a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

mg ca ratios of two globigerinoides ruber white morphotypes implications for reconstructing past tropical subtropical surface water conditions 1 tests of the planktonic foraminifer globigerinoides ruber white d orbigny have become a standard tool for reconstructing past oceanic environments paleoceanographers often utilize the mg ca ratios of the foraminiferal tests for reconstructing low latitude ocean glacial interglacial changes in sea surface temperatures sst we report herein a comparison of mg ca measurements on sample pairs n 20 of two g ruber white morphotypes g ruber sensu stricto s s and g ruber sensu lato s l from surface and downcore samples of the western pacific and indian oceans g ruber s s refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide high arched aperture whereas g ruber s l refers to a more compact test with a diminutive final chamber and small aperture the g ruber s s specimens generally show significantly higher mg ca ratios compared to g ruber s l our results from the mg ca ratio analysis suggest that g ruber s l specimens precipitated their shells in slightly colder surface waters than g ruber s s specimens this conclusion is supported by the differences in 18o and 13c values between the two morphotypes although it is still unclear if these two morphotypes represent phenotypic variants or sibling species our findings seem to support the hypothesis of depth and or seasonal allopatry within a single morphospecies

delayed holocene reappearance of g menardii the planktonic foraminifera globorotalia menardii absent in the atlantic ocean during the last glacial period reappeared during the holocene as it was present in the indian ocean during glacial time its reappearance might be thought to have been connected to rejuvenation of conveyor circulation but as first shown by glenn jones and confirmed here it was a significant contributor to the atlantic s foraminifer population only after 7000 years ago

salinity controls on na incorporation in red sea planktonic foraminifera whereas several well established proxies are available for reconstructing past temperatures salinity remains challenging to assess reconstructions based on the combination of in organic temperature proxies and foraminiferal stable oxygen isotopes result in relatively large uncertainties which may be reduced by application of a direct salinity proxy cultured benthic and planktonic foraminifera showed that na incorporation in foraminiferal shell calcite provides a potential independent proxy for salinity here we present the first field calibration of such a potential proxy living planktonic foraminiferal specimens from the red sea surface waters were collected and analyzed for their na ca content using laser ablation quadrupole inductively coupled plasma mass spectrometry using the red sea as a natural laboratory the calibration covers a broad range of salinities over a steep gradient within the same water mass for both globigerinoides ruber and globigerinoides sacculifer calcite na ca increases with salinity albeit with a relatively large intraspecimen and interspecimen variability the field based calibration is similar for both species from a salinity of 36 8 up to 39 6 while values for g sacculifer deviate from this trend in the northernmost transect it is hypothesized that the foraminifera in the northernmost part of the red sea are partly expatriated and hence should be excluded from the na ca salinity calibration incorporation of na in foraminiferal calcite therefore provides a potential proxy for salinity although species specific calibrations are still required and more research on the effect of temperature is needed

seasonal variation of planktonic foraminiferal isotopic composition from sediment traps in the south china sea abstract the imprint of seasonal hydrographic changes on two widely distributed tropical subtropical planktonic foraminifer species globigerinoides sacculifer without sac and globigerinoides ruber white variety has been investigated using specimens collected in sediment traps deployed in the northern south china sea scs october 2000 october 2002 the faunal assemblage is dominated by g ruber during the warm summer months whereas g sacculifer is consistently present year round at abundances of less than 20 in general the measured 18o and 13c isotopic compositions of g ruber are more depleted than those of g sacculifer and the 18o difference between seasons summer vs winter is comparable to that of the local glacial interglacial cycle ca 1 the lowest 13c values are associated with relatively heavy 18o values in january and march for both species and suggest higher nutrient levels in the surface water that are likely related to the prevailing winter monsoon this speculation is supported by the increase in terrigenous input to the traps brought by the winter monsoon the ratio between 18o and 13c in g ruber is approximately two times that of g sacculifer with a 18o 13c slope of 1 18 vs 0 55 and differs from that in most biogenic carbonates 0 25 0 33 based on culture and field studies which indicate enhanced kinetic fractionation at higher ambient carbonate ion concentrations co3 however similar regression slopes of 18o 13c 0 52 to 0 6 are also derived for g sacculifer collected from plankton tows factors other than the carbonate ion effect hence appear to be responsible for the negative relationship between 18o and 13c in this region

an intensity ratio calibration method for the accurate determination of mg ca and sr ca of marine carbonates by icp aes an inductively coupled plasma atomic emission spectroscopy icp aes method for the accurate and precise simultaneous measurement of the mg ca and sr ca content of carbonates was established while a precision of 0 3 1 standard deviation sd is easily obtainable for both mg ca and sr ca analysis a ca matrix effect complicates achieving similar levels of accuracy with conventional calibration procedures an alternative ratio calibration procedure is proposed which overcomes the ca matrix effects and ensures the accuracy of the mg ca and sr ca analysis of marine carbonates to 0 3 almost an order of magnitude better than conventional calibration methods the longer term precision is 0 1 if the batch run average values are corrected for longer term drift the method is suitable for analysis of foraminiferal calcite and coral aragonite and can easily be adjusted for the analysis of other carbonates or microsamples

evaluating the utility of b ca ratios in planktic foraminifera as a proxy for the carbonate system a case study of globigerinoides ruber b ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system however the carbonate system controls on b ca ratios are not straightforward with inline image inline image in situ inline image at saturation correlating best with b ca ratios in benthic foraminifera rather than ph inline image or inline image as a simple model of boron speciation in seawater and incorporation into caco3 would predict furthermore culture experiments have shown that in planktic foraminifera properties such as salinity and b sw can have profound effects on b ca ratios beyond those predicted by simple partition coefficients here we investigate the controls on b ca ratios in g ruber via a combination of culture experiments and core top measurements and add to a growing body of evidence that suggests b ca ratios in symbiont bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions we find that while b ca ratios in culture experiments covary with ph in open ocean sediments this relationship is not seen in fact our b ca data correlate best with inline image a previously undocumented association and in most regions salinity these findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite regardless our results underscore the need for caution when attempting to interpret b ca records in terms of the ocean carbonate system at the very least in the case of mixed layer planktic foraminifera

incorporation and preservation of mg in globigerinoides sacculifer implications for reconstructing the temperature and 18o 16o of seawater using bathymetric transects of surface sediments underlying similar sea surface temperatures but exposed to increasing dissolution we examined the processes which affect the relationship between foraminiferal mg ca and 18o we found that globigerinoides saccculifer calcifies over a relatively large range of water depth and that this is apparent in their mg content on the seafloor foraminiferal mg ca is substantially altered by dissolution with the degree of alteration increasing with water depth selective dissolution of the chamber calcite formed in surface waters shifts the shell s bulk mg ca and 18o toward the chemistries of the secondary crust acquired in colder thermocline waters the magnitude of this shift depends on both the range of temperatures over which the shell calcified and the degree to which it is subsequently dissolved in spite of this shift the initial relationship between mg ca and 18o determined by their temperature dependence is maintained we conclude that paired measurements of 18o and mg ca can be used for reconstructing 18owater though care must be taken to determine where in the water column the reconstruction applies

habitats abundance patterns and isotopic signals of morphotypes of the planktonic foraminifer globigerinoides ruber d orbigny in the eastern mediterranean sea since the marine isotopic stage 12 article i nfo the chemical composition of shells of the planktonic foraminifer globigerinoides ruber white is frequently used to determine past sea surface conditions recently it has been shown that arbitrarily defined morphotypes within this species exhibit different chemical and isotopic signatures here we investigate the occurrence through time and in space of morphological types of g ruber white in late quaternary and holocene sediments of the central and the eastern mediterranean sea in 115 samples representing two distinct time intervals mis 1 2 and mis 9 12 at odp site 964 and the piston core geotu sl96 we have defined three morphological types within this species and determined their relative abundances and stable isotopic composition a quantitative analysis of morphological variation within g ruber white in four samples revealed that the subjectively defined morphotypes occupy separate segments of a continuous and homogenous morphospace we further show that the abundance of the morphotypes changes significantly between glacials and interglacials and that the three morphotypes of g ruber show significant offsets in their stable isotopic composition these offsets are consistent within glacial and interglacial stages but their sign is systematically reversed between the two sites since the isotopic shifts among the three g ruber morphotypes are systematic and often exceed 1 their understanding is essential for the interpretation of all g ruber based proxy records for the paleoceanographic development of the mediterranean during the late

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

isotopic signals in two morphotypes of globigerinoides ruber white from the south china sea implications for monsoon climate change during the last glacial cycle abstract based on the study of surface and downcore sediment samples from the south china sea scs two morphotypes of globigerinoides ruber white have been differentiated by taxonomic criteria at species and or subspecies level and also by their stable isotopic compositions of oxygen and carbon the two morphotypes g ruber sensu stricto s s and g ruber sensu lato s l represent two groups with different depth habitats with g ruber s s living in the upper 30 m of the water column and g ruber s l living at depths below 30 m the different depth habitats are indicated by the comparison between the present oceanographic data and isotopic signals of the two morphotypes in the surface sediment from the scs application of this information to a hemipelagic sediment core in the northern scs shows that drastic changes existed in the morphotypes isotopic records during the last glacial cycle the isotope difference between the two morphotypes diminished during 18 o stage 2 especially during the last glacial maximum it is inferred that this is the result of intensified monsoon winds which caused mixing of the upper layer of the water column during stage 2 the proportion of g ruber s l increased which is interpreted as a result of the increased productivity due to mixing of the subsurface nutrient rich water into the surface layer

mapping the response of riparian vegetation to possible flow reductions in the snake river idaho abstract this study was initiated to determine the general effects of potential flow reductions in the middle snake river swan falls dam downstream to the idaho oregon border on its riparian vegetation considerable water from the river is currently used to irrigate the adjacent snake river plain and increased demand for water in the future is likely the problem was subdivided into several research components including field investigation of the existing riparian vegetation and river environment hydrological modeling to calculate the effects of one flow scenario on hydrological regime and integration of vegetation and hydrological modeling results with a geographic information system gis to map the riverbed island and bank conditions under the scenario flow field work was conducted in summer 1990 riparian vegetation along 40 u s geological survey cross sections was sampled at approximately 1 25 mile intervals within the 50 mile long study area cross section and flow data were provided by the u s geological survey gis mapping of land water cover using arc info was based on 1987 aerial photographs riverbed contour maps were produced by linking cross section data topographic contouring software anudem and gis the maps were used to spatially display shallow areas in the channel likely to become vegetated under reduced flow conditions the scenario would reduce flow by approximately 20 160 maf and lower the river an average of 0 5 ft the scenario flow could cause a drop in the elevation of the riparian zone comparable to the drop in mean river level and expansion of the lower riparian zone into shallow areas of the channel the gis maps showed that the shallow areas of the channel more likely to become vegetated under the scenario flow are located in wide reaches near islands some possible ecological consequences of the scenario flow include a greater area of riparian habitat reduced flow velocity and sedimentation in shallow channels leading to channel deactivation increased island visitation and nest predation by predatory mammals due to loss of a water barrier between some islands and banks and larger populations of alien plant species in the new riparian vegetation

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

the effect of chemical pretreatment of sediment upon foraminiferal based proxies 1 paleoceanographic studies routinely combine different foraminiferal proxies i e weight abundance trace metal and stable isotope measurements into a cohesive narrative the application of chemical treatment to disaggregate ocean sediments in the most efficient way to isolate the fossils of foraminifera from the other sediment components is dictated by the time available and the material used yet few studies have aimed to test both the physical and geochemical effects associated with such practices in this study we use samples with different sedimentological characteristics i e varying percentages of caco3 and of terrigenous material to test the impact upon these proxies of three processing methods and a control 1 no chemicals contol run 2 soaking in sodium hexametaphosphate calgon 3 soaking in hydrogen peroxide and 4 soaking in a sodium pyrophosphate the samples were analyzed for faunal abundance shell weight stable isotope 18o 13c and trace metal mg ca geochemistry for four species of planktonic foraminifera globigerina bulloides globigerinoides ruber globorotalia inflata and globorotalia menardii results show that apart from the calgon solution the values of faunal abundance shell weight mg ca and stable isotopes are similar irrespective of the cleaning treatment utilised and therefore warrant cross comparison of results obtained with different preparation techniques the use of calgon in pretreatment shows statistically different values for only foraminiferal shell weight

a test of different factors influencing the isotopic signal of planktonic foraminifera in surface sediments from the northern south china sea abstract the stable isotope composition of planktonic foraminifera is one of the most important proxies in paleoenvironmental research in this study three parameters affecting the stable isotope values of globigerinoides ruber from surface sediment from the northern south china sea were tested different cleaning methods different morphotypes and different size fractions our results show that in the small size fraction there is a small but significant effect on 13c by oxidizing the tests prior to measurement our data also confirm a small but significant difference between different morphotypes of g ruber however the variability caused by the seasonal effect stable isotope value is larger than the effect caused by different cleaning protocols or different morphotypes the large spread of the isotope values up to 2 have some implications to paleoceanographic reconstructions when measurements are performed on a small number of foraminiferal tests the isotope value does not necessarily reflect yearly average or a certain season but is a random value of the seasonal variability in that region

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

a high resolution sea surface temperature record from the tropical south china sea 16 500 3000 yr b p the timing and magnitude of sea surface temperature sst changes in the tropical southern south china sea scs during the last 16 500 years have been reconstructed on a high resolution c 14 dated sediment core using three different foraminiferal transfer functions simmax28 ram fp 12e and geochemical u 37 k sst estimates in agreement with climap reconstructions both the fp 12e and the u 37 k sst estimates show an average late glacial interglacial sst difference of 2 0 degreesc whereas the ram and simmax28 foraminiferal transfer functions show only a minor 0 6 degreesc or no consistent late glacial interglacial sst change respectively both the u 37 k and the fp 12e sst estimates as well as the planktonic foraminiferal delta o 18 values indicate an abrupt warming ca 1 degreesc in 200 yr at the end of the last glaciation synchronous within dating uncertainties with the bolling transition as recorded in the greenland ice sheet project 2 gisp2 ice core whereas the ram derived deglacial sst increase appears to lag during this event by ca 500 yr the similarity in abruptness and timing of the warming associated with the bolling transition in greenland and the southern scs suggest a true synchrony of the northern hemisphere warming at the end of the last glaciation in contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the younger dryas yd climate event in the tropical scs the u 37 k sst estimates show a cooling of ca 0 2 0 6 degreesc compared to the bolling allerod period these u 37 k sst estimates from the southern scs argue in favor of a northern hemisphere wide synchronous cooling during the yd period c 2001 university of washington