Wetland, Kashmir Himalaya. The accelerator mass spectrometer (AMS) assisted 14C dating of the sediment core showed 14C age reversals related to occasional disturbances. The vertical distribution of various fractions revealed increased concentrations of organic carbon (OC), OM, and nutrients (N and P) in the upper part of the sediment core, largely related to increased anthropogenic inputs from the catchment areas during recent decades. Further, the low to high C/N ratio (1.3–36.4) suggests a combination of both the autochthonous and allochthonous inputs as the major contributors of OM to the wetland ecosystem. The linear regression model showed significant (p < 0.05) positive and negative relationships among various analyzed parameters. Principal component analysis (PCA) resulted in three principal components (PCs) accounting for a cumulative variance of 83.6%. The PCA suggests that the primary production, human activities such as extraction of Lotus stems (Nadru) and fishing, and terrestrial inputs (sewage disposal and fertilizer runoff) are the major factors controlling the distribution of organic fractions and nutrients. This study provides important insights into the sources and distribution of sedimentary OM and nutrients crucial for assessing the risks of pollution and for adopting the socially, politically, and scientifically robust strategies for the management of wetlands.

Glycerol dialkyl glycerol tetraether signatures in tropical mesotidal estuary sediments of Qua Iboe River, Gulf of Guinea

The continuous supply of land derived organic carbon by rivers is significant to the ocean carbon cycle. In river-estuary systems, the composition and distribution of sedimentary organic matter (OM) can provide detailed information on the balance of land-derived inputs and in situ productivity. This insight is significant for an improved understanding of anthropogenic activity and the changing climate. In the Gulf of Guinea (GoG), high rainfall, coupled with flooding and a warmer climate have direct impacts on OM distributions. Glycerol dialkyl glycerol tetraethers (GDGTs) have been used extensively to investigate OM. In this study, we focused on the widespread occurrence of isoprenoid GDGTs (isoGDGTs), branched GDGTs (brGDGTs), H-tetraethers (H-isoGDGTs and H-brGDGTs), hydroxyl GDGTs (OH-GDGTs), isoGDGT isomers, methylated isoGDGTs (Me-GDGTs), butanetriol and pentanetriol tetraethers (BDGTs and PDGTs), in short sediment cores collected from the inner and outer Qua Iboe River Estuary, located in the GoG. We further determined total organic carbon (Corg), total nitrogen (TN), long chain hydrocarbons (LCA; C27–C33n-alkanes), dinosterol, brassicasterol and phytol, to estimate OM sources, flooding activity, OM degradation, to reconstruct pH and to determine past tropical temperatures. The distribution patterns of GDGTs, use of principal component analysis (PCA), heatmap hierarchical cluster analysis, correlation models, the ratios of isoGDGTs/brGDGTs, ring index (RI), brGDGT-IIIa/IIa, branched and isoprenoid tetraether (BIT), Corg/TN and terrestrial-marine biomarker ratio (TMBR) were all sensitive for indicating terrestrial vs marine OM contributions to the total OM of the tropical estuarine sediments. Marine OM persisted from subsurface to bottom sediment layers (8–38 cm) in the outer estuary site, while a mixed OM source was observed in inner estuary sediments. The Cren/Cren’ ratio >58.5 (up to 83.8), pointed to a predominance of Thaumarchaeota group I.1a microbes. The Methane Index (MI) and isoGDGT-0/Cren ratio indicated significant imprints of a non-methanotrophic archaeal community. A positive linearity of total BDGTs and PDGTs plotted against MI and isoGDGT-0/Cren suggested that these compounds are produced by the same group of the non-methanogenic archaeal community in this tropical estuary. Thus, Methanomassiliicoccus luminyensis is not the only source of BDGTs and PDGTs in the marine environment. Further, the calculated CBT5me derived pH reflected in situ measured sediment pH (6.3). TEX86H-derived sea surface temperature (SST), within error, reflected water column temperature. Calculated brGDGT mean annual air temperatures (MAATs) reflected average annual atmospheric temperatures. Ring index OH-GDGTs temperature proxies (RI-OH SSTsummer and RI-OHꞌ SST) reflected mean dry season (November to February) temperatures. A newly derived MAAT proxy, calculated from H-brGDGT, also reflected the tropical annual air temperature (23–28 °C). Altogether, as expected, the OM sources are traced largely to both terrestrial and marine inputs. The terrestrial OM was deposited by excess flooding and surface runoff occasioned by torrential monsoon rains in recent years, triggered by climate change, while mesotidal currents introduced marine OM into the Qua Iboe River Estuary system. This study further contributes to our understanding of OM distributions in warmer climate conditions.

Oceanographic and human impacts on the compositions of sedimentary organic matter along the southern coast of Zhoushan

Three sediment cores were collected from the southern coastal area of Zhoushan Island, and their lignin-derived phenol, bulk elemental composition, stable carbon isotope, particle size and 210 Pb activities were determined. The objective of this study was to determine the compositional changes of the sedimentary organic matter along this coastal area in the past 80 years as a result of anthropogenic and oceanographic-related processes. The results of this study showed that the sources and distribution of sedimentary organic matter along this coastal area were affected by the accelerated development on these islands and mainland China. Moreover, the increased contribution of terrestrial organic matter from the rivers in the mainland from the 1930s to the 1980s was likely the result of human activities. The drastic increase in the vanillic acid to vanillin ratio, (Ad/Al)v, in the 1970s and 1980s coincided with the start of rapid development in Zhoushan, resulting in the increased erosion of more degraded terrestrial organic matter along the coast. Trends of increasing marine organic matter toward the present could be due to a combination of reduced river input and sea level rise. Overall, our results showed that the sedimentary organic matter along the southern coastal zone of Zhoushan main island was affected by riverine input from the mainland, and showed a tendency toward decreasing terrestrial organic matter and particle size. Thus, local input and increased phytoplankton production will play a more important role in the carbon dynamics in this coastal area in the future. (245 words). • Sedimentary organic matter along the southern coast of Zhoushan main island was affected by human activities. • There was increased signal of marine organic matter due to sea level rise. • Decreased terrestrial organic matter and particle size toward the present could be due to river input from the mainland.

Hydrocarbon sedimentary organic matter composition from different water-type floodplain lakes in the Brazilian Amazon

Amazon rivers and flooded areas can be categorized into three types of water: white, black, and clear. These categories present unique physical–chemical characteristics that influence the characteristics and distribution of sedimentary organic matter (SOM). A geochemical assessment of the short sedimentary cores of four floodplain lakes within the Brazilian Amazon basin was performed. Two black, one white, and one clear-water floodplain lakes were selected to evaluate the variability of OM composition based on aliphatic biomarker and carbon isotopic ratios, as proxies for an enhanced methane cycle, anoxia, and to determine the origin of predominant aliphatic biomass. Gas chromatography was coupled to flame ionization detection (GC–FID), mass spectrometry (GC–MS) and combustion-isotope ratio mass spectrometry (GC–C–IRMS). These were used to determine aliphatic biomarker ratios, for quantification, and to measure carbon isotopic compositions. The TOC content was inversely proportional to the expected OM productivity; one black water (low OM productivity) presented the highest TOC content, and white water (high productivity) presented the lowest. Also, clear water lake (intermediate productivity) presented TOC content between the other lakes. Based on n-alkane proxies and profiles, as well as bacterial and plant-derivative terpene distribution, we observed a mostly terrigenous contribution for the black and clear water lakes (allochthonous SOM), as well as a prevalence of aquatic organisms in white water lake (autochthonous SOM). Only in the most superficial section of the white water lake, was intense OM degradation substantiated with n-alkanes showing an even-short-chain predominance, indicative of OM cycling. Also, for one black water lake, we detected depleted n-alkane and diploptene δ13C values (–42‰) associated with methanotrophic archaea and higher relative concentrations of des-A-triterpenes commonly associated with anoxic sedimentation. Based on these data, the influence of water-type on the SOM composition was verified. The approach helps to understand the application of n-alkane proxies to differentiate Amazonian environments.

Amino acids and amino sugars as indicators of the source and degradation state of sedimentary organic matter

Amino acids (AAs) and amino sugars (ASs), compounds ubiquitous to living organisms, can provide information regarding degradation states and bacterial contributions to sedimentary organic matter (SOM). However, very few studies have utilized the combination of AAs and ASs as a proxy to assess the influence of bacterial degradation on SOM in the Yellow Sea (YS). In this study, surface sediments from the YS were analyzed for AAs, ASs, total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C), and grain size. The concentrations of AAs and ASs ranged from 3.29 to 26.65 μmol g−1 and from 0.50 to 9.11 μmol g−1, respectively, and together contributed 13.1% to TOC and 27.5% to TN. The concentrations of AAs and ASs were both positively correlated with the relative abundance of clay (<4 μm) (R2 = 0.73 and 0.79, respectively, p < 0.01), suggesting that hydrodynamic sorting influenced the distribution of SOM in the study area. Comparisons of the degradation indices (TOC normalized yields of AAs and ratio of AAs to ASs) indicated that the SOM in the South Yellow Sea (SYS) was more degraded than that in the North Yellow Sea (NYS). Variations in the glycine/serine and glucosamine/galactosamine ratios reflected a transition from fresh phytoplankton sourced organic matter (OM) to bacterial OM. Based on the yields of muramic acid (Mur), the bacterial OM contributed 17 ± 13% and 26 ± 19% to TOC and TN, respectively. High ratios of glucosamine to Mur (GlcN/Mur) indicated that the fraction of bacterial debris in the SYS was larger than that in the NYS. This study demonstrated the importance of bacteria in regulating the source and fate of SOM in the YS.

Spatiotemporal variations of biogenic elements and sources of sedimentary organic matter in the largest oyster mariculture bay (Maowei Sea), Southwest China

China is the largest mariculture producer in the world, but detailed information on the spatiotemporal variations of biogenic elements and sources of sedimentary organic matter (SOM) via mariculture is limited. The primary objective of this study was to assess the influence of mariculture on the origin of SOM in relation with biogenic elements and geochemical paramaters due to the importance of SOM as a potential source of nutrients and energy in coastal marine environments. Surface sediments from the Maowei Sea were collected in August (summer) and December (winter), 2016 for grain size, total organic carbon (TOC), total nitrogen (TN), organic phosphorus (OP), biogenic silica (BSi), δ13C and δ15N analyses. Significant correlation (p < 0.01) was observed between TOC and TN in summer and winter respectively, indicating that they have common source in both seasons. The spatiotemporal distributions of TOC, TN, OP and BSi were influenced by the sources and distribution of SOM, grain sizes and hydrodynamic conditions in the Maowei Sea. The overall ranges of δ13C (−26.86‰ to −23.01‰) and δ15N (2.54‰ to 9.82‰) and C/N ratio (5.83 to 18.67) showed that SOM is derived from mixed sources. The δ13C and δ15N-based three-end-member mixing model results revealed that >40% of the deposited SOM originates from terrestrial source during two seasons. The SOM from shellfish mariculture was seasonal, mainly deposited in the intensive mariculture areas, and its proportions were only higher than contributions from marine plankton in summer. Generally, this study indicates that shellfish biodepositions can significantly influence the cycle of carbon and other biogenic elements in the intensive mariculture areas. Nevertheless, the overall dominance of terrestrial and marine SOM suggests that the sources of SOM and factors influencing carbon cycling in the Maowei Sea do not exclusively depend on the intensity of mariculture activities.

Total organic carbon and pyrolysis analysis of the Lower Cretaceous in Compton Bay and Atherfield, Isle of Wight (England)

The Wessex Basin (United Kingdom) includes hundreds of meters of Lower Cretaceous clays, silts, and sands deposited in a wide range of depositional environments. Studies have investigated these depositional systems from the organic matter (OM) perspective. However, questions remain concerning the composition, source, and the overall depositional constraints on the distribution of sedimentary OM in this area. Elemental (carbonate % and total organic carbon - TOC) and pyrolysis analyses were conducted on representative lithofacies of the Lower Cretaceous from the Wessex Basin at the Compton Bay and Atherfield sections, Isle of Wight. The highest TOC contents were determined in the upper part of the Ferruginous Sands and Sandrock formations. These elevated TOC intervals are associated with predominantly estuarine deposition. Except for one sample from the Vectis Formation, Hydrogen Index (HI) in all studied units is low and indicates Type IV kerogen assemblages, interpreted to be linked with strongly variable climates (with pronounced dry periods) and significant water table fluctuations in the source area and during transport. The one sample with a Type II-III kerogen assemblage from the lagoonal Vectis Formation supports previous studies which suggested that OM in the Vectis Formation varied vertically as a function of fluvial sediment and terrestrial organic matter input to the lagoonal environment with changes in salinity, sediment resuspension, and turbulence as a result controlling the abundance of dinoflagellate cysts.

The impact of Quaternary sea-level changes on the sedimentary organic matter of the Paraíba do Sul Deltaic Complex area, southeastern Brazil

The Paraíba do Sul Deltaic Complex (PSDC) landscapes diversified markedly over the last 123,000 years B.P. The PSDC is characterized by non-marine to marine deposits, and very complex non-marine deposits in its uppermost part. In such a setting, the characterization of the sedimentary organic matter is a useful tool for conduction paleoenvironmental reconstruction. Sea level changes during this interval are reflected in the stratigraphic distribution of sedimentary organic matter recorded in the four sections of the onshore portion of Campos Basin, southeastern Brazil. The succession is dominated by the woody material (phytoclasts), related to a continuous terrigenous input on the area and is characterized by a long-term regressive trend. The stratigraphical distribution of five palynofacies association reveal a wide variety of depositional paleoenvironments. The palynofacies associations attributed to alluvial fan, fluvial, shallow marine and lagoon were recognized. The alluvial fan, in the lowermost part of the succession, is characterized by high contents of opaque and pseudoamorphous particles. The fluvial deposits, in the lower and uppermost parts of the succession, are dominated by wood material (non-opaque) and sporomorphs. The marine deposits (shallow marine and lagoon), in the middle parts of the succession, appear to be related to the dinoflagellate cysts, microforaminifera linings and amorphous organic matter and suggest a notable marine incursion.

Spatial and temporal distribution in the biochemical composition of sedimentary organic matter in a tropical estuary along the west coast of India

Distribution of sedimentary organic matter was undertaken in Cochin estuary, the second largest wetland ecosystem in India. Surface sediment samples were collected from twenty-seven stations during 2016 constituting the pre- and post-monsoon periods. The sediment samples were analysed for labile fractions of biochemical constituents such as carbohydrates (CHO), proteins (PRT) and lipids (LPD). Irrespective of the sampling periods, proteins (71%, 38%) constitute the major labile fraction, followed by carbohydrate (23%, 36%) and finally lipids (5%, 24). The application of biochemical index using PRT:CHO ratio revealed the presence of freshly deposited as well as the presence of aged organic matter in the estuary. The LPD:CHO ratio revealed low nutritional quality of sedimentary organic matter during the pre-monsoon and enhanced quality in post-monsoon. The trophic state classification based on biopolymeric carbon (BPC), PRT and CHO values unveils the fact that estuarine sediment nature varied between mesotrophic, eutrophic and meso-oligotrophic status. Low BPC:TOC ratios were observed pointing less availability of food to benthic source, and the organic matter present was mainly refractory in nature.

Sources and distribution of sedimentary organic matter in the Beibu Gulf, China: Application of multiple proxies

Geochemical and biomarker methods were combined to investigate the sources of sedimentary organic matter (OM) and their spatial distribution in the Beibu Gulf, a subtropical estuary in southern China. We measured the total organic carbon (TOC) and total nitrogen (TN) content, the glycerol dialkyl glycerol tetraethers (GDGTs) concentration, as well as the isotopic composition of sedimentary OM (δ13Corg and δ15N) in surface sediments collected from the Beibu Gulf. The spatial distribution of the bulk organic parameters (TOC, TN, C/N ratio, δ13Corg, and δ15N) revealed a generally decreasing trend in terrestrial OM from the Maowei Sea to the outer Qinzhou Bay, and from the tributary rivers to the outer bay. The BIT (branched/isoprenoid tetraether) indices also decreased seaward from the Maowei Sea to the Qinzhou Bay, and from rivers to the outer bay, showing that soil OM was mainly delivered to the bay by rivers. The spatial patterns of these bulk parameters suggest that the terrigenous OC is constrained to the coast and adjacent regions. The relatively high GDGT-0/Crenarchaeol ratios and increasing δ15N values along the coast of the Maowei Sea indicate the anthropogenic nitrogen in the Beibu Gulf. Our results show how important a multiproxy approach can be to fully understand and quantify the relative contributions of terrestrial and marine OC components and the biogeochemical processes in the Beibu Gulf, especially in the context of growing anthropogenic activities.

Historical changes in organic matter input to the muddy sediments along the Zhejiang-Fujian Coast, China over the past 160 years

The burial of sedimentary organic matter (SOM) in large river-influenced estuarine-coastal regions is affected by hydrodynamic sorting, diagenesis and human activities. Typically, the inner shelf region of the East China Sea is a major carbon sink for the Yangtze River-derived fine-grained sediments. Most of the previous work concentrated on studies of surface sediments or used a single-proxy in this region. In this study, two cores from the Zhejiang-Fujian Coast were analyzed using bulk (TOC, TN and δ13CTOC) and molecular biomarker (n-alkane, brassicasterol, dinosterol and glycerol dialkyl glycerol tetraether lipids) techniques to clarify the sources, spatiotemporal distribution and fate of SOM in the Yangtze River Estuary and adjacent shelf. Results indicated that the effects of diagenesis and diffusion on different sedimentary biomarkers resulted in overestimation of the relative contribution of terrestrial organic matter (%OMterr), compared with those based on δ13CTOC. The amount of terrestrial plant organic matter (OMplant) and %OMterr in sediments decreased offshore. In contrast, the amount of marine organic matter (OMmarine) increased offshore, but closer to the Yangtze River mouth, the amount of soil organic matter (OMsoil) increased. Moreover, the amounts of TOC, OMplant and OMmarine biomarkers increased, but OMsoil and %OMterr decreased over time in recent decades. Our study suggests that spatial OM distribution patterns in marine shelf sediments were controlled primarily by hydrodynamic sorting and nutrient concentration, and temporally diverse patterns were controlled predominantly by anthropogenic influence (e.g. dam construction and soil conservation, reclamation and agricultural plantations, anthropogenic nutrient input, dust storms, eutrophication, etc.) and climate events (e.g. interdecadal climatic jump and heavy rain events) in the geological period.

Sources and distribution of sedimentary organic matter along the Andong salt marsh, Hangzhou Bay

Abstract Lignin oxidation products, δ 13 C values, C/N ratios and particle size were used to investigate the sources, distribution and chemical stability of sedimentary organic matter (OM) along the Andong salt marsh located in the southwestern end of Hangzhou Bay, China. Terrestrial OM was highest at the upper marshes and decreased closer to the sea, and the distribution of sedimentary total organic carbon (TOC) was influenced mostly by particle size. Terrestrial OM with a C3 signature was the predominant source of sedimentary OM in the Spartina alterniflora -dominated salt marsh system. This means that aside from contributions from the local marsh plants, the Andong salt marsh received input mostly from the Qiantang River and the Changjiang Estuary. Transect C, which was situated nearer to the Qiantang River mouth, was most likely influenced by input from the Qiantang River. Likewise, a nearby creek could be transporting materials from Hangzhou Bay into Transect A (farther east than Transect C), as Transect A showed a signal resembling that of the Changjiang Estuary. The predominance of terrestrial OM in the Andong salt marsh despite overall reductions in sedimentary and terrestrial OM input from the rivers is most likely due to increased contributions of sedimentary and terrestrial OM from erosion. This study shows that lower salt marsh accretion due to the presence of reservoirs upstream may be counterbalanced by increased erosion from the surrounding coastal areas.

Sources and distribution of sedimentary organic matter along the northern Bering and Chukchi Seas

In this study, lignin-derived phenols were used to determine the sources and distribution of sedimentary organic matter along the northern Bering Sea and Chukchi Sea of the Arctic Ocean. The lignin parameter syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ratios are used to indicate vegetation sources; and the ratios of vanillic acid/vanillin, (Ad/Al)v and syringic acid/syringaldehyde, (Ad/Al)s are used as indicators of lignin diagenesis. Results showed the predominance of woody gymnosperm signal at the easternmost location in the northern Bering Sea, a mixture of refractory non-woody angiosperm and fresher gymnosperm tissues in the Chukchi Sea, and signal of fresher woody gymnosperm tissues in the northernmost locations in the Chukchi Sea. The lignin materials showed gradual increase in decomposition stage during transport along the northern Bering Sea. Hydrodynamic sorting process, which is the retention of coarser materials nearshore and transportation of finer particles farther offshore, most probably occurred along the east coast of the northern Bering Sea. In Chukchi Sea, the non-woody angiosperm tissues could have originated from the Canadian Arctic and gymnosperm tissues could be from the Russian Arctic side. The fresher materials in the northernmost Chukchi Sea could have been transported here via the ice-rafting process. Detection of fresh lignin materials and the occurrence of lignin decomposition mean that this region could be sensitive to the impact of climate change.

Distribution and sources of organic matter in sediments of the south-eastern Baltic Sea

Temporal and spatial distribution of sedimentary organic matter (SOM) as well as its sources in the south-eastern Baltic Sea were investigated. Organic matter was characterized by the organic carbon content, δ13C and δ15N signatures and C/N ratios. The sampling was performed in the coastal, offshore areas and in the Curonian Lagoon in the period from May 2012 to September 2014. The average elemental (C/N~6.4) and isotopic composition (δ13C from −29.6‰ to −24.9‰) of SOM suggested that during most of the year it was composed of both freshwater and marine phytoplanktonic material. Elevated δ15N values (average ranging from 5.6‰ to 6.7‰) were detected in SOM from the Curonian Lagoon. This most likely reflected the increased isotopic signal of the Nemunas River (δ15N~8‰) derived from the anthropogenic input in the basin area. At the Baltic Sea offshore sites, SOM had lower δ15N values (δ15N~3.5‰ on average), indicating phytoplankton blooms.A two-end member mixing model based on the carbon stable isotopic composition showed that a large proportion (~90%) of SOM in the northern part of the Curonian Lagoon was of the freshwater origin. The allochthonous organic matter accounted for about 47% of SOM in the studied Baltic Sea area with the highest contribution (about 75%) within the Curonian Lagoon plume zone in the coastal waters.

The Distribution of Sedimentary Organic Matter and Implication of Its Transfer from Changjiang Estuary to Hangzhou Bay, China

In this study, a comparison was made between the Changjiang Estuary and the Hanghzou Bay, in terms of the sources and diagenesis of the sedimentary organic matter (OM). To achieve this purpose, surface sediments from the estuary and bay were analyzed for lignin-derived phenols, stable carbon isotope and TOC/TN (total organic carbon/total nitrogen) molar ratio. The signal of land-derived OM decreased, and the vanillic acid to vanillin ratio, (Ad/Al)v, increased with increasing distance from the Changjiang Estuary and the Hangzhou Bay. These results corresponded with the contribution of the terrigenous OM from the rivers to the coastal zone, and the predominance of marine OM farther offshore, and that the land-derived OM underwent decomposition during transport along the estuary and bay. It should be noted that besides the Qiantang River, Hangzhou Bay is also receiving more than half of its materials from Changjiang Estuary, which flows into the Hangzhou Bay at the north, and leaves via the southern part of the bay. This important aspect of the hydrological cycle in Hangzhou Bay corresponded to higher Λ (total lignin in mg/100 mg OC), higher TOC and C/N ratios and more elevated (Ad/Al)v and (Ad/Al)s values in the bay than the Changjiang Estuary, thus, rendering the bay as a site for the accumulation and rapid cycling of terrigenous OM.

Distribution and nature of sedimentary organic matter in a tropical estuary: An indicator of human intervention on environment

Sediment texture controls the spatial distribution of sedimentary organic matter (SOM) in the Vembanad Lake. Influences of marine derived organic matter (OM) on SOM decreased inner-wards in the northern part of the lake. However, SOM from the southern part of the lake was dominated by terrestrial OM. Marine-derived OM showed the highest affinity for the clay-sized fraction (<2μm) of the sediment in the northern part of the lake. However, aged and humified soil-derived OM was predominant in the clay-sized fractions from the southern part. Alteration of sediment texture led to a change in the distribution pattern of SOM in the lake after bund construction. Human intervention and changes in land-use pattern were also found to influence the SOM content in the southern part of the lake.

Seasonal variations in the source of sea bottom organic matter off Catalonia coasts (western Mediterranean): links with hydrography and biological response

Analyses of the total organic carbon (TOC), total nitrogen (TN), C/N ratio and isotopic (δ 13C and δ 15N) composition of organic matter (OM) in surficial sediments, integrated with hydrographic measurements, have been used to evaluate the sources and distribution of sedimentary organic matter on the Catalonian shelf and slope (northwest Mediterranean Sea). We examined the effects of the variations on meiofauna. Settled OM in February, April and October displayed δ 13C relatively closer to marine algae (mean −22.4 ‰ ± 0.1) than that in July (−23.3, −23.7 and −22.7 ‰ at 60, 600 and 800 m, respectively). Lowest δ 13C (−23.7 ‰) and high C/N (~10), indicative of mixed continental and marine organic contributions, were detected principally at the head of the Buscarro Canyon (at 600 m) in July, ca. 2–3 months after the maximum river discharge. We observed significant changes in total meiofaunal density among seasons in the canyon, with the highest values in July and October. On the adjacent slope at 800 m there was no significant increase of total meiofauna in those months. Although export of marine organic matter from surface layers was the main food source in the study area (on average 71.2 % estimating marine and terrestrial OC by binary models; 68–71 % at the most by SIAR models), advection of organic matter from the continental edge and/or resuspension of organic matter along submarine canyons may seasonally alter the composition of deposits on the slope, particularly in July with % OC of terrestrial origin reaching 48.7 % in Buscarro canyon, shifting the basal food-web of deep ecosystems.