Anthropogenic Supply Research Articles

Nutrient dynamics in small west-flowing tropical mountainous rivers of India

In this study, the distribution of dissolved inorganic nitrate (DIN), phosphorus (DIP), and silicate (DSi) in surface waters of 70 coastal rivers in India's Western Ghats (WG) has been determined. The nutrient concentrations in individual rivers appear to be influenced by catchment geology, land use, and climate. The entire WG region contributes 0.31 Tg of DIN, 0.03 Tg of DIP, and 5.65 Tg of DSi annually to the coastal Arabian Sea. The annual ratios of N:P, Si:N, and Si:P suggest that most of these rivers are limited by P rather than N, and there is an excess supply of Si, primarily from natural sources. P limitation is severe during monsoon periods, while N limitation is observed in the Deccan Traps region. The annual export of 0.31 Tg of DIN from WG rivers could support 2.05 Tg of carbon (new production) on the Arabian Sea coast, indicating that the riverine export of DIN can significantly remove atmospheric CO2 through biological pumps in the Arabian Sea. The study also confirms that the excess input of Si from natural processes relative to the anthropogenic supply of limited P and N further supports the idea that riverine nutrient inputs from small west-flowing tropical mountainous rivers do not contribute to coastal eutrophication along the Eastern Arabian Sea coast.

Anthropogenic supply of nutrients in a wildlife reserve may compromise conservation success

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mineral lick provision to wildlife nutrient intake across a community of mammalian herbivores (>10 kg) in the southern Kalahari Desert. Based on predicted daily nutrient intake and a faecal nutrient assessment, many large herbivore species appear deficient in phosphorus (P), sodium (Na), or zinc (Zn). For these nutrients, anthropogenic salt and mineral licks constitute an important source of nutrient intake helping to reduce or overcome requirement deficits. Larger-bodied species disproportionately consumed licks, acquiring more nutritional benefits. A comprehensive assessment of animal body condition indicated that, in general, large herbivores display good health. However, bulk grazers, non-ruminants and females displayed poorer body condition. We discuss how provisioning of anthropogenic mineral licks may inflate large herbivore populations beyond the long-term carrying capacity of the reserve by decoupling wildlife fecundity from nutrient-related feedbacks on population growth. Over time, this could compromise ecosystem integrity through habitat degradation, modified species interactions and trophic cascades. Based on results presented here, it is clear that anthropogenic provisioning of mineral licks should be considered cautiously by wildlife managers aiming to conserve natural processes in landscapes.

The lower shoreface of the Dutch coast – An overview

The lower shoreface, defined here as between about 8 and 20 m water depth, forms the transition between the inner shelf and upper shoreface. Knowledge of lower shoreface hydro- and morphodynamics is essential for coastal management and maintenance.The shoreface of the Dutch coast is a complex area. It is partly determined by its evolution in the past, whereas present-day processes are influencing or even changing it. The present situation and large-scale anthropogenic supply of sediment will determine its future development.The shoreface morphology varies along the Dutch coast, depending on the coastal slope and superposition of ridges (central Holland coast) and ebb-tidal deltas (Delta area, Wadden Sea). The architecture of the shoreface-connected ridges off the central Holland coast indicates that they are still active today. The development of most ebb-tidal deltas along the Dutch coast is largely influenced by interventions in the tidal inlets and tidal basins.The Kustgenese 2.0 Lower Shoreface project comprised both field data collection in 2017 and 2018 and numerical modelling. Field data was collected in study areas at Ameland Inlet, Terschelling and Noordwijk. Sediment cores and multibeam sonar surveys provided information on the Holocene deposits, geomorphology and sediments. Instrumented frames placed at the seabed collected a wealth of process data.The variation in shoreface composition and morphology is larger than anticipated previously. In general, the lower part of the shoreface consists of older Holocene deposits overlain by an active sand layer that responds to variations in tidal, wave and wind conditions. The deposits at the lower shoreface of Terschelling were comparable to the ebb-delta channel deposits at the ebb-delta front at Ameland Inlet. At Noordwijk, deposits of the Late-Holocene prograded barrier shoreface overlie those of back-barrier tidal channels and river channels. The large-scale morphology of the lower shoreface seems rather stable. Decadal time series show an erosional trend. Small-scale bedforms can change over an interval of days to weeks.The multibeam surveys revealed unexpected details such as geology-based shoreface irregularities between −12m and −18m that probably act as conduits for downslope currents and sand transport. After a high-energy wave event, more erosional features were discovered that suggest seaward sand transport.Measured orbital velocities at the seabed at 14–16 m depth reached 1.5 m per second under high-wave events. This caused high sediment mobility under sheet-flow conditions with abundant sediment suspension. It is not clear what this means for the net sand transport at the lower shoreface.The modelled alongshore-directed sand transport is much larger than the cross-shore transport. The largest transports at the 20m depth contour occurs along the northern part of the Holland coast. Here, transport is parallel to the coast or directed to deeper water. Transports at 20 m depth along the other parts of the coast are directed to shallower water.The modelled total landward sand transport over the −20m contour is c. 4 million m3 per year and c. 7 million m3 per year over the −16m contour. This suggests a yearly erosion of c. 4 million m3 in-between, in case of no alongshore transport gradients.The results of the sand transport calculations imply a net landward sediment transfer that needs to be further tested against the morphological changes in the shoreface.

Evaluation of new rice genotypes of Kuban breeding in conditions of environmental testing in the Republic of Adygea

In solving the problems of modern rice growing associated with yield increase, resource/energy efficiency and profitability, development of new varieties and their timely introduction into production as a result of close cooperation of scientists and production workers is central. In this regard, the assortment of rice varieties of Kuban breeding is annually replenished with more productive ones having increased resistance to adverse biotic, abiotic and anthropogenic factors, technologization and energy supply during cultivation, and different cooking characteristics. Crop productivity is one of the main value indicators and the main requirement of production. It consists of number of plants per unit area and productivity of each of them. Therefore, in order to evaluate rice varieties and determine their suitability for cultivation in this agroclimatic zone, it is necessary to consider important agronomic traits and their variability during a certain time. The article presents the results of environmental testing of 20 rice varieties over three years (2016-2018). The variability of yield and number of productive stems per unit area in varieties was determined. The average and weak inter-varietal variability of productive plant stand (13.9; 10.3 and 13.5%) and yield (12.4; 9.2 and 9.9%) during the research period determines the optimal level of agricultural farming. The varieties that have formed a significantly high yield with its insignificant variability are recommended for cultivation in conditions of the Republic of Adygea.

Nutritive value and herbage mass in hybrids of Paspalum plicatulum × Paspalum guenoarum fertilized with nitrogen or in mixture with temperate legumes

AbstractRecent efforts placed on breeding Paspalum species made available novel genetic resources for livestock production systems. Nitrogen (N) is an important factor to increase warm‐season grass nutritive value and production, either as anthropogenic supply or in mixture with legumes. Dry matter yield (DMY) and nutritive value in Paspalum plicatulum Michx. × Paspalum guenoarum Arechav. hybrids in response to different rates of N or in mixture with temperate legumes were evaluated for two years. The experiment was a randomized complete block design in split‐plot arrangement with three replications. Treatments were six N supply systems: 0, 60, 120, 240, 480 kg N/ha and grass–legume mixture [white clover (Trifolium repens L.) + birdsfoot trefoil (Lotus corniculatus L.)] as whole plots, and six genotypes (hybrids: 1020133, 102069, 103084, 103061, P. guenoarum ecotype ‘Azulão’ and Megathyrsus maximus cv. ‘Aruana’ used as controls) as subplots. Higher N rates increased DMY and provided variability among genotypes. In general, grass–legume mixture showed greater crude protein and digestibility, and lower neutral and acid detergent fiber than N fertilized grass (p < .05). Hybrid 1020133 had DMY similar to Aruana and Azulão in years 1 and 2. Hybrids 103084 and 103061 exhibited higher nutritive value than Aruana and Azulão in year 1 (p < .05), and similarly in year 2. These three hybrids were identified as potential releases. Supplying N by fertilization or mixture with legumes increased DMY and improved nutritive value in Paspalum pastures.

Testing the Effect of Snag and Cavity Supply on Deadwood-Associated Species in a Managed Boreal Forest

Standing deadwood is an important attribute of old-growth boreal forests and it provides essential microhabitats for deadwood-associated species. In managed boreal forests, short rotations tend to limit the amount and diversity of standing deadwood. This study evaluates if the anthropogenic supply of deadwood attributes through tree girdling or by providing nest boxes may favor deadwood-associated species. We studied the short-term response of saproxylic beetles, foraging woodpeckers, and secondary cavity users to snag and cavity supply in 50 to 70-year-old black spruce stands. In spring 2015, we girdled 8000 black spruce according to two spatial distributions (uniform and clustered), and we also installed 450 nest boxes of six different sizes at three distances from the forest edge. Using trunk window traps, we captured significantly more beetles in sites with girdled trees than in control sites in both 2015 and 2016. We also recorded a trend of a greater abundance of beetles in clusters of girdled trees than within uniformly distributed girdled trees. Trypodendron lineatum (Oliver) dominated beetle assemblages, representing 88.5% of all species in 2015 and 74.6% in 2016. The number of beetles captured was 7× higher in 2015 than in 2016. In contrast, we observed greater amounts of woodpecker foraging marks in fall 2016 than in either fall 2015 or spring 2016. Woodpeckers foraged significantly more in clusters of girdled trees than within uniformly distributed girdled trees. Woodpeckers’ foraging mark presence was positively associated with the proportion of recent cuts at 1 km around the study sites. Five Boreal Chickadee (Poecile hudsonicus Forster) pairs used nest boxes and occupied smaller box sizes that were located away from the forest edge. Our study showed that structural enrichment can be effective in rapidly attracting deadwood-associated species within managed forest stands.

Distribution and metal contamination in core sediments from the North Al-Wajh area, Red Sea, Saudi Arabia

Forty-one bottom sediment samples were collected from three cores at the mouth of Wadi Haramel, Wadi Antar, Wadi Dumaygh, north of Al-Wajh, Red Sea, Saudi Arabia, to evaluate the levels of heavy metal contamination, using the enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (Cf), soil pollution index (SPI), and multivariate statistical analysis (hierarchical cluster analysis and principal component analysis). Fe, Al, Pb, Mn, Cu, Ni, Co, Cd, Sr, V, Hg, and Total Organic Matter (TOM%) were quantified by Atomic Absorption Spectrophotometer. The vertical distribution of the heavy metals concentrations increased upwards indicating high heavy metals input. The results of enrichment factor and soil pollution index calculations indicate a strong anthropogenic supply of Cd and Sr (SPI = 1.10, 2.70, EF = 18.25, 17.99 respectively) while Cu and Ni show moderate anthropogenic input from urban, industrial activities and some new projects in the northern coast of Saudi Arabia.

Organic-inorganic interactions in an aridisoil of Oman along vertical and lateral trends of the soluble major, trace and rare-earth elements

Major, trace and rare-earth elements dissolved in successive water and acetic-acid leaching of soil samples were determined along a vertical and a lateral trend relative to a reference aridisoil covered by palm trees. The total content of the organic carbon ranges from 0.07 to 2.7% with the highest values in the topsoil closely below vegetation, confirming its higher organic activity. The water-removed elements decrease irregularly with depth and with increasing distance from vegetated area, the highest concentrations being observed at 20 cm depth and 18 m away from vegetation. The nutrients removed by acetic-acid decrease with depth and until 22 m from vegetation. Maximum leaching was observed in the surface sample and 32 m away from vegetation. In fact, no straight trends were obtained in both the vertical and horizontal samplings; it looks that the elemental contents of each soil layer are only representative for themselves. The metallic trace elements are more abundant in the topsoil than in the subsoil, suggesting some anthropogenic supply. Mainly controlled by solid organic exudates, the REEs are the only ones with general vertical and horizontal trends: they decrease at depth, together with an increase laterally away from vegetation. The Ce and Eu positive anomalies increase deeper below the vegetation and away: an oxidation-reduction change is visible for the former anomaly, probably due to decreasing organic activity. The latter anomaly away from vegetation could reflect a larger contribution of soluble minerals to the leachates.

Hydrocarbons of Surface Waters in the Transantarctic Section

The data obtained for 2015–2017 on the content and composition of aliphatic hydrocarbons (HCs) in particulate matter at the river–sea geochemical barriers (the Ob, Yenisei, Lena, Khatanga, Indigirka, and Kolyma rivers–the Kara, Laptev, and East Siberian seas) are presented. It was shown that the HC distribution coincided roughly with the content of particulate matter. The losses of the HC concentrations in mixing zones of riverine and marine waters in some cases exceeded 90% of the riverine supply. The HC concentrations in the pelagic zones of the seas were about the background values (2–7 µg/L). The behavior and composition of HCs are determined by the features of riverine drainage areas, sampling seasons, and time (high or low tide). The influence of anthropogenic supply was registered exclusively in the Gulf of Ob where the composition of alkanes was close to that of oil, with a HC concentration of 86 µg per mg of particulate matter. In other samples, natural HCs prevailed.

Short-Term Effects of Drying-Rewetting and Long-Term Effects of Nutrient Loading on Periphyton N:P Stoichiometry

Nitrogen (N) and phosphorus (P) concentrations and N:P ratios critically influence periphyton productivity and nutrient cycling in aquatic ecosystems. In coastal wetlands, variations in hydrology and water source (fresh or marine) influence nutrient availability, but short-term effects of drying and rewetting and long-term effects of nutrient exposure on periphyton nutrient retention are uncertain. An outdoor microcosm experiment simulated short-term exposure to variation in drying-rewetting frequency on periphyton mat nutrient retention. A 13-year dataset from freshwater marshes of the Florida Everglades was examined for the effect of long-term proximity to different N and P sources on mat-forming periphyton nutrient standing stocks and stoichiometry. Field sites were selected from one drainage with shorter hydroperiod and higher connectivity to freshwater anthropogenic nutrient supplies (Taylor Slough/Panhandle, TS/Ph) and another drainage with longer hydroperiod and higher connectivity to marine nutrient supplies (Shark River Slough, SRS). Total P, but not total N, increased in periphyton mats exposed to both low and high drying-rewetting frequency with respect to the control mats in our experimental microcosm. In SRS, N:P ratios slightly decreased downstream due to marine nutrient supplies, while TS/Ph increased. Mats exposed to short-term drying-rewetting had higher nutrient retention, similar to nutrient standing stocks from long-term field data. Periphyton mat microbial communities may undergo community shifts upon drying-rewetting and chronic exposure to nutrient loads. Additional work on microbial species composition may further explain how periphyton communities interact with drying-rewetting dynamics to influence nutrient cycling and retention in wetlands.

Organization and scaling in water supply networks.

Public water supply is one of the society's most vital resources and most costly infrastructures. Traditional concepts of these networks capture their engineering identity as isolated, deterministic hydraulic units, but overlook their physics identity as related entities in a probabilistic, geographic ensemble, characterized by size organization and property scaling. Although discoveries of allometric scaling in natural supply networks (organisms and rivers) raised the prospect for similar findings in anthropogenic supplies, so far such a finding has not been reported in public water or related civic resource supplies. Examining an empirical ensemble of large number and wide size range, we show that water supply networks possess self-organized size abundance and theory-explained allometric scaling in spatial, infrastructural, and resource- and emission-flow properties. These discoveries establish scaling physics for water supply networks and may lead to novel applications in resource- and jurisdiction-scale water governance.

Coordination environment of Zn in foraminifera Elphidium aculeatum and Quinqueloculina seminula shells from a polluted site

Foraminifera, unicellular organisms that are widespread throughout marine ecosystems, build Ca-carbonate shells that may incorporate trace metals present in the ocean waters because of natural or anthropogenic supply. In this study, we focussed on the trace element Zn, which is abundant in both contaminated and clean waters. We used X-ray and electron spectromicroscopy to investigate the Zn coordinative environment in individual shells of two species of benthic foraminifera, Elphidium aculeatum and Quinqueloculina seminula, that were sampled from a heavy-metal polluted area of Sardinia, Italy. These species synthesise the Ca‑carbonate in extracellular and intracellular spaces, respectively, which implies some diversity in their physiologies and cation transport processes, and they can adapt and survive in metal-polluted environments.Our analyses of X-ray micro-fluorescence (μ-XRF) maps and Zn-K μ-X-ray absorption near-edge spectroscopy (XANES) reveal that although 50% of Zn occurs as a Ca substitute in calcite or as a tetracoordinate oxygen-adsorbed ion, detectable amounts can also be found in other Zn-independent mineral phases, particularly hydrozincite, whose formation is due to foraminiferal cellular processes. Other Zn phases, sphalerite (attributed to early diagenetic process) and Zn-phosphate, were recognised. Moreover, we found distinct differences in the Zn concentration, distribution and chemical speciation at the micro- and nano-metric scales of the investigated E. aculeatum and Q. seminula species. In the calcite needles of Q. seminula, Zn is uniformly distributed and recognised in a disordered local environment, which suggests that it is incorporated in the calcite phase during the intracellular calcification process. These findings offer insight into Zn incorporation in foraminifera and its potential application in biomonitoring and environmental studies.

Spatial and temporal distribution of heavy metals in coastal core sediments from the Red Sea, Saudi Arabia

Summary Jeddah is the most industrialized city on the west coast of Saudi Arabia and is under increasing influence of human activities. Heavy metals data were obtained from four near-coast Red Sea sediment cores in close proximity to Jeddah. Chromium, manganese, iron, copper, zinc, and lead were analyzed from depth-resolved sections of each core via heavy acid digestion and inductively coupled plasma-mass spectrometry (ICP-MS). The average concentrations of all four sites were 245.96 mg kg −1 , 478.45 mg kg −1 , 8506.13 mg kg −1 , 251.82 mg kg −1 , 623.09 mg kg −1 , and 362.75 mg kg −1 , respectively. The depth-resolved results showed that highest concentrations of Mn, Cu, and Pb were found in the top 15 cm of the core profile distributions compared to other depth sub-samples. Heavy metal concentrations in core sediments are increased near central Jeddah and have become higher in recent years. The results of enrichment factor calculations indicate little anthropogenic supply of Mn and Cr while Pb, Zn, and Cu show strong anthropogenic input. The Pollution Load Index was higher in the two sites closer to central Jeddah where power and desalination plants and wastewater release are known. This indicates that the area has suffered from heavy metal pollution compared to other non-industrialized sites in the Red Sea. Heavy metal contaminations due to anthropogenic activity should be taken into account to protect the Red Sea during future growth. The results of this work should be considered as a baseline for heavy metals monitoring in the sediments of the Red Sea coast near Jeddah, Saudi Arabia.

Recovery Assessment of Two Nearby Sandy Beaches with Contrasting Anthropogenic and Sediment Supply Settings

ABSTRACT Senechal, N.; Pavon, J.; Asselot, R.; Castelle, B.; Taaouati, M.; Ferreira, S., and Bujan, S., 2016. Recovery assessment of two nearby sandy beaches with contrasting anthropogenic and sediment supply settings. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 462–466. Coconut Creek (Florida), ISSN 0749-0208. The aim of this study is to provide the preliminary results of the comparisons of two field sites exposed to the same environmental conditions but with contrasting beach management strategies. Truc Vert beach and Biscarrosse beach are both low sandy beaches situated on the 250km long linear French coast exposed to the Atlantic swells and are about 35km distant. While Truc Vert beach is a fully natural beach, Biscarrosse beach is in an urban area where several coastal defences have been deployed. Data indicate that Biscarrosse beach is l...

The production of ammonia by multiheme cytochromes C.

The global biogeochemical nitrogen cycle is essential for life on Earth. Many of the underlying biotic reactions are catalyzed by a multitude of prokaryotic and eukaryotic life forms whereas others are exclusively carried out by microorganisms. The last century has seen the rise of a dramatic imbalance in the global nitrogen cycle due to human behavior that was mainly caused by the invention of the Haber-Bosch process. Its main product, ammonia, is a chemically reactive and biotically favorable form of bound nitrogen. The anthropogenic supply of reduced nitrogen to the biosphere in the form of ammonia, for example during environmental fertilization, livestock farming, and industrial processes, is mandatory in feeding an increasing world population. In this chapter, environmental ammonia pollution is linked to the activity of microbial metalloenzymes involved in respiratory energy metabolism and bioenergetics. Ammonia-producing multiheme cytochromes c are discussed as paradigm enzymes.

Historical pattern and mass balance of trace metals in sediments of the northwestern Adriatic Sea Shelf

In view of the recent action in Marine Strategy Framework Directive, reconstructing the history of anthropogenic metal inputs and calculating the budgets for the northwestern part of the Italian Adriatic basin can provide a benchmark for comparison with new evidences and enlighten recent environmental changes. Among the metals, the attention was focused on Pb and Zn, as they provide the most significant anthropogenic signals. In 1988, areal distributions clearly identified the Po, Adige and Brenta rivers as the main sources of contaminants. The study area was divided in three compartments. The area in front of the Po delta represented a sink for metals but the accumulation of Zn and Pb integrated over the entire study area suggests an effective export throughout southern boundary. Most concentration-depth/year profiles in cores showed an upward increase from the Italian Unification (1861), with a still significant anthropogenic supply at the time of sampling.

Rhenium in Indian rivers: Sources, fluxes, and contribution to oceanic budget

The abundance and distribution of dissolved and particulate Rhenium (Re) has been measured in several rivers draining the Himalaya and Peninsular India, from their origin to outflow into the Bay of Bengal and the Arabian Sea. The large data set resulting from this study on rivers flowing through a variety of lithologies e.g., the crystallines and sediments of the Himalaya, Deccan basalts, Vindhyan sediments and the Indian shield significantly enhances our understanding of the aqueous geochemistry of Re and also constrains its sources to rivers and fluxes to the sea. The concentration of dissolved Re in rivers of the Himalaya and the Peninsular India shows wide range; 1.4 to 72.7 pmol/kg (mean 7.8 pmol/kg) and 0.5 to 122 pmol/kg (mean 15 pmol/kg) respectively. The discharge weighted average annual flux of dissolved Re transported by the rivers from these regions are ∼5800 and ∼15,700 mol/year respectively. The major source of dissolved Re, as determined from inter‐element associations, is black shales for the Himalayan rivers and pyrites in basalts for the east flowing Deccan rivers. In addition, there are evidences of considerable anthropogenic supply of Re to some of the rivers that have very high Re concentrations. Estimates of anthropogenic supply based on their Re/K ratios suggest that this source accounts for most of the Re in the Peninsular rivers, particularly the Godavari. The annual flux of anthropogenic Re transported by the Peninsular rivers is ∼14,600 mol, most of which is from the Godavari. This anthropogenic flux accounts for ∼70% of the total Re supply by the Indian rivers to the adjacent seas and 3.4% of the global riverine flux to the oceans. The global average, pre‐anthropogenic (natural) concentration of dissolved Re in rivers is estimated to be ∼3 pmol/kg based on Re−K correlation. This value is much lower than the contemporary average determined from the measured concentrations and earlier estimate of natural Re based on Re−SO4 link.

Rhenium in rivers and estuaries of India: Sources, transport and behaviour

The concentration of dissolved and particulate Re have been measured in the Narmada, Tapi and the Mandovi estuaries in the Arabian Sea and the Hooghly estuary in the Bay of Bengal. Re concentration in water and particulate matter of these estuaries is highly variable. Re in river waters analysed varies from 1 to 41 pmol/kg, the lowest in the Mandovi and the highest in the Mahi river. Re concentrations in the rivers analysed except in the Mandovi river are higher than the average global riverine Re concentration of 2.1 pmol/kg. Based on this study and the available data, the contemporary global annual flux of dissolved riverine Re is estimated to be ~ 350 × 10 3 mol with an average concentration of ~ 9.2 pmol/kg, much higher than the earlier estimates. Residence time of Re in the oceans based on this estimate is 175,000 years, ~ 4 times lower compared to earlier estimates. Re behaves conservatively in all the estuaries studied. Re concentrations of seawater in the Bay of Bengal and in the Arabian Sea, estimated from the data of the Hooghly and the Mandovi estuaries respectively are ~ 40 pmol/kg, similar to the open ocean Re values of the Arabian Sea measured in this study and the values reported for in other oceanic regions. However, the dissolved Re in the Gulf of Cambay is 2 to 5 times higher, consistent with the high Re measured in the Mahi estuary and in the coastal waters of the Gulf of Cambay. The source of high Re in the Gulf of Cambay seems to be anthropogenic, measurements of Re in rivers and industrial waste waters draining into the Gulf supply amount to ~ 2300 mol of Re annually. This anthropogenic supply coupled with high residence time of water in the Gulf contribute to its high Re. Re concentration in suspended sediments of the Narmada estuary varies from 1 to 2 pmol/g, and does not show any discernible trend with salinity. The contemporary global riverine Re supply to the oceans estimated in this study is ~ 2–4 times higher compared to its removal in the reducing (anoxic/suboxic) sediments, indicating non-steady state of Re in the ocean. High dissolved riverine Re flux coupled with high Re content in the Gulf of Cambay highlights the need of a detailed study of Re in the various global rivers and in oceans including coastal regions and semi enclosed basins of the world to understand its behaviour in various reservoirs and to constrain the residence time of Re in the ocean.

CO2 Supersaturation and Net Heterotrophy in a Tropical Estuary (Cochin, India): Influence of Anthropogenic Effect

Carbon biogeochemistry of a tropical ecosystem (The Cochin Estuary, India) undergoing increased human intervention was studied during February (premonsoon), April (early monsoon) and September (monsoon) 2005. The Cochin estuary sustains high levels of pCO2 (up to 6000 μatm) and CO2 effluxes (up to 274 mmolC m−2 d−1) especially during monsoon. A first-order estimate of the carbon mass balance shows that net production of dissolved inorganic carbon is an order of magnitude higher than the net loss of dissolved and particulate organic carbon from the estuary. This imbalance is attributed to the organic inputs to the estuary through anthropogenic supplies. The bacteria-mediated mineralization of organic matter is mainly responsible for the build-up of pCO2 and increased CO2 emission to the atmosphere indicating heterotrophy. The linear correlation between excess CO2 and apparent oxygen utilization indicates respiration as the chief mechanism for CO2 supersaturation. An increase in the net negative ecosystem production (–ve NEP) between premonsoon (−136 mmolC m−2 d−1 or −376 MgC d−1) and monsoon (−541 mmolC m−2 d−1 or −1500 MgC d−1) is supported by a corresponding increase in O2 influxes from 17 mmol O2 m−2 d−1 (126 MgC d−1) to −128 mmol O2 m−2 d−1 (−946 MgC d−1) and CO2 emissions from 65 mmolC m−2 d−1 (180 MgC d−1) to 267 mmolC m−2 d−1 (740 MgC d−1). There is a significant north-south gradient in metabolic rates and CO2 fluxes attributable to the varying flow patterns and anthropogenic inputs into the estuary. The study reveals that the Cochin estuary, a previously autotrophic (CO2 sink) system, has been transformed to a heterotrophic (CO2 source) system following rapid urbanization and industrialization. Moreover, the export fluxes from the Cochin estuary appear to be quite important in sustaining net heterotrophy in the southeastern Arabian Sea.

Soil degradation caused by a high-intensity rainfall event: Implications for medium-term soil sustainability in Burgundian vineyards

The purpose of this paper is to provide a sediment-flux quantification in a vineyard context (Vosne-Romanee, Burgundy, France) where medium-term soil budget and sustainability are controlled by complex interactions between natural processes (rill erosion) and anthropogenic processes (earth supply transferred back into the rills by the winegrowers). Concentrated overland flows during the rainfall event resulted in the incision of 13 major rills in the inter-rows, carrying a sediment volume of about 4.77 m3. Most of the rills were rectilinear and displayed a U shape with strong vertical walls. Rill incision began about 30 m from the upper plot boundary. In the buffer zone located at the lower border of the plot, seven fan systems developed from the material originating in one or two contributory rows. Accumulated volume is estimated at 1.6 m3. Data from grain-size distribution, and rill and fan volumes, show that erosion is dominated by rilling (70% of the sediment yield) over sheet process (30% of the sediment yield). The net exported soil loss, corresponding to the balance between natural soil loss and anthropogenic supply, ranges between 24±3 t ha−1 and 48 t ha−1, over the plot during one hydrologic event. Analyses of the grain-size distribution in the reference soil sample and in the fans reveal that size selectivity has occurred, with preferential export of the fine material ( 2 mm) in the fans. To evaluate the relative importance in grain-size distribution of natural processes (material loss) over anthropogenic processes (rill-filling by winegrowers), we simulated the temporal evolution of grain-size distribution in surface soil during five successive rainfall events. Our results clearly show that more than 30% of fine material in surface soil was lost in these few events, despite anthropogenic rill filling. This fine-fraction removal may have considerable impact on vineyard sustainability.