amino acid and amino sugar transformation during sedimentation in lacustrine systems abstract we compared the degradation behaviour of amino sugars ass and amino acids aas during sedimentation in two lakes concentrations of individual ass and aas were measured in plankton sediment trap and sediment samples from lake zug lz eutrophic stratified permanently anoxic below 170 m and lake brienz lb oligotrophic oxic throughout the water column in the plankton samples aas comprised 37 50 of the organic carbon c org and 41 65 of the n with increasing water depth the fraction of c org and n as aas almost halved in both lakes at the sediment surface the contribution of aas to the c org pool was slightly greater but in the sediments the proportion further decreased downwards to values of 1 of the c org pool in lb and 8 in lz and 3 and 17 of the n pool respectively ass contributed to a smaller extent to the planktonic organic matter om within the water column the contribution decreased in both lakes in contrast in the sediments the contribution of ass to the c org and n pools increased slightly with depth indicating as accumulation we applied degradation indices based on ass aas and chlorins which all revealed transformation with om sedimentation however some indices were more sensitive to early degradation e g reactivity index and others to an intermediate level of degradation e g chlorin index and non protein aas despite the different trophic status and redox conditions the general pattern of degradation was similar in both lakes but was more pronounced in the sediments of the eutrophic lz

sedimentology and c isotope geochemistry of the sturtian cap carbonate south australia abstract a combined sedimentary and isotopic analysis of the sturtian aged tindelpina cap carbonate in south australia has revealed a strong relationship between sedimentary facies and 13 c carb depositional water depths for the cap carbonate are difficult to constrain however a lack of diagnostic shallow water structures and the inferred magnitude of post glacial transgression several 100 m indicates a relatively deep water environment for each key facies the shallowest facies peloidal dolomite has 13 c values ranging between 3 6 and 0 3 in comparison to deeper water laminated limestones which have lighter values ranging between 5 5 and 3 5 equivalent calcareous shales deposited at basinal depths show even more 13 c depletion with values ranging between 6 7 and 3 7 the average difference in 13 c between the shallowest and deepest cap facies is up to 3 6 and may be an approximation of the seawater 13 c depth gradient at the time of deposition we interpret this high 13 c depth gradient as the result of prolonged physical ocean stratification both during and after deglaciation variations in the rates of upwelling mixing under this stratified regime may have significantly influenced the climate as well as controlling the precipitation and isotopic composition of the cap carbonate

neutral carbohydrate geochemistry of particulate material in the central equatorial pacific abstract neutral carbohydrate compositions were determined for particulate samples from plankton net tows shallow floating sediment traps mid depth and deep moored sediment traps and sediment cores collected along a north south transect in the central equatorial pacific ocean during the u s jgofs eqpac program total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon oc fluxes attenuating with depth high near the equator and decreasing poleward oc normalized total aldose tch 2 o yields along the transect and with depth do not show any consitent patterns relative to a planktonic source neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose and preferential preservation of structural carbohydrates rich in rhamnose xylose fucose and mannose there is also evidence for an intermediately labile component rich in galactose it appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway relative to other types of organic matter neutral carbohydrates are better preserved in calcareous oozes from 12 s to 5 n than in red clays at 9 n based on oc normalized tch 2 o yields due to either differing sources or sorption characteristics weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial pacific region based on weight per cent glucose comparisons of samples between survey i el nion and survey ii non el nino indicate that during survey i organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere

the turbidity maximum zone of the yenisei river siberia and its impact on organic and inorganic proxies a general overview of the processes taking place in the summer mixing zone of the fresh yenisei river water with the marine waters of the kara sea is given in this study with special emphasis on the interaction between bulk total suspended matter inorganic fe mn and organic suspended organic carbon suspended nitrogen proxies within the mixing zone a zone of enhanced turbidity maximum turbidity zone was observed comparable to studies in other rivers flocculation of particles due to changes in salinity and hydrography cause this maximum turbidity zone and resuspension additionally enhances the turbidity in the near bottom layers organic matter behaves conservatively in the mixing zone in terms of its percentage of suspended matter it however undergoes degradation as revealed by amino acid data inorganic redox and salinity sensitive proxies mn fe behave non conservatively dissolved iron is removed at low salinities 2 due to precipitation of iron oxyhydroxides and adsorption of manganese on suspended particles enhancing the mn al ratio of the suspended matter in the same zone at higher salinities within the mixing zone fe al and mn al ratios of the suspended particles are depleted due to resuspension of sediment with lower fe al and mn al ratios dissolved manganese concentrations are significantly higher in the near bottom layers of the mixing zone due to release from the anoxic sediment all things considered the yenisei river mixing zone shows patterns similar to other world s rivers

hydraulic control of a highly stratified estuarine front abstract observations at the mouth of the fraser river british columbia canada indicate an abrupt frontal transition between unstratified river outflow and a highly stratified river plume with differences in salinity greater than 25 psu across a few meters in the vertical direction and several hundred meters in the horizontal direction the front roughly follows a natural break in the bathymetry crossing the channel at an angle of approximately 45 and is essentially stationary for a period of approximately 3 5 h centered on the low tide following the larger of two daily ebbs the location of the front is coincident with observations of significantly supercritical internal froude numbers at the front based on velocities in the along flow direction this observation contradicts the one dimensional theory which indicates that the froude number should be 1 however because the front is oriented obliquely to the outflow a coordinate system can be selected that is normal to the front and for which a c

early diagenesis in differing depositional environments the response of transition metals in pore water the cycling of fe mn ni co cu cr v and mo during early diagenesis was investigated in sediments from five different depositional environments in the california borderland dissolved o2 no3 no2 and so4 were also measured at each site to establish the position of redox boundaries pertinent to this study sites were chosen to allow the comparison of several parameters of potential importance to the cycling of these metals bottom water o2 concentration sediment redox conditions cycling of metal oxide carrier phases and the relative contribution of biogenic and terrigenous material to the detrital metal flux at 10 m oxygen and above the sequence of terminal electron acceptor utilization was typical of pelagic sediments differing only in scale under these conditions the recycling of mn oxides resulted in an enriched layer near the interface at bottom water 02 concentrations 5 m mn oxides are not recycled under these conditions fe oxides and so42 are important oxidants the depth of the zone of manganese oxidation with respect to the interface affects the efficiency of metal scavenging by manganese oxides trapping and recycling of ni and co with mn oxides results in remobilization from reducing sediments and enrichment in oxic sediments scavenging of these metals is favored by a deep oxic zone in the sediments in contrast cr v and mo appear to be transported to the sediments as reduced species and are released from the sediments by oxidation the source of the reduced species is assumed to be biogenic material the accumulation of these metals is favored by reducing conditions in the sediments cu is enriched in the sediments by transport with detrital biogenic material followed by adsorption onto sediment solids cu is released at the interface and rapidly removed onto the solids at all sites except the one pelagic site at the base of the slope the magnitude of cu released in the slowly accumulating pelagic sediment exceeds the cu binding capacity of the solids resulting in pore water cu concentrations in excess of 100 nm in general metal cycling associated with the early diagenesis of sediments was observed to decouple transport processes from burial processes for the transition metals measured in this study

simulating the formation and fate of dense water in a midlatitude marginal sea during normal and warm winter conditions 1 dense shelf water production and the deep convection process in the adriatic sea are investigated considering two case studies the first is representative of the present climatic situation whereas the second may be expected in a scenario characterized by mild winter conditions over the basin dense water production and spreading are studied using a high resolution implementation of the massachusetts institute of technology general circulation model that is initialized and forced with realistic conditions this paper provides qualitative and quantitative information on mass transport dense water pathways thermohaline structures and the mixing properties of the basin in the northern adriatic shelf seawater temperature is the key element for winter dense water production because it contributes more relevantly than salinity in determining density in the southern adriatic sea a small amount of dense water that cascades directly into the pit can be formed on the narrow western shelf only during cold winter conditions moreover open ocean deepwater formation occurs in the middle of the southern basin in late winter and spring although only when winter conditions have been sufficiently cold northern adriatic dense shelf water forms a subsurface stream of which the densest part rapidly sinks in the southern pit along the shelf break whereas its lighter part flows southward and reaches the otranto strait the frequent occurrence of mild winter conditions could lead to lower dense water production with a reduced dense water flow from the adriatic sea to the ionian sea and a potential great impact on the eastern mediterranean thermohaline circulation

topographic control of wind driven circulation in the northern adriatic 1 two synoptic wind driven situations of the circulation in the northern adriatic were studied using the princeton ocean model over the northern adriatic sea napom in both situations the basin was driven by a relatively steady wind 8 m s along and across the basin over three days in the first situation 28 30 october 2008 the sse southern jugo or scirocco wind blew along the basin and in the second 19 21 march 2009 the ene bora wind blew across the basin cyclonic turn was present in the first situation while the cyclonic branch of a known double gyre circulation north of the strip of wind minima was evident in the second we show that during the jugo the model does not confirm quantitatively the simple topographic control of a wind driven circulation suitable for elongated basins while qualitatively the model meets expectations with downwind transport in shallow areas close to shorelines and upwind transport in places with greater depths during the bora wind however the wind driven circulation in the gulf of trieste is well explained by this topographic control 82 of the flux through the transect

hydrolysable amino acids in sediments from the porcupine abyssal plain northeast atlantic ocean abstract the distributions of hydrolysable amino acids have been examined in replicate sediment cores from the porcupine abyssal plain in the northeastern atlantic ocean the amino acid concentrations in surficial sediments ranged from 11 4 to 12 6 mol g 1 dry sediment with a mean of 11 8 mol g 1 dry sediment and decreased with increasing sediment depth but showed a marked maximum between 20 and 40 mm albeit with significant variability in their abundance at that depth normalisation of the concentrations of hydrolysable amino acids to total organic carbon showed that the organic matter at the surface and in the sub surface maximum was relatively fresh the vertical concentration profiles of hydrolysable amino acids were also reflected by organic carbon and total nitrogen and are attributed to the transfer of relatively fresh organic matter from the sediment surface by bioturbation probably by large detritovores the depth of the zone of bioturbation i e 40 mm is consistent with the zone of maximum biological activity in the porcupine abyssal plain sediments

comparison of model simulated and observed currents in the central adriatic during dart 1 numerical simulations of the adriatic sea were performed with the navy coastal ocean model ncom during the dynamics of the adriatic in real time dart experiments conducted between october 2005 and september 2006 grid resolution was 1 km model forcing included tides surface fluxes from the aire limitee adaptation dynamique developpement international aladin atmospheric model relaxation to a daily satellite sea surface temperature analysis extensive river and runoff discharges and open boundary conditions south of otranto specified from a global model currents predicted by the model were compared with currents from 12 acoustic doppler current profiler adcp moorings located along a line between the gargano peninsula italy and split croatia the nontidal comparisons were performed with detided currents correlations between the model and adcp currents were highest in the western adriatic current wac which flows southeastward along the italian coast lowest correlations were in the interior of the adriatic likely because of instability processes correlations between the aladin winds and the model and adcp currents at the mooring locations were also highest in the wac for november 2005 through august 2006 the model and adcp mean wac transports were 0 321 and 0 304 sv respectively with a temporal correlation of 0 79 comparison of current variance showed best agreement near the italian and croatian coasts in the interior the ncom current variance compared fairly well with that of the adcps for november january but decreased significantly relative to the adcps for february august spectral analyses indicate most of the difference in variance to be at periods exceeding 2 days

enigmatic chambered structures in cryogenian reefs the oldest sponge grade organisms abstract previously undescribed chambered structures are common and widespread in the cryogenian post sturtian glacial carbonates of the oodnaminta reef complex adelaide geosyncline south australia the rasthof berg aukas formation namibia and the gauss formation namibia these carbonate structures have millimetre to centimetre scale chambers separated by well defined and generally thin micritic walls chamber walls now consist of dolomite but were probably originally aragonitic the chambers may have a lobate polygonal or dendritic morphology and are often further divided into smaller chambers chambered structures occur as reefal growth frameworks as cavity fillings in neptunean dykes and growth cavities and as intercolumnar material within stromatolite frameworks in the oodnaminta reef complex these structures are only present in the sub photic deep water framework these structures probably represent the calcified remains of an organism or community of organisms that was globally distributed and widespread for a significant time period following the sturtian glaciation no precisely analogous structures have been previously described from modern or ancient settings but the complexity and degree of organization suggests a significant evolutionary advance over older proterozoic fossils the closest morphological analogues for the structures are a some types of reef dwelling sponges and b some complex microbialites from archaean and paleoproterozoic carbonates the structures lack spicules and ostia found in sponges ruling out a true poriferan origin however it is plausible that they are proto sponges sponge grade organisms or complex microbial precursors to sponge grade organisms whatever their affinity we suggest these structures record a significant evolutionary event on the path towards organic complexity

tidal dynamics in the northern adriatic sea tides in the northern adriatic sea are investigated using two distinct numerical models first a two dimensional 2 d finite difference model is implemented with very high horizontal resolution 556 m to simulate the northern adriatic after calibration of open boundary conditions the model gives very satisfactory results the averaged vectorial difference between observed and simulated elevations is 1 3 cm for each of the seven major tidal constituents next a 3 d finite element model is applied to the entire sea in order to provide a better simulation of the tidal currents in the vicinity of the open boundary of the first model results show that the northern adriatic behaves like a narrow rotating channel in which the instantaneous sea surface elevation sse contours are aligned with the depth averaged velocity vectors and in which the sse is always higher to the right of the local current these features emphasize the rotational character that tides can exhibit in a relatively small basin wave fitting to the current elevation structure shows that semidiurnal tidal constituents are well represented with a system of two frictionless kelvin waves incident and reflected in contrast the diurnal constituents are best described as a topographic wave propagating across not along the basin from the croatian coast to the italian shore despite this obvious disparity the semidiurnal and diurnal tides can be understood as distinct members of a single family of linear waves which exist under the combined actions of gravity and topography

elemental and major biochemical changes across an oxidation front in a relict turbidite an oxygen effect abstract the elemental and major biochemical compositions of the relict f turbidite sampled in two cores from the madeira abyssal plain were determined this fine grained distal sequence occurs at ca 9 m core depth and includes a surficial oxidized horizon defined by a distinct color change oxygen diffused downward through sediments above this interface and in ca 10 kyr destroyed 80 of the organic substances that below the front had survived degradation in the presence of porewater sulfate for ca 140 kyr these deposits provide an opportunity to establish the extent and selectivity of oxic sedimentary degradation under natural conditions without the usual complications of bioturbation and varying sources or sedimentation rates in both cores a sample from the upper oxidized layer was compared to two samples from the underlying unoxidized layers the unoxidized sequences of both turbidities contained 0 93 1 02 wt organic carbon oc and 0 10 0 11 wt total nitrogen tn approximately 20 of the initial oc and 40 of the initial tn remained in the oxidized horizons with a consequent decrease in atomic c n ratio from ca 11 to ca 5 all samples gave very low yields of lignin phenols and comparable oc normalized yields of total aldoses and amino acids and indicated predominantly marine organic matter om and nonselective oxic degradation of these biochemical classes compositions of individual aldoses and amino acids generally were also similar in surface and deep sediments except that the oxidized horizons yielded markedly elevated 3 5x percentages of nonprotein amino acids this study clearly demonstrates that prolonged exposure to oz can lead to organic matter alteration which is far more extensive than that obtained with sulfate alone in comparison to early diagenesis however alteration of the measured biochemicals was largely nonselective such oxidation reactions could control the distribution and composition of organic matter in slowly accumulating continental rise and deep ocean environments

extreme ocean anoxia during the late cryogenian recorded in reefal carbonates of southern australia abstract the neoproterozoic was a time of great change in the earth s surface and marine environments including extensive climate variability the widespread oxygenation of the oceans and the accompanying rise of animal life however the timing of ocean oxygenation remains uncertain particularly in regard to cryogenian seas which were disrupted by large periods of global glaciation interglacial cryogenian reef complexes in the northern adelaide fold belt of australia contain abundant primary marine dolomite cements these cements have well preserved textural and growth zonation indicating they preserve their original marine chemistry and can be used as geochemical proxies for late cryogenian paleooceanography analysis of marine cements from peritidal nearshore facies shallow platformal facies and deep framework facies of the reef complexes reveals significant geochemical gradients with paleo depth while nearshore cements have low fe contents and commonly contain iron oxide inclusions the shallow and deep cements have very high fe concentrations chalcophile elements cu cd pb zn etc are most abundant in the nearshore cements whereas rare earth elements are found in highest concentrations in the deeper facies cements rare earth element profiles are unusual with shallow and deep facies having convex profiles with negligible ce ce anomalies and positive eu eu anomalies being constrained by sedimentology this carbonate geochemistry provides a window into interglacial cryogenian ocean chemistry and structure the marine cements reveal pronounced chemical stratification in this late cryogenian ocean a thin veneer of oxic surface waters existed at the ocean surface in peritidal facies with increasingly anoxic and fe rich seawater at depth the distribution of strongly chalcophile elements like cd and cu across the chemocline suggests that although ferruginous deeper anoxic waters probably contained some dissolved sulphide these conditions describe a ferro sulfidic ocean and encompass some of the most extreme anoxia yet documented during the late precambrian a return to archean like ocean conditions at this time suggests large scale disruption of the ocean system during the neoproterozoic

nature of organic matter in surface sediments from the pakistan continental margin and the deep arabian sea amino acids the role of organic carbon input sedimentation rate and bottom water oxygenation bwo for organic matter om degradation was investigated using surface sediments collected from above within and below the oxygen minimum zone omz within varying sedimentary regimes along the pakistan continental margin for this samples from 47 box cores and multi cores were analyzed for their bulk component organic carbon total nitrogen carbonate opal and amino acid concentrations the results are compared to plankton net samples from the arabian sea sinking particles collected at the pakistan continental margin cultured sedimentary deep sea bacteria and data from the deep arabian sea basins high organic carbon and amino acid concentrations were found in the laminated sediments of the omz in bioturbated sediments immediately below the omz and below regions of high productivity in the western arabian sea the contribution of amino acids to organic carbon and total nitrogen as well as the molar contribution of certain non protein amino acids do not mirror these differences in oc contents no clear trend in relation to sediment structure or water depth is observed in contrast to these established indicators of om degradation the molar contribution of the aromatic amino acid tyrosine tyr exhibits a distinct pattern its contribution is relatively high in sediments at depths above the omz and further increases towards the center of the omz below the omz it decreases continuously with increasing water depth in addition for samples from similar depths and bottom water oxygen contents tyr shows systematic differences between varying sedimentary regimes the lack of a distinct trend for the established indicators does not support the idea of a predominant control of bwo on quantitative om preservation nevertheless the variability of tyr in relation to water depth or the sedimentary regime suggests that i the productivity related oc input ii the bulk accumulation rate and iii bwo influence the alteration of the sedimentary om by controlling its oxygen exposure time

uranium removal in oceanic sediments and the oceanic u balance pore water uranium data from the nw atlantic ocean cariaco trench black sea and san clemente basin are used to calculate fluxes across the sediment water interface all samples were collected in situ and show depletions in pore water u relative to the overlying water concentration the uptake rate of u derived from pore water gradients reflects the redox environment with lowest fluxes 10 g cm 2 ky in oxic su ic sediments of the nw atlantic dominated by no 3 reduction and higher fluxes 25 70 g cm 2 ky in the anoxic sulfate reducing sediments of the cariaco trench black sea and san clemente basin the anoxic fluxes compare well with previous estimates based on solid phase data calculations indicate that the areally integrated removal of u into su ic hemipelagic sediments is of greater magnitude than that into anoxic sulfate reducing sediments these fluxes are discussed in the context of the oceanic u balance the removal of u in all oceanic sediments is estimated to account for about 65 of the riverine input and this sink plus removal of u in altered oceanic crust balances the most probable value for riverine input

influence of diagenesis on sedimentary delta n 15 in the arabian sea over the last 130 kyr abstract sedimentary 15n records are valuable archives of ocean history but they are often modified during early diagenesis here we quantify the effect of early diagenetic enrichment on sedimentary n isotope composition in order to obtain the pristine signal of reactive n assimilated in the euphotic zone this is possible by using paired data of 15n and amino acid composition of sediment samples which can be applied to estimate the degree of organic matter degradation we determined 15n and amino acid composition in coeval sediments from ocean drilling program odp hole 772 b in the central arabian sea and from hole 724 c situated on the oman margin in the western arabian sea coastal upwelling area the records span the last 130 kyr and include two glacial interglacial cycles these new data are used in conjunction with data available for surface sediments that cover a wide range of organic matter degradation states and with other cores from the northern and eastern arabian sea to explore spatial variations in the isotopic signal in order to reconstruct pristine n values we apply the relationship between organic matter degradation and 15n enrichment in surface sediments to correct the core records for early diagenetic enrichment reconstructed 15n values suggest a significant role of n2 fixation during glacial stages an evaluation of two preservation indices based on amino acid composition reactivity index ri jennerjahn and ittekkot 1997 and the degradation index di dauwe et al 1999 in both recent sediments and core samples suggests that the ri is more suitable than the di in correcting arabian sea 15n records for early diagenetic enrichment

seasonality and interannual variability of particle fluxes to the deep bay of bengal influence of riverine input and oceanographic processes abstract results from sediment trap experiments conducted from october 1987 until november 1997 in the deep northern central and southern bay of bengal northern indian ocean revealed significant monsoon induced seasonal and interannual variations in total and component fluxes distinct regional differences occurred related to the variable effect of terrestrial input and the development of relatively small scaled oceanographic processes the enormous fluvial input to the bay during swm is reflected in the high average content of lithogenic matter between 39 at the northernmost and 12 6 at the most distal sampling site in the southern bay of bengal generally the riverine input supports a relative increase in the fluxes of biogenic opal at the stations nearest to the continent nbbt n cbbt terrestrial inputs determine seasonal and interannual variabilities lateral supply of lithogenic matter from the shelf regions lead to distinct increase of fluxes with depth high flux events of 300 mg m 2 d 1 consisting of 50 lithogenics occur in the central bay of bengal during nem and in the northern bay of bengal during swm in response to resuspension of shelf sediments and severe floods when riverine input by ganges brahmaputra and the offshore propagation of the river plume during swm is reduced the advection from an upwelling area along the east coast of india during ne sw intermonsoon becomes the most prominent control mechanism for both biogenic and lithogenic fluxes at nbbt n in the central bay of bengal cbbt fluxes are characterized by a bimodal pattern high carbonate dominated fluxes during swm and nem occur mainly due to wind induced nutrient supply whereas high opal rich fluxes during sw ne intermonsoon are controlled by both upwelling as well as supply of riverine and shelf derived matter wind forcing is the dominant factor controlling particle fluxes at the most distal stations nbbt s sbbt leading to distinct maxima during swm with high abundance of biogenic components here interannual variations of particle fluxes are associated with changes in marine productivity induced by oceanographic processes this is most obvious for sbbt where the advection of upwelled water from the west coast of india in some years results in highest swm fluxes and a distinct shift towards biogenic opal

ales a multi mission adaptive subwaveform retracker for coastal and open ocean altimetry satellite altimetry has revolutionised our understanding of ocean dynamics thanks to frequent sampling and global coverage nevertheless coastal data have been flagged as unreliable due to land and calm water interference in the altimeter and radiometer footprint and uncertainty in the modelling of high frequency tidal and atmospheric forcing our study addresses the first issue i e altimeter footprint contamination via retracking presenting ales the adaptive leading edge subwaveform retracker ales is potentially applicable to all the pulse limited altimetry missions and its aim is to retrack both open ocean and coastal data with the same accuracy using just one algorithm ales selects part of each returned echo and models it with a classic open ocean brown functional form by means of least square estimation whose convergence is found through the nelder mead nonlinear optimisation technique by avoiding echoes from bright targets along the trailing edge it is capable of retrieving more coastal waveforms than the standard processing by adapting the width of the estimation window according to the significant wave height it aims at maintaining the accuracy of the standard processing in both the open ocean and the coastal strip this innovative retracker is validated against tide gauges in the adriatic sea and in the greater agulhas system for three different missions envisat jason 1 and jason 2 considerations of noise and biases provide a further verification of the strategy the results show that ales is able to provide more reliable 20 hz data for all three missions in areas where even 1 hz averages are flagged as unreliable in standard products application of the ales retracker led to roughly a half of the analysed tracks showing a marked improvement in correlation with the tide gauge records with the rms difference being reduced by a factor of 1 5 for jason 1 and jason 2 and over 4 for envisat in the adriatic sea at the closest point to the tide gauge

changes in organic matter from surface waters to continental slope sediments off the sao francisco river eastern brazil abstract suspended matter settling particles and sediments from the continental margin off the sao francisco the largest river of eastern brazil were analyzed for amino acids hexosamines and carbohydrates their concentrations and spectral distributions are comparable to those observed in other marine regions and exhibit variations which are related to the degree of dilution with lithogenic material preferential degradation and transformation of organic constituents within the water column during settling affect the nature and quantity of organic matter the variations in the amino acid spectra indicate that high bottom water oxygen contents and low sedimentation rates are the factors responsible for severe degradation of organic matter at the sediment water interface

unsteady diagenetic processes and sulfur biogeochemistry in tropical deltaic muds implications for oceanic isotope cycles and the sedimentary record abstract sedimentary s cycling is usually conceptualized and interpreted within the context of steadily accreting 1 d transport reaction regimes unsteady processes however are common in many sedimentary systems and can result in dramatically different s reaction balances and diagenetic products than steady conditions globally important common examples include tropical deltaic topset and inner shelf muds such as those extending from the amazon river 1600 km along the guianas coast of south america these deposits are characterized by episodic reworking of the surface seabed over vertical depths of 0 1 3 m reworked surface sediments act as unsteady suboxic batch reactors unconformably overlying relict anoxic often methanic deposits and have diagenetic properties largely decoupled from net accumulation of sediment despite well oxygenated water and an abundant reactive organic matter supply physical disturbance inhibits macrofauna and benthic communities are dominated by microbial biomass across immense areas in the surficial suboxic layer molecular biological analyses tracer experiments sediment c s fe compositions and 34s 18o of pore water so 4 2 indicate close coupling of anaerobic c s and fe cycles 18o so 4 2 can increase by 2 3 during anaerobic recycling without net change in 34s so 4 2 demonstrating so 4 2 reduction coupled to complete anaerobic reoxidation to so 4 2 and a 18o so 4 2 reduction reoxidation fractionation factor 12 summed magnitudes s reoxidation must be coupled to fe oxide reduction contributing to high dissolved fe2 1 mm and fe mobilization export the reworking of amazon guianas shelf muds alone may isotopically alter 18o so 4 2 equivalent in mass to 25 of the annual riverine delivery of so 4 2 to the global ocean unsteady conditions result in preservation of unusually heavy 34s isotopic compositions of residual cr reducible s ranging from 0 to 30 in physically reworked deposits in contrast bioturbated facies adjacent to physically reworked regions accumulate isotopically light s 34s to 20 in otherwise similar decomposition regimes the isotopic patterns of both physically and biologically reworked regions can be simulated with simple diagenetic models heavy s isotopic signatures are largely a consequence of unsteady diffusion and progressive anaerobic burndown into underlying deposits whereas isotopically depleted bioturbated deposits predominantly reflect biogenic diffusive scaling and isotopic distillation diffusive pumping associated with reoxidation in burrow walls immediately adjacent to reduced zones the s isotopic transition from unsteady physically controlled regions of the amazon delta moving laterally into bioturbated facies mimics the transition of s isotopic patterns temporally in the geologic record during the rise of bioturbation no special role for s disproportionation is required to explain these differences the potential role of unsteady suboxic diagenesis and dynamic reworking of sediments has been largely ignored in models of the evolution of surficial elemental cycling and interpretations of the geologic record

authigenic cadmium enrichments in suboxic sediments precipitation and postdepositional mobility the postdepositional mobility of cd and u has been investigated in north atlantic turbidites in order to validate their utility as proxies of paleo organic carbon fluxes in this region pelagic sediments are interspersed with relatively organic rich turbidites following instantaneous emplacement of turbidite units an oxidation front progressively migrated downwards into the suboxic turbidite thereby leading to redistribution of authigenic phases according to their affinity to different redox conditions authigenic cd concentrations show a large peak at the redox boundary and are significantly lower in the oxidized portion than in the deeper unoxidized part of the turbidite this distribution indicates that cd has been continuously remobilized by the oxidation front thereby suggesting high sensitivity of the cd species to the redox state and an efficient immobilization mechanism for cd under reducing conditions we propose the precipitation of cds as a plausible mechanism for removal of cd in reducing sediments rather than adsorption onto mineral surfaces this proposal is consistent with porewater data indicating diffusion of cd toward and uptake by suboxic sediments solubility calculations suggest that precipitation of cds may occur in suboxic sediments in the presence of trace levels of h2s below routine detection limits there is no evidence for release of cd or u back into seawater upon oxidation of reducing sediments the strong coupling between precipitation of authigenic cd and u and the early diagenetic degradation of organic carbon offers the potential of reconstructing paleo productivity using records of cd and u however postdepositional redistribution of authigenic cd and u may significantly alter records of authigenic cd and u thereby rendering paleo productivity reconstructions uncertain we propose that the cd u authigenic ratio may provide a qualitative indicator to assess the relative role of steady state incorporation relative to transient burn down enrichments

numerical study of the role of wind forcing and freshwater buoyancy input on the circulation in a shallow embayment gulf of trieste northern adriatic sea 1 this paper investigates the role of wind forcing and river discharge on a small scale shallow embayment the gulf of trieste the qualitative and quantitative analysis of these dominant processes is carried out using a high resolution numerical model initialized and forced with experimental data the simulations are focused on short term transient events which occurred during the stratification season spring and summer two significant case studies are analyzed in detail a strong wind event during summer and a river flood during spring the model output is also checked against the results of a nondimensional scale analysis and against buoy and satellite observed data these comparisons show a good correlation validating the numerical simulations for the two case studies the model shows that strong wind events blowing on stably stratified water cause coastal upwelling and almost entirely mix the water column in a few hours strong wind driven currents can flush the whole basin in almost 3 days on the contrary river floods affect mainly the upper layer down to 5 m the circulation is estuarine with a sharp vertical density gradient and horizontal fronts at the interface between plume freshwater and ambient salty water given the length scale of the basin the effect of rotation is weak and a local coastal current in geostrophic balance is not formed during the simulated time period 20 days

introduction to special section recent advances in oceanography and marine meteorology of the adriatic sea 1 owing to its strategic location rich fisheries and natural resources the adriatic sea possesses a long history of scientific exploration cushman roisin et al 2001 provides a comprehensive review the two volumes of this adriatic sea special section contribute to this rich literature by collecting results from a recent period of intense research activity during 2002 2003 the combined efforts of several large multi disciplinary international programs brought an exceptional array of observational and numerical resources to bear on contemporary questions in adriatic research supported by the u s office of naval research nato the croatian ministry of science and technology and the italian ministry of the environment and ministry of universities and research scientists from several countries pursued interrelated collaborative research programs broad ranging studies included investigations of circulation at kilometer to basin scales physical and biological response to bora wind forcing sediment transport and mucilage formation extensive numerical efforts contributed to the success of many of these programs providing interpretation and understanding and in some cases extensions into short term forecasting

a model for the distribution of trace elements between calcite and dolomite abstract a crystal growth model is proposed which allows ions of a trace element to enter the ca and mg sites of dolomite in proportion to the size of the ions relative to that of ca and mg ions and which assigns equal portions of the trace element to the ca site of dolomite and the ca site of associated calcite the model produces calcite dolomite distribution coefficients of 0 79 for mn and 0 43 for fe which may be compared with 0 85 and 0 28 as observed in marble and a distribution coefficient of 2 0 for sr and ba which may be compared with observed values of 2 3 for sr and 1 8 for ba

accumulation of prokaryotic remains during organic matter diagenesis in surface sediments off peru bacterial biomarkers d amino acids and muramic acid were investigated in surface sediments 0 1 cm at 22 stations in the peru margin concentrations were used to quantitatively estimate the relative importance of peptidoglycan in the preservation of prokaryotic remains during diagenesis the bacterial imprint in organic matter was also evident from low molar ratios average of 1 6 of glucosamine and galactosamine estimates of the fraction of biomarkers associated with intact peptidoglycan showed that peptidoglycan became a progressively less important component of prokaryotic remains with ongoing diagenesis whereas other prokaryotic biomolecules increased in importance the exact nature of these biomolecules remains unknown but constant ratios between individual d amino acids and amino sugars observed in this study provide novel information on their molecular composition examination of total hydrolyzable amino acids revealed systematic compositional changes with increasing water depth and age of the sediment reflecting increased diagenetic alteration of the organic matter the time scale integrated in the upper 1 cm of the sediment was ca 2 yr at the shallow sites and up to 20 yr at the deeper stations the alteration stages of organic matter ranged from coastal and ocean margin sediments at shallow water depth to organic matter as degraded as hemipelagic surface sediments at greater water depths

neoproterozoic aragonite dolomite seas widespread marine dolomite precipitation in cryogenian reef complexes the extraordinary abundance of dolomite in the proterozoic challenges our understanding of precambrian marine environments here we show that synsedimentary marine dolomite precipitation was pervasive within cryogenian reef complexes from the adelaide fold belt south australia although these reefs are composed of dolomite textural evidence indicates an originally aragonitic mineralogy for depositional components in common with many other neoproterozoic carbonates allochthonous slope debris from the reefs invariably contains both limestone and dolomite clasts indicating synsedimentary dolomitization in the reefs we describe several new forms of fibrous marine dolomite cement from the reefs that have a length slow optical character these fascicular slow radial slow and rhombic dolomite cements have finely preserved cathodoluminescent growth zones and optical characteristics that indicate they originally precipitated as dolomite rather than replacing calcite or aragonite cements abundant early marine dolomite precipitation implies a radically different seawater chemistry for the cryogenian perhaps these aragonite dolomite seas are associated with extreme neoproterozoic glacial events and or ocean anoxia

drivers of the carbonate system seasonal variations in a mediterranean gulf abstract the effects of different physical and biogeochemical drivers on the carbonate system were investigated in a semi enclosed coastal area characterized by high alkalinity riverine discharge gulf of trieste northern adriatic sea mediterranean sea our 2 year time series showed that a large part of the seasonal carbonate chemistry variation was controlled by the large seasonal change of seawater temperature though air sea co 2 exchange biological activity primary production respiration and riverine inputs also exerted a significant influence with the exception of summer the gulf of trieste was a sink of atmospheric carbon dioxide showing a very strong co 2 fluxes from atmosphere into the sea 16 10 mmol m 2 day 1 during high wind speed event of north easterly bora wind the co 2 influx was particularly evident in winter when the biological activity was at minimum and the low seawater temperature enhanced co 2 solubility during spring the drawdown of co 2 by primary production overwhelmed the co 2 physical pump driving a significant decrease of dissolved inorganic carbon dic co 2 and increase of ph t25 c in summer the primary production in surface waters occurred with the same intensity as respiration in the bottom layer so the net biological effect on the carbonate system was very low and the further reduction of seawater co 2 concentration observed was mainly due to carbon dioxide degassing induced by high seawater temperature finally during autumn the respiration was the predominant process which determined an overall increase of dic co 2 and decrease of ph t25 c this was particularly evident when the breakdown of summer stratification occurred and a large amount of co 2 generated by respiration and segregated below the pycnocline was released back to the whole water column local rivers also significantly affected the carbonate system by direct input of total alkalinity a t coming from the chemical weathering of carbonate rocks which dominate the river watershed our finding clearly demonstrates a high a t concentration in low salinity surface waters a t max 2742 8 mol kg 1 and a negative a t salinity correlation as a result the gulf of trieste revealed a low revelle factor 10 1 and one of the highest buffer capacities of the mediterranean sea s dic 0 31 mmol kg 1 which allows the system to store a significant amount of atmospheric co 2 with a small decrease of seawater ph

facies dependent δ13c variation from a cryogenian platform margin south australia evidence for stratified neoproterozoic oceans abstract analysis of a cryogenian interglacial platform margin in the adelaide geosyncline reveals a strong carbonate 13 c facies relationship detailed chronostratigraphic correlation between sections ranging from shallow platform facies to deep basinal facies indicates the presence of a carbon isotopic gradient of between 8 and 11 in time equivalent strata shallow water back reef facies have 13 c values up to 8 2 while equivalent basinal sediments have 13 c values between 3 and 0 allochthonous blocks that have been transported from the platform margin into basinal environments retain their heavy 13 c values 4 9 and are surrounded by basinal calcareous shales with light 13 c values ave 0 8 the regional and stratigraphic consistency of these 13 c trends suggests a primary marine origin we interpret this 13 c facies correlation to be the result of ocean stratification stagnation that significantly reduced the rate of deep ocean ventilation and produced a large deep water organically derived carbon reservoir we suggest that stratification may have been a persistent feature of the global ocean throughout much of neoproterozoic time ocean stratification may explain many of the unusual features that characterise the sedimentary record of this era including large scale 13 c variation extreme climatic fluctuations and the presence of cap carbonates a highly variable climatic regime would be expected with the development of a large deep water carbon reservoir small changes in ocean circulation could rapidly transfer or remove large volumes of carbon to and from the surface ocean and atmospheric reservoirs leading to intense greenhouse or icehouse conditions respectively

estuary plumes and fronts in shelf waters a layer model abstract a layer model that treats fronts as discontinuities is developed to study the steady state behavior of shallow estuary plumes on the continental shelf the complete range of earth rotation effect is evaluated from small scale or nonrotating plumes kelvin number equal zero to large scale rotating plumes kelvin number equal order one supercritical flow is assumed in the outlet channel and the method of characteristics is used to compute the flow downstream nonrotating plumes have strong boundary fronts and concentrate their greatest layer depth and mass transport offshore near the front but form no coastal current rotating plumes have boundary fronts that weaken soon after discharge form a turning region where coriolis action deflects the flow toward shore and subsequently set up a coastal current soon after its formation this coastal current is bounded offshore by a strong front called the coastal front across which the momentum balance changes from nearly inertial in the turning regi

a process study of the adriatic ionian system baroclinic dynamics the driving mechanisms behind the decadal reversal of the ionian sea upper layer circulation recently sparked a considerable discussion in the mediterranean scientific community it has been suggested that the reversal can be driven by variations in wind stress curl over the basin baroclinic dynamics acting within the adriatic ionian system aisys or baroclinic dynamics driven by thermohaline properties at the aisys eastern boundary here we perform numerical simulations in order to assess the relative importance of remote forcings wind stress thermohaline fluxes thermohaline open boundary conditions on the vorticity and energy budget of the ionian sea a mechanistic understanding of the aisys dynamics is achieved with an approach based on an increasing complexity in the model forcings and domain our experiments suggest that wind stress does not play a leading role in the vorticity and energy budgets of the ionian sea wind stress can reinforce or weaken the circulation but it is not able to reverse its sign its role becomes dominant only in the absence of inflows through the antikythira strait and cretan passage instead reversals in the upper layer circulation of the ionian sea take place only in the presence of an active boundary on the aegean sea levantine basin side and appear to be correlated with substantial exchanges of availalble potential energy between the two basins as observed at the end of the eastern mediterranean transient from an energetic point of view aisys can be explained therefore only if the role of the aegean sea is explicitly condidered this article is protected by copyright all rights reserved

surface circulation in the gulf of trieste northern adriatic sea from radar model and adcp comparisons 1 high resolution high frequency hf radar observations of surface currents in the gulf of trieste got are presented and compared to moored subsurface current measurements and to high resolution simulations from the northern adriatic princeton ocean model napom oceanographic model dominant circulation modes of the got were resolved and numerical model capabilities in reconstructing them were assessed the time frame covers march 2011 through october 2012 napom reconstructs the dominant surface circulation features observed by the radar such as the general basin wide cyclonic circulation scheme and the coastal jet outflowing the got but is in general less energetic than radar currents comparisons between radar adcp and model currents suggest that the model underestimates originate within the low frequency diurnal semidiurnal and inertial bands and that both radar and model currents do not reproduce the diurnal tidal ellipse structure observed by the moored current meter however radar model results for the semidiurnal tides are spatially consistent using empirical orthogonal function eof decomposition the coherent spatial scales and corresponding temporal scales were extracted findings suggest that hf radar current observations complement model simulations in regions of enhanced topographic variability where variance of model currents at the surface is distorted by the effects of the sigma layer grid on the contrary model results complement radar observations in areas with poor radar coverage and furthermore provide spatial and temporal continuity of ocean state forecasts

silicoflagellates in the eastern mediterranean and black seas seasonality distribution and sedimentary record abstract silicoflagellate populations and fluxes were analyzed from water samples and sediment traps in several basins of the eastern mediterranean and black sea to show species distribution in response to ecological factors and compared with the quaternary records of the region in the eastern mediterranean dictyocha stapedia was the most abundant species represented by two varieties var stapedia smaller and with an apex spine that dominated in the pelagic settings and var aspinosa larger and lacking an apex spine that dominated in the north adriatic sea dictyocha aculeata was the second most abundant species octactis pulchra was seasonally dominant in the adriatic sea stephanocha speculum occurred sporadically in the adriatic sea with 6 sided normal sized specimens but was nearly absent from pelagic assemblages in the black sea assemblages and fluxes were characterized by larger 7 sided skeletons of d speculum with apex spines and a lower abundance of o pulchra