Influx Of Terrestrial Organic Matter Research Articles

Characterizing fluvial impact on the biochemical composition of particulate organic matter in the Laptev Sea and Western East Siberian Sea during the late summer of 2018

The Laptev Sea (LS) and Western East Siberian Sea (W-ESS) are paradigmatic examples of seas dominated by terrestrial organic matter, attributed to substantial Siberian River discharges and coastal erosion. The influx of terrestrial organic matter significantly alters the biochemical composition of particulate organic matter (POM) in these Arctic coastal regions, potentially reducing the nutritional quality available to higher trophic levels. This study investigated the origin and qualitative characteristics of POM in the LS and W-ESS during the late summer of 2018 by analyzing elemental ratios (C/N ratio), stable carbon isotopes (δ13C), and biochemical compositions (biomolecular and amino acid (AA) compositions). The conspicuously depleted δ13C values (mean ± standard deviation (SD) = −30.2 ± 0.5 ‰) and alongside elevated molar C/N ratios (mean ± SD = 18.1 ± 6.2) suggest that terrestrial organic matter is the predominant source of POM in the study area. Although carbohydrates (CHO) were the dominant biomolecules, their prevalence was higher in the river-influenced W-ESS region (67.7 ± 6.6 %) than in the LS region (58.6 ± 13.9 %; p < 0.05). Furthermore, the CHO composition was closely associated with freshwater content and river fraction, suggesting that the heightened contribution of CHO may stem from terrestrial organic matter delivered by river inputs. Lower concentrations of particulate hydrolyzable AA (PAA) and carbon and nitrogen normalized yields of AAs (AA-POC% and AA-PON%) along with reduced contribution of glycine suggested a substantial contribution of terrestrial POM to both LS and W-ESS POM. Overall, this study provides valuable insights into the terrestrial influence on POM composition in Arctic marine ecosystems, emphasizing the need for continued monitoring of the consequences of terrestrial carbon inputs in the changing Arctic environment.

Deciphering dissolved organic matter characteristics and its fate in a glacier-fed desert river—the Tarim river, China

The bioavailable diverse dissolved organic matter (DOM) present in glacial meltwater significantly contributes to downstream carbon cycling in mountainous regions. However, the comprehension of molecular-level characteristics of riverine DOM, from tributary to downstream and their fate in glacier-fed desert rivers remains limited. Herein, we employed spectroscopic and high-resolution mass spectrometry techniques to study both optical and molecular-level characteristics of DOM in the Tarim River catchment, northwest China. The results revealed that the DOC values in the downstream were higher than those in the tributaries, yet they remained comparable to those found in other glacier-fed streams worldwide. Five distinct components were identified using EEM-PARAFAC analysis in both tributary and downstream samples. The dominance of three protein-like components in tributary samples, contrasting with a higher presence of humic-like components in downstream samples, which implied that the dilution and alterations of the glacier DOM signature and overprinting with terrestrial-derived DOM. Molecular composition revealed that thousands of compounds with higher molecular weight and increased aromaticity were transformed, generated and introduced from terrestrial inputs during downstream transportation. The twofold rise in polycyclic aromatic and polyphenolic compounds observed downstream compared to tributaries indicated a greater influx of terrestrial organic matter introduced into the downstream during water transportation. The study suggests that the glacier-sourced DOM experienced minimal photodegradations, with limited influence from human activities, while also being shaped by terrestrial inputs during its transit in the alpine-arid region. This unique scenario offers valuable insights into comprehending the fate of DOM originating from glacial meltwater in arid mountainous regions.

Geochemical and depositional environment of an Upper Cretaceous greensand giant (Münsterland Cretaceous Basin, Germany)

Based on integrated geochemical, mineralogical and stratigraphic-sedimentological analyses of core section KB 4507/1001 Essen-Bedingrade from the Münsterland Cretaceous Basin (northern Germany), the geochemical and depositional environment of a Late Cretaceous greensand giant has been elucidated. The >100-m-thick Cretaceous succession comprises the Essen Greensand (Cenomanian), Büren (lower Turonian), Duisburg (middle Turonian to lower Coniacian) and Emscher formations (middle to upper Coniacian), essentially consisting of alternating greensand and marl lithofacies. X-ray diffraction analyses showed that the abundant green grains undoubtedly constitute glauconitic minerals with high-order, 1M-type layer stacking. The depositional environment can be characterized as a shallow-marine setting in which nearshore greensands interfingered with mid-shelf marls. Inorganic geochemical analyses normalized to Al and compared to average shale (AS) show that most element/Al (E/Al) ratios are higher than AS values, including the chemical index of alteration (CIX). This suggest that an intensely chemically weathered wet hinterland provided for a constant supply of essential elements required for nearshore glaucony authigenesis under variably reducing or oxidizing conditions and slightly increased palaeoproductivity. The leaching of paleosols and swamp-like coastal wetlands during transgressive phases related to eustatic early Late Cretaceous sea-level changes was an important source for trace metals and nutrients while the considerable influx of terrestrial organic matter suggests a significant input of K related to plant decay. In a nutshell, our new integrated data from the Münsterland Cretaceous Basin provide important novel insights into the formative processes of authigenic glauconitic minerals during warm-humid climate phases of Earth history.

Fossil‐Bearing Concretions of the Araripe Basin Accumulated During Oceanic Anoxic Event 1b

AbstractFossils from the Araripe Basin (northeastern Brazil) are known for their remarkable preservation of vertebrates and invertebrates, even including soft tissues. They occur in carbonate concretions within organic carbon‐rich strata assigned to the Romualdo Formation. Here we present integrated stable isotope, elemental and microfossil records from the Sítio Sobradinho outcrop, Araripe Basin, northeastern Brazil. Our results imply that black shales hosting fossil‐bearing carbonate concretions within the lower Romualdo Formation were deposited during Oceanic Anoxic Event (OAE) 1b (Kilian sub‐event). Our high‐resolution multi‐proxy approach allows identifying four phases of environmental evolution. After a pre‐event phase, an early phase (onset of the negative carbon isotope excursion—nCIE) of water column stratification and reduced oxygenation likely preconditioned the system for organic carbon burial and preservation. A second phase (peak nCIE) was characterized by an intensified hydrological cycle and continental runoff, as well as increased influx of terrestrial organic matter. High input of continent‐derived nutrients might have enhanced biological productivity in the epicontinental sea, ultimately leading to increased organic carbon fluxes and burial, as well as carbonate dissolution at the seafloor. All together, these paleoenvironmental conditions resulted in expansion of an oxygen minimum zone (OMZ), favoring taphonomic processes that led to the excellent preservation of diverse macro‐ and microfossils. The nCIE recovery phase was characterized by reduced nutrient supply and organic carbon burial. Organic carbon sequestration in such paleoenvironments likely contributed to the recovery (increase) of stable carbon isotope (δ13C) records in the deep ocean during the Kilian sub‐event of OAE 1b.

Large Sea Surface Temperature, Salinity, and Productivity‐Preservation Changes Preceding the Onset of the Messinian Salinity Crisis in the Eastern Mediterranean Sea

AbstractThe Messinian Salinity Crisis (MSC; 5.97–5.33 Ma) is an enigmatic episode of paleoceanographic change, when kilometer‐thick evaporite units were deposited in the Mediterranean basin. Here we use geochemical (biomarker and isotope) data to reconstruct sea surface temperature, salinity, and productivity‐preservation changes in the Mediterranean basin just before the MSC. The proxy data indicate that the Mediterranean Sea was significantly saltier and colder between 6.415 and 6.151 Ma, than between 6.151 and 5.971 Ma. Salinity decrease at 6.151 Ma seems to be a relatively fast event just preceding the inception of a warming phase that lasted almost uninterrupted until the MSC onset. The water exchange with the Paratethys could have caused, along with the African rivers, an increased freshwater supply, resulting in normal marine Mediterranean waters between 6.151 and 5.971 Ma, despite the severe restriction of marine connections with the Atlantic at that time. Sea surface temperature changes determined a sharp drop in productivity and/or preservation of organic matter, marked by deposition of calcareous marls. Productivity and preservation were relatively high and constant until 6.01 Ma. Afterward, increased influx of terrestrial organic matter and probably enhanced water column stratification prevailed. Around 5.971 Ma, modifications in aquatic versus terrestrially derived biomarkers indicate changes in organic matter influx at the MSC onset.

Is the Kornati National Park Still an Acceptable Reference Area for Environmental Studies?

The Kornati National Park (Croatia) is considered an environment with minimal anthropogenic input. The purpose of this study was to determine the isotopic characteristics of the sediment and muscle tissues of the banded dye-murex Hexaplex trunculus. We selected locations in the park according to their estimated risk of anthropogenic pollution (large, lower, and minimal). Isotopic analyses of the sedimentary organic carbon (δ13Corg values) showed that the sedimentary organic matter in locations with P. oceanica meadows (Piškera, Vrulje) was enriched in 13C compared to that of locations with the influx of terrestrial organic matter. The δ13C and δ15N values of the muscle tissues of H. trunuclus were the highest in the two locations with the highest possible anthropogenic impact (−14.47‰ and −15.66‰ for δ13Corg, +8.87‰ and +10.4‰ for δ15N). The high δ values may indicate the presence of the pigment indirubin (C16H10O2N2) and other derivatives that cause the purple coloration but are also elevated because of the discharge of untreated sewage from a nearby marina and village.

A spike of woody plant biomarkers in the deep-sea iridium layer at the Cretaceous/Paleogene boundary

At the Cretaceous/Paleogene (K/Pg) boundary, 66millionyears ago, the Chixulub impact resulted in significant environmental changes and a mass extinction of dinosaurs and marine invertebrates such as ammonites. Here, we report that accumulation of woody plant biomarkers in the deep water occurred in the iridium anomaly at ~700km from the impact crater. The results reveal that the concentration of terrestrial organic molecules derived from woody plants, namely biphenyl and dibenzofuran, shows synchronized changes and increases abruptly in the red layer (fine ejecta), which has an iridium spike, above tsunami-like coarse deposits indicating a significant increase in the influx of woody plant fragments into the ocean a few years after the impact. Long-chain n-alkanes and cadalene derived from land vegetation in the tsunami-like coarse deposits prior to the transportation of trees were also transported to the deep sea. This implies that transportation of grass to the deep sea started within a few days of the bolide impact. Transportation of trees then began a few years later. A rapid increase in the concentration of dibenzothiophenes also occurs in the red layer, indicating that low-dissolved-oxygen conditions had expanded in the bathypelagic zone over the seafloor. An increase in the influx of terrestrial organic matter into the deep ocean could have resulted in the low-dissolved-oxygen conditions. Furthermore, the stratigraphic distribution of planktonic foraminifera at Beloc shows that Cretaceous planktonic foraminifera became extinct as the result of an asteroid impact.

Living, dead and fossil benthic foraminifera on a river dominated shelf (northern Gulf of Cadiz) and their use for paleoenvironmental reconstruction

Same-area comparison between patterns of Recent (living) and Holocene benthic foraminiferal assemblage composition is essential to validate their utility as proxies for paleoenvironmental reconstructions. Such reconstructions have scarcely been attempted in shelf environments. In this study, we compared living (stained), dead and Holocene benthic foraminiferal assemblages from the Gulf of Cadiz continental shelf off the Guadiana River. On average, 99% of the living benthic foraminiferal species were preserved in the dead assemblage and 95% in the fossil record. Several common species were assessed as indicators for certain environmental factors, including river discharge, supply of terrestrial organic matter, heavy metal concentrations, oxygen levels, substrate properties, hydrodynamic energy levels, sea-level rise and human impact. The paleoenvironmental reconstruction depicted five stages of Holocene environmental evolution of the Guadiana shelf over the last 11,500calyr BP. The characteristics of the stages, and the transitions between them, were in particular driven by changes in sea-level, influx of terrestrial organic matter and limits of productivity.

Untangling the influence of in-lake productivity and terrestrial organic matter flux on 4,250 years of mercury accumulation in Lake Hambre, Southern Chile

There is ongoing debate about the relative influence of aquatic production, flux, and sedimentation of aquatic and terrestrial organic matter on mercury accumulation in lake sediments. In this study, lake sediments spanning the past 4,250 years, were collected from remote, organic-rich Lake Hambre, Patagonia (53° S) and investigated for changes in the accumulation of pre-anthropogenic mercury and organic matter of aquatic and terrestrial origin. Natural mercury accumulation varied by up to a factor of four, comparable to the recent anthropogenic forcing of the mercury cycle (factor 3–5). Hydrogen and Oxygen indices (HI and OI, Rock–Eval©) and nitrogen/carbon ratios of the organic matter, combined with multi-element sediment data, reveal intense changes in aquatic productivity as well as influx of terrestrial organic matter into the lake. Evaluation of the multi-element dataset using Principal Component Analysis shows clear covariation of mercury with other soil-derived elements such as copper and yttrium. This covariance reflects a common transport mechanism, i.e. leaching of trace-element-bearing organic matter complexes from catchment soils. Correlation between changes in aquatic productivity and mercury concentrations occurs in some sections of the record, but we do not suggest they are linked by a direct causal relationship. Mass balance approaches suggest that mercury scavenging and accumulation in this organic-rich lake is controlled by the supply of mercury from catchment soils rather than the amount of organic material produced within the water column. A common controlling mechanism, i.e. changing climate, however, is thought to independently drive variations in both the flux of terrestrial organic matter mercury complexes and aquatic productivity.

Significant changes in land vegetation and oceanic redox across the Cretaceous/Paleogene boundary

The impact of an extraterrestrial body 65.5Ma caused the so-called Cretaceous/Paleogene (K/Pg) event that resulted in a mass extinction and rapid changes in the surface environment on Earth. Here we report changes in land vegetation and oceanic redox across the K/Pg boundary at Caravaca, southeastern Spain, using biomarkers. The results reveal that the basal 3-mm-thick layer of the K/Pg boundary clay is marked by a rapid increase in the concentration of terrestrial long-chain n-alkanes and dibenzofuran, indicating the destruction of land vegetation and an increase in the supply of terrestrial organic matter into the marine environment during the deposition of the K/Pg boundary clay. This layer also records a rapid increase in the concentration of dibenzothiophenes, which indicates a change in redox conditions from oxic to anoxic/euxinic conditions in the intermediate water over the seafloor. The low-oxygen conditions could have been caused by an increase in the influx of terrestrial organic matter into the ocean. A rapid increase in the concentration of retene and retene/cadalene occurred during the deposition of the upper part of the boundary clay 10kyr after the mass extinction, indicating the recovery of conifers, which greatly decreased at the K/Pg boundary.

Non-linear Holocene climate evolution in the North Atlantic: a high-resolution, multi-proxy record of glacier activity and environmental change from Hvítárvatn, central Iceland

Iceland is well situated to monitor North Atlantic Holocene climate variability. Terrestrial sites there offer the potential for well-dated, high-resolution, continuous records of environmental change and/or glacier activity. Laminated sediments from the proglacial lake Hvítárvatn provide a continuous record of environmental change and the development of the adjacent Langjökull ice cap for the past 10.2 ka. Replicate lake sediment cores, collected from multiple locations in the basin, are placed in a secure geochronology by splicing a varve chronology for the past 3 ka with a tephra-constrained, paleomagnetic secular variation derived chronology for older sediments. Multiple proxies, including sedimentation rate, bulk density, ice-rafted debris, sediment organic matter, biogenic silica, and diatom abundance, allow annual to multi-decadal resolution and reveal a dynamic Holocene terrestrial climate. Following regional deglaciation of the main Iceland Ice Sheet, summer temperatures were high enough that mountain ice caps had already melted, or were contributing insignificant sediment to the lake. Pronounced increases in sedimentation rate, sediment density, and the influx of terrestrial organic matter, between 8.7 and 7.9 ka suggest early Holocene warmth was interrupted by two distinct pulses of cold summers leading to widespread landscape destabilization and possibly glacier growth. The Holocene thermal maximum (HTM; 7.9 to 5.5 ka) was characterized by high within-lake productivity and ice-free conditions in the watershed. Neoglaciation is recorded as a non-linear transition toward cooler summers, landscape destabilization, and the inception and expansion of Langjökull beginning ca 5.5 ka, with notable increases in ice cap size and landscape instability at 4.2 and 3.0 ka. The past two millennia are characterized by the abrupt onset of sustained cold periods at ca 550 and 1250 AD, separated by an interval of relative warmth from ca 950 to 1150 AD. The greatest Holocene extent of Langjökull occurred in the nineteenth century and is coincident with peak landscape instability, followed by ice recession throughout the twentieth century.

Winter regulation of tundra litter carbon and nitrogen dynamics

Mass and nitrogen (N) dynamics of leaf litter measured in Alaskan tussock tundra differed greatly from measurements of these processes made in temperate ecosystems. Nearly all litter mass and N loss occurred during the winter when soils were mostly frozen. Litter lost mass during the first summer, but during the subsequent two summers when biological activity was presumably higher than it is during winter, litter mass remained constant and litter immobilized N. By contrast, litter lost significant mass and N over both winters of measurement. Mass loss and N dynamics were unaffected by microsite variation in soil temperature and moisture. Whether wintertime mass and N loss resulted from biological activity during winter or from physical processes (e.g., fragmentation or leaching) associated with freeze-thaw is unknown, but has implications for how future climate warming will alter carbon (C) and N cycling in tundra. We hypothesize that spring runoff over permafrost as soils melt results in significant losses of C and N from litter, consistent with the observed influx of terrestrial organic matter to tundra lakes and streams after snow melt and the strong N limitation of terrestrial primary production.

Distribution and geochemical characteristics of metal enrichment in the New Albany Shale (Devonian-Mississippian), Indiana

Black shale beds in the uppermost part of the Clegg Creek Member of the New Albany Shale (Devonian-Mississippian) in southern Indiana have organic C contents from approximately 12 to 25 wt percent and are enriched in Cu, Pb, Zn, Ni, Cd, Mo, and V. Brownish-black to olive-black shale located lower in the formation has normal metal contents and organic C abundances up to 12 wt percent. Shale units lower in the section were deposited under anaerobic conditions, but C-S-Fe relationships and sulfur isotope values suggest that the H 2 S-O 2 boundary occurred near or at the sediment-water interface. Conversely, the carbon- and metal-rich beds near the top of the formation were deposited under strongly euxinic conditions with the chemocline located within the water column. Metal sulfide formation was limited by the availability of metals. A sharp increase in slope at 12 to 14 wt percent C organic is observed in organic C-metal plots and is related to organic carbon preservation and metal adsorption due to the presence of an H 2 S-bearing water column.Sequential chemical analyses and electron microprobe studies indicate that Zn, Cu, and Cd are held in sulfide minerals, Pb as a selenide, Mo both as a sulfide ( approximately 56-85%) and within kerogen (20%), Ni within kerogen (50%) and as a sulfide (45%), and V primarily within clay minerals. Petrographic studies also indicate that the beds in the upper part of the Clegg Creek Member are characterized by the highest proportion of inertinite and vitrinite found in the New Albany Shale.A conceptual model is developed whereby trace metals adsorbed on surfaces of organic material were preserved from release by oxidative degradation in the water column due to the high elevation of the H 2 S-O 2 boundary. Transition metal contents of the Clegg Creek Member may have been locally high due to an increase in the influx of terrestrial organic matter. Once delivered to the sea floor, metals took part in diagenetic reactions that produced metal sulfides and vanadiferous clays. Only Mo and Ni remained significantly enriched in kerogen. Although Ni and V contents are high in the soluble organic material from the shale, their abundance constitutes less than 1 percent each of the whole-rock metal content.

Upwelling in Cretaceous Western Interior Seaway: Sharon Springs Member, Pierre Shale: ABSTRACT

Upwelling zones are characterized by the following features: (1) facies distribution, which is related to oxygenation of bottom waters, of laminated, organic-rich sediment, phosphate, and glauconite; (2) abundant organic-rich fecal pellets; (3) abundant marine biota at all trophic levels; (4) high organic carbon accumulation rates, with predominance of marine organic matter; and (5) a distribution of the anoxic facies that is not controlled by bathymetry. By contrast, stratified stagnant basins characteristically (1) lack significant phosphate; (2) show little or no evidence of high biologic productivity; (3) have high organic carbon accumulation rates with significant influx of terrestrial organic matter; and (4) have an anoxic facies that is confined to the deepest part of the basin. The Sharon Springs Member of the Pierre Shale, usually described as a stagnant-basin deposit, shares more features in common with upwelling zones than with stratified stagnant basins. Specifically, the overall facies distribution of the Sharon Springs includes a basinward zone of laminated, highly organic-rich strata bounded on the west by phosphate, which is, in turn, bounded at the western shoreline by glauconitic sandstone. The same facies distribution might be expected on the eastern shoreline, but the Sharon Springs is truncated there by erosion. The organicmore » matter in the Sharon springs is almost entirely contained in fecal pellets and is predominantly marine in origin, organic carbon accumulation rates are comparable to those of upwelling zones. Finally, the Sharon Springs is noted for high concentrations of bones of marine reptiles. These bones occur in a band that may mark the zone of highest biologic productivity.« less

Role of climate in affecting late Jurassic and early Cretaceous sedimentation in the North Atlantic

Summary Both regional and temporal changes in the influx of terrestrial organic matter, siliciclastic sediments and kaolinite are related to climate over the continents adjacent to the opening North Atlantic, reflecting a change from humid to arid and back to humid in North America and Europe, and more persistent aridity in Africa. Small-scale sedimentary cycles of laminated organic-rich and non-laminated organic-poor claystones have previously been interpreted in terms either of periodic influx of detrital plant material, or variations in sedimentation rate. They are here interpreted as the result of periodic stirring of bottom waters related possibly to Milankovich cycles.