monsoonal and fertility controls on recent marginal sea and continental shelf coccolith assemblages from the western pacific and northern indian oceans gephyrocapsa oceanica is often overwhelmingly dominant in coccolith assemblages found in monsoonal regions including the marginal seas of the western pacific and the more open seas and continental shelf of the northern indian ocean the dominance of g oceanica is thought to reflect its preference for elevated nutrient levels and a tolerance of lithogenic particles emiliania huxleyi is subordinate in assemblages deposited in monsoonal regions coccolith assemblages with dominant e huxleyi are restricted to marginal seas with lagoonal anti estuarine circulation e g red sea and open seas and continental shelves with strong oceanic influences but no monsoonal effects e g southern great barrier reef coral sea and great australian bight

identification of sulfur sources and isotopic equilibria in submarine hot springs using multiple sulfur isotopes abstract multiple sulfur isotopes were measured in metal sulfide deposits elemental sulfur and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents areas studied include the eastern manus basin and lau basin back arc spreading centers and the unsedimented basalt hosted southern east pacific rise sepr and sediment hosted guaymas basin mid ocean ridge spreading centers chalcopyrite and dissolved hydrogen sulfide h 2 s 34 s values range from 5 5 to 5 6 in manus basin samples 2 4 to 6 1 in lau basin samples and 3 7 to 5 7 in sepr samples values of 34 s for cubic cubanite and h 2 s range from 1 4 to 4 7 in guaymas basin samples multiple sulfur isotope systematics in fluid mineral pairs from the sepr and lau basin show that crustal host rock and thermochemical reduction of seawater derived dissolved sulfate so 4 are the primary sources of sulfur in mid ocean ridge and some back arc systems at pacmanus and susu knolls hydrothermal systems in the eastern manus basin a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide so 2 while the remaining sulfur is derived from crustal host rocks and so 4 reduction at the sedimented guaymas basin hydrothermal system sulfur sources include crustal host rock reduced seawater so 4 and biogenic sulfide vent fluid flow through fresher less mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34 s enriched so 4 while fluid interaction with more highly altered sediments results in h 2 s characterized by a small but isotopically significant input of 34 s depleted biogenic sulfides near zero 33 s values in all samples implicate the abiotic processes of so 4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid ocean ridge and at a back arc system 33 s values indicate that so 2 disproportionation is an additional process that contributes sulfur to a different back arc system and to acid spring type hydrothermal fluid circulation at the sedimented guaymus basin near zero 33 s values are also observed despite negative 34 s values that indicate inputs of biogenic pyrite for some samples in contrast with previous studies reporting isotope disequilibrium between h 2 s and chalcopyrite the 34 s values of chalcopyrite sampled from the inner 1 2 mm of a chimney wall are within 1 of 34 s values for h 2 s in the paired vent fluid suggesting equilibrium fluid mineral sulfur isotope exchange at 300 400 c isotopic equilibrium between hydrothermal fluid h 2 s and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity

variable morphologic expression of volcanic tectonic and hydrothermal processes at six hydrothermal vent fields in the lau back arc basin ultrahigh resolution bathymetric maps 25 cm grid are used to quantify the physical dimensions of and spatial relationships between tectonic volcanic and hydrothermal features at six hydrothermal vent fields in the lau back arc basin supplemented with near bottom photos and nested within regional dsl 120a side scan sonar data these maps provide insight into the nature of hydrothermal systems along the eastern lau spreading center elsc and valu fa ridge vfr along axis transitions evident in localized volcanic morphology and tectonic characteristics include a change from broad low relief volcanic domes hundreds of meters wide 10 m tall that are dominated by pillow and lobate lava morphologies and are cut by faults and fissures to higher aspect ratio volcanic domes tens of meters wide tens of meters tall dominated by aa type lava morphologies with finger like flows and few tectonic structures these along axis differences in localized seafloor morphology suggest differences in hydrothermal circulation pathways within the shallow crust and correlate with regional transitions in a variety of ridge properties including the large scale morphology of the ridge axis shallow axial valley to axial high seafloor lava compositions and seismic properties of the upper crust differences in morphologic characteristics of individual flows and lava types were also quantified providing an important first step toward the remote characterization of complex terrains associated with hydrothermal vent fields

calculation of coccolith volume and its use in calibration of carbonate flux estimates abstract estimates of coccolith volume help in determining total coccolith carbonate fluxes and the relative contributions of various coccolith species it is argued here that the best approach to deriving such coccolith volumes is to calculate shape factors k s for each species separately based on reconstruction of cross profiles and to determine mean sizes from measurement of size variation in the sample of interest then volume k s l 3 values of k s are given for the most important extant coccolith species based on reconstruction of cross sections followed by calculation of a volume of rotation using an iterative routine implemented in an image analysis package substantial errors ca 50 are inevitable in such calculations but the resultant data are nonetheless of value coccolith assemblages from north atlantic 47 n 20 w jgofs 1989 sediment trap samples are analysed as a test case calculated coccolith pic fluxes constitute 30 80 of the chemically determined total pic fluxes

phyto_ and zooplankton paleofluxes during the deposition of sapropel s1 eastern mediterranean biogenic carbonate preservation and paleoecological implications abstract the relative and absolute abundances and accumulation rates of foraminifera and calcareous nannofossils were quantified in a box core containing sapropel s1 from the florence rise area se of cyprus 2302 m water depth the main objective of this study was to reconstruct in detail variations in paleoecological conditions of water masses during the deposition of this sapropel in particular we qualitatively evaluated the importance of carbonate dissolution on planktonic assemblages to better interpret the abundance profiles obtained from the two investigated taxa selective carbonate corrosion in the core is shown by 1 the decrease in shell mass weight of selected species of planktonic foraminifera 2 the decrease in accumulation rate of dissolution susceptible holococcoliths and coccolith species and 3 the absence of pteropods however the presence of other relatively dissolution susceptible coccolith species throughout all of the s1 interval suggests moderate dissolution florisphaera profunda shows a marked increase in paleofluxes within the sapropel coupled with a decrease in the accumulation rate of the upper middle photic zone coccoliths suggesting an ecological depth separation of the water column probably characterised by higher nutrient availability at depth and nutrient depleted surface waters between 10 and 6 5 kyr bp in the same interval turborotalita quinqueloba and globigerina bulloides two foraminiferal species frequently occurring during periods of high fertility increase in relative abundance the maximum increase in relative abundance of globigerinoides ruber var alba and rosea marks the climatic optimum phase and the maximum stratification in surface water that occurred at the beginning of sapropel s1 deposition when the bottom waters were anoxic an important change in foraminiferal assemblages occurs at 8 kyr bp and corresponds with a negative shift in caco 3 ba and c org contents this short interval marks the establishment of relatively less anoxic conditions in the bottom water introducing the last phase of sapropel formation after 6 5 kyr bp a progressive re establishment of normal oceanographic conditions occurred before the real end of the sapropel s1 this transition is well recorded by the reoccurrence and major accumulation rate of the mixing indicator foraminiferal species globorotalia inflata and by the gradual decrease in abundance of f profunda

integrated fe and s isotope study of seafloor hydrothermal vents at east pacific rise 9 10 n abstract in this study we report on coupled fe and s isotope systematics of hydrothermal fluids and sulfide deposits from the east pacific rise at 9 10 n to better constrain processes affecting fe isotope fractionation in hydrothermal environments we aim to address three fundamental questions 1 is there significant fe isotope fractionation during sulfide precipitation 2 is there significant variability of fe isotope composition of the hydrothermal fluids reflecting sulfide precipitation in subsurface environments 3 are there any systematics between fe and s isotopes in sulfide minerals the results show that chalcopyrite precipitating in the interior wall of a hydrothermal chimney displays a limited range of 56fe values and 34s values between 0 11 to 0 33 and 2 2 to 2 6 respectively the 56fe values are on average slightly higher by 0 14 relative to coeval vent fluid composition while 34s values suggest significant s isotope fractionation 0 6 0 2 during chalcopyrite precipitation in contrast systematically lower 56fe and 34s values relative to hydrothermal fluids by up to 0 91 and 2 0 respectively are observed in pyrite and marcasite precipitating in the interior of active chimneys these results suggest isotope disequilibrium in both fe and s isotopes due to s isotopic exchange between hydrothermal h2s and seawater so42 followed by rapid formation of pyrite from fes precursors thus preserving the effects of a strong kinetic fe isotope fractionation during fes precipitation in contrast 56fe and 34s values of pyrite from inactive massive sulfides which show evidence of extensive late stage reworking are essentially similar to the hydrothermal fluids multiple stages of remineralization of ancient chimney deposits at the seafloor appear to produce minimal fe isotope fractionation similar affects are indicated during subsurface sulfide precipitation as demonstrated by the lack of systematic differences between 56fe values in both high temperature fe rich black smokers and lower temperature fe depleted vents

precessional forcing of nutricline dynamics in the equatorial atlantic climate control of nutricline depth in the equatorial atlantic can be monitored by variations in the abundance of the phytoplankton species florisphaera profunda a conceptual model based on in situ evidence associates high abundances of f profunda with a deep nutricline and low abundances with a shallow nutricline a 200 000 year record of f profunda relative abundances obtained from a deep sea core sited beneath the region of maximum equatorial divergence at 10 w has 52 percent of its variance centered on the 23 000 year precessional band cross spectral analysis between the signals of f profunda and sea surface temperature independently derived from zooplankton species shows their 23 000 year cycles to be coherent and nearly in phase abundance minima of f profunda coincide with times of december perihelion whereas abundance maxima coincide with june perihelion these relations indicate that nutricline dynamics in the divergence region of the equatorial atlantic are controlled by variations in the tropical easterlies forced by the precessional component of orbital insolation on time scales greater than 10 000 years

seasonality and variability of coccolithophore fluxes in response to diverse oceanographic regimes in the bay of bengal sediment trap results a study on coccolithophores from the sediment trap samples collected over a period of one year january 1992 december 1992 from three trap locations in the bay of bengal bob were used to understand their production and export processes in relation to diverse oceanographic regimes associated with the reversing monsoons a total of 25 species of coccolithophores were identified which include some of the ecologically important species viz gephyrocapsa oceanica umbilicosphaera sibogae florisphaera profunda umbellosphaera irregularis emiliania huxleyi oolithotus antillarum u tenuis helicosphaera carteri and calcidiscus leptoporus the total coccolithophore fluxes increased from the northern to southern bay of bengal where g oceanica u sibogae and e huxleyi were dominant species displaying seasonality with peak fluxes occurring during southwest sw and northeast ne monsoons reflecting their affinity for nutrient rich waters brought in by river plumes divergences and cyclonic eddies u irregularis an indicator of oligotrophic warm water recorded peak abundance fluxes only during the spring intermonsoon period at all trap locations thus inferring its preference for oligotrophic conditions caused by increased sea surface temperature sst stratification and lack of nutrient supply due to weak wind velocities the deep dwelling species f profunda recorded high fluxes during the fall intermonsoon october november in the northern and southern traps during the spring intermonsoon the peak fluxes observed during the spring intermonsoon april may in the central and southern traps indicated the prevalence of a deep nutricline when oligotrophic conditions prevailed at the surface the interannual variability of coccolithophore assemblages between the years 1992 and 1994 may be attributed to the prevalence of enso el nino southern oscillation and negative iod indian ocean dipole during 1992 and moderate enso and positive iod with different ocean dynamics in 1994 interestingly dissolution was encountered as evidenced by the presence of corroded coccoliths similarly mechanical breakage of coccoliths was also observed it is believed that the biologically mediated processes were the main factors responsible for both the dissolution and mechanical breakage of coccoliths

seasonal occurrence of coccoliths in sediment traps from west caroline basin equatorial west pacific ocean abstract coccolith fluxes were investigated by sediment trap studies in the west caroline basin which is located in the equatorial western pacific the investigation was conducted from june 1991 to march 1992 at two water depths 1592 and 3902 m as part of the northwest pacific carbon cycle study nopaccs program two seasonal maxima of coccolith fluxes were observed during september early october and late december january the average coccolith and coccosphere fluxes at the depth of the shallow trap were 1800 106 coccoliths m 2 day 1 and 1 9 106 coccospheres m 2 day 1 respectively the flux of coccoliths followed the same trend as the total flux and was closely correlated with the flux of organic matter flux florisphaera profunda gladiolithus flabellatus gephyrocapsa oceanica umbilicosphaera sibogae var sibogae emiliania huxleyi and oolithotus fragilis were the most abundant species together comprising more than 85 of the total flora observed seasonal changes of the species composition of coccolith flora as well as analysis of the r mode cluster revealed that during the summer the assemblage was marked by the dominance of g oceanica and u sibogae however during the winter the assemblage was dominated by e huxleyi and o fragilis these assemblage changes were influenced by monsoonal events which were observed off the new guinea coast f profunda dominated the community in the shallow trap throughout most of the year peak values of this species were recorded during the winter the coccosphere assemblage was dominated by g oceanica at both water depths in the deep trap the sedimentation pattern was similar to that observed at the shallow depth mean coccolith and coccosphere fluxes at the deep trap were 2000 106 coccolith m 2 day 1 and 0 08 106 coccospheres m 2 day 1 respectively the increase in coccolith flux with water depth suggests a lateral influx the estimated average daily mass of caco3 flux in coccoliths and coccospheres was 16 6 mg m 2 day 1 at the 1592 m trap and 17 9 mg m 2 day 1 at the 3902 m trap respectively these calculated values contributed only 23 3 to the total caco3 flux at the shallow trap and 27 9 at the deep trap

distribution of living coccolithophores in the california current system southern california borderland the distribution of living coccolithophores in the california current system of southern california at 10 m water depth was investigated on two dates in march and june 1982 six closely spaced stations were sampled in march of which three were resampled in june thirty six euphotic species were identified of which four emiliania huxleyi umbilicosphaera sibogae gephyrocapsa oceanica andrhabdosphaera longistylis respectively were the most abundant both the cold and warm morphotypes ofe huxleyi were present in varying proportions large ranges in community structure diversity 0 35 2 64 natural bels and standing crop 1 0 104 6 2 105cells l were recorded this range of end member values is approximately that found in the open ocean from 0 to about 65 latitude the distributions of four coccolithophore assemblages recognized in march samples from the borderland area appear to reflect the following distinct water masses 1 california current 2 southern california counter current 3 transitional zone 4 near shore the coccolithophore assemblages from the june stations were more uniform indicating that the borderland was experiencing more stable conditions than in march

calcareous phytoplankton response to the half century of interannual climatic variability in santa barbara basin california 1 a high resolution study of calcareous phytoplankton in a box core from the santa barbara basin sbb reveals floral assemblage fluctuations which can be related to climatic and paleoceanographic changes during the last half century 1940 1996 in particular gephyrocapsa oceanica production increased during el nino periods in response to high temperatures silica depletion and increased iron availability conversely helicosphaera carteri flux increases in conjunction with lower surface temperatures associated with la nina episodes increasing abundances of florisphaera profunda and umbilicosphaera sibogae after 1970 reflect a warming trend and increased stratification within the basin associated with the warm phase of the pacific decadal oscillation pdo conversely increased abundances of coccolithus pelagicus and calcidiscus leptoporus before 1970 mark the cold phase of pdo these coccolithophore production rate data are consistent with instrumental records of surface and thermocline temperatures monitored since 1950 this is the first study to document the response of calcareous phytoplankton to surface water warming occurring in sbb since 1970

seasonal change in foraminiferal production in the western equatorial pacific warm pool evidence from sediment trap experiments seasonal changes in the flux of individual planktonic foraminifera in the deep ocean have been studied in the western equatorial pacific warm pool using material collected by sediment traps over a period of 1 yr 1991 1992 mean total foraminiferal fluxes tffs were 171 and 97 shells m 2 day 1 at sites n1 2 59 8 n 135 01 5 e and n2 4 07 5 n 136 16 6 e respectively the seasonal change in tffs was much higher than for organic matter om and carbonate fluxes the major species of planktonic foraminifera were pulleniatina obliquiloculata neogloboquadrina dutertrei globigerinoides sacculifer globigerinella aequilateralis and globigerinoides ruber symbiont bearing species and n dutertrei were predominant in the western equatorial pacific warm pool comparison between the warm pool and upwelling deep sea research ii 43 1996 1257 mar micropaleontology 33 1998 157 indicates that the foraminiferal assemblage trapped at the western equatorial pacific warm pool was comparable with the south equatorial and subtropical assemblages during a plankton tow study conducted at 140 w in 1992 it suggests that fairly oligotrophic conditions prevailed in the western equatorial pacific warm pool in association with terrestrial nutrient inputs or temporary mixing by wind bursts the om flux was more positively correlated with the 63 m carbonate fraction mainly composed of coccoliths r 0 87 and biogenic opal which suggests that om fluxes were more affected by phytoplankton productivity although food availability is generally important for foraminiferal production tffs were poorly correlated with om fluxes at sites n1 and n2 which is partly attributed to the significant influence of symbiont photosynthesis the 18o values of p obliquiloculata and n dutertrei showed maxima in association with high om fluxes during period 2 from august to october and period 4 from late december to april at site n1 reflecting thickening of the mixed layer following wind bursts g sacculifer showed a lunar reproduction cycle when between july and october carbonate production was more predominant than biogenic opal production a similar profile was evident for g ruber orbulina universa and g aequilateralis these four species are generally predominant at low latitudes therefore the lunar reproduction cycle may significantly affect the fluctuation in carbonate production in the equatorial ocean

distribution and malformation of extant calcareous nannoplankton in the indonesian seas abstract the calcareous nannoplankton distribution has been determined from surface and subsurface water samples and floating and moored sediment trap samples taken during the indonesian dutch snellius ii expedition in july 1984 may 1985 from the banda sea and adjacent seas an area with seasonally changing upwelling and downwelling conditions the surface water 0 5 m coccolithophorid standing crop and species diversity were very low to zero in the subsurface water 50 300 m coccolithophorids were more abundant a total of 36 living species were recorded seasonal changes in coccolithophorid abundance in the surface water and previous pigment data suggest that coccolithophorids are present but devoid of coccoliths during the northwest monsoon in january february it seems that low salinity and nutrient depletion of the surface waters during the northwest monsoon january february restrict coccolith formation since normal coccoliths do develop during the southeast monsoon august when upwelling causes nutrient enrichment and normal salinity of the surface layer during the change of the northwest to the southeast monsoon may conditions for calcification become more favourable during the initial phase of this change the coccolithophorids produce malformed coccoliths in the flores and java seas further west the influence of the banda sea vertical mixing is limited and malformation persists in the surface and subsurface water during the southeast monsoon two types of malformation as a result of incomplete calcification are found in placolith bearing species 1 coccoliths with a weakly developed central tube that easily disintegrates and 2 placoliths with incomplete shields but with a solid central tube

regional and interannual productivity of biogenic components and planktonic foraminiferal fluxes in the northwestern pacific basin abstract time series sediment trap experiments at subtropical wct 1 and subarctic wct 2 stations in the northwestern pacific indicate seasonal latitudinal and depth variations in total particulate biogenic and foraminiferal fluxes at the subtropical station the average total mass flux was 19 4 mg m 2 day 1 in the shallow trap 1060 m and 21 5 26 1 mg m 2 day 1 in the deep trap 3930 m during the sampling period at subarctic station these values were 91 5 176 9 mg m 2 day 1 in the shallow and 68 6 112 3 mg m 2 day 1 in the deep trap we recognized 12 and 15 planktonic foraminiferal species at station wct 1 and station wct 2 respectively the planktonic foraminiferal flux and species turnover are related to seasonal and interannual changes in source water and water column conditions at both stations at station wct 1 the highest flux was recorded during the summer with a peak in mid to late june associated with similar flux patterns of the dominant species globigerinoides ruber and globigerinita glutinata the total flux of foraminiferal tests at the shallow and deep traps is similar in numbers and magnitude at station wct 2 the peaks of total flux of foraminiferal tests at the two trap depths differ in number and their magnitude in the deep trap is almost half of that in the shallow trap a distinctive seasonal pattern occurred in the shallow and the deep trap with a peak in total foraminiferal flux in mid june to mid july globigerina quinqueloba neogloboquadrina pachyderma and neogloboquadrina dutertrei dominate the planktonic population throughout the year subtropical station wct 1 was characterized by low total foraminiferal fluxes and low total mass flux which is dominated by calcium carbonate and depleted in opal whereas high foraminiferal fluxes and a high total mass flux dominated by high biogenic opal and less calcium carbonate and organic matter characterize subarctic station wct 2 the foraminiferal carbonate that reaches the seafloor accounts for an average 20 27 and 22 23 of the total calcium carbonate at station wct 1 and station wct 2 respectively the primary reason for the difference in flux at both stations thus lies in the different contributions of siliceous and calcareous planktonic assemblages the seasonal variation in biogenic particulate flux at both stations implies that temporal changes in biological productivity are governed by large scale seasonal climatic variability and local hydrography

coccolithophore export production during the 1997 1998 el nino event in santa barbara basin california the response of coccolithophore export production to non el nino and el nino conditions was monitored during a two year period 26 march 1996 3 april 1998 in the centre of the santa barbara basin 34 14 n 120 02 w california borderland during the 1997 1998 el nino the seasonal cycle of the surface water conditions was altered by the presence of a relatively warm low nutrient and low salinity water mass throughout the studied period the total mass flux is dominated by lithogenic components with terrigenous input being highest during el nino period although the annual biogenic sediment fluxes were largely dominated by silica with diatoms as the major contributor to the opal flux the coccolith flux was high during the entire studied period during winter 1998 carbonate fluxes were unusually high for this time of the year moreover a strong positive correlation between organic carbon and opal flux indicates that siliceous phytoplankton production is the most important factor controlling organic carbon flux in the santa barbara basin a positive correlation between carbonate and organic carbon fluxes existed indeed during the final phase of el nino when the correlation between organic carbon and opal fluxes is poor the sinking coccolithophore assemblage was dominated by emiliania huxleyi followed by florisphaera profunda umbilicosphaera sibogae gephyrocapsa oceanica helicosphaera carteri gephyrocapsa muellerae and calcidiscus leptoporus the intensification of el nino 1997 1998 conditions altered the typical hydrographic structure of the santa barbara basin weakening the spring upwelling as reflected by reduced diatom fluxes in contrast the coccolith flux was relatively high during el nino particularly for the tropical species g oceanica that showed a pronounced increase in its flux when the spring upwelling was reduced under el nino conditions in addition we have found that this species has a strong correlation with nitrite phosphate and iron availability in surface water

floral and solution patterns of coccoliths in surface sediments of the north pacific coccolith assemblages from core top samples of the north pacific seafloor follow the distribution of surface water masses gephyrocapsa caribbeanica umbellosphaera tenuis and coccolithus pelagicus are the most important identifiers of surface water mass different multivariate statistical techniques group shallow samples in somewhat different spatial patterns factor analysis condenses the information contained in sixteen ies percentages to four new variables that can be interpreted as species assemblages by canonical correlation analysis these assemblages can in turn be related to the environment the first canonical correlation indicates that factor 2 the g caribbeanica assemblage is represented in samples underlying cooler surface water a second possible correlation describes a direct relationship between factor 3 the umbilicosphaera sibogae assemblage and the remaining environmental variable surface water salinity factor 1 the g oceanica assemblage and factor 4 the emiliania huxleyi assemblage are not as closely related to the selected environmental measures of temperature salinity dissolved oxygen and inorganic phosphate phosphorus as are factor 2 and factor 3 because samples were coded according to their overlying water mass group separations produced by discriminant analysis are easily interpreted in terms of the environment overlap of group assignments occurs for samples from the south china sea and extreme western pacific even partially dissolved samples retain the signature of surface water mass group assignment for those samples is generally reliable with the exception of samples from the central water mass where almost half of the shallow and half of the deep samples show strongest affinities with one of the other three water masses selective solution therefore only partially obscures the record of floral provinciality partial dissolution of coccolith assemblages does not proceed according to one systematic rank order the sequence of species removal is variable from region to region the more abundant species tend to consistently appear at an extreme of the ranking for example umbilicosphaera sibogae is among the least resistant and c leptoporus and g oceanica are among the most resistant species maximum depths of coccolith lysocline and compensation depth occur generally in the central part of the basin and shoal towards its margins as previously observed for planktonic foraminifera

export production of coccolithophores in an upwelling region results from san pedro basin southern california borderlands a seven month long time series sediment trap project was carried out in san pedro basin southern california borderlands in order to evaluate the response of calcareous nannoplankton to seasonal hydrographic changes this region is periodically influenced by upwelling particularly during the spring and early summer the highest fluxes of both whole coccospheres and individual coccoliths occurred during winter january february a period when the fluxes of diatoms and planktic foraminifera were low the highest coccolithophore fluxes were recorded in the mid february with 860 106 coccoliths m 2 day 1 8 106 whole coccospheres m 2 day 1 and 80 mg of coccolith carbonate m 2 day 1 coccolith carbonate fluxes in january and february account for most of the total carbonate fluxes measured during this period the season of maximum coccolithophore production in this region winter is correlated with weak stratification of the upper water column low total primary production low nutrient contents and low temperatures emiliania huxleyi and florisphaera profunda are the two most abundant species in this region while e huxleyi displays no distinct seasonal changes in flux f profunda shows a clear preference for cold low nutrient water conditions and low light levels helicosphaera spp flux is positively correlated to the total coccosphere fluxes and is indicative of high coccolithophore productivity

mass dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles abstract sulfur isotope studies of post archean terrestrial materials have focused on the ratio 34s 32s because additional isotopes 33s and 36s were thought to carry little information beyond the well known mass dependent relationship among multiple isotope ratios we report high precision analyses of 33s and 36s values defined as deviations of 33s and 36s from ideal mass dependent relationships for international reference materials and sedimentary sulfides of phanerozoic age by using a fluorination technique with a dual inlet isotope ratio mass spectrometer measured variations in 33s and 36s are explained as resulting from processes involve branching reactions two or more reservoirs formed or mixing irreversible processes in closed systems rayleigh distillation amplify the isotope effect we outline how this new isotope proxy can be used to gain new insights into fundamental aspects of the sulfur biogeochemical cycle including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation the isotope systematics discussed here cannot explain the much larger variation of 33s and 36s observed in archean rock records furthermore phanerozoic samples we have studied show a characteristic 33s and 36s relationship that differs from those measured in archean rocks and laboratory photolysis experiments thus high precision analysis of 33s and 36s can be used to distinguish small non zero 33s and 36s produced by mass dependent processes from those produced by mass independent processes in archean rocks and extraterrestrial materials

chemistry of hot springs along the eastern lau spreading center abstract the eastern lau spreading center elsc is the southernmost part of the back arc spreading axis in the lau basin west of the tonga trench and the active tofua volcanic arc over its 397 km length it exhibits large and systematic changes in spreading rate magmatic tectonic processes and proximity to the volcanic arc in 2005 we collected 81 samples of vent water from six hydrothermal fields along the elsc the chemistry of these waters varies both within and between vent fields in response to changes in substrate composition temperature and pressure ph water rock ratio and input from magmatic gases and subducted sediment hot spring temperatures range from 229 to 363 c at the five northernmost fields with a general decrease to the south that is reversed at the mariner field the southernmost field vai lili emitted water at up to 334 c in 1989 but had a maximum venting temperature of only 121 c in 2005 due to waning activity and admixture of bottom seawater into the subseafloor plumbing system chloride varies both within fields and from one field to another from a low of 528 mmol kg to a high of 656 mmol kg and may be enriched by phase separation and or leaching of cl from the rock concentrations of the soluble elements k rb cs and b likewise increase southward as the volcanic substrate becomes more silica rich especially on the valu fa ridge iodine and 7li increase southward and 11b decreases as b increases apparently in response to increased input from subducted sediment as the arc is approached species that decrease southward as temperature falls are si h2s li na cl fe mn and 87sr 86sr whereas ph alkalinity ca and sr increase oxygen isotopes indicate a higher water rock ratio in the three systems on valu fa ridge consistent with higher porosity in more felsic volcanic rocks vent waters at the mariner vent field on the valu fa ridge are significantly hotter more acid and metal rich less saline and richer in dissolved gases and other volatiles including h2s co2 and f than the other vent fields consistent with input of magmatic gases the large variations in geologic and geophysical parameters produced by back arc spreading along the elsc which exceed those along mid ocean ridge spreading axes produce similar large variations in the composition of vent waters and thus provide new insights into the processes that control the chemistry of submarine hot springs

the effect of metamorphic fluid flow on the nucleation and growth of garnets from troms north norway a spatial association is observed between the size distribution of garnet porphyroblasts and the size distribution of quartz veins in greenschist facies metapelites from troms north norway the size distribution of quartz veins reflects the flow regime of metamorphic fluids the hypothesis that the flow regime of metamorphic fluids is also responsible for the size distribution of garnet crystals was tested by ascribing empirical acceleration parameters to the nucleation and growth rates of garnet crystals in regions where fluid flow was interpreted as pervasive acceleration parameters for nucleation were high whereas in regions where fluid flow was interpreted as channelled acceleration parameters for growth were high accelerated crystal growth is further implied from the chemical zoning and crystal morphologies of garnets collected near discrete veins this spatial association may imply that fluid flow can be instrumental in controlling garnet crystallization fluid flow could affect garnet crystallization kinetics by facilitating thermal advection and or mass transfer in the study area rhodochrosite mnco3 veins provide evidence for mass transfer of mn by fluid flow an influx of mn would expand the stability field of garnet to lower temperatures the resulting thermal overstep could accelerate nucleation and or growth of garnets the corollary of this study is that size distributions and chemical zoning of garnets or other porphyroblast phases can be used to study metamorphic fluid flow