layer thicknesses and velocities of wave overtopping flow at seadikes abstract seadikes often fail due to wave overtopping and a failure of the landward slope therefore these aspects have to be taken into account for the design of seadikes in present design the calculation of the crest height of seadikes is essentially based on using a design water level and the corresponding wave run up height an average overtopping rate is generally considered for wave overtopping which can not account for the stresses and other effects due to extreme individual overtopping events landward slope design is more or less based on experience it can be concluded from failure analysis that dike failures on the landward slope are rather initiated by individual overtopping events in particular by the related overtopping flow velocities and layer thicknesses which are relevant for the prediction of erosion infiltration and slip failure therefore overtopping flow velocities and layer thicknesses are required in addition to average overtopping rates as hydraulic boundary conditions for the geotechnical stability analysis of seadikes the objective of the present paper is the theoretical and experimental determination of overtopping flow velocities and layer thicknesses on the seaward slope the dike crest and the landward slope of a seadike overtopping parameters are derived on the basis of small scale model tests which are required for the design of the landward slope and to avoid dike failures by wave overtopping in the future for the prediction of the layer thicknesses and the velocities of the overtopping flow on the seaward slope the dike crest and the landward slope a set of theoretical formulas is derived and validated by hydraulic scale model tests

effect of organic carbon flux and dissolved oxygen on the benthic foraminiferal oxygen index bfoi variations in oceanic primary productivity flux of organic carbon to the sediments and dissolved oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size wall thickness morphology and species composition of assemblages by many foraminiferal paleontologists aspects of these processes should be reflected by the benthic foraminiferal oxygen index bfoi based on these foraminiferal characteristics however analyses indicate that the bfoi correlates most strongly with dissolved oxygen levels in overlying water r2 0 81 weakly with oceanic primary productivity r2 0 55 and weakly with organic carbon flux to the sediments r2 0 51 although both dissolved oxygen and organic carbon flux are main controlling factors for benthic foraminiferal assemblages the bfoi is a useful indicator extracted from benthic foraminiferal assemblages for estimating the condition of dissolved oxygen in cretaceous and cenozoic oceans

recent deep sea benthic foraminiferal distributions in the south china and sulu seas thirty nine surface sediment samples collected from the south china and sulu seas were examined to determine the bathymetric distribution of benthic foraminifera in these two basins and the factors responsible for these distributions the benthic foraminiferal faunas of both basins are highly diverse but have low absolute abundances benthic number and species diversity systematically decrease with increasing water depth four faunal assemblages were identified for each basin byq mode principal component analysis theglobocassidulina subglobosa uvigerina assemblage 1500 m and theuvigerina assemblage 1400 m represent the shallowest assemblages in the south china sea and sulu sea respectively and are found within the oxygen minimum zone of each basin where the sedimentary organic carbon content is highest and the pore water oxygen penetration depth zo is shallowest thebulimina aculeata assemblage occurs at water depths between 1700 and 2000 m in the southeastern south china sea and is also associated with relatively high sedimentary organic carbon content theastrononion pusillum assemblage is found in south china sea at the depths between 1500 and 3200 m below the lysocline 3200 m in the south china sea this assemblage is replaced by the agglutinatedrhabdammina abyssorum assemblage this assemblage reflects the presence of a water mass that is highly undersaturated with respect to calcite in the sulu sea thepyrgo murrhina assemblage occupies water depths from 1400 to 2200 m below 2200 m two deep water assemblages are present that are both dominated byoridorsalis umbonatus a correlation between various environmental and benthic foraminiferal variables indicates that salinity temperature sediment grain size water depth and bottom water oxygen concentration are not key factors controlling the benthic foraminiferal distribution in either the south china sea or the sulu sea rather organic carbon content and oxygen penetration depth in sediments appear to play important roles in determining the distribution of benthic foraminifera in both basins

variations of okhotsk sea oxygen minimum zone comparison of foraminiferal and sedimentological records for latest mis 12 11c and latest mis 2 1 abstract benthic foraminiferal assemblage compositions foraminiferal and sedimentological proxies were analyzed in core md01 2415 from the northern slope of the okhotsk sea to compare variations of productivity and oxygen minimum zone omz intensity during the latest marine isotope stage mis 12 11c and latest mis 2 1 the benthic assemblages reveal close similarity between the two climatic cycles the absence of benthic assemblages during the latest mis 12 and the presence of the low productivity angulogerina angulosa assemblage during the latest mis 2 suggest the disappearance of the omz this regime was related to almost perennial ice cover with periods of active ice rafting during the latest mis 12 while it was attributed to prolonged seasonal ice cover low surface productivity and enhanced formation of well oxygenated water masses in the okhotsk sea during the latest mis 2 in deglacial times the omz gradually intensified as evidenced by the high productivity uvigerina akitaensis assemblage during the early termination t tv and early ti and the low oxygen tolerant bolivina spissa assemblage during the late tv and late ti the orbitally forced similar rises of the global sea level during tv and ti caused a large offshore supply of organic matter synchronously nutrients from the melting sea ice and shelf erosion promoted high surface mainly carbonate productivity as a result a high and sustained flux of particulate degraded and refractory organic matter enhanced oxygen consumption in bottom waters and sediments leading to the similar gradual omz intensifications the b spissa assemblage also points to expansion of oxygen depleted water mass from the north pacific into the okhotsk sea fostering the omz intensifications the phytodetritus related islandiella norcrossi assemblage indicates weakening of the omz during full interglacial times of mis 11c and mis 1 after stabilization of the global sea level nutrients were mainly delivered by regional upwelling and fluvial discharge favoring increased biogenic opal and carbonate production in the surface water similar to the present in this way moderate to high although less than deglacial and pulsed flux of predominantly particulate organic matter caused the weakening of the oxygen consumption and omz notably during mis 11c the benthic assemblage with the dominance of the taxa with dissolution resistant tests such as miliammina herzensteini karreriella baccata and martinottiella communis reflects carbonate dissolution events in sediments these events might have been resulted from an interruption of the local surface carbonate production and inflow of more carbonate corrosive water masses from the north pacific driven by a drawdown of the global ocean carbonate saturation

biofaciological zonation of benthic foraminifera of the continental shelf of campos basin se brazil data on the microbiofaciological zonation of benthic foraminifera were obtained from 82 sub samples from the subsurface sediments of the continental shelf of campos basin in southeastern brazil the abundance and distribution of the 93 species identified during the study were related to depth and temperature of the water as well as to sediment grain size four biofacies were established biofacies i represented by the sandier coastal sediments and dominated by pseudononion atlanticum and miliolids biofacies ii associated with carbonated substrates and represented by amphistegina lessonii and miliolids biofacies iii represented by mini cores a2 where bulimina marginata is predominant in all the samples and biofacies iv associated with the muddy substrates of the outer continental shelf dominated by b marginata discorbis orbicularis and globocassidulina subglobosa in general the miliolids were more abundant in sandy sediments except a2 while the bolivinids and buliminids predominated in the sediments with a silt fraction which were normally associated with higher levels of organic matter the highest species diversity and equitability and lowest dominance indices were recorded in the sandy sediments whereas the silty sediments were characterized by a predominance of opportunists such as bolivina spp and bulimina spp species that were abundant in one stratum of a mini core tended to be abundant throughout the core indicating stable conditions over long periods which guaranteed the settlement of these species 2014 elsevier ltd and inqua

paleoceanographic significance of deep sea benthic foraminiferal species diversity at southeastern indian ocean hole 752a during the neogene abstract diversity parameters of neogene deep sea benthic foraminifera were measured at ocean drilling program odp hole 752a southeastern indian ocean water depth of 1086 3 m using information function h equitability e number of species s and sander s rarefaction values these parameters combined with population abundance of dominant benthic foraminifera bulimina macilenta nuttallides umbonifera cibicides wuellerstorfi cibicides lobatulus bolivina pusilla ehrenbergina carinata gavelinopsis lobatulus cassidulina laevigata globocassiulina subglobosa reveal significant paleoceanographic changes in the southeastern indian ocean during the neogene the values of all the diversity parameters show a decrease from 25 to 23 ma and thereafter an increase with peak values at 13 5 ma the late oligocene to earliest miocene was an interval of more unstable conditions at hole 752a dominated by species characteristic of low organic carbon well ventilated carbonate corrosive high energy conditions the highest values of diversity parameters coincide with the early middle miocene climatic optimum all these parameters show a declining trend and gradual decrease from 13 5 to 4 5 ma coinciding with the major build up of ice sheets in the antarctic region major increase in b pusilla and e carinata population during this time suggests high nutrient levels and low oxygen conditions at hole 752a this interval corresponds with the so called biogenic bloom and an intense oxygen minimum zone as observed throughout the indo pacific region deep waters were warmer from 4 5 to 3 ma marked by an increase in species diversity values coinciding with the early middle pliocene warmth the species diversity values abruptly decreased in the younger interval contemporaneous with the major northern hemisphere glaciation during this time species characteristics of high energy bottom currents and relatively cold deep water were dominant

late quaternary paleoproductivity and deep water circulation in the eastern south atlantic ocean evidence from benthic foraminifera abstract two late quaternary sediment cores from the northern cape basin in the eastern south atlantic ocean were analyzed for their benthic foraminiferal content and benthic stable carbon isotope composition the locations of the cores were selected such that both of them presently are bathed by north atlantic deep water nadw and past changes in deep water circulation should be recorded simultaneously at both locations however the areas are different in terms of primary production one core was recovered from the nutrient depleted walvis ridge area whereas the other one is from the continental slope just below the coastal upwelling mixing area where present day organic matter fluxes are shown to be moderately high recent data served as the basis for the interpretation of the late quaternary faunal fluctuations and the paleoceanographic reconstruction during the last 450 000 years nadw flux into the eastern south atlantic ocean has been restricted to interglacial periods with the strongest dominance of a nadw driven deep water circulation during interglacial stages 1 9 and 11 at the continental margin high productivity faunas and very low epibenthic 13c values indicate enhanced fluxes of organic matter during glacial periods this can be attributed to a glacial increase and lateral extension of coastal upwelling the long term glacial interglacial paleoproductivity cycles are superimposed by high frequency variations with a period of about 23 000 yr enhanced productivity in surface waters above the walvis ridge far from the coast is indicated during glacial stages 8 10 and 12 during these periods cold nutrient rich filaments from the mixing area were probably driven as far as to the southeastern flank of the walvis ridge

multidecadal variations in the early holocene outflow of red sea water into the arabian sea we present holocene stable oxygen isotope data from the deep arabian sea off somalia at a decadal time resolution as a proxy for the history of intermediate upper deep water these data show an overall 18o reduction by 0 5 between 10 and 6 5 kyr b p superimposed upon short term 18o variations at a decadal centennial timescale the amplitude of the decadal variations is 0 3 prior and up to 0 6 subsequent to 8 1 kyr b p we conclude from modeling experiments that the short term 18o variations between 10 and 6 5 kyr b p most likely document changes in the evaporation precipitation balance in the central red sea changes in water temperature and salinity cause the outflowing red sea water to settle roughly 800 m deeper than today

live rose bengal stained and dead benthic foraminifera from the oxygen minimum zone of the pakistan continental margin arabian sea live rose bengal stained and dead benthic foraminiferal communities hard shelled species only from the pakistan continental margin oxygen minimum zone omz have been studied in order to determine the relation between faunal composition and the oxygenation of bottom waters during r r s charles darwin cruises 145 and 146 12 march to may 28 2003 11 multicores were taken on the continental margin off karachi pakistan two transects were sampled constituting a composite bathymetric profile from 136 m above the omz in spring 2003 down to 1870 m water depth cores surface area 25 5 cm2 were processed as follows for stations situated above and in the upper part of the omz sediment slices were taken for the 0 0 5 and 0 5 1 cm intervals and then in 1 cm intervals down to 10 cm for the lower part of the omz the second centimetre was also sliced in half centimetre intervals each sample was stored in 10 borax buffered formalin for further processing onshore the samples were wet sieved over 63 m 150 m and 300 m sieves and the residues were stained for one week in ethanol with rose bengal after staining the residue was washed again the stained faunas were picked wet in three granulometric fractions 63 150 m 150 300 m and 300 m down to 10 cm depth to gain more insight into the population dynamics we investigated the dead unstained foraminifera in the 2 3 cm level for the fractions 150 300 m and 300 m the fractions 300 m and 150 300 m show nearly the same faunal distribution and therefore the results are presented here for both fractions combined i e the 150 m fraction live foraminiferal densities show a clear maximum in the first half centimetre of the sediment only few specimens are found down to 4 cm depth the faunas exhibit a clear zonation across the pakistan margin omz down to 500 m water depth uvigerina ex gr u semiornata and bolivina aff b dilatata dominate the assemblages these taxa are largely restricted to the upper cm of the sediment they are adapted to the very low bottom water oxygen values ab 0 1 ml l in the omz core and the extremely high input of organic carbon on the upper continental slope the lower part of the omz is characterized by cosmopolitan faunas containing also some taxa that in other areas have been described in deep infaunal microhabitats

rans modelling applied to random wave interaction with submerged permeable structures abstract this paper is the second part of the work presented by garcia et al garcia n lara j l losada i j 2004 2 d numerical analysis of near field flow at low crested breakwaters coastal engineering 51 10 991 1020 in the mentioned paper flow conditions at low crested rubble mound breakwaters under regular wave attack were examined using a combination of measured data of free surface bottom pressure and fluid velocities from small scale experiments and numerical results provided by a vof type model cobras based on the reynolds averaged navier stokes rans equations this paper demonstrates the capability of the cobras model to reproduce irregular wave interaction with submerged permeable breakwaters data provided by the numerical model are compared to experimental data of laboratory tests and the main processes of wave structure interaction are examined using both experimental and numerical results the numerical model validation is carried out in two steps first the procedure of irregular wave generation is verified to work properly comparing experimental and numerical data of different cases of irregular wave trains propagating over a flat bottom next the validation of the numerical model for wave interaction with submerged rubble mound breakwaters is performed through the simulation of small scale laboratory tests on different incident wave spectra results show that the numerical model adequately reproduces the main aspects of the interaction of random waves with submerged porous breakwaters especially the spectral energy decay at the structure and the spectrum broadening past the structure the simulations give good results in terms of height envelopes mean level spectral shape root mean square height for both free surface displacement and dynamic pressure inside the breakwater moreover large scale simulations have been conducted on both regular and irregular incident wave conditions the overall pattern of the wave interaction with a large scale submerged breakwater is adequately reproduced by the numerical model the processes of wave reflection shoaling and breaking are correctly captured the good results achieved at a near prototype scale are promising regarding the use of the numerical model for design purposes

the importance of the oxygen minimum zone and sediment geochemistry in the distribution of recent benthic foraminifera in the northwest indian ocean abstract the relationship between the distribution of benthic foraminifera and sediment type and depositional environment in the arabian sea is discussed the benthic foraminiferal fauna were sampled in nineteen recent surface sediment samples and geochemical variables of the sediment of the same samples were measured the water depths for the box core samples varies from 440 to 4040 m a total of 103 species and six species complexes were identified the geochemical properties were found to correspond well to the sediment type and depositional environment and six different sediment depositional environment types could be distinguished analysis of the benthic foraminiferal fauna reveals specific faunal assemblages that are closely related to these sediment depositional environment types

late holocene long arid phase in the indian subcontinent as seen in shallow sediments of the eastern arabian sea abstract multi proxy record of benthic and planktic foraminifera total organic carbon and carbon and oxygen isotope ratios from core sk291 gc15 off the coast of goa eastern arabian sea reveals significant paleoceanographic and paleoclimatic turnovers during 6000 to 1700 calibrated years before the present cal yr bp benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies the record suggests centennial to millennial scale changes in the surface conditions driven by monsoon linked upwelling in the eastern arabian sea during the studied interval various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle holocene the results suggest that during 5400 4700 and 3000 2500 cal yr bp the southwest sw monsoon was strong leading to intense upwelling in the study area as reflected by increased globigerina bulloides percentages these were generally warmer intervals in the northern hemisphere the sw monsoon significantly weakened abrupt decrease in g bulloides population during 4700 3400 cal yr bp roughly coinciding with a long arid phase in the indian subcontinent and a cold interval in europe our record suggests an abrupt increase in sw monsoon intensity during 3000 to 2500 cal yr bp when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub surface conditions our data document a prolong weak sw monsoon phase beginning at 4600 cal yr bp little earlier than 4 2 ka event in the eastern arabian sea

spatial distribution of wave overtopping water behind coastal structures spatial distribution of random wave overtopping water behind coastal structures was investigated using a numerical model based on reynolds averaged navier stokes solver rans and volume of fluid vof surface capturing scheme rans vof the computed spatial distributions of wave overtopping water behind the structure agree well with the measurements by pullen et al 2008 for a vertical wall and lykke andersen and burcharth 2006 for a 1 2 sea dike a semi analytical model was derived to relate spatial distribution of wave overtopping water behind coastal structures to landward ground level velocity and layer thickness on the crest this semi analytical model agrees reasonably well with both numerical model results and measurements close to coastal structures our numerical model results suggest that the proportion of wave overtopping water passing a landward location increases with a seaward slope when it is less than 1 3 and decreases with a seaward slope when it gets steeper the proportion of wave overtopping water passing a landward location increases with landward ground level and overtopping discharge it also increases with the product of incident wave height and wavelength but decreases with increasing relative structure freeboard and crest width we also found that the extent of hazard area due to wave overtopping is significantly reduced by using a permeable structure crown findings in this study will enable engineers to establish the extent of hazard zones due to wave overtopping behind coastal structures

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

foraminiferal response to the northeast monsoon in the western and southern arabian sea abstract sediments from the western and southern part of the arabian sea were collected periodically in the spring intermonsoon between march and may 1997 and additionally at the end of the northeast monsoon in february 1998 assemblages of rose bengal stained living deep sea benthic foraminifera their densities vertical distribution pattern and diversity were analysed after the northeast monsoon and short time changes were recorded in the western arabian sea foraminiferal numbers increased steadily between march and the beginning of may especially in the smaller size classes 30 63 m 63 125 m at the same time the deepening of the foraminiferal living horizon variable diversity and rapid variations between dominant foraminiferal communities were observed we interpret these observations as the time dependent response of benthic foraminifera to enhanced organic carbon fluxes during and after the northeast monsoon in the southern arabian sea constant low foraminiferal abundances during time no distinctive change in the vertical distribution reduced diversity and more stable foraminiferal communities were noticed which indicates no or little influence of the northeast monsoon to benthic foraminifera in this region

distribution biomass and diversity of benthic foraminifera in relation to sediment geochemistry in the arabian sea the distribution biomass and diversity of living rose bengal stained deep sea benthic foraminifera 30 mu m were investigated with multicorer samples from seven stations in the arabian sea during the intermonsoonal periods in march and in september october 1995 water depths of the stations ranged between 1916 and 4425 m the distribution of benthic foraminifera was compared with dissolved oxygen organic carbon calcium carbonate ammonium silica chloroplastic pigment equivalents sand content pore water content of the sediment and organic carbon flux to explain the foraminiferal patterns and depositional environments a total of six species communities comprising 178 living species were identified by principal component analysis the seasonal comparison shows that at the western stations foraminiferal abundance and biomass were higher during the spring intermonsoon than during the fall intermonsoon the regional comparison indicates a distinct gradient in abundance biomass and diversity from west to east and for biomass from north to south highest values are recorded in the western part of the arabian sea where the influence of coastal and offshore upwelling are responsible for high carbon fluxes estimated total biomass of living benthic foraminifera integrated for the upper 5 cm of the sediment ranged between 11 mg corg m 2 at the southern station and 420 mg corg m 2 at the western station foraminifera in the size range from 30 to 125 mu m the so called microforaminifera contributed between 20 and 65 to the abundance but only 3 to 28 to the biomass of the fauna highest values were found in the central and southern arabian sea indicating their importance in oligotrophic deep sea areas the overall abundance of benthic foraminifera is positively correlated with oxygen content and pore volume and partly with carbon content and chloroplastic pigment equivalents of the sediment the distributional patterns of the communities seem to be controlled by sand fraction dissolved oxygen calcium carbonate and organic carbon content of the sediment but the critical variables are of different significance for each community

middle late miocene benthic foraminifera in a western equatorial indian ocean depth transect paleoceanographic implications abstract middle through upper miocene 17 5 ma benthic foraminiferal faunas 63 m from a depth transect in the western equatorial indian ocean dsdp site 237 odp sites 707 709 and 710 water depth 1500 3800 m underwent significant faunal changes at 14 13 ma and 11 8 ma these faunal changes are not easily interpreted because of the complex factors controlling benthic foraminiferal distribution and abundance at 14 13 ma the relative abundance of high productivity taxa bolivina bulimina melonis and uvigerina species although highly variable generally increased at the two shallower sites 237 and 707 as did the percentage of epistominella exigua indicative of seasonal productivity and nuttallides umbonifera indicative of corrosive bottom waters at the two deeper sites 709 and 710 the latter species had a peak in abundance at the deepest site 710 between 11 and 9 ma benthic foraminiferal accumulation rates bfars increased strongly at the shallower sites starting at 11 ma peaking between 9 and 8 ma and increased weakly at the deeper two sites starting at 11 ma elongate cylindrical taxa decreased in abundance between 12 and 11 ma at all sites the abundance of planktic foraminiferal fragments was as expected overall higher at the deeper sites with some high values after 12 13 ma at the shallower sites the faunal changes suggest that overall the food supply to the sea floor increased but also became more pulsed or seasonal peaking at 9 8 ma while deep and intermediate waters may have become more ventilated the first phase of faunal change 14 13 ma was coeval with the global increase in benthic foraminiferal oxygen isotope values worldwide turnover in benthic foraminiferal faunas and possibly increased production of antarctic bottom water aabw and northern component water ncw the overall faunal turnover may reflect the composite faunal response to increased food input resulting from heightened productivity and increased bottom water ventilation associated with a combination of monsoonal intensification global cooling and changes in ocean circulation but there is no unequivocal evidence for the presence of tethyan outflow water tow over the studied time and depth range in contrast to earlier publications

the role of the north atlantic drift in the millennial timescale glacial climate fluctuations abstract the greenland ice core records show that the overall cold climate of the last glacial period was repeatedly interrupted by short rapid warmings the events known as dansgaard oeschger d o events are strongly imprinted in the north atlantic marine records suggesting that they were linked to north atlantic circulation changes however the causes of the d o events are poorly understood and they represent one of the most intriguing puzzles of the last glacial period in order to investigate a possible mechanism we have studied variations in the distribution of benthic and planktonic foraminifera oxygen isotopes and ice rafted debris during the last glacial period in eight cores from the north atlantic and the nordic seas taken at mid depth from 853 to 1760 m the parameters indicate in agreement with previous studies that the circulation system during the interstadials resembled the present system atlantic surface water flowed north into the nordic seas where most of it sank through convection and as cold deep water flowed back into the north atlantic during the stadials a halocline was established in the nordic seas and in the northernmost part of the north atlantic and the outflow from the nordic seas stopped however below the cold light surface layer the relatively warm water of the north atlantic drift continued to flow across the north atlantic and into the nordic seas here warming up the deep water masses we suggest that the warm water gradually made the water column unstable the pivotal abrupt climate warmings were caused by sudden upwelling of the deep warm water masses causing overturning of the entire water column and onset of convection

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

variations in deep sea benthic foraminifera at odp hole 756b southeastern indian ocean evidence for changes in deep ocean circulation abstract seventy three core samples of 10 cc volume were analysed from ocean drilling program odp site 756 hole b with an average interval of 236 kyr per sample factor and cluster analyses of 37 high ranking species of benthic foraminifera enabled us to identify four clusters representing four biofacies biofacies sl om is characterised by stilostomella lepidula orthomorphina modesta robulus gibbus bulimina miolaevis and cibicides cf lucidus this biofacies dominates the latest oligocene to early miocene interval 24 21 ma and 18 75 16 5 ma indicating low to intermediate dissolved oxygen organic carbon rich environment warm and sluggish deep waters during 21 18 75 ma the biofacies gp nu globocassidulina pacifica nuttallides umbonifera trifarina angulosa quinqueloculina weaveri robulus gibbus and pullenia bulloides dominates the benthic assemblage at hole 756b this biofacies also has a short lived presence at 16 5 ma this was an interval of intense circulation of cold and corrosive deep water similar to antarctic intermediate water aaiw and intermediate to high flux of organic matter to hole 756b the antarctic circumpolar current acc initiated during this time from 16 5 to 10 6 ma the benthic assemblage at hole 756b is dominated by biofacies ub gs characteristic species uvigerina buzasi globocassidulina subglobosa laticarina pauperata indicating intermediate to high food supply and cold deep water this interval coincides with the middle miocene positive oxygen isotope shift and permanent build up of antarctic ice sheets the late miocene interval 10 6 6 5 is characterised by biofacies ec bs dominant species ehrenbergina carinata bolivina spathulata osangularia culter and pullenia osloensis indicating low oxygen condition with high food supply in the study area this corresponds to an interval of global biogenic bloom

deep sea faunal provinces and their inferred environments in the indian ocean based on distribution of recent benthic foraminifera abstract multivariate analysis was performed on percentages of 46 species of unstained deep sea benthic foraminifera from 131 core top to near core top samples 322 5013 m from across the indian ocean faunal data are combined with geosecs geochemical data to investigate any relationship between benthic foraminifera assemblages and species and deep sea properties in general benthic foraminifera show a good correlation to surface productivity organic carbon flux to the sea floor deep sea oxygenation and to a lesser extent to bottom temperature without correlation with the water depths the foraminiferal census data combined with geochemical data has enabled the division of the indian ocean into two faunal provinces province a occupies the northwestern indian ocean arabian sea region where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor making the deep sea one of the most oxygen deficient regions in the world ocean with a pronounced oxygen minimum zone omz this province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including uvigerina peregrina robulus nicobarensis bolivinita pseudopunctata bolivinita sp bulimina aculeata bulimina alazanensis ehrenbergina carinata and cassidulina carinata province b covers southern southeastern and eastern parts of the indian ocean and is dominated by nuttallides umbonifera epistominella exigua globocassidulina subglobosa uvigerina proboscidea cibicides wuellerstorfi cassidulina laevigata pullenia bulloides pullenia osloensis pyrgo murrhina oridorsalis umbonatus gyroidinoides gyroidina soldanii and gyroidinoides cf gemma suggesting well oxygenated cold deep water with low oligotrophic and pulsed food supply

foraminiferal faunal responses to monsoon driven changes in organic matter and oxygen availability at 140 and 300 m water depth in the ne arabian sea the faunal responses of benthic foraminifera were investigated during 2003 at two contrasting sites in the pakistan margin oxygen minimum zone omz bottom water dissolved oxygen concentrations at the seasonally hypoxic 140 m site varied from 2 06 ml l 1 92 4 m during the intermonsoon period april to 0 11 ml l 1 5 0 0 4 m during the post monsoon period october corresponding values at the 300 m site in the omz core were 0 053 and 0 057 ml l 1 2 36 0 09 and 2 56 0 29 m live macrofaunal 300 m foraminifera including soft walled species and metazoa were examined in replicate multicore samples taken at each site during the 2003 intermonsoon and post monsoon seasons a low diversity foraminiferal assemblage was dominated 60 by calcareous species at both sites a total of 36 species was recognised and diversity was not greatly affected by water depth or season at both sites 86 of foraminifera were restricted to the 0 1 cm layer of sediment and the ald5 decreased from the intermonsoon to the post monsoon periods densities increased from 124 intermonsoon to 153 post monsoon indiv 10 cm 2 at 140 m and from 86 to 122 indiv 10 cm 2 at 300 m much of this increase was accounted for by the dominant species uvigerina ex gr semiornata at 140 m foraminifera were 3 6 times more abundant than metazoans during the intermonsoon period rising to 13 9 times during the post monsoon period the corresponding proportions at 300 m where metazoans were rare were 12 4 and 14 5 we conclude that calcareous foraminifera in particular u ex gr semiornata play a central role in om cycling on the sea floor in the upper part of the pakistan margin omz

uvigerina proboscidea abundances and paleoceanography of the northern indian ocean dsdp site 214 during the late neogene abstract this study attempts to understand the significance of uvigerina proboscidea in paleoceanographic reconstructions at the northern tropical indian ocean dsdp site 214 from the late miocene through the pleistocene in this interval at this site u proboscidea is the most abundant species of the benthic assemblage and shows abrupt frequency changes about 1 74 based on relative percentages of u proboscidea calibrated with oxygen and carbon isotope record and the sediment accumulation rates the modern distribution of the species in the indian ocean and other evidence the peaks of abundance of u proboscidea are inferred to represent times of high surface productivity this productivity is related to intensified trade winds during strong southwest sw indian monsoons causing widespread upwelling along equatorial divergence in the indian ocean the sudden increase of u proboscidea abundance at approximately 8 5 7 5 ma reflects significant upwelling at the equatorial divergence this event corresponds to the permanent build up of west antarctic ice sheets and a major increase in sw indian monsoons related upwelling in the northwestern indian ocean the chron 6 carbon shift at approximately 6 2 ma is marked by another peak of abundance reflecting widespread ocean fertility the highest abundances of u proboscidea and highest sediment accumulation rates occur between 5 8 and 5 1 ma which coincides with the greatest development of antarctic ice sheets and strong southwest monsoons the higher percentages at 3 2 3 1 ma approximately 2 4 ma and 1 6 ma all represent phases of high productivity at the equatorial divergence

recent benthic foraminifera from the eastern south atlantic ocean dependence on food supply and water masses abstract sixty surface sediment samples from the eastern south atlantic ocean including the walvis ridge the angola and cape basins and the southwest african continental margin were analysed for their benthic foraminiferal content to unravel faunal distribution patterns and ecological preferences live stained with rose bengal and dead faunas were counted separately and then each grouped by q mode principal component analysis into seven principal faunal end members then multiple regression technique was used to correlate recent assemblages with available environmental variables and to finally differentiate between four principal groups of environmental agents acting upon the generation of benthic foraminiferal assemblages 1 seasonality of food supply and organic carbon flux rates together with oxygen content in the pore and bottom waters 2 lateral advection of deep water masses 3 bottom water carbonate corrosiveness and 4 energetic state at the benthic boundary layer and grain size composition of the substrate food supply and corresponding dissolved oxygen contents in the pore and bottom waters turned out to be the most important factors which control the distribution pattern of the recent benthic foraminifera at the continental margin in the zone of coastal upwelling and its mixing area benthic foraminiferal assemblages are dominated by stenobathic high productivity faunas characterized by elevated standing stocks low diversities and a large number of endobenthic living species at the continental shelf and upper continental slope the live assemblages are characterized by rectuvigerina cylindrica uvigerina peregrina s 1 uvigerina auberiana and rhizammina spp while the dead assemblages are characterized by cassidulina laevigata bolivina dilatata bulimina costata and b mexicana at the lower continental slope strong influence of high organic matter fluxes on the species composition is restricted to the area off the cunene river mouth where the live assemblage is dominated by uvigerina peregrina s 1 the corresponding dead assemblage by melonis barleeanum and m zaandamae in the adjacent areas of the lower continental slope the biocoenosis is characterized by reophax bilocularis and epistominella exigua which becomes dominant in the corresponding dead assemblage at the walvis ridge and in the abyssal angola and cape basins where organic matter fluxes are low and highly seasonal benthic foraminiferal assemblages reflect both the oligotrophic situation and the deep and bottom water mass configuration the top and flanks of the walvis ridge are inhabited by the rhizammina psammosphaera and r bilocularis live assemblages the corresponding dead assemblages are dominated by g subglobosa on the ridge top and e exigua on the flanks within the highly diverse e exigua dead assemblage several associated epibenthic species coincide with the core of nadw between about 1600 and 3700 m water depth these species include osangularia culter cibicidoides kullenbergi melonis pompilioides bolivinita pseudothalmanni and bulimina alazanensis the assemblages of the abyssal cape and angola basins are characterized by nuttallides umbonifer and a high proportion of agglutinated species these species are adapted to very low organic matter fluxes and a carbonate corrosive environment

factors influencing the distribution patterns of recent deep sea benthic foraminifera east of new zealand southwest pacific ocean abstract this study investigates which combination of environmental factors most strongly influences the distribution patterns of benthic foraminferal tests 0 63 m in a region bisected by the subtropical front east of new zealand seafloor sample sites extend from outer shelf 90 m to abyssal 4700 m depths across substrates ranging from biogenic terrigenous gravelly sand to hemipelagic mud and occur under the influence of antarctic intermediate water aaiw and circumpolar deep waters as well as receiving detritus from both subtropical and subantarctic surface water masses elevated values of the planktic foraminiferal fragmentation index and reworked small paleogene planktic foraminifera at outer shelf and bathyal depths coincide with areas of strong bottom currents q mode cluster analysis on the census counts of 398 benthic species clusters the 66 samples into three large groups shallow bathyal abyssal and at a lower level 10 mappable associations are recognised a combination of canonical correspondence analysis and a correlation coefficient matrix was used to relate the faunal data to a set of measured environmental proxies these analyses show that factors that have a relationship with depth are the most significant in determining foraminiferal distribution the principal environmental factors which appear to most strongly influence this benthic foraminiferal distribution are dissolved oxygen content in bottom waters sustainability of organic carbon flux rates seasonality of food supply lateral advection of water masses bottom water carbonate corrosiveness energetic state at the benthic boundary layer grain size composition of substrate salinity and temperature of the bottom waters shallow water associations 90 1250 m dominated by cassidulina carinata and trifarina angulosa occur within coarse substrates under well oxygenated high energy regimes and sustained food input the occurrence of the bathyal associations 230 2840 m dominated by c carinata alabaminella weddellensis and abditodentrix pseudothalmanni closely mirrors the distribution of aaiw within a region of variable food supply the sustainability of food supply combined with bottom water type and associated ventilation and dissolution strongly influence the composition of abyssal associations 1200 4700 m mostly dominated by epistominella exigua and a weddellensis

benthic foraminiferal extinctions linked to late pliocene pleistocene deep sea circulation changes in the northern indian ocean odp sites 722 and 758 during the late pliocene middle pleistocene 63 species of elongate bathyal upper abyssal benthic foraminifera extinction group stilostomellidae pleurostomellidae some nodosariidae declined in abundance and finally disappeared in the northern indian ocean odp sites 722 758 as part of the global extinction of at least 88 related species at this time the detailed record of withdrawal of these species differs by depth and geography in the indian ocean in northwest indian ocean site 722 2045 m the extinction group of 54 species comprised 2 15 of the benthic foraminiferal fauna in the earliest pleistocene but declined dramatically during the onset of the mid pleistocene transition mpt at 1 2 1 1 ma with all but three species disappearing by the end of the mpt 0 6 ma in northeast indian ocean site 758 2925 m the extinction group of 44 species comprised 1 5 of the benthic foraminiferal fauna at 3 3 2 6 ma but declined in abundance and diversity in three steps at 2 5 1 7 and 1 2 ma with all but one species disappearing by the end of the mpt at both sites there are strong positive correlations between the accumulation rate of the extinction group and proxies indicating low oxygen conditions with a high organic carbon input in both sites there was a pulsed decline in extinction group abundance and species richness especially in glacial periods with some partial recoveries in interglacials we infer that the glacial declines at the deeper site 758 were a result of increased production of colder well ventilated antarctic bottom water aabw particularly in the late pliocene and during the mpt the extinction group at shallower water depths site 722 were not impacted by the deeper water mass changes until the onset of the mpt when cold well ventilated glacial north atlantic intermediate water gnaiw production increased and may have spread into the indian ocean increased chemical ventilation at various water depths since late pliocene particularly in glacial periods possibly in association with decreased or more fluctuating organic carbon flux might be responsible for the pulsed global decline and extinction of this rather specialised group of benthic foraminifera d 2005 elsevier b v all rights reserved

indian ocean high productivity event 10 8 ma linked to global cooling or to the initiation of the indian monsoons uplift of the himalayas and tibetan plateau ca 10 8 ma has been said to be the main cause of the origin or intensification of the indian monsoon system because mountains modulate the land sea thermal contrast the intensification of the monsoons in turn is seen as the cause of major changes in fauna and flora on land as a result of changing precipitation patterns as well as in the indian ocean where the monsoons drive increased upwelling and thus increased productivity we argue that the interactions between the elevation of the himalayas and tibetan plateau the onset of the monsoons and their effects on the indian ocean biota remain uncertain the timing of these events uplift monsoons and biotic change is not well constrained neogene deep sea benthic foraminiferal faunal and isotope records of the ninetyeast ridge combined with published data show that a major increase in bio genic productivity occurred at 10 8 ma throughout the indian ocean the equatorial pacific and southern atlantic we suggest that this indian ocean high productivity event was not simply the result of monsoon induced upwelling or nutrient delivery from the weathering of newly uplifted mountains but may have been caused by strengthened wind regimes resulting from global cooling and the increase in volume of the antarctic ice sheets

numerical investigations of wave overtopping at coastal structures under the numerical modelling work package of the eu funded clash project the time accurate free surface capturing incompressible navier stokes solver amazon sc has been applied to study impulsive wave overtopping at samphire hoe near dover in the united kingdom the simulations show that the overtopping process on this vertical sheet pile seawall is dominated by impulsive aerated near vertical overtopping jets in order to perform the simulations amazon sc has been extended to incorporate an isotropic porosity model and for validation purposes the solver has been applied to study overtopping of a low crested sea dike and a 10 1 battered wall the results obtained for the battered wall and samphire hoe tests are in good agreement both with predicted overtopping discharges calculated using the uk overtopping manual and with available experimental results

holocene strengthening of the oxygen minimum zone in the northwestern arabian sea linked to changes in intermediate water circulation or indian monsoon intensity abstract a high resolution 14 000 year old record of benthic foraminifera from odp hole 723a was produced to understand changing intensity of the nw arabian sea oxygen minimum zone omz and its links with intermediate water circulation and indian monsoon intensity during the latest pleistocene the omz was very weak marked by the abundance of oxic species from early to mid holocene period up to 6500 years bp intense sw monsoon related high surface productivity led to the development of an omz in the arabian sea however presence of oxic and suboxic species indicate that omz intensification was minimized by cyclic incursions of oxygen rich intermediate waters from the south the middle holocene was a transitional period to intense omz conditions the intensification of the omz could be due to replacement of oxygen rich southern source sub antarctic mode and antarctic intermediate waters samw aaiw with oxygen poor red sea water rsw from the north during the middle holocene as the intensity of the summer monsoon weakened during the late holocene 4200 years bp onwards the arabian sea omz intensified suggesting total cut off from the oxygenated samw aaiw spectral analysis of information function h benthic foraminifer bolivina spp and oxic species of benthic foraminifera indicate that the intensity of the omz and deep water conditions respond closely to solar cycles

a 23000 year old record of paleoclimatic and environmental changes from the eastern arabian sea abstract climate of the eastern arabian sea is highly influenced by both global climate and indian monsoon we produced multi proxy records of benthic foraminiferal biofacies and stable isotope ratio 13c and 18o planktic foraminifera and total organic carbon wt content of sediments from core sk291 gc11 in the upper continental shelf off mangalore off eastern arabian sea eas to decipher paleoenvironmental and paleoclimatic changes during the past 23 000 years the monsoon was weak during the last glacial maximum 23 000 18 000 calibrated years before present cal yr bp when sea level was lower globigerinoides ruber populations fluctuate from 30 to 60 in the studied interval with a maximum during 6000 5000 cal yr bp and a minimum during 19 000 17 000 cal yr bp the 18o values of benthic foraminifer ammonia gaimardii suggest pronounced cooling phases during 23 000 18 000 cal yr bp and a short term cooling at 6000 cal yr bp several intervals of high organic productivity and low oxygen conditions were identified based on benthic foraminiferal biofacies during 23 247 682 cal yr bp wind induced surface mixing was intense during 3200 530 cal yr bp as evidenced by high globigerina bulloides abundances the core was affected by moderate chemical weathering and solar variability appears to have been an important forcing factor in shaping climate of the region

the influence of the ne winter monsoon on productivity changes in the gulf of aden nw arabian sea during the last 530ka as recorded by foraminifera abstract benthic and selected planktic foraminifera and stable isotope records were determined in a piston core from the gulf of aden nw arabian sea that spans the last 530 ka the benthic foraminifera were grouped into four principal assemblages using q mode principal component analyses comparison of each of these assemblages with the fauna of the nearby regions enabled us to identify their specific environmental requirements as a function of variability in food supply and strength of the oxygen minimum zone and by that to use them as indicators of surface water productivity the benthic foraminiferal productivity indicators coupled with the record of globigerina bulloides a planktic foraminifer known to be sensitive to productivity changes in the region all indicate higher productivity during glacial intervals and productivity similar to present or even reduced during interglacial stages this trend is opposite to the productivity pattern related to the sw summer monsoon of the arabian sea and indicates the role of the ne winter monsoon on the productivity of the gulf of aden a period of exceptionally enhanced productivity is recognized in the gulf of aden region between 60 and 13 kyr indicating the intensification of the ne winter monsoon to its maximal activity contemporaneous indication of increased productivity in other parts of the arabian sea unexplained so far by the sw summer monsoon variability might be related to the intensification of the ne winter monsoon another prominent event of high productivity second in its extent to the last glacial productivity event is recognized between 430 and 460 kyr these two events seem to correspond to periods of similar orbital positioning of rather low precession and eccentricity amplitude for a relatively long period glacial boundary conditions seem to control to a large extent the ne winter monsoon variability as also indicated by the dominance of the 100 ka cycle in the investigated time series secondary in their importance are the 23 and 41 ka cycles which seem also to contribute to the ne monsoonal variability following the identification of productivity events related to the ne winter monsoon in the gulf of aden it is possible now to extend this observation to other parts of the arabian sea and consider the contribution of this monsoonal system to the productivity fluctuations preserved in the sedimentary records

numerical analysis of wave overtopping of rubble mound breakwaters abstract the paper describes the results of a two dimensional 2 d numerical modelling investigation of the functionality of rubble mound breakwaters with special attention focused on wave overtopping processes the model cobras uc is a new version of the cobras cornell breaking waves and structures based on the volume averaged reynolds average navier stokes varans equations and uses a volume of fluid technique vof method to capture the free surface the nature of the model equations and solving technique provides a means to simulate wave reflection run up wave breaking on the slope transmission through rubble mounds overtopping and agitation at the protected side due to the combined effect of wave transmission and overtopping also two dimensional experimental studies are carried out to investigate the performance of the model the computations of the free surface and pressure time series and spectra under regular and irregular waves are compared with the experimental data reaching a very good agreement the model is also used to reproduce instantaneous and average wave overtopping discharge comparisons with existing semi empirical formulae and experimental data show a very good performance the present model is expected to become in the near future an excellent tool for practical applications

three dimensional investigations of wave overtopping on rubble mound structures to study the influence of wave obliquity and directional spreading on wave overtopping of rubble mound breakwaters a total of 736 three dimensional model tests were carried out at aalborg university the results of these tests are presented and analysed in this paper yielding a new empirical reduction factor to describe the influence of wave obliquity and directional spreading on the average wave overtopping discharges the study shows that perpendicularly incident long crested waves result in conservative values of the overtopping discharge for the tested cross section

earth s eccentricity cycles and indian summer monsoon variability over the past 2 million years evidence from deep sea benthic foraminifer spectral analysis of a uvigerina proboscidea time series from dsdp site 214 using the lomb scargle method for unevenly sampled data exhibits two dominant power peaks at 412 and 94 kyrs over the last 2 million years which correspond to the earth s eccentricity cycles the results indicate that the sw monsoon varied at about 100 kyr and 400 kyr periodicities within earth s eccentricity domain milankovitch range over the past 2 million years wavelet transform analysis reveals the non stationary nature of monsoon upwelling over this interval the amplitude of the 400 kyr cycle in the u proboscidea time series began to increase at 900 kyrs as has also been observed in few recent studies we do not see a strong relation between eccentricity highs and intense summer monsoons over the studied interval

large organic walled protista gromia in the arabian sea density diversity distribution and ecology abstract the genus gromia includes large marine protists gromiids with filose pseudopodia and sack like organic tests the first deep water species were discovered in the 1990s on the oman margin of the arabian sea and subsequently found on the pakistan margin we present a survey of gromiids in samples collected off oman in 2002 and off pakistan in 2003 in addition to the two species gromia sphaerica and gromia pyriformis already described from this area at least eight undescribed gromiid species were present sausage shaped grape shaped and spherical morphotypes were represented among this material on the oman margin gromiids occurred in densities up to several thousand individuals m 2 at 1400 and 1700 m but were much less common at 1100 and 2000 m apart from g pyriformis which was fairly common several hundred individuals m 2 at 1000 m gromiids were uncommon in core samples taken off pakistan with 11 indiv m 2 at 1200 m and 19 indiv m 2 at 1850 m on both margins these protists occurred at depths 1000 m where bottom water oxygen concentrations exceeded 0 2 ml l 1 8 92 m l 1 land sediments were fully bioturbated and oxidised however they were not observed at similar oxygen levels above the omz most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria we conclude that these large protists may play an important ecological role in the bathyal arabian sea particularly in carbon cycling but also in structuring the surficial sediments in addition their tests particularly those of g sphaerica provide substrates for attached foraminifera

latest miocene pleistocene productivity and deep sea ventilation in the northwestern indian ocean deep sea drilling project site 219 knowledge of the biology of deep sea benthic foraminifera was used to interpret the results of multivariate analyses factor and cluster on relative abundance data of benthic foraminifera at deep sea drilling project site 219 southeastern arabian sea 1764 m depth in combination with carbon and oxygen isotope data faunal data document major changes in deep sea ventilation and productivity over the past 5 5 ma including the end of the miocene pliocene indo pacific biogenic bloom period at 4 0 ma interestingly there is no simple correlation between high productivity and low oxygenation productivity fluctuated but became overall more pulsed whereas overall oxygenation increased we interpret the records as a combination of local to regional fluctuations in productivity probably caused by changes in monsoonal development particularly its seasonality and changes in oxygenation of intermediate depth waters in the indian ocean caused by global changes in climate and ocean circulation

east west similarities and differences in the surface and deep northern arabian sea records during the past 21kyr abstract this study analyses monsoon proxy globigerina bulloides from ocean drilling program odp hole 723a western arabian sea and hole abp 25 02 northeastern arabian sea as well as dominant benthic foraminifera pteropods total organic carbon toc inorganic carbon ic and stable isotope values of benthic foraminifera from hole abp 25 02 to understand summer monsoon driven changes in the western and eastern arabian sea and their impacts on deep sea ventilation during the past 21 kyr we have also combined published toc data from odp hole 724b to understand if deep sea conditions in the arabian sea were same throughout the region during the studied interval the summer monsoon was generally weaker during cold intervals including the last glacial maximum the younger dryas and the bond events of the holocene from 20 to 10 kyr the deep northeastern arabian sea was better oxygenated with less organic carbon supply except during 14 12 5 kyr when toc values increased indicating a weaker summer monsoon and a weak oxygen minimum zone omz the toc values and the abundance of the eutrophic benthic foraminiferal species bulimina aculeata melonis barleeanum and uvigerina peregrina increased during the late holocene whereas well oxygenated low organic carbon benthic species sphaeroidina bulloides as well as pteropods decreased indicating an intense omz and an increased supply of refractory organic material to the arabian sea it is important to note that although the surface response to monsoon variability was more or less similar in the western and northeastern arabian sea the deep sea conditions show a marked contrast in the two regions during the past 21 kyr

global deep sea extinctions during the pleistocene ice ages the dark near freezing environment of the deep oceans is regarded as one of the most stable habitats on earth and this stability is generally reflected in the slow turnover rates extinctions and appearances of the organisms that live there by far the best fossil record of deep sea organisms is provided by the shells of benthic foraminifera protista a little known global extinction of deep sea benthic foraminifera occurred during the pleistocene ice ages in the southwest pacific it caused the disappearance of at least two families 15 genera and 48 species 15 25 of the fauna of dominantly uniserial elongate foraminifera with distinctive apertural modifications these forms progressively died back and became extinct during glacial periods in the late pliocene to middle pleistocene ca 2 5 0 6 ma most extinctions occurred between 1 0 and 0 6 ma at the time of the middle pleistocene climatic revolution this first high resolution study of this extinction event indicates that it was far more significant for deep sea diversity loss than previously reported 10 species the middle pleistocene extinction was the most dramatic last phase of a worldwide decline in the abundance of these elongate forms a phase that began during cooling near the eocene oligocene boundary and continued during the middle miocene clearly these taxa declined when the world cooled but the reason is yet to be resolved

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

changes in the distribution of uvigerinidae species over the past 775 kyr implications for the paleoceanographic evolution of the japan sea abstract the distribution of benthic foraminifera of the uvigerinidae family which are abundant in middle to upper pleistocene samples from the yamoto basin in the japan sea have been analyzed quantitatively and used for paleoceanographic interpretations twenty three uvigerinidae species are reported from iodp site u1426 6 of which are present in at least three or more samples with 10 or more abundance and considered as dominant species the abundance and ecological preferences of dominant uvigerinidae species comprised of uvigerina mediterranea uvigerina yabei uvigerina sp 1 uvigerina peregrina suggest dysoxic conditions with high influx of organic matter between 775 and 475 ka in response to the enhanced flow of the tsushima warm current the end of mis 13 marked the onset of more extreme glacial interglacial climate cycles in the japan sea glacial interglacial alternations of uvigerina peregrina and trifarina angulosa from 475 ka to the holocene indicate major fluctuations in circulation and productivity within this semi enclosed basin both u peregrina and t angulosa respond to 100 kyr variability reflecting the paleoclimatic shift and global ice volume changes associated with the middle pleistocene transition

south equatorial current sec driven changes at dsdp site 237 central indian ocean during the plio pleistocene evidence from benthic foraminifera and stable isotopes abstract this study attempts to analyse paleoceanographic changes in the central indian ocean deep sea drilling project site 237 linked to monsoon variability as well as deep sea circulation during the plio pleistocene we used factor and cluster analyses of census data of the 34 most dominant species of benthic foraminifera that enabled us to identify five biofacies astrononion umbilicatulum uvigerina proboscidea au up pullenia bulloides bulimina striata pb bs globocassidulina tumida nuttallides umbonifera gt nu gyroidinoides nitidula cibicides wuellerstorfi gn cw and cassidulina carinata cassidulina laevigata cc cl biofacies knowledge of the environmental preferences of modern deep sea benthic foraminifera helped to interpret the results of factor and cluster analyses in combination with oxygen and carbon isotope values the biofacies indicative of high surface productivity resulting from a stronger south equatorial current au up and pb bs biofacies dominate the early pliocene interval 5 6 4 5 ma of global warmth an intense indo pacific biogenic bloom and strong oxygen minimum zone extended to intermediate depths 1000 2000 m over large parts of the indian ocean in the early pliocene since 4 5 ma the food supply in the central indian ocean dropped and fluctuated while deep waters were corrosive biofacies gt nu gn cw the pleistocene interval is characterized by an intermediate flux of organic matter cc cl biofacies

changes in intermediate circulation in the bay of bengal since the last glacial maximum as inferred from benthic foraminifera assemblages and geochemical proxies benthic foraminiferal assemblages and geochemical tracers delta o 18 delta c 13 and c 14 have been analyzed on benthic and planktonic foraminifera from core md77 176 located in the northern bay of bengal in order to reconstruct the evolution of intermediate circulation in the northern indian ocean since the last glaciation results indicate that during the last glacial maximum lgm southern sourced water masses were dominant at the core site a high relative abundance of intermediate and deep infaunal species during the lgm reflects low oxygen concentration and or mesotropic to eutrophic deep water conditions associated with depleted benthic delta c 13 values during the holocene benthic foraminiferal assemblages indicate an oligotropic to mesotrophic environment with well ventilated bottom water conditions compared with lgm higher values for benthic foraminifera delta c 13 and b p c 14 age offsets suggest an increased contribution of north atlantic deep water to the northern bay of bengal during the late holocene compared to the lgm millennial scale events punctuated the last deglaciation with a shift in the delta c 13 and the epsilon nd values coincident with low b p c 14 age offsets providing strong evidence for an increased contribution of antarctic intermediate water at the studied site this was associated with enhanced upwelling in the southern ocean reflecting a strong sea atmospheric co2 exchange through southern ocean ventilation during the last deglaciation

numerical study of combined overflow and wave overtopping over a smooth impermeable seawall abstract a numerical wave flume is used to investigate the discharge characteristics of combined overflow and wave overtopping of impermeable seawalls the numerical procedure computes solutions to the reynolds averaged navier stokes equations and includes the generation of an irregular train of waves the simulation of wave breaking and interaction with a sloping impermeable wall the numerical model is first tested against published experimental observations approximate analytical solutions and empirical design formulae for the cases of pure overflow and pure overtopping a sequence of numerical experiments simulating combined overflow and overtopping are described the results are used to determine empirical discharge formulae of the form used in current practice

glacial interglacial variations in sediment organic carbon accumulation and benthic foraminiferal assemblages on the bermuda rise odp site 1063 during mis 13 to 10 glacial times organic d 13 c values are less negative during mis 12 and mis 10 than during mis 11 which is consistent with greater glacial stage marine productivity high relative abundances of oridorsalis umbonatus during glacial intervals probably records a low but sustained flux of highly degraded organic material large recurrent fluctuations in the abundance of epistominella exigua at the beginnings of the mis 12 and mis 10 glaciations suggest a marked increase in local phytoplankton blooms at these times and consequent delivery of phytodetritus to the seafloor the most likely causes of these variations are changes in the position and strength of the gulf stream and its associated cold ring eddies combined with increased advection of terrigenous sediments from northerly locations during glacial lowstands

initiation of northern hemisphere glaciation and strengthening of the northeast indian monsoon ocean drilling program site 758 eastern equatorial indian ocean the indian monsoon system as recorded by ocean floor biota benthic foraminifera at ocean drilling program site 758 in the eastern equatorial indian ocean has varied dramatically over the past 5 5 m y long after the onset of the monsoons at 10 8 ma benthic foraminifera that thrive with high productivity year round were common before the formation of northern hemisphere continental ice sheets ca 3 1 2 5 ma indicating that the summer southwest monsoon had high intensity and long seasonal duration ca 2 8 ma benthic faunas became dominated by taxa that flourish with a seasonally strongly fluctuating food supply indicating that the northeast winter monsoon during which primary productivity is relatively low increased in duration and strength to form a system similar to that of today the change occurred coeval with the initiation of the northern hemisphere glaciation documenting a close link between the development of the indian monsoon and northern hemisphere glaciation

benthic foraminiferal response to late glacial and holocene sea level rise and rainfall variability off east africa analogous to west and north africa east africa experienced more humid conditions between approximately 12 and 5 kyr bp relative to today while timing and extension of wet phases in the north and west are well constrained this is not the case for the east african humid period here we present a record of benthic foraminiferal assemblages and sediment elemental compositions of a sediment core from the east african continental slope in order to provide insight into the regional shallow indian ocean paleoceanography and east african climate history of the last 40 kyr during glacial times the dominance of a benthic foraminiferal assemblage characterized by bulimina aculeata suggests enhanced surface productivity and sustained flux of organic carbon to the sea floor during heinrich stadial 1 h1 the nuttallides rugosus assemblage indicates oligotrophic bottom water conditions and therefore implies a stronger flow of southern sourced aaiw to the study site during the east african humid period the saidovina karreriana assemblage in combination with sedimentary c n and fe ca ratios suggest higher river runoff to the indian ocean and hence more humid conditions in east africa between 8 5 and 8 1 kyr contemporaneous to the globally documented 8 2 kyr event a severe reduction in river deposits implies more arid conditions on the continent comparison of our marine data with terrestrial studies suggests that additional moisture from the atlantic ocean delivered by an eastward migration of the congo air boundary during that time period could have contributed to east african rainfall since approximately 9 kyr the gaining influence of the millettiana millettii assemblage indicates a redevelopment of the east african fringe reefs

recent abyssal benthic foraminiferal biofacies of the eastern equatorial indian ocean abstract study of recent abyssal benthic foraminifera from core top samples in the eastern equatorial indian ocean has identified distinctive faunas whose distribution patterns reflect the major hydrographic features of the region above 3800 m indian deep water idw is characterized by a diverse and evenly distributed biofacies to which globocassidulina subglobosa pyrgo spp uvigerina peregrina and eggerella bradyi are the major contributors nuttalides umbonifera and epistominella exigua are associated with indian bottom water ibw below 3800 m within the ibw fauna n umbonifera and e exigua are characteristic of two biofacies with independent distribution patterns nuttalides umbonifera systematically increases in abundance with increasing water depth the e exigua biofacies reaches its greatest abundance in sediments on the eastern flank of the ninetyeast ridge and in the wharton cocos basin the hydrographic transition between idw and ibw coincides with the level of transition from waters supersaturated to waters undersaturated with respect to calcite and with the depth of the lysocline carbonate saturation levels possibly combined with the effects of selective dissolution on the benthic foraminiferal populations best explain the change in faunas across the idw ibw boundary and the bathymetric distribution pattern of n umbonifera the distribution of the e exigua fauna cannot be explained with this model epistominella exigua is associated with the colder more oxygenated ibw of the wharton cocos basin the distribution of this biofacies on the eastern flank of the ninetyeast ridge agrees well with the calculated bathymetric position of the northward flowing deep boundary current which aerates the eastern basins of the indian ocean

a benthic foraminiferal proxy of pulsed organic matter paleofluxes in the temperate open ocean of the modern northeast atlantic the spring bloom of phytoplankton leads to a seasonal pulse of detrital organic material phytodetritus to the ocean floor opportunistic benthic foraminifera rapidly colonise this food resource producing large numbers of individuals whose tests are ultimately added to the sediment one of these taxa epistominella exigua shows periodic peaks in abundance in the fossil record at many open ocean sites previously such peaks have been commonly interpreted to result from changes in physicochemical properties of bottom water mass and thus deep sea circulation the main purpose of this paper is to propose thate exigua may be used as a proxy of pulsed organic matter inputs to the deep ocean and therefore as an indicator of relative changes in productivity

late oligocene miocene paleoceanographic evolution of the southeastern indian ocean evidence from deep sea benthic foraminifera odp site 757 abstract we quantitatively analyzed deep sea benthic foraminifera from 125 m size fraction from ocean drilling program odp site 757 to understand deep sea paleoceanographic changes in the southeastern indian ocean during the late oligocene miocene 26 5 5 35 ma we used the knowledge of the ecology of recent deep sea benthic foraminifera for environmental interpretations factor and cluster analyses were run using percentages of 46 highest ranked species that helped identify six biofacies defining six clusters of samples the faunal data document a major shift in deep sea ventilation organic carbon flux and productivity at 8 3 ma coinciding with the major intensification of the indian ocean monsoon system this marks a change from cold and well oxygenated deep waters with low and pulsed organic carbon flux during 26 5 to 8 3 ma to oxygen poor deep waters with sustained flux of organic matter from 15 0 to 7 6 ma the deep sea currents were stronger in the southeastern indian ocean probably due to major expansion of the east antarctic ice sheet and increased production of deep waters and in turn increased deep sea circulation the productivity increased in the indo pacific region in the late miocene and the modern monsoon regime probably established at 8 3 ma

numerical simulation of wave overtopping of coastal structures using the non linear shallow water equations a one dimensional high resolution finite volume model capable of simulating storm waves propagating in the coastal surf zone and overtopping a sea wall is presented the model amazon is based on solving the non linear shallow water nlsw equations a modern upwind scheme of the godunov type using an hll approximate riemann solver is described which captures bore waves in both transcritical and supercritical flows by employing a finite volume formulation the method can be implemented on an irregular structured boundary fitted computational mesh the use of the nlsw equations to model wave overtopping is computationally efficient and practically flexible though the detailed structure of wave breaking is of course ignored it is shown that wave overtopping at a vertical wall may also be approximately modelled by representing the wall as a steep bed slope the amazon model solutions have been compared with analytical solutions and laboratory data for wave overtopping at sloping and vertical seawalls and good agreement has been found the model requires more verification tests for irregular waves before its application as a generic design tool

the impact of the mediterranean outflow water mow on benthic foraminiferal assemblages and surface sediments at the southern portuguese continental margin benthic foraminifera and surface sediments were analyzed from 23 box core and core top samples from 250 to 3600 m depth at the southern portuguese continental margin between 37 and 38 n this area is affected by the mow which flows northwards along the slope between 600 and 1500 m waterdepth sediment structures grain size distribution and clay mineral assemblages of surface sediments indicate active winnowing in the upper part of the mow and deposition of the fine fraction near its lower boundary r mode cluster analyses of foraminiferal census data from the 250 m fraction revealed four associations the shelf edge association occurs on glauconitic shelf and upper slope sands down to 268 m the upper slope association is recognized between 498 and 1300 m where sand silt clays to clayey silts are encountered the lower slope association is found between 1405 and 2985 m and differs markedly from assemblages below 3000 m deep water association where the near surface sediments are soft hemipelagic clays the boundary layer association shows no significant depth limits but abundance maxima both in the density interface above the mow and in the interval of decreasing turbulence below it the boundaries of the shelf edge and upper slope association correspond to these hydrographic boundary layers whereas the boundary between lower slope and deep water assemblage is related to threshold values of nutrient flux to the benthic community examination of hard substrates reveals 27 different species of epibenthic foraminifera six of these the epibenthos group were found attached to elevated substrates only within the mow above the mow elevated substrates were inhabited by different species whilst below the mow they were not used by any epibenthic foraminifers evidently the hydrodynamic environment of the mow current provides an ecological niche which is efficiently used by opportunistic suspension feeders the epibenthos group is more abundant in the middle part of the study area between 37 20 and 37 40 n where the sand content of surface sediments is also higher both indicate an enhanced sediment water interaction in this area which results from an obstruction of the mow flow by the principes d avis basement spur

exploring quaternary paleolake evolution and climate change in the western qaidam basin based on the bulk carbonate geochemistry of lake sediments abstract this study focuses on the concentration of major and trace elements in the diluted acetic acid soluble fraction of sg 1 core lacustrine sediments from the western qaidam basin tibetan plateau in order to explore the potential of applying bulk carbonate analysis to tracing paleolake evolution and climate change the sg 1 core sediments are considered highly suited to the exploration of the paleoenvironmental significance of bulk carbonate geochemistry because most carbonates in the core are authigenic in origin based on a principal component analysis of the elemental composition of diluted acetic acid leachate four major components with distinct characteristics have been extracted accounting for 80 of the total variance the first and most important component is associated with a high positive loading of mn p y sc and rare earth elements ree the second component is characterized by a high positive loading of ca sr and u the third component displays a high negative loading of mg li and b and the fourth component is associated with a relatively high positive loading of fe v and cr after considering the geochemical behavior of these element assemblies during acid leaching we have concluded that these four components contain information indicative of watershed climate conditions carbonate precipitation lake water salinity and iron oxide content respectively reconstructions of watershed climate change and paleolake evolution using the component scores are comparable to those reconstructed from other independent proxy records indicating a long term trend of lake shrinkage and climatic drying since 2 7 ma with abrupt drying events at 2 5 ma 1 8 ma 1 2 ma and 0 6 ma our results suggest that lake carbonates bear more information about watershed climate and lake evolution than expected and that occurrences of some elements in particular trace elements in the diluted acetic acid leachate are not solely and necessarily linked to carbonate minerals

faunal responses to oxygen gradients on the pakistan margin a comparison of foraminiferans macrofauna and megafauna the pakistan margin is characterised by a strong mid water oxygen minimum zone omz that intercepts the seabed at bathyal depths 150 1300 m we investigated whether faunal abundance and diversity trends were similar among protists foraminiferans and gromiids metazoan macrofauna and megafauna along a transect 140 1850 m water depth across the omz during the 2003 intermonsoon march may and late post monsoon august october seasons all groups exhibited some drop in abundance in the omz core 250 500 m water depth o2 0 10 0 13 ml l 1 4 46 5 80 m but to differing degrees densities of foraminiferans 63 m were slightly depressed at 300 m peaked at 738 m and were much lower at deeper stations foraminiferans 300 m were the overwhelmingly dominant macrofaunal organisms in the omz core macrofaunal metazoans reached maximum densities at 140 m depth with additional peaks at 850 940 and 1850 m where foraminiferans were less abundant the polychaete linopherus sp was responsible for a macrofaunal biomass peak at 950 m apart from large swimming animals fish and natant decapods metazoan megafauna were absent between 300 and 900 m o2 0 2 ml l 1 8 92 m the progressively deeper abundance peaks for foraminiferans 63 m linopherus sp and ophiuroids probably represent lower omz boundary edge effects and suggest a link between body size and tolerance of hypoxia macro and megafaunal organisms collected between 800 and 1100 m were dominated by a succession of different taxa indicating that the lower part of the omz is also a region of rapid faunal change species diversity was depressed in all groups in the omz core but this was much more pronounced for macrofauna and megafauna than for foraminiferans oxygen levels strongly influenced the taxonomic composition of all faunal groups calcareous foraminiferans dominated the seasonally and permanently hypoxic sites 136 300 m agglutinated foraminiferans were relatively more abundant at deeper stations where oxygen concentrations were 0 13 ml l 1 5 80 m polychaetes were the main macrofaunal taxon within the omz calcareous macrofauna and megafauna molluscs and echinoderms were rare or absent where oxygen levels were lowest the rarity of larger animals between 300 and 700 m on the pakistan margin compared with the abundant macrofauna in the omz core off oman is the most notable contrast between the two sides of the arabian sea this difference probably reflects the slightly higher oxygen levels and better food quality on the western side

benthic foraminiferal assemblages from the eastern south atlantic polar front region between 35 and 57 s distribution ecology and fossilization potential abstract surface sediment samples taken with a multiple corer from the polar front region along two profiles in the eastern south atlantic sector between 35 and 57 s have been investigated for their benthic foraminiferal content live fauna was differentiated from the death assemblage based on the dead assemblages potential fossil assemblages dead fauna reduced by non resistant agglutinants were calculated for comparison with upper neogene core material the distribution of the potential fossil assemblages defined byq mode principal component analysis mirrors the recent hydrographic as well as the trophic situation in the eastern south atlantic ocean circulation and productivity two southern component bottom water faunas reflect the northward flow of antarctic bottom water aabw and lower circum polar deep water lcdw an assemblage dominated by the arenaceousmultifidella nodulosa below the calcite compensation depth ccd and anuttallides umbonifer dominated assemblage above the ccd in the region of highest bio silicious primary productivity south of the polar front and north of the winter sea ice limit these faunas are overprinted by a southern high productivity fauna dominated by infaunal species such aspullenia bulloides melonis pompilioides andm zaandamae north atlantic deep water nadw meets the circum polar deep water cdw at intermediate depth as reflected in the distribution of the northern component deep water fauna dominated byepistominella exigua the high productivity assemblage overprinting this fauna the northern high productivity fauna is dominated by the shallow endobenthicbulimina aculeata a strong bottom current fauna dominated byangulogerina angulosa characterizes areas between 400 and 900 m water depth with sandy sediment independent from water mass characteristics and food supply

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia

2 d numerical analysis of near field flow at low crested permeable breakwaters abstract this paper describes the capability of a numerical model named cornell breaking waves and structures cobras lin p liu p l f 1998 a numerical study of breaking waves in the surf zone journal of fluid mechanics 359 239 264 liu p l f lin p chang k a sakakiyama t 1999 numerical modeling of wave interaction with porous structures journal of waterway port coastal and ocean engineering 125 322 330 liu p l f lin p hsu t chang k losada i j vidal c sakakiyama t 2000 a reynolds averaged navier stokes equation model for nonlinear water wave and structure interactions proc coastal structures 99 169 174 based on the reynolds averaged navier stokes rans equations to simulate the most relevant hydrodynamic near field processes that take place in the interaction between waves and low crested breakwaters the model considers wave reflection transmission overtopping and breaking due to transient nonlinear waves including turbulence in the fluid domain and in the permeable regions for any kind of geometry and number of layers small scale laboratory tests were conducted in order to validate the model with different wave conditions and breakwater configurations in the present study regular waves of different heights and periods impinging on a wide crested structure are considered three different water depths were tested in order to examine the influence of the structure freeboard the experimental set up includes a flow recirculation system aimed at preventing water piling up at the lee of the breakwater due to overtopping the applicability and validity of the model are examined by comparing the results of the numerical computations with experimental data the model is proved to simulate with a high degree of agreement all the studied magnitudes free surface displacement pressure inside the porous structure and velocity field the results obtained show that this model represents a substantial improvement in the numerical modelling of low crested structures lcs since it includes many processes neglected previously by existing models the information provided by the model can be useful to analyse structure functionality structure stability scour and many other hydrodynamic processes of interest

distribution and constraining factors of planktonic and benthic foraminifers in bottom sediments of the southern south china sea abstract a total of 93 surface sediment samples were collected to analyze the environmental factors constraining the foraminiferal distribution pattern in the southern south china sea scs species distributions and stable isotopic compositions were combined to reveal the controlling factors such as depth salinity substrate runoff currents and cold seep activities water depth is the dominant factor controlling both assemblage composition and 18o of benthic foraminiferal tests the 1000 m isobath separates the sites into two clusters cluster a and b which are dominated by deep water species and shallow water species respectively the sites in the deep water zone cluster a are characterized by lower absolute abundances species richness and shannon index values a measure of diversity and higher proportions of planktonic foraminifers compared with the sites in the shallow water zone cluster b increasing proportions of agglutinated tests with depth and rapidly decreasing proportions of planktonic foraminifera in the nansha trough basin provide evidence of calcium dissolution occurring at a depth corresponding with previous reports oxygen stable isotopes 18ob of benthic foraminifera become more positive with depth only up to 1000 m and remain constant beyond differences in the proportion of agglutinated and porcelaneous tests in the shallow water zone suggest that terrestrial runoff from nearby river systems mekong river and northern borneo rivers and seasonal surface currents scs southern cyclonic gyre and scs southern anticyclonic gyre jointly influence the distribution patterns of foraminifera in the study area enrichment of planktonic 18o is a response to cold waters brought by the scs southern cyclonic gyre during winter an upwelling current winter natuna off shelf current containing higher amounts of organic matter nutrients contributes to the depleted 13c of planktonic foraminifera and to the abnormal abundance of foraminifera at the sites within its area of influence the dominance of the foraminifer melonis barleeanus at sites belonging to subcluster a1 and the stable isotope compositions of benthic foraminifera 18o 0 13c