Total Particulate Organic Matter Research Articles

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long‐Term No‐Till Production

: Soil quality indicators and nematode abundance were characterized in a loessial soil under long‐term conservation tillage to evaluate the effects of no‐till, double‐disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no‐till system amounted to 10887 kg over the 24 years or 454 kg ha−1 year−1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha−1 year−1) was due to SOM sequestration with no till. No‐till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics.

Fácies orgânica: conceitos, métodos e estudos de casos na indústria do petróleo

The concept of organic facies, as well as the definitions and means of the different facies became a very important tool to petroleum exploration. The application of this concept is the best way to integrate microscopy and geochemical techniques to study kerogen contained in sedimentary rocks. Thus, palynofacies analysis and bulk geochemical methods are used to characterize the total particulate organic matter. Palynofacies analysis involves the integrated study of all aspects of the kerogen assemblage: identification of the individual particulate components, assessment of their absolute and relative proportions and preservation states. The correlation between palynofacies and geochemical data provides the organic facies models that point out the depositional environmental conditions and hydrocarbon source rock potential.

Fácies orgânica: conceitos, métodos e estudos de casos na indústria do petróleo

The concept of organic facies, as well as the definitions and means of the different facies became a very important tool to petroleum exploration. The application of this concept is the best way to integrate microscopy and geochemical techniques to study kerogen contained in sedimentary rocks. Thus, palynofacies analysis and bulk geochemical methods are used to characterize the total particulate organic matter. Palynofacies analysis involves the integrated study of all aspects of the kerogen assemblage: identification of the individual particulate components, assessment of their absolute and relative proportions and preservation states. The correlation between palynofacies and geochemical data provides the organic facies models that point out the depositional environmental conditions and hydrocarbon source rock potential.

On the treatment of particulate organic matter sinking in large-scale models of marine biogeochemical cycles

Abstract. Various functions have been suggested and applied to represent the sedimentation and remineralisation of particulate organic matter (POM) in numerical ocean models. Here we investigate some representations commonly used in large-scale biogeochemical models: a constant sinking speed, a sinking speed increasing with depth, a spectrum of particles with different size and different size-dependent sinking velocities, and a model that assumes a power law particle size distribution everywhere in the water column. The analysis is carried out for an idealised one-dimensional water column, under stationary boundary conditions for surface POM. It focuses on the intrinsic assumptions of the respective sedimentation function and their effect on POM mass, mass flux, and remineralisation profiles. A constant and uniform sinking speed does not appear appropriate for simulations exceeding a few decades, as the sedimentation profile is not consistent with observed profiles. A spectrum of size classes, together with size-dependent sinking and constant remineralisation, causes the sinking speed of total POM to increase with depth. This increase is not strictly linear with depth. Its particular form will further depend on the size distribution of the POM ensemble at the surface. Assuming a power law particle size spectrum at the surface, this model results in unimodal size distributions in the ocean interior. For the size-dependent sinking model, we present an analytic integral over depth and size that can explain regional variations of remineralisation length scales in response to regional patterns in trophodynamic state.

Evaluation of sustainability of mixed food crop fields by monitoring particulate organic matter (POM) status and nutrient concentrations

Particulate organic matter (POM) status is a useful indicator to assess labile soil organic matter (SOM) and to evaluate soil fertility under different agricultural systems, mainly in low-input agriculture as practiced in most of the sub-Saharan region of Africa. Total POM (53–4000 µm), different sized POM fraction characteristics (mass, C and N contents), and nutrient concentrations of soils were evaluated under 2 mixed food crop field types: a preceding forest fallow (forest) and a preceding fallow dominated by Chromolaena odorata (King & Robinson) (Chromolaena spp.) in the 0–0.10 m horizon of Rhodic Kandiudult, Typic Kandiudult, and Typic Kandiudox soils. The mass and C and N contents of total POM were higher in the Typic Kandiudox than in the Typic Kandiudult, while the Rhodic Kandiudult was intermediate. The pH was lower in the Typic Kandiudox (4.67). Forest had higher pH, Ca2+ and Mg2+ concentrations, and effective cation exchange capacity, while Chromolaena had higher C content in medium (2000–250 µm) and fine (250–53 µm) POM fractions and higher N content in coarse POM (4000–2000 µm). Considering nutrient concentrations, forest appears to be more suitable for a mixed-crop field-crop system than Chromolaena; however, the opposite was found when considering POM status.

Evaluation of the performance of HPLC–CHEMTAX analysis for determining phytoplankton biomass and composition in a turbid estuary (Schelde, Belgium)

In the upper Schelde estuary in 2002, phytoplankton biomass and community composition were studied using microscopic and pigment analyses. Chlorophyll a concentration was a good predictor of phytoplankton biomass estimated from cell counts and biovolume measurements. The phytoplankton carbon to chlorophyll a ratio, however, was often unrealistically low (<10). CHEMTAX was used to estimate the contribution of the major algal groups to total chlorophyll a. The dominant algal groups were diatoms and chlorophytes. While diatom equivalents in chlorophyll a predicted diatom biomass relatively well, chlorophyte equivalents in chlorophyll a were only weakly related to chlorophyte biomass. The pigment-based approach to study phytoplankton overestimated phytoplankton biomass in general and chlorophyte biomass in particular in late autumn and winter, when phytoplankton biomass was low. A possible explanation for this overestimation may be the presence of large amounts of vascular plant detritus in the upper Schelde estuary. Residual chlorophyll a, chlorophyll b and lutein in this detritus may result in an overestimation of total phytoplankton and chlorophyte biomass when the contribution of phytoplankton to total particulate organic matter is low.

Edaphic Controls on Soil Organic Carbon Retention in the Brazilian Cerrado: Soil Structure

Soil structure can be an important factor affecting soil organic carbon (SOC), but it is also a dynamic property affected by texture, mineralogy, land use, soil fauna, and also SOC. Assuming that structure affects SOC mostly by occlusion of particulate organic matter (POM) within aggregates, it was hypothesized that structure exerts a major control on SOC retention in soils of the Brazilian Cerrado region. Water‐stable aggregates (WSA) were obtained from the 1‐m depth of three different‐textured, uncultivated soils. The mean weight diameter (MWD) of WSA was used as a structural indicator, and SOC concentrations were determined in intact WSA and their respective sand fractions (estimating occluded POM). Clay + silt content in bulk soils was correlated with MWD in all depths but more strongly in the top 10 cm. Although equally correlated with clay + silt contents, SOC concentrations were well correlated with MWD only in the 0‐ to 5‐cm layer. Sand‐free SOC concentrations in WSA fractions were proportional to sand content, indicating that the SOC dilution effect reported in particle size fractionations occurs naturally in the soil fabric. Occlusion of POM within aggregates was proportional to clay + silt contents, but this did not result in larger total POM pools, and the weak correlations obtained did not warrant predictive models. Aggregates produced by macrofauna comprised a minor but significant part of the soil and were mostly SOC enriched. We concluded that the structural control on SOC retention is less significant than the textural and mineralogical controls, since aggregation depends on those properties and is not as strongly correlated with SOC concentration and POM occlusion.

Assessment of changes in soil organic matter after invasion by exotic plant species

Invasive exotic plants can modify soil organic matter (SOM) dynamics and other soil properties. We evaluated changes in particulate organic matter (POM) and carbon (C) mineralisation in adjacent plots invaded by Solidago gigantea, Prunus serotina, Heracleum mantegazzianum and Fallopia japonica, and non-invaded control plots on different soils in Belgium. Litter decomposition of S. gigantea and P. serotina was compared to that of the native species Epilobium hirsutum, Betula pendula and Fagus sylvatica. Disregarding the differences in site characteristics (soil texture, parental material and plant species), we argued that the invasion by S. gigantea and P. serotina enhance SOM dynamics by increasing C mineralisation in 2 out of 3 sites invaded by S. gigantea and in 1 out of 3 sites invaded by P. serotina; C in coarse POM (cPOM, 4,000–250 μm) and fine POM (fPOM, 250–50 μm) in 1 site invaded by S. gigantea and C content in total POM (tPOM, 4,000–50 μm) and the organo-mineral fraction (OMF, 0–50 μm) in 1 site invaded by P. serotina. H. mantegazzianum and F. japonica slowed down SOM dynamics by reducing C mineralisation in three out of four sites; C and nitrogen (N) of fPOM in the invaded compared with the non-invaded plots at one site invaded by H. mantegazzianum. However, N content of cPOM (4,000–250 μm) was higher in the invaded sites by F. japonica compared with the non-invaded plots. Our results indicated that the effects of invasion by exotic plant species were not species-specific but site-specific.

Chemical Compositions of Fine Particulate Organic Matter Emitted from Chinese Cooking

Food cooking can be a significant source of atmospheric particulate organic matter. In this study, the chemical composition of particulate organic matter (POM) in PM2.5 emitted from four different Chinese cooking styles were examined by gas chromotography-mass spectrometry (GC-MS). The identified species are consistent in the emissions from different Chinese cooking styles and the quantified compounds account for 5-10% of total POM in PM2.5. The dominant homologue is fatty acids, constituting 73-85% of the quantified compounds. The pattern of n-alkanes and the presence of beta-sitosterol and levoglucosan indicate that vegetables are consumed during Chinese cooking operations. Furthermore, the emissions of different compounds are impacted significantly by the cooking ingredients. The candidates of organic tracers used to describe and distinguish emissions from Chinese cooking in Guangzhou are tetradecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid, levoglucosan, mannosan, galactosan, nonanal, and lactones. During the sampling period, the relative contribution of Chinese cooking to the mass concentration of atmospheric hexadecanoic acid should be less than 1.3% in Guangzhou.

Picoplankton removal by the coral reef community of La PrÈvoyante, Mayotte Island

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 44:59-70 (2006) - doi:10.3354/ame044059 Picoplankton removal by the coral reef community of La Prévoyante, Mayotte Island F. Houlbréque1,4,*, B. Delesalle2, J. Blanchot3, Y. Montel3, C. Ferrier-Pagés1 1Centre Scientifique de Monaco, Av. Saint Martin, 98000, Monaco2Laboratoire des Ecosystèmes aquatiques tropicaux et méditerranéens, Ecole Pratique des Hautes Etudes, UMR CNRS 8046, Université de Perpignan, 52, Av. Paul Alduy, 66860 Perpignan Cedex, France3Centre IRD de la Réunion Jean Blanchot IRD La Réunion BP 172, 97492 Sainte-Clotilde Cedex La Réunion, France4Present address: Geological & Environmental Sciences, Stanford University, 450 Serra Mall, Bldg 320, Room 118, Stanford,California 94305-2115, USA *Email: fannyh1@stanford.edu ABSTRACT: We examined the trophic contribution of pico- and nanoplankton to a patch reef dominated by scleractinian corals and located at Mayotte Island (Comoro Archipelago). Pico- and nanoplankton concentrations, as well as total particulate organic matter, were measured on a sandy-bottom and a patch reef transect. Results showed that particles <10 µm accounted for 74% of the chlorophyll a concentration and for 47% of the total living carbon. Synechococcus sp. represented 65% of the chlorophyll <3 µm and 53 and 67% of the autotrophic carbon and nitrogen, respectively, followed by picoeukaryotes, nanoeukaryotes and Prochlorococcus sp. Concentrations of total chlorophyll a, as well as picoplankton groups, were depleted 30 to 45% above the reef compared to in the adjacent waters and in sandy-bottom samples. Concentrations of nanoflagellates and total particulate organic matter, by contrast, remained unchanged during their passage across the reef. These results suggest selective grazing of picoplankton by the benthic community and compound the importance of picoplankton for the benthic-pelagic coupling and trophic dynamics on coral reefs. KEY WORDS: Picoplankton · Nanoplankton · Benthos · Coral reef communities · Particle removal Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 44, No. 1. Online publication date: August 16, 2006 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2006 Inter-Research.

The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones: What way for energy transfer?

Estuarine ecosystems are characterized by high zooplanktonic biomasses, essentially constituted by copepods and mysids whose nutritional requirements are mainly provided by phytoplankton, an easily available carbon form. The Gironde estuary is characterized by high turbidities which limit light penetration in the water column and therefore primary production. Consequently, primary production is low and its availability for higher trophic level is very limited. The main goal of this study was to characterize the total vegetal particulate organic matter (POM) in high turbidity zones of the Gironde estuary during summer (a critical period characterized by high heterotrophic bacterial degradation and high zooplanktonic biomasses) and to analyse its utilization by zooplankton, using prey/predator experiments and trophic biomarkers (fatty acids). The specific goals were to define (i) how vegetal POM was exploited by the different zooplanktonic groups (protozoa, copepods and mysids) and (ii) which alternative preys could be used when vegetal POM was not sufficient to ensure their nutritional requirements. Chlorophyll biomass was very low in the MTZ during summer 2002 (0.48 ± 0.03 mg m − 3 ). Total zooplankton grazing was low (19% d − 1 ) probably due to a large contribution of detritus originating from terrestrial plants in vegetal POM compared to phytoplankton. The highest grazing pressure was exercised by the mysid Mesopodopsis slabberi due to its high abundances and by its almost entirely herbivorous diet (phytoplankton and small terrestrial detritus). Grazing rates (19.7 ± 4.2 and 9.6 μgC cop − 1 d − 1 for juveniles and adults, respectively) seemed to be sufficient to satisfy their daily carbon requirement. Grazing rate of the copepod Eurytemora affinis (139 ngC cop − 1 d − 1 ) seemed to be insufficient to cover its nutritional requirements and the copepods probably needed to complete a great part of their diet from protozoa. Grazing rates of the mysid Neomysis integer (24.7 ± 0.01 and 20.89 ± 8.45 μgC cop − 1 d − 1 for juveniles and adults, respectively) were higher than those of M. slabberi when feeding only on phytoplankton. However, when other preys were introduced in its environment, N. integer only fed on the copepod E. affinis with a preference for nauplii. The study revealed the great importance of protozoa and bacteria in the trophic transfers between vegetal POM and zooplankton in the MTZ during summer, despite the low protozoa grazing pressure on vegetal POM (3.1%). The detritic food chain probably implies various trophic transfers with little direct relationships between vegetal POM and zooplankton.

Short-term variation in behavior of allochthonous particulate organic matter accompanying changes of river discharge in Ise Bay, Japan

The composition and behavior of allochthonous particulate organic matter (POM) in the northern part of Ise Bay, Japan were investigated to elucidate the short-term variation in POM accompanying changes in river discharge. The behavior of POM was significantly regulated by hydrographic conditions, but behavior was different in the upper layer versus the middle and lower layers. The former showed simple dynamics controlled by the river plume, while the latter showed complex dynamics because of changes in river discharge and subsequent variation in estuarine circulation. During normal discharge, the contribution of riverine materials to POC in the surface water within the bay was negligible because most riverine organic matter is deposited before flowing into the bay. During high discharge, on the other hand, the contribution of riverine organic matter to total POM increased to 50% at ∼10 km from the river mouth. Though riverine organic matter loads increased, the total amount of POC decreased around the river mouth due to flushing of phytoplankton. After river discharge, the contribution decreased rapidly. The behavior of POM in the middle and lower layers differed from that in the surface layer. At normal discharge, the influence of riverine organic matter was weak. During high discharge, high flooding temporarily weakened the bottom inflow, resulting in heavier riverine organic matter distributed from the river mouth to mid regions within the bay in the lower layer. The maximum contribution of riverine organic matter to total POM was estimated to be ∼60% around 25 km from the river mouth. After high discharge, riverine POM in the lower layer was pushed to the bay head by enhanced estuarine circulation and was uplifted to the middle layer. The behavior of riverine POM dynamically changed in relation to river discharge, and exerted a significant influence on bottom water conditions in the bay.

Composition of torched crude oil organic particulate emitted by refinery and its similarity to atmospheric aerosol in the surrounding area

The absolute contents and relative distributions of organic aerosols [ n-alkanes, n-alkanoic and n-alkenoic acids, n-alkan-2-ones and polycyclic aromatic hydrocarbons (PAH)] were determined in torched gases emitted during the crude oil extraction and in the free atmosphere of the Hassi-Messaoud city (Algeria). Monocarboxylic acids, both saturated and monounsaturated (from 9802 to 20 057 ng m −3), accounted for the major fraction of the total particulate organic matter identified both in torch exhaust and atmospheric particulate. n-Alkanes were also abundant both in the direct emission (from 460 to 632 ng m −3) and city atmosphere (462 ng m −3) and displayed a peculiar fingerprint characterised by the presence of a set of branched congeners around even carbon-numbered homologues and a strong even-to-odd predominance along the whole carbon number range (C 16–C 34). Whilst n-alkan-2-ones were absent in the city and poor in smokes emitted from the torches (from 31 to 42 ng m −3), PAH were present at low extents in all sites (from 18 to 65 ng m −3). The incomplete thermal combustion of torched crude oil was very likely the main source of these particle-bound organic constituents in the city and its surrounding region.

Major chemical components of PM2.5 in Milan (Italy)

PM2.5 speciation for the major chemical components has been performed on 109 daily samples collected by a high-volume gravimetric automatic sequential sampler. The 24-h sampling campaigns have been performed at an urban background (UB) site and at a tunnel site in the city of Milan. PM2.5-loaded filters are analysed for the main ionic components (chloride, nitrate, sulphate, ammonium) and the carbon species, elemental carbon (EC) and organic carbon (OC). The species analysed identify on average about 90% of the total mass sampled in the UB site and about 80% of the total mass sampled in the tunnel site. For the latter site a more complete characterisation, accounting for elemental composition, is performed: mass closure that also includes crustal fraction and metal oxides results in a slight overestimation (5%) of the total PM2.5 mass. Based on elemental composition data, the role of the potential sources of crustal and anthropogenic components is identified by the enrichment factor technique. The values obtained for the speciation are typical of urban areas and point out a strong contribution of the secondary source and a small contribution from the emissions of stationary sources in winter. A 0.9 value for the ratio between organic compounds and elemental carbon in PM2.5 samples collected at the tunnel site is observed. Applying the OC/EC ratio approach, this value, representative of the real traffic emissions for the circulating vehicle fleet in Milan, is used for the determination of primary organic aerosols due to traffic in ambient PM2.5. The primary contribution of the traffic source, in terms of carbonaceous matter (EC and primary organic aerosols), is estimated in 6% and 11% of the total PM2.5 mass, respectively, in the cold and warm season. The same OC/EC ratio approach also allows for the evaluation of secondary organic aerosols (SOA) presence in warm season PM2.5 samples: SOA is about 85% of total particulate organic matter and 30% of the total PM2.5 mass. Results obtained for the primary contribution of traffic and for SOA contribution to PM2.5 concentration levels confirm that traffic restriction interventions are not effective to provide relevant short-term air quality improvement. The need to control the emission of the precursors of PM2.5 secondary components is pointed out.

Comparative study of soil properties under Chromolaena odorata, Pueraria phaseoloides and Calliandra calothyrsus

Fallows improve soil fertility and allow sustainable agriculture. Soil fertility was assessed under different types of fallow through pH, nutrient concentrations and particulate organic matter (POM) quantity and quality. The two year-fallows were under Chromolaena odorata, Calliandra calothyrsus and Pueraria phaseoloides on a Typic Kandiudult. Soils were sampled from 0–10 cm and 10–20 cm depth. The weight of POM was 2 mg g−1 of soil under Calliandra, 3.9 mg g−1 under Chromolaena and 3.7 mg g−1 under Pueraria in the 0–10 cm layer. The tPOM-C (proportion of C in the total POM) and tPOM-N (proportion of N in total POM) were 26.1% and 14.5% under Calliandra, 39.6% and 18.8% under Chromolaena and 37.0% and 16.7% under Pueraria. However, despite the improvement of soil fertility under Pueraria as compared to planted Calliandra, the effect of Pueraria on nutrient concentration and POM status remained similar to that of Chromolaena. Calliandra increased soil acidity and allowed a deterioration of nutrient concentration (Ca, K), ECEC and an impoverishment of POM status.

Primary consumers and particulate organic matter: Isotopic evidence of strongselectivity in the estuarine transition zone

The freshwater−saltwater transition zones of upper estuaries often contain high concentrations of particulate organic matter (POM) that could potentially support their productive food webs. Our objectives were to define the carbon and nitrogen isotopic characteristics of POM across the estuarine transition zone (ETZ) of the St. Lawrence River, Canada, and to determine the availability of this material to primary consumers. The δ13C of seston from upstream freshwater samples (−26.3 ± 0.9‰) indicated a large contribution of terrestrially derived organic material, whereas downstream sites had higher values (−24.8 ± 0.5‰) attributable to dilution with marine phytoplankton. The ETZ turbidity maximum had more negative values (−27.0 ± 1.6‰), especially the &lt;5−mm fraction (−30.0 ± 1.3‰) that contributed 56−86% of the POM. The δ13C of the dominant consumer species in the ETZ (Bosmina longirostris, Keratella sp., Eurytemora affinis, and adult Dreissena polymorpha) averaged −21.0 ± 0.9‰, well above the seston values. The δ15N of the three animals of lowest trophic position averaged 7.3 ± 0.8‰, less than 2‰ above the seston δ15N (5.7 ± 0.2‰ for all sites). Our results imply that the bulk POM is largely detrital and unavailable to the ETZ food web and that the primary consumers feed selectively on phytoplankton despite its low contribution (&lt;10%) to total POM. A cross−system comparison of isotopic data shows that the large enrichment of 13C in consumers relative to POM is unusual, underscoring the distinctive character of turbid, upper estuarine ecosystems.

Dynamics of Particulate Organic Matter following biomass addition from fallow-improvement species in southern Mali

Knowledge about the nature and turnover rates of soil organic matter (SOM) is a key to soil fertility maintenance, especially in traditional farming systems. Particulate organic matter (POM), rather than total SOM content, is now considered a better measure of the soil's fertility. Fractionation of SOM, based on particle-size distribution after dispersion, was carried out on soil samples collected from a field experiment at N'Tarla, Mali (12.25° N latitude, 5.42° W longitude, Typic Plinthustalf). Biomass of off-site grown Gliricidia sepium (Jacq.) Walp. (gliricidia), Pterocarpus erinaceus Poir.(pterocarpus), and Stylosanthes hamata (L.) Taub.(stylosanthes) was applied to a maize (Zea mays L.) crop for two consecutive years. A significant decrease was noted in the soil's POM and POM-N contents after harvest of maize in both years as compared with the initial value measured at the beginning of the experiment. Small POM fraction (0.053 to 0.250 mm, POM53) contributed more to total POM than large POM fraction (0.250 to 2.000 mm, POM250). The POM N content was better correlated with maize grain yield than POM total weight, and the N content of POM53 was better related to maize grain yield (R2 = 0.55) than that of POM250 (R2 = 0.20). Total SOM was poorly correlated with maize grain yield (R2 = 0.14). The results indicate that the quality of the applied biomass is of greater value than its quantity in sustaining maize grain yield, and POM53 might be a better indicator of soil fertility status than POM250 and total POM.

Depth variation in terrestrial particulate organic matter exploitation by marine coastal benthic communities off the Rhone River delta (NW Mediterranean)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 275:47-57 (2004) - doi:10.3354/meps275047 Depth variation in terrestrial particulate organic matter exploitation by marine coastal benthic communities off the Rhone River delta (NW Mediterranean) Audrey M. Darnaude1,2,*, Chantal Salen-Picard1, Mireille L. Harmelin-Vivien1 1Centre d¹Océanologie de Marseille, CNRS UMR 6540, Université de la Méditerranée, Station Marine d¹Endoume, 13007 Marseille, France 2Present address: The Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK *Email: a.darnaude@cefas.co.uk ABSTRACT: Carbon and nitrogen stable isotopes were used to study depth variation in terrestrial particulate organic matter (POM) sedimentation off the mouth of the Rhone River delta, and its use by the main benthic invertebrates (polychaetes, crustaceans, molluscs and echinoderms) and flatfishes (Arnoglossus laterna, Buglossidium luteum and Solea solea). Coastal water POM and surface sediment exhibited low δ13C values, denoting dominance of terrestrial material in their carbon pools (25 to 80% and >50%, respectively), but the importance of river input differed as a function of depth. Terrestrial organic matter contribution to the total POM was greatest at 30-50 m (72 to 99%), and least at 70-100 m depth (25 to 77%). Most of the invertebrate groups studied (δ13C = -24.5 to -17.5‰ δ15N = 4.3 to 9.7 ‰) mainly relied on marine primary production irrespective of depth. However, deposit-feeding polychaetes mainly exploited terrestrial POM, and carnivorous and suspension-feeding polychaetes, bivalves, brachyurans and shrimps (Caridea) showed a partial uptake of terrestrial POM, depending on its availability. Incorporation of terrestrial POM by flatfishes (δ13C = -22.4 to -16.8 ‰ δ15N = 9.7 to 11.2 ‰) was species- and depth-dependent. It was related not only to the fishes¹ diets but also to the trophic adaptability of their prey. S. solea, the main consumer of deposit-feeding polychaetes, showed the lowest δ13C irrespective of depth, but flatfish exploitation of terrestrial POM peaked at 30-50 m, where both polychaete consumption by fishes and terrestrial POM use by the benthos were maximal. Unlike most estuarine systems, terrestrial inputs in deltaic areas can therefore peak at intermediate depths, where some of the marine macrobenthos, including flatfishes, efficiently exploit them. These results allow better assessment of the role of river input to marine coastal zones in increasing fish abundance, and will therefore be of major interest for demersal fisheries management off deltaic areas. KEY WORDS: River inputs · Coastal ecosystems · Macrobenthos · Flatfishes · Stable isotopes Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 275. Online publication date: July 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivity

SUMMARY 1. The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13‐month period.2. Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water.3. The mean C : N ratio and δ13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; −33‰) to the main channel (8.4; −25‰). At the dynamic floodplain site, the C : N ratio and the δ13C signature of the POM increased with hydrological connectivity (expressed as water age).4. Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (&gt;80% of the total POM pool) and a δ13C signature of POM of more than −25‰ in the dynamic floodplain.5. Plankton derived carbon, indicated by C : N ratios less than eight and δ13C values lower than −25‰, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages.6. At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non‐refractory POM compared with prerestoration conditions.

Effects of light and nutrients on the net accumulation and elemental composition of epilithon in boreal lakes

1. Two experiments in the Experimental Lakes Area (ELA) in north‐western Ontario, Canada examined the effects of light and two key elements on the net accumulation and elemental composition of epilithon. In Lake (L) 224, benthic algae were grown under different light intensity and phosphorus supply, while in L302S we provided three levels of two different carbon sources (bicarbonate and glucose) to algae colonizing nutrient‐diffusing substrata. After 1 month of accumulation, we sampled biofilms for chlorophyll (chl), carbon (C), phosphorus (P) and algal C.2. Increased C supply did not significantly affect algal growth (C or chl) or elemental composition (C/P ratios) in L302S. However, P enrichment increased chl and algal C, dramatically reduced the C/P ratio of epilithon, and did not affect total organic C in L224. Phosphorus enrichment also increased the proportion of algal material in the total particulate organic matter and altered the taxonomic composition of algae in L224 biofilms. Shading had no significant effect on the C/P ratio and total organic C in epilithon from the L224 experiment.3. Our results demonstrate that P supply affects the elemental composition of organic matter that collects on rock substrata. It thus appears that low availability of P relative to C and light drives the formation and retention of high C/P organic matter on rock surfaces in oligotrophic boreal lakes.