stable isotopes δ18o and δ13c trace and minor element compositions of recent scleractinians and last glacial bivalves at the santa maria di leuca deep water coral province ionian sea special issue the aplabes programme physical chemical and biological characterization of deep water coral ecosystems from the ionian sea mediterranean 16 pages 13 figures 3 tables 2 appendix

boron isotopes and b ca in benthic foraminifera proxies for the deep ocean carbonate system abstract accurate records of the state of the ocean carbonate system are critical for understanding past changes in pco 2 ocean acidification and climate the chemical principles underlying the proxy of oceanic ph provided by the boron isotope ratio of foraminiferal carbonate are relatively well understood but the proxy s reliability has been questioned we present 76 new multi collector inductively coupled plasma mass spectrometry mc icpms 11 b measurements on a range of benthic foraminifera from 23 late holocene samples from the atlantic that reaffirm the utility of the 11 b ph proxy our boron isotope measurements on 10 benthic foraminifera tests typically yield a precision of 0 25 at 2 s d equivalent to 0 03 ph units 11 b values of epifaunal species are within analytical uncertainty of those predicted from a simple model assuming sole incorporation of b oh 4 from seawater and no vital effects using the independently determined fractionation factor of 1 0272 between 11 b 10 b of aqueous boron species infaunal foraminifera are consistent with this model but record the combined effects of lower pore water 11 b and ph no influence of partial dissolution or shell size on 11 b is observed we have also measured the b ca ratios of the same samples for individual cibicidoides species b ca shows a good correlation with co 3 2 but the b ca of different co occurring species morphotypes varies considerably these effects are not seen in 11 b which may therefore provide a more robust proxy of the ocean carbonate system whilst in theory 11 b and b ca can be combined to provide a quantitative reconstruction of alkalinity and dissolved inorganic carbonate dic in practice this is precluded by propagated uncertainties 11 b data give significant constraints on foraminifera calcification mechanisms and seem most simply explained by incorporation of b oh 4 into a hco 3 pool which is then completely incorporated in foraminiferal caco 3 our demonstration of the predictable variation of 11 b with ph across a wide range of species and locations provides confidence in the application of mc icpms measurements of foraminiferal 11 b to reconstruct past changes in the ocean carbonate system

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

boron carbon and oxygen isotopic composition of brachiopod shells intra shell variability controls and potential as a paleo ph recorder abstract the boron isotopic composition of biogenic carbonates has been used to reconstruct seawater ph and atmospheric pco 2 on pleistocene and cenozoic timescales because of their excellent preservation and extensive fossil record throughout the phanerozoic brachiopods are a promising candidate for extending the boron isotope record as far back as the cambrian here we present stable carbon oxygen and boron isotopic measurements of modern terebratulid brachiopod calcite in comparison with environmental ph estimates calculated from oceanographic data geochemical transects along the length and depth of single shells confirm previously published trends in carbon and oxygen isotopic composition in the outer surface primary and outermost secondary layers 11 b covaries with 13 c and 18 o with more negative values in the outer and more positive values in the middle of the shell however 11 b deviates from 13 c and 18 o in the inner part of the secondary layer where the 13 c and 18 o values are more positive and near equilibrium whereas 11 b returns to more negative values a comparison of different specimens of the species terebratalia transversa sowerby 1846 and laqueus californianus kuster 1844 microsampled from the middle part of the fibrous secondary layer demonstrates a clear correlation to ambient ph with a sensitivity similar to other empirical calibration curves for cultured planktic foraminifers corals and inorganic calcite the relationship in other species is less clear and significantly offset necessitating the use of a single species or a cross calibration method with other species in paleo ph reconstructions

modern and late pleistocene b ca ratios of the benthic foraminifer planulina wuellerstorfi determined with laser ablation icp ms incorporation of boron into foraminiferal shells is thought to be primarily governed by the carbonate chemistry of the ambient seawater suggesting that it can be reconstructed from b ca ratios to this end b ca ratios of the benthic foraminifer planulina wuellerstorfi from south atlantic core top samples have been analyzed using laser ablation inductively coupled plasma mass spectroscopy la icp ms to provide additional information on intratest trace element heterogeneity results show that boron is heterogeneously distributed within and between shells with content variations of approximately 43 displayed within a single shell b ca is higher in the youngest chambers opposite to the observed between chamber variability of mg ca this may be explained by ontogenetic changes of physiological processes that increase the ph of the calcifying fluid and thus the borate concentration while decreasing mg ca to promote calcification despite this heterogeneity mean b ca ratios are positively correlated with the deepwater calcite saturation state co32 in line with previous studies we apply this empirical relationship to reconstruct co32 for the late pleistocene to holocene using samples from a depth transect in the equatorial atlantic reconstructed co32 values confirm previous studies suggesting that caco3 oversaturated north atlantic deep water was reduced during glacial periods whereas caco3 undersaturated antarctic bottom water expanded vertically and propagated northwards in summary our data demonstrate that bulk b ca in p wuellerstorfi reliably reflects variations in co32 despite the strong physiological control of boron incorporation

variations in seawater sr ca recorded in deep sea bamboo corals 1 a depth transect of deep sea bamboo corals along the california margin provides evidence that coral strontium to calcium ratios sr cacoral record seawater sr ca ratios sr casw a calibration was constructed utilizing sr cacoral ratios and previously published pacific sr casw data r2 0 53 n 12 p 0 01 sr cacoral mmol mol 4 62 sr casw mmol mol 36 64 sr casw is ultimately governed by the remineralization of sr containing shells of surface water derived marine organisms e g acantharia at intermediate water depths california margin sr cacoral records from 792 and 1295 m document fluctuations in sr casw that appear decadal scale these results suggest that sr casw may not be as stable as previously assumed and may be influenced by surface productivity on short timescales

distribution of magnesium in coral skeleton ion micro probe imaging of the aragonite skeleton of pavona clavus a massive reef building coral shows that magnesium and strontium are distributed very differently in contrast to strontium the distribution of magnesium is strongly correlated with the fine scale structure of the skeleton and corresponds to the layered organization of aragonite fibers surrounding the centers of calcification which have up to ten times higher magnesium concentration this indicates a strong biological control over the magnesium composition of all structural components within the skeleton magnesium may be used by the coral to actively control the growth of the different skeletal crystal components

modern and pleistocene boron isotope composition of the benthic foraminifer cibicidoides wuellerstorfi abstract here we present the first species specific study of boron isotopes in the epibenthic foraminifer species cibicidoides wuellerstorfi coretop samples from a water depth profile from 1000 to 4500 m on the northern flank of the walvis ridge are 4 4 lower than the values expected based on calculations of the 11bborate of ambient seawater similar values for this foraminifer species are presented from odp site 668b at the sierra leone rise in the equatorial atlantic the consistency between data of the same species suggests the offsets are primary rather than diagenetic glacial c wuellerstorfi from odp 668b and walvis ridge have boron isotope compositions only slightly different to interglacial samples that is no larger than 0 10 ph units or 23 mol kg 1 in co32 above the reconstructed glacial lysocline and 0 07 ph units or 14 mol kg 1 in co32 below we use these results to suggest that glacial deep water ph in the atlantic was similar to interglacial ph the new data resolve the inconsistency between the previously reported high bottom water ph and the lack of significant carbonate preservation of the glacial deep ocean

empirical relationship between ph and the boron isotopic composition of globigerinoides sacculifer implications for the boron isotope paleo ph proxy culture experiments were carried out with the planktonic foraminifera globigerinoides sacculifer at three different ph values 7 6 0 05 8 20 0 05 8 60 0 05 in order to establish the ph dependence of the boron isotopic fractionation between the calcitic tests of g sacculifer and seawater additional objectives were to compare the ph dependences of boron isotopic composition of g sacculifer with that of orbulina universa and inorganic calcite in order to evaluate the robustness of the boron isotope paleo ph proxy the relationship between the boron isotopic composition of g sacculifer and the culture water ph shows heavier boron isotopic values at higher ph this empirical relationship is similar but slightly offset by 3 per mil from that of o universa indicating the presence of biogenic influence vital effect on the boron isotopic composition of foraminifera however comparison of the boron isotopic composition of o universa and g sacculifer with that of inorganic calcite grown over a common ph range shows that inorganic processes are the dominant control on the boron isotopic composition of foraminifera and the vital effects play a small but not insignificant role the results imply that in spite of a small biogenic influence the variation in boron isotopic composition of foraminiferal shells with ph at least for o universa and g sacculifer is consistent with that for inorganic calcite demonstrating the potential of this isotopic signature in foraminifera as a reliable paleo ph proxy

evidence for ocean acidification in the great barrier reef of australia geochemical records preserved in the long lived carbonate skeleton of corals provide one of the few means to reconstruct changes in seawater ph since the commencement of the industrial era this information is important in not only determining the response of the surface oceans to ocean acidification from enhanced uptake of co2 but also to better understand the effects of ocean acidification on carbonate secreting organisms such as corals whose ability to calcify is highly ph dependent here we report an 200 year d 11 b isotopic record extracted from a long lived porites coral from the central great barrier reef of australia this record covering the period from 1800 to 2004 was sampled at yearly increments from 1940 to the present and 5 year increments prior to 1940 the d 11 b isotopic compositions reflect variations in seawater ph and the d 13 c changes in the carbon composition of surface water due to fossil fuel burning over this period in addition complementary ba ca d 18 o and mg ca data was obtained providing proxies for terrestrial runoff salinity and temperature changes over the past 200 years in this region positive thermal ionization mass spectrometry ptims method was utilized in order to enable the highest precision and most accurate measurements of d 11 b values the internal precision and reproducibility for d 11 b of our measurements are better than 0 2 2r which translates to a precision of better than 0 02 ph units our results indicate that the long term pre industrial variation of seawater ph in this region is partially related to the decadal interdecadal variability of atmospheric and oceanic anomalies in the pacific in the periods around 1940 and 1998 there are also rapid oscillations in d 11 b compositions equivalent changes in ph of almost 0 5 u the 1998 oscillation is co incident with a major coral bleaching event indicating the sensitivity of skeletal d 11 b compositions to loss of zooxanthellate symbionts importantly from the 1940s to the present day there is a general overall trend of ocean acidification with ph decreasing by about 0 2 0 3 u the range being dependent on the value assumed for the fractionation factor a b3 b4 of the boric acid and borate species in seawater correlations of d 11 b with d 13 c during this interval indicate that the increasing trend towards ocean acidification over the past 60 years in this region is the result of enhanced dissolution of co2 in surface waters from the rapidly increasing levels of atmospheric co2 mainly from fossil fuel burning this suggests that the increased levels of anthropogenic co2 in atmosphere has already caused a significant trend towards acidification in the oceans during the past decades observations of surprisingly large decreases in ph across important carbonate producing regions such as the great barrier reef of australia raise serious concerns about the impact of greenhouse gas emissions on coral calcification 2009 elsevier ltd all rights reserved

the influence of skeletal micro structures on potential proxy records in a bamboo coral assessing the physicochemical variability of the deeper ocean is currently hampered by limited instrumental time series and proxy records bamboo corals isididae form a cosmopolitan family of calcitic deep sea corals that could fill this information gap via geochemical information recorded in their skeletons here we evaluate the suitability of high resolution chemical imaging of bamboo coral skeletons for temperature and nutrient reconstruction the applied elemental mapping techniques allow to verify the suitability of the chosen transect on the sample section for paleo reconstructions and enhance the statistical precision of the reconstruction we measured mg ca via electron microprobe at 1 m resolution and ba ca via laser ablation icp ms at 35 m resolution in a historic specimen of keratoisis grayi from the blake plateau off eastern florida long term growth temperatures of 7 1 3 4 c 2 sd that are in agreement with recent ambient temperature range can be reconstructed from mg ca ratios provided that anomalously mg enriched structural features around the central axis and isolated features related to tissue attachment are avoided for reconstruction skeletal ba ca measurements reflect mean seawater barium ba sw concentrations ba sw 51 24 nmol kg 1 2 sd in agreement with instrumental data 47 nmol kg 1 we show for the first time that ba ca forms concentric structures in a bamboo coral skeleton section our investigations suggest that while bamboo coral skeletons do record environmental parameters in their mean chemical composition the magnitude of environmental variability reconstructed from high resolution chemical maps exceeds that expected from instrumental time series this necessitates additional investigation of the factors driving bamboo coral skeletal composition

a refined method for calculating paleotemperatures from linear correlations in bamboo coral carbon and oxygen isotopes bamboo corals represent an emerging paleoclimate archive with the potential to record variability at intermediate depths throughout much of the global ocean realizing this potential has been complicated by biologically mediated vital effects which are evident in linear correlations of skeletal carbon 13c and oxygen 18o isotope composition previous efforts to develop a bamboo coral 18o paleothermometer by accounting for such vital effects have not been completely successful as they still rely on empirical calibrations that are offset from the temperature dependence of abiogenic experiments here we describe an approach that better corrects for bamboo coral vital effects and allows paleotemperatures to be calculated directly from the abiogenic temperature dependence the success of the method lies in calculating apparent equilibrium carbon and oxygen isotope fractionation at the temperature ph and growth rate of each coral as well as in the use of model ii regressions rigorous propagation of uncertainty suggests typical errors of 2 3 c but in select cases errors as low as 0 98 c can be achieved for densely sampled and strongly correlated data sets this lower limit approaches the value attributed to uncertainty in ph and growth rate estimates alone as predicted by a series of pseudoproxy experiments the incorporation of isotopically light metabolic co2 appears to be negligible in most pacific corals but may be significant in atlantic specimens potentially requiring an additional correction the success of the method therefore hinges on how well complex environmental systems and biomineralization strategies are constrained with the most reliable temperatures occurring when calcifying fluid ph growth rate and incorporation of metabolic carbon into skeletal calcite are constrained using multiple geochemical proxies

an improved boron isotope ph proxy calibration for the deep sea coral desmophyllum dianthus through sub sampling of fibrous aragonite abstract the isotopic composition of boron 11 b in marine carbonates is well established as a proxy for past ocean ph however its robust application to palaeo environments relies on the generation of species specific calibrations existing calibrations utilising the deep sea coral dsc desmophyllum dianthus highlight the potential application of this pervasive species to ph reconstructions of intermediate depth waters nevertheless considerable uncertainty remains regarding the estimation of seawater ph from these bulk skeletal 11 b measurements likely resulting from microstructural heterogeneities in 11 b of d dianthus to circumvent this problem thus improving the reliability of the d dianthus 11 b ph calibration we present a new 11 b calibration of micro sampled fibrous aragonite from this species modern coral specimens recovered from the atlantic pacific and southern oceans micro sampled using microdrilling micromilling and laser cutting extraction were analysed for trace element b ca mg ca sr ca and u ca and boron isotopic composition we find the best calibration against the 11 b of borate in local ambient seawater a function of ph and taken from hydrographic data sets ph range 7 57 to 8 05 utilises 11 b measurements of fibres with likely slow growth rates and minimal contamination from adjacent microstructures identified by low mg ca for each coral specimen this new calibration exhibits a stronger and better defined dependence on ambient seawater ph compared to bulk coral 11 b 11 b fibre 0 93 0 17 11 b borate 12 02 2 63 we suggest that the majority of the variability in measured 11 b between replicate bands of fibrous aragonite from a d dianthus specimen can be explained by small incorporation of non fibrous aragonite and surface impurities during microsampling and growth rate effects this study confirms the utility of d dianthus as an archive of precise palaeo ph 0 07 ph units provided that suitable sampling strategies are applied

the geochemistry of deep sea coral skeletons a review of vital effects and applications for palaeoceanography deep sea corals were discovered over a century ago but it is only over recent years that focused efforts have been made to explore the history of the oceans using the geochemistry of their skeletal remains they offer a promising archive of past oceanic environments given their global distribution layered growth patterns longevity and preservation as well as our ability to date them using radiometric techniques this paper provides an overview of the current state of the art in terms of geochemical approaches to using deep sea coral skeletons to explore the history of the ocean deep sea coral skeletons have a wide array of morphologies e g solitary cup corals branching colonial corals and materials calcite aragonite and proteins as such their biomineralization strategies are diverse leading to complex geochemistry within coral skeletons notwithstanding these complications progress has been made on developing methods for reconstructing the oceanographic environment in the past using trace elements and isotopic methods promising approaches within certain coral groups include clumped isotopes and mg li for temperature reconstructions boron isotopes and radiocarbon for carbon cycling end and radiocarbon for circulation studies and 15 n p ca and ba ca for nutrient tracer studies likewise there is now a range of techniques for dating deep sea corals skeletons e g u series radiocarbon and determining their growth rates e g radiocarbon and 210 pb dating studies on historic coral populations in the atlantic southern ocean and pacific point to climate and environmental changes being dominant controls on coral populations over millennial and orbital timescales this paper provides a review of a range of successes and promising approaches it also highlights areas in which further research would likely provide new insights into biomineralization palaeoceanography and distribution of past coral populations

environmental and biological controls on mg and li in deep sea scleractinian corals abstract deep sea scleractinian corals precipitate aragonite skeletons that provide valuable archives of past ocean conditions during calcification biological mediation causes variability in trace metal incorporation and isotopic ratios of the aragonite such that signals caused by environmental controls can be overwhelmed this complicates the interpretation of geochemical proxies used for paleo reconstructions in this study we examine the environmental controls on the mg li ratio of 34 individuals from seven genera of deep sea scleractinian corals desmophyllum balanophyllia caryophyllia enallopsammia flabellum trochocyanthus and lophelia in addition we examine the microscale distributions of mg and li in desmophyllum and balanophyllia using laser ablation inductively coupled plasma mass spectrometry la icp ms both mg ca and li ca ratios increased by more than a factor of two in the center of calcification regions compared to the outer fibrous regions of the coral skeleton as a result replicate 10 mg subsamples of coral show less variability in the mg li ratio than mg ca microscale mg and li results are consistent with rayleigh type incorporation of trace metals with additional processes dominating the composition within centers of calcification comparison of mg li to seawater properties near the site of collection shows that the ratio is not controlled by either carbonate ion or salinity it appears that temperature is the major control on the mg li ratio for all 34 samples the temperature correlation r2 0 62 is significantly better than for mg ca r2 0 06 for corals of the family caryophyllidae the r2 value increases to 0 82 with the exclusion of one sample that was observed to have an altered chalky texture despite this excellent correlation the scatter in the data suggests that the mg li ratio of deep sea corals cannot be used to reconstruct temperature to better than approximately 1 6 c without better temperature control and additional calibration points on modern coral samples

oceanic ph control on the boron isotopic composition of foraminifera evidence from culture experiments culture experiments were carried out with the species orbulina universa at four different ph values 7 70 0 05 8 15 0 05 8 60 0 05 and 9 00 0 10 in order to establish the ph dependence of boron isotope fractionation between seawater and foraminifera a clear relationship between the boron isotopic composition of the foraminifera and the ph of the seawater culture solutions was found showing heavier boron isotopic composition at higher ph this finding supports the viability of boron isotopes as a paleo ph tool it is important to note that orbulina universa cultured in natural seawater as well as those obtained from coretop samples have a significantly lighter boron isotopic ratio than globigerinoides sacculifer from coretop samples suggesting that at least for this species a vital effect is active

intra skeletal calcite in a live collected porites sp impact on environmental proxies and potential formation process geochemical proxies measured in the carbonate skeleton of tropical coral porites sp have commonly been used to reconstruct sea surface temperature sst and more recently seawater ph nevertheless both reconstructed sst and ph depend on the preservation state of the skeleton here made of aragonite i e diagenetic processes and its related effects should be limited in this study we report on the impact of the presence of intra skeletal calcite on the skeleton geochemistry of a live collected porites sp the porites skeleton preservation state was analyzed using x ray diffraction and scanning electron microscopy sr ca mg ca u ca ba ca li mg and b ca ratios were measured at a monthly and yearly resolution using solution icp ms and multi collector icp ms the 11b signatures and the calcite percentages were acquired at a yearly timescale the coral colony presents two parts one with less than 3 calcite referred to as no calcite skeleton the other one corresponding to the skeleton formed during the last 4 yrs of growth with calcite percentages varying from 13 to 32 referred to as with calcite skeleton this intra skeletal calcite replaces partly or completely numerous center of calcification cocs all geochemical tracers investigated are significantly impacted by the presence of calcite the reconstructed sst decreases by about 0 1 c per calcite percent as inferred from the sr ca ratio such impact reaches up to 0 26 c per calcite percent for temperature deduced from the li mg ratio so less than 5 of such intra skeletal calcite does not prevent sst reconstructions using sr ca ratio but the percentage and type of calcite have to be determined before fine sst interpretation seawater ph reconstruction inferred from boron isotopes drop by about 0 011 ph unit per calcite percent such sensitivity to calcite presence is particularly dramatic for fine paleo ph reconstructions here we suggest that after being brought to shallow waters following a cyclone the studied coral was seasonally subjected to rainfall related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs nevertheless the process of calcite precipitation remains to be determined

surface ocean ph response to variations in pco2 through two full glacial cycles abstract knowledge of past atmospheric pco 2 is important for evaluating the role of greenhouse gases in climate forcing ice core records show the tight correlation between climate change and pco 2 but records are limited to the past 900 kyr we present surface ocean ph and pco 2 data reconstructed from boron isotopes in planktonic foraminifera over two full glacial cycles 0 140 and 300 420 kyr the data co vary strongly with the vostok pco 2 record and demonstrate that the coupling between surface ocean chemistry and the atmosphere is recorded in marine archives allowing for quantitative estimation of atmospheric pco 2 beyond the reach of ice cores

boron and magnesium isotopic composition of seawater the isotopic systems of boron and magnesium are increasingly being used as proxies for a number of environmental variables and processes the isotopic composition of seawater for both systems plays a central role in these studies and is an important interlaboratory standard given the long residence times of both elements 10 7 years it is commonly assumed that seawater is isotopically homogenous for these systems yet no systematic studies currently exist here we present the b and mg isotopic composition of 26 28 seawater samples from a number of ocean basins that encompass a significant range in salinity 32 to 38 psu temperature 0 3 to 25 9c and water depth 0 to 1240 m we find no significant or systematic variation for either system in accordance with their long residence times we recommend that the mean values we report 11 b 39 61 0 04 2 s e n 28 25 mg 0 43 0 01 2 s e n 26 26 mg 0 82 0 01 2 s e n 26 be used in future studies involving mg and b isotopes copyright 2010 by the american geophysical union

evaluation of boron isotope ratio as a ph proxy in the deep sea coral desmophyllum dianthus evidence of physiological ph adjustment the boron isotope ratio 11b of foraminifers and tropical corals has been proposed to record seawater ph to test the veracity and practicality of this potential paleo ph proxy in deep sea corals samples of skeletal material from twelve archived modern desmophyllum dianthus d dianthus corals from a depth range of 274 1470 m in the atlantic pacific and southern oceans ambient ph range 7 57 8 05 were analyzed for 11b the 11b values for these corals spanning a range from 23 56 to 27 88 are found to be related to seawater borate 11b by the linear regression 11bcoral 0 76 0 28 11bborate 14 67 4 19 1 standard error se the d dianthus 11b values are greater than those measured in tropical corals and suggest substantial physiological modification of ph in the calcifying space by a value that is an inverse function of seawater ph this mechanism partially compensates for the range of ocean ph and aragonite saturation at which this species grows enhancing aragonite precipitation and suggesting an adaptation mechanism to low ph environments in intermediate and deep waters consistent with the findings of trotter et al 2011 for tropical surface corals the data suggest an inverse correlation between the magnitude of a biologically driven ph offset recorded in the coral skeleton and the seawater ph described by the equation ph ph recorded by coral seawater ph 0 75 0 12 phw 6 88 0 93 1 se error analysis based on 95 confidence interval ci and the standard deviation of the regression residuals suggests that the uncertainty of seawater ph reconstructed from 11bcoral is 0 07 to 0 12 ph units this study demonstrates the applicability of 11b in d dianthus to record ambient seawater ph and holds promise for reconstructing oceanic ph distribution and history using fossil corals

seawater ph control on the boron isotopic composition of calcite evidence from inorganic calcite precipitation experiments experiments involving boron co precipitation with calcite have been carried out inorganically under controlled ph conditions 7 9 0 05 8 3 0 05 and 8 6 0 05 to determine the dependence of the boron isotopic composition 11b of calcite on the ph of seawater another purpose of these experiments was to estimate the magnitude of the biogenic influence on the 11b value of foraminifera by comparing their boron isotopic composition with that of the inorganic calcite over a common ph range the results show a clear relationship between 11b of inorganic calcite and the ph of artificial seawater the variation of boron isotopic fractionation between seawater and calcite with ph estimated from these experiments is similar to that estimated for cultured o universa and the theoretically predicted trend the results also support the hypothesis that b oh 4 is the dominant species incorporated into the calcite structure however the boron isotopic fractionation between seawater and inorganic calcite is lower than that estimated for o universa indicating the presence of a biogenic effect on the boron isotopic composition at least of this species of foraminifera most importantly the results imply that in spite of a small biogenic influence on the boron isotopic composition of foraminifera the variation in 11b of foraminiferal shells with ph at least for o universa is comparable to that for inorganic calcite supporting the potential of this isotopic signature in foraminifera as a reliable paleo ph proxy

ph control on oxygen isotopic composition of symbiotic corals abstract boron carbon and oxygen isotopic compositions were determined at the micrometre scale by high resolution ion microprobe in a sample of modern coral massive hermatypic coral porites lutea the ion probe data show for b and o much larger isotopic variations at the micrometre scale than those measured at the millimetre scale by conventional techniques 18opdb values range from 10 6 0 9 to 0 2 0 5 and 11b values range from 18 6 1 5 to 30 6 1 6 by contrast 13c values show the same range of variations from 4 6 0 65 to 2 2 0 67 at the micrometre and millimetre scales the range of 11b values indicates that significant ph variations from 7 1 to 9 0 are present at the sites of calcification the largest 18o variations correspond to the highest 11b values i e to the highest phs this measurement of ph allows modelling the oxygen isotopic fractionation occurring during aragonite precipitation taking into account the rate of o isotopic equilibrium between dissolved carbonate species h2co3 hco3 and co32 and water via the two reactions of hydration and hydroxylation the full range of 18o values measured at the micrometre scale can be modelled for residence times of dissolved carbonates in the calcifying fluid ranging between 1 h and at maximum 12 h the ph controls the 18o of the growing carbonate through the relative fractions of dissolved carbonate species and through the kinetics of their isotopic equilibration with water via hydration and hydroxylation the so called vital effect systematically observed for 18o in corals can thus be understood as representing an average of rapid ph variations due to coral biology during coral growth selectively measuring 18o values in the zones of coral skeletons that have low 11b values i e formed at low ph should significantly improve the quality of palaeoclimatic reconstructions based on 18o values

influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater abstract the ratio of boron to calcium b ca in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric co 2 concentrations however precise controls on b ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties to help establish a firm inorganic basis for interpreting the b ca records we examined the effect of a suite of chemical parameters ca 2 ph dic salinity and po 4 3 on b ca in inorganic calcite precipitated in artificial seawater these parameters were primarily varied individually while keeping all others constant but we also tested the influence of ph and dic at a constant calcite precipitation rate r by concurrent ca 2 adjustments in the simple ca 2 ph and dic experiments both r and b ca increased with these parameters in the ph ca 2 and dic ca 2 experiments at constant r on the other hand b ca was invariant at different ph and decreased with dic respectively these patterns agree with the behavior of solution b total dic ratio such that at a fixed b total it is independent of ph but decreases with dic based on these results r and b total dic ratio appear to be the primary controls on b ca in inorganic calcite suggesting that both b oh 4 and b oh 3 are possibly involved in b incorporation moreover b ca modestly increased with salinity and po 4 3 inorganic calcite precipitated at higher r and in the presence of oxyanions such as so 4 2 and po 4 3 in growth solutions often undergoes surface roughening due to formation of crystallographic defects vacancies and occasionally amorphous hydrous caco 3 these non lattice sites may provide additional space for b particularly b oh 3 consequently besides the macroscopic influence of r and bulk solution chemistry molecular scale processes associated with calcite nucleation can be an important consideration for b incorporation especially in complex ionic solutions lastly the covariance of b ca with dic and salinity observed here qualitatively agrees with those in planktic foraminifers it follows that their impact on foraminiferal b ca is partly inorganically driven which may explain why the effect is evident across different species

effects of seawater ph and biomineralization on the boron isotopic composition of deep sea bamboo corals abstract the ocean is currently absorbing excess carbon from anthropogenic emissions leading to reduced seawater ph termed ocean acidification instrumental records of ocean acidification are unavailable from well ventilated areas of the deep ocean necessitating proxy records to improve spatio temporal understanding on the rate and magnitude of deep ocean acidification here we investigate boron carbon and oxygen isotopes on live collected deep sea bamboo corals genus keratoisis from a phtot range of 7 5 8 1 these analyses are used to explore the potential for using bamboo coral skeletons as archives of past deep sea ph and to trace anthropogenic acidification in the subsurface north atlantic ocean 850 2000 m water depth boron isotope ratios of the most recently secreted calcite of bamboo coral skeletons are close to the calculated isotopic composition of borate anion in seawater 11bborate for north atlantic corals and 1 2 higher than 11bborate for pacific corals within individual coral skeletons carbon and oxygen isotopes correlate positively and linearly a feature associated with vital effects during coral calcification 11b variability of 0 5 2 is observed within single specimens which exceeds the expected anthropogenic trend in modern north atlantic corals 11b values are generally elevated in pacific corals relative to 11bborate which may reflect ph driven physiological processes aiding coral calcification in environments unfavorable for calcite precipitation elevated 11b values are also observed proximal to the central axis in multiple atlantic and pacific specimens relative to 11bborate which might reflect ontogenetic variability in calcification rates although the observed boron isotope variability is too large to resolve the present anthropogenic ocean acidification signal at the studied depths in the north atlantic 0 03 0 07 ph units ph changes 0 1 units might still be reconstructed using 11b measurements in bamboo corals

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

reproducibility of trace element profiles in a specimen of the deep water bamboo coral keratoisis sp abstract bamboo corals order gorgonacea family isididae are attractive prospects for deep sea paleoceanographic reconstruction capturing trace elements in their calcitic skeletons that may serve as environmental proxies with subdecadal resolution over multi century timescales we study the reproducibility and fidelity of trace element profiles ba mg sr mn u pb in a 420 year old specimen of the bamboo coral keratoisis sp from the se usa using laser ablation icp ms to obtain multiple replicate profiles we use spectral techniques to distinguish noise and irreproducible variations from fully reproducible geochemical fluctuations that are candidates for environmental signals by quantifying variability between profiles we assess the fidelity with which the corals potentially record environmental information barium is the most reproducible element in the skeleton with large fluctuations along different growth radii reproducing to within 4 both mg and sr have very uniform levels within the coral but display low amplitude irreproducible variations that might represent an internal biological process in the case of mg which has been proposed as a paleotemperature proxy this irreproducibility would represent an intrinsic uncertainty of 0 1 to 0 4 c both mn and pb contain some irreproducibility superimposed upon broad reproducible profiles that may be environmental signals some of the irreproducible pb fluctuations correlate with cracks and dark bands in the sample suggesting detrital or surface contamination uranium displays large amplitude variations which are not reproducible along different radii this suggests that uranium cannot be used for paleoenvironmental reconstruction and may show signs of early diagenesis a possibility that could complicate attempts to date young keratoisis sp samples by u series geochemistry the highly reproducible ba signal allows precise alignment of profiles and thus we can show that growth rate along one radius can vary by a factor of two relative to growth along a different radius there is no evidence that this large variation in relative growth rate affects either the mg or sr incorporation in addition geochemical anomalies in ba and mg indicate that the very central axis of the specimen may represent a different mode of growth this study suggests that keratoisis sp corals are imperfect recorders of geochemical information but do contain reproducible variations which are good candidates for environmental signals

linear correlations in bamboo coral δ 13 c and δ 18 o sampled by sims and micromill evaluating paleoceanographic potential and biomineralization mechanisms using δ 11 b and 47 composition abstract bamboo corals represent an intriguing paleoceanographic archive with the potential to reconstruct variations throughout the water column over multiple centuries realizing this potential partially depends on if and at what resolution timeseries of variability can be generated recent work demonstrates that bamboo coral growth temperature averaged over its entire lifespan can be derived from linear correlations in its carbon and oxygen isotope composition 13 c 18 o when the apparent equilibrium fractionations for a coral s growth rate and calcifying ph are used building on this method this study applies it to coeval coral skeleton to assess the possibility of extracting paleoceanographic timeseries from bamboo coral skeletons using boron isotope 11 b based ph estimates micromilled samples yield accurate paleotemperatures with uncertainties of 2 c this is attributed to the inability to measure 13 c and 18 o in exactly the same skeleton as is the case for micromilled samples a micromilled sampling strategy is therefore likely the most practical means of applying the method carbonate clumped isotopes 47 estimate temperatures slightly warmer than observed suggesting they may not accurately record the subtle variations of the latest holocene when interpreted in conjunction 18 o 11 b and 47 data suggest that ph up regulation plays a role in generating linear 13 c 18 o trends however oxygen isotope fractionation and 47 are lower than would be predicted by ph alone potential explanations for this discrepancy include biological processes that favor the incorporation of carbonate ion into coral skeleton uncertainties in the 11 b ph proxy the influence of magnesium on calcite fluid isotope fractionation or uncertainties in the fractionation factors used to calculate apparent equilibrium despite some remaining uncertainties the method can resolve many observed decadal scale thermocline temperature anomalies suggesting that appropriately located bamboo corals could help constrain the behavior of similar temporal variability prior to instrumental monitoring

deep sea coral aragonite as a recorder for the neodymium isotopic composition of seawater deep sea corals have been shown to be useful archives of rapid changes in ocean chemistry during the last glacial cycle their aragonitic skeleton can be absolutely dated by u th data freeing radiocarbon to be used as a water mass proxy for certain species of deep sea corals the growth rate allows time resolution that is comparable to ice cores an additional proxy is needed to exploit this opportunity and turn radiocarbon data into rates of ocean overturning in the past neodymium isotopes in seawater can serve as a quasi conservative water mass tracer and initial results indicate that deep sea corals may be reliable archives of seawater nd isotopes here we present a systematic study exploring nd isotopes as a water mass proxy in deep sea coral aragonite we investigated five different genera of modern deep sea corals caryophyllia desmophyllum enallopsamia flabellum lophelia from global locations covering a large potential range of nd isotopic compositions comparison with ambient seawater measurements yields excellent agreement and suggests that deep sea corals are reliable archives for seawater nd isotopes a parallel study of nd concentrations in these corals yields distribution coefficients for nd between seawater and coral aragonite of 1 10 omitting one particular genus enallopsamia the corals and seawater did however not come from exactly the same location and further investigations are needed to reach robust conclusions on the incorporation of nd into deep sea coral aragonite lastly we studied the viability of extracting the nd isotope signal from fossil deep sea corals by carrying out stepwise cleaning experiments our results show that physical removal of the ferromanganese coating and chemical pre cleaning have the highest impact on nd concentrations but that oxidative reductive cleaning is also needed to acquire a seawater nd isotope signal

reproducibility of ba ca variations recorded by northeast pacific bamboo corals trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions the concentration of dissolved barium basw a bioactive nutrientlike element is linked to biogeochemical processes such as the cycling and export of nutrients recent work has calibrated bamboo coral ba ca a new basw proxy using corals spanning the oxygen minimum zone beneath the california current system however it was previously unclear whether ba cacoral records were internally reproducible here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for ba cacoral analyses and test the internal reproducibility of ba ca among replicate radial transects in the calcite of nine bamboo corals collected from the gulf of alaska 643 720 m and the california margin 870 2054 m data from replicate ba ca transects were aligned using visible growth bands to account for nonconcentric growth smoothed data were reproducible within 4 for eight corals n 3 radii coral this intracoral reproducibility further validates using bamboo coral ba ca for basw reconstructions sections of the ba ca records that were potentially influenced by noncarbonate bound ba phases occurred in regions where elevated mg ca or pb ca and coincided with anomalous regions on photomicrographs after removing these regions of the records increased ba cacoral variability was evident in corals between 800 and 1500 m these findings support additional proxy validation to understand basw variability on interannual timescales which could lead to new insights into deep sea biogeochemistry over the past several centuries

variability and renewal of labrador sea water in the irminger basin in 1991 2004 1 labrador sea water lsw property variations are analyzed using the data from six hydrographic sections occupied in 1991 2004 in the southern irminger basin between cape farewell and the reykjanes ridge from 1991 to 1996 the lsw layer became steadily colder and fresher the decrease in salinity of the lsw detected in 1994 was caused by the local convection reaching into the weakly stratified layer of lsw advected from the labrador sea another indication of local deep convection is in the lateral distribution of dissolved oxygen concentrations in the lsw layer 1000 2000 m obtained in 1997 from the section across the labrador sea and four sections running 100 135 and 180 true azimuth from cape farewell a separate lateral maximum of oxygen content in the lsw layer is revealed in the southern irminger sea the concentrations increased from the labrador sea eastern edge toward the irminger sea rather than the reverse as would be expected if there was no local modification of lsw via deep convection since 1996 the two modal structure of lsw has been observed in the irminger basin the upper mode of lsw detected in 1996 was formed in situ during the winter of 1996 1997 the upper mode was locally renewed from 1997 to 2004 the temperature and salinity signatures of the deeper mode considerably eroded due to the lack of the renewal of the deeper lsw reservoir in the labrador sea while the annually renewed upper mode on the contrary became more pronounced in the property patterns

deep sea coral evidence for rapid change in ventilation of the deep north atlantic 15 400 years ago coupled radiocarbon and thorium 230 dates from benthic coral species reveal that the ventilation rate of the north atlantic upper deep water varied greatly during the last deglaciation radiocarbon ages in several corals of the same age 15 41 0 17 thousand years and nearly the same depth 1800 meters in the western north atlantic ocean increased by as much as 670 years during the 30 to 160 year life spans of the samples cadmium calcium ratios in one coral imply that the nutrient content of these deep waters also increased our data show that the deep ocean changed on decadal centennial time scales during rapid changes in the surface ocean and the atmosphere

quantifying the ph vital effect in the temperate zooxanthellate coral cladocora caespitosa validation of the boron seawater ph proxy boron isotopic and elemental systematics are used to define the vital effects for the temperate shallow water mediterranean coral cladocora caespitosa the corals are from a range of seawater ph conditions pht 7 6 to 8 1 and environmental settings 1 naturally living colonies harvested from normal ph waters offshore levanto 2 colonies transplanted nearby a subsea volcanic vent system and 3 corals cultured in aquaria exposed to high 700 atm and near present day 400 atm pco2 levels b ca compositions measured using laser ablation inductively coupled mass spectrometry la icpms show that boron uptake by c caespitosa cultured at different pco2 levels is independent of ambient seawater ph being mainly controlled by temperature dependent calcification in contrast the boron isotope compositions 11bcarb of the full suite of corals determined by positive thermal ionisation mass spectrometry ptims shows a clear trend of decreasing 11bcarb from 26 7 to 22 2 with decreasing seawater ph reflecting the strong ph dependence of the boron isotope system the 11bcarb compositions together with measurements of ambient seawater parameters enable calibration of the boron ph proxy for c caespitosa by using a new approach that defines the relationship between ambient seawater ph phsw and the internally controlled ph at the site of calcification phbiol c caespitosa exhibits a linear relationship between phsw and the shift in ph due to physiological processes ph phbiol phsw giving the regression phclad 4 80 0 52 phsw for this species we further apply this method ph phsw to calibrate tropical species of porites acropora and stylophora reported in the literature the temperate and tropical species calibrations are all linearly correlated r2 0 9 and the biological fractionation component ph between species varies within 0 2 ph units our ph phsw approach provides a robust and accurate tool to reconstruct palaeoseawater phsw for both temperate and tropical corals further validating the boron fractionation factor b3 b4 1 0272 determined experimentally by klochko et al 2006 and the boron isotope ph proxy both of which have been the foci of considerable debate

calibration and application of b ca cd ca and δ11b in neogloboquadrina pachyderma sinistral to constrain co2 uptake in the subpolar north atlantic during the last deglaciation the north atlantic and norwegian sea are prominent sinks of atmospheric co 2 today but their roles in the past remain poorly constrained in this study we attempt to use b ca and 11 b ratios in the planktonic foraminifera neogloboquadrina pachyderma sinistral variety to reconstruct subsurface water ph and pco 2 changes in the polar north atlantic during the last deglaciation comparison of core top results with nearby hydrographic data shows that b ca in n pachyderma s is mainly controlled by seawater b oh 4 hco 3 with a roughly constant partition coefficient k d b ca caco 3 b oh 4 hco 3 seawater of 1 48 0 15 10 3 2 and 11 b in this species is offset below 11 b of the borate in seawater by 3 38 0 71 2 these values represent our best estimates with the sparse available hydrographic data close to our core tops more culturing and sediment trap work is needed to improve our understanding of boron incorporation into n pachyderma s application of a constant k d of 1 48 10 3 to high resolution n pachyderma s b ca records from two adjacent cores off iceland shows that subsurface pco 2 at the habitat depth of n pachyderma s 50 m generally followed the atmospheric co 2 trend but with negative offsets of 10 50 ppmv during 19 10 ka these b ca based reconstructions are supported by independent estimates from low resolution 11 b measurements in the same cores we also calibrate and apply cd ca in n pachyderma s to reconstruct nutrient levels for the same down cores like today s north atlantic past subsurface pco 2 variability off iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column because surface pco 2 at 0 m water depth is always lower than at deeper depths and if the application of a constant kd is valid our results suggest that the polar north atlantic has remained a co 2 sink during the calcification seasons of n pachyderma s over the last deglaciation

an evaluation of benthic foraminiferal b ca and δ11b for deep ocean carbonate ion and ph reconstructions reliable reconstructions of deep ocean carbonate ion concentration co32 and ph are crucial to understand mechanisms responsible for the past atmospheric co2 variations observed in ice cores however it is challenging to reconstruct past deep water co32 and ph and literature results from different proxies conflict warranting careful investigations on possible reasons for the existing inconsistencies here we present the first down core b ca and 11b records measured in an epifaunal benthic foraminifer cibicidoides wuellerstorfi from the caribbean sea during the last 160 kyr the two proxies yield quantitatively comparable deep water co3 2 and ph results showing high values during glacials relative to inter glacials differences in co32 and ph are 35 mol kg and 0 15 respectively consistent with past ocean circulation changes in the caribbean sea our data provide convincing evidence that both proxies serve as faithful proxies to estimate deep ocean co32 and ph despite our incomplete understanding of boron incorporation into foraminiferal carbonates

effect of environmental conditions and skeletal ultrastructure on the li isotopic composition of scleractinian corals the lithium isotope compositions li 7 li 6 and li ca ratios of shallow water and deep sea corals porites lutea cladocora caespitosa lophelia pertusa and desmophyllum cristagalli were measured using a cameca ims 1270 ion microprobe the two c caespitosa samples were grown under controlled conditions at co2 partial pressures pco 2 of 416 29 mu atm and 729 30 mu atm respectively in situ analyses show that all samples are isotopically homogeneous within analytical precision 1 1 parts per thousand 1 sigma and display significantly lower delta li 7 values relative to seawater indicating a significant isotope fractionation during aragonite formation in contrast to all other elements analysed so far there is no relationship between the li isotopic compositions and the skeletal ultrastructure however li ca does show variation correlated with ultrastructure albeit with significant differences between species this implies that the bio mineralization mechanisms which are supposed to be different for the different skeletal components do not influence the li isotopic composition in corals in particular the model of rayleigh fractionation in a semi enclosed calcifying fluid is incompatible with the homogeneity of the li isotope compositions at the micrometer scale we also show that changes in pco 2 and ph do not significantly affect the li isotope signature nevertheless a small but significant and systematic difference in li isotopic composition is observed between deep sea azooxanthellate and shallow water zooxanthellate corals the lack of dependence on ph and pco 2 and on skeletal ultrastructure indicates that the u isotopic signature of corals could be used as a proxy for reconstructing the paleo delta li 7 of seawater and potentially for deconvolving past continental weathering rates c 2009 elsevier b v all rights reserved

geochemical perspectives on coral mineralization corals open an exceptional window into many phenomena of geological geochemical climatic and paleontological interest from the paleozoic to the present corals provide some of the finest high resolution archives of marine conditions corals are likewise exceptional for chronometric purposes and even the terrestrial 14c timescale has now been calibrated against coral 230th 234u corals also represent a testing ground for basic ideas about mineralogy and geochemistry the shapes sizes and organization of skeletal crystals have been attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth the coupling between calcification and photosynthesis in symbiotic corals is likewise attributed to everything from photosynthetic alkalinization of the water to efforts by the coral to prevent photosynthetic alkalinization corals also leave a significant geochemical imprint on the oceans their aragonite skeletons accept about 10 times more strontium than does calcite hence the proportion of marine aragonite precipitation affects the oceanic chemical balance biological carbonates represent the biosphere s largest carbon reservoir hence calcareous organisms affect the ocean s ph co2 content and ultimately global temperatures through the greenhouse gas connection finally corals present some geochemical puzzles for ecology and conservation how do symbiotic corals obtain nutrients in some of the most nutrient deficient parts of the planet are global geochemical changes partially responsible for the widespread declines in coral reefs during recent decades we will address many of these issues but will concentrate on coral skeletal structure and calcification mechanism these topics bear most directly on the biomineralization process and generally affect the choice of skeletal materials and analytical techniques used in geochemical investigations the coral reef is probably the planet s most spectacular biomineralization product these grand and complex ecosystems build on the accumulated skeletal debris of countless generations of organisms especially calcareous algae and symbiotic

calibration of the boron isotope proxy in the planktonic foraminifera globigerinoides ruber for use in palaeo co2 reconstruction abstract the boron isotope ph proxy applied to mixed layer planktic foraminifera has great potential for estimating past co2 levels which in turn is crucial to advance our understanding of how this greenhouse gas influences earth s climate previous culture experiments have shown that although the boron isotopic compositions of various planktic foraminifera are ph dependent they do not agree with the aqueous geochemical basis of the proxy here we outline the results of culture experiments on globigerinoides ruber white across a range of ph 7 5 8 2 and analysed via multicollector inductively coupled plasma mass spectrometry mc icpms and compare these data to core top and sediment trap samples to derive a robust new species specific boron isotope ph calibration consistent with earlier culture studies we show a reduced ph dependency of the boron isotopic composition of symbiont bearing planktonic foraminifera compared to borate ion in seawater we also present evidence for a size fraction effect in the 11b of g ruber finally we reconstruct atmospheric co2 concentrations over the last deglacial using our new calibration at two equatorial sites odp site 999a and site geob1523 1 these data provide further grounding for the application of the boron isotope ph proxy in reconstructions of past atmospheric co2 levels

crystal growth rate effect on mg ca and sr ca partitioning between calcite and fluid an in situ approach abstract partition coefficients of mg and sr kmg and ksr between calcite and fluid were determined in crystals grown under different rates v where v is defined as the crystal extension per unit of time nm s addition of rare earth elements ree into the fluid leads to ree preservation in the calcite this preservation allows for a direct determination of the values of v by measuring the widths of the ree spiked zones the edge to edge spot analyses of mg ca sr ca and ree ca in the individual crystals were conducted using secondary ion mass spectrometry sims the mg ca and sr ca ratios in the fluids from which calcites precipitated were also measured with inductively coupled plasma atomic emission spectroscopy icp oes this allowed for the first time to evaluate kmg in situ in the individual crystals without averaging the data from the multiple calcite crystals results show that ksr increases by a factor of six with increasing calcite growth rate from 0 001 to 4 nm s kmg decreases by a factor of three with the same increase of v values these ksr and kmg behaviors were described quantitatively using a growth entrapment model gem according to the gem simulations sr is enriched and mg is depleted in the near surface layer of calcite relative to the bulk lattice this distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth this process causes disequilibrium partitioning of sr and mg through growth entrapment

experimental measurement of boron isotope fractionation in seawater abstract the boron isotopic composition of marine carbonates is considered to be a tracer of seawater ph use of this proxy benefits from an intimate understanding of chemical kinetics and thermodynamic isotope exchange reactions between the two dominant boron bearing species in seawater boric acid b oh 3 and borate ion b oh 4 however because of our inability to quantitatively separate these species in solution the degree of boron isotope exchange has only been known through theoretical estimates in this study we present results of a spectrophotometric procedure wherein the boron isotope equilibrium constant 11 10 k b is determined empirically from the difference in the dissociation constants of 11 b oh 3 and 10 b oh 3 in pure water 0 6 mol kg 1 h 2 o kcl and artificial seawater within experimental uncertainty our results show no dependence of 11 10 k b on temperature but 11 10 k b at 25 c in pure water was statistically different than results obtained in solutions at high ionic strength 11 10 k b of the seawater s 35 b t 0 01 mol kg 1 h 2 o at 25 c is 1 0272 0 0006 this result is significantly larger than the theoretical value used in numerous paleo ph studies 11 10 k b 1 0194

a core top screen for trace element proxies of environmental conditions and growth rates in the calcite skeletons of bamboo corals isididae abstract we test for trace element proxies in the high magnesium calcite fraction of bamboo coral internodes by comparing environmental conditions and growth rates to the specimen mean compositions of 73 corals that were live caught at depths ranging from 3 to 3950 m and collected from habitats ranging from tropical coral reefs to the antarctic slope comparisons were done at a large geographic scale lgs and for a well sampled area south of australia across depths at a single site in order to help separate the effects of environmental variables that co vary at one spatial scale but not the other thirty seven trace elements were measured using solution based sector field icp ms of which seventeen were significantly detected in more than a third of the specimens only eight element calcium ratios correlated significantly with any environmental variable at the large geographic scale and only four did so at the local level at the lgs the highest correlation was between ambient temperature and mg ca which accounted for 89 of the variance across specimens spanned all four isidid sub families and was independently significant in the two best sampled sub families the predictive geometric mean relationship is t c 23 9 2 46 0 34 0 25 mg ca mmol mol spanning a temperature range of 1 9 to 26 8 c mg ca ratios from 58 6 to 155 1 mmol mol and an uncertainty rms of 2 78 c the numbers in parentheses are 95 cis the slope of the regression does not differ significantly from that of abiotic high mg calcites which suggests that the temperature dependent incorporation of mg into the carbonate results from kinetic reactions at the crystal surface analysis at the sh scale for the sub set of specimens for which we had data suggests is also affected by growth rates there were no obvious trace element correlates at either spatial scale of salinity or oxygen levels that could not be accounted for by covariance between these environmental parameters and in most cases temperature single and multiple correlation analyses also confirm previous suggestions that ba ca in bamboo coral calcite is a proxy for seawater barium and hence refractory nutrients suggest that sr ca is influenced by specimen mean mg ca ratios and water temperature as well as possibly seawater sr ca and falsify for bamboo corals p ca as well as p cd and cd ca as a proxy for seawater phosphate levels the predictive relationship between isidid skeletal mean ba ca and seawater silicate concentrations appears to be linear and is given by silicate mol kg 1 56 7 20 8 9217 1632 ba ca mmol mol spanning a silicate range of 0 5 to 120 mol kg 1 a ba ca range of 0 0042 to 0 0195 mmol mol and with an uncertainty rms of 33 1 mol kg 1 mn ca differences among specimens and sites are highly significant and appear to reflect seawater mn suggesting a proxy for this micronutrient the compilation of growth rate data across 34 specimens indicates a wide range of growth rates even among con familial specimens from within a single habitat and suggests both ambient temperature and food availability underlie at least part of this variability

eastern north atlantic deep sea corals tracing upper intermediate water δ14c during the holocene abstract paired 230th u and 14c dating were performed on deep sea corals lophelia pertusa and madrepora oculata from the northeastern north atlantic at 730 m bsl to investigate past changes of the thermohaline circulation these were estimated using the 14c value of the upper intermediate waters based on the 14c ages of the top and base of each coral where possible and the 230th u dating the reliability of these estimates was checked by dating two very young corals of the species l pertusa one of these corals collected alive in 1999 ad gave a 230th u age of 1995 4 ad after correction for non radiogenic 230th another coral the top of which dated to 1969 6 ad recorded the atmospheric 14c 12c increase due to the nuclear tests in the early 1960s the calculated 14c values from these two corals agree with those measured at geosecs station 23 in 1972 1973 ostlund et al earth planet sci lett 23 1974 69 86 and 1991 1992 nydal and gisfelos radiocarbon 38 1996 389 406 this together with the 100 aragonite content and the 234u and 230th 232th values of all the dated corals indicates that none of the corals behaved as open systems with respect to their u series nuclides and that they closely represent the water mass properties in which they lived the pre anthropogenic 14c value of the north atlantic intermediate waters was estimated at 69 4 the reservoir age varies from 400 years to 600 years and this variation is due to atmospheric 14c 12c changes a reservoir age of 610 80 years close to the pre anthropogenic value was determined from one coral dated at 10 430 120 cal yr bp when the global sea level was approximately at 35 m bard et al nature 382 1996 241 244 this suggests a modern like pattern of the oceanic circulation prevailed in the northeast atlantic ocean at this time although the deglaciation was not completely achieved

sr ca and mg ca vital effects correlated with skeletal architecture in a scleractinian deep sea coral and the role of rayleigh fractionation deep sea corals are a new tool in paleoceanography with the potential to provide century long records of deep ocean change at sub decadal resolution complicating the reconstruction of past deep sea temperatures mg ca and sr ca paleothermometers in corals are also influenced by non environmental factors termed vital effects to determine the magnitude pattern and mechanism of vital effects we measure detailed collocated sr ca and mg ca ratios using a combination of micromilling and isotope dilution icp ms across skeletal features in recent samples of desmophyllum dianthus a scleractinian coral that grows in the near constant environment of the deep sea sr ca variability across skeletal features is less than 5 2 relative standard deviation and variability of sr ca within the optically dense central band composed of small and irregular aragonite crystals is significantly less than the surrounding skeleton the mean sr ca of the central band 10 6 0 1 mmol mol 2 standard error and that of the surrounding skeleton 10 58 0 09 mmol mol are statistically similar and agree well with the inorganic aragonite sr ca temperature relationship at the temperature of coral growth in the central band mg ca is greater than 3 mmol mol more than twice that of the surrounding skeleton a general result observed in the relative mg ca ratios of d dianthus collected from separate oceanographic locations this large vital effect corresponds to a 10 c signal when calibrated via surface coral mg ca temperature relationships and has the potential to complicate paleoreconstructions outside the central band mg ca ratios increase with decreasing sr ca we explain the correlated behavior of mg ca and sr ca outside the central band by rayleigh fractionation from a closed pool an explanation that has been proposed elsewhere but which is tested in this study by a simple and general relationship we constrain the initial solution and effective partition coefficients for a rayleigh process consistent with our accurate metal ca measurements a process other than rayleigh fractionation influences mg in the central band and our data constrain a number of possible mechanisms for the precipitation of this aragonite understanding the process affecting tracer behavior during coral biomineralization can help us better interpret paleoproxies in biogenic carbonates and lead to an improved deep sea paleothermometer

large δ13c gradients in the preindustrial north atlantic revealed the carbon isotopic composition 13 c 12 c expressed as 13 c of fossil foraminifera is the primary tracer used to infer changes in past ocean ventilation and its variations are interpreted by using the modern oceanic 13 c distribution as a framework however the present ocean 13 c distribution is strongly overprinted by isotopically light anthropogenic carbon dioxide a correction for this oceanic c 13 suess effect in the north atlantic na shows that the pristine na 13 c distribution has a richer and more detailed structure that is more clearly related to water mass distributions our results revise some fundamental perceptions regarding glacial interglacial ocean 13 c differences and allow paleo 13 c variations to be understood within the context of modern climate variability

temperature and vital effect controls on bamboo coral isididae isotope geochemistry a test of the lines method deep sea bamboo corals hold promise as long term climatic archives yet little information exists linking bamboo coral geochemistry to measured environmental parameters this study focuses on a suite of 10 bamboo corals collected from the pacific and atlantic basins 250 2136 m water depth to investigate coral longevity growth rates and isotopic signatures calcite samples for stable isotopes and radiocarbon were collected from the base the corals where the entire history of growth is recorded in three of the coral specimens samples were also taken from an upper branch for comparison radiocarbon and growth band width analyses indicate that the skeletal calcite precipitates from ambient dissolved inorganic carbon and that the corals live for 150 300 years with extension rates of 9 128 m yr a linear relationship between coral calcite 18o and 13c indicates that the isotopic composition is influenced by vital effects 18o 13c slope of 0 17 0 47 as with scleractinian deep sea corals the intercept from a linear regression of 18o versus 13c is a function of temperature such that a reliable paleotemperature proxy can be obtained using the lines method although the coral calcite 18o 13c slope is maintained throughout the coral base ontogeny the branches and central cores of the bases exhibit 18o 13c values that are shifted far from equilibrium we find that a reliable intercept value can be derived from the 18o 13c regression of multiple samples distributed throughout one specimen or from multiple samples within individual growth bands

late holocene radiocarbon variability in northwest atlantic slope waters abstract deep sea gorgonian corals secrete a 2 part skeleton of calcite derived from dissolved inorganic carbon at depth and gorgonin derived from recently fixed and exported particulate organic matter radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters respectively using specimens collected from northwest atlantic slope waters we generated radiocarbon records for surface and upper intermediate water layers spanning the pre and post bomb 14 c eras in labrador slope water lsw convective mixing homogenizes the pre bomb 14 c signature 67 4 to at least 1000 m depth surface water bomb 14 c signals were lagged and damped peaking at 45 in the early 1980s relative to other regions of the northwest atlantic and intermediate water signals were damped further off southwest nova scotia the vertical gradient in 14 c is much stronger in surface water pre bomb 14 c averaged 75 5 at 250 475 m depth pre bomb 14 c oscillated quasi decadally between 80 and 100 likely reflecting interannual variability in the presence of labrador slope water vs warm slope water wsw finally subfossil corals reveal no systematic changes in vertical 14 c gradients over the last 1200 yr

warming and salinification of intermediate and deep waters in the irminger sea and iceland basin in 1997 2006 1 recent intra decadal changes in temperature and salinity of the labrador sea water and nordic overflow waters are quantified on the basis of the ctd data from the repeats of the zonal transatlantic section along 60 n carried out in 1997 2002 2004 and 2006 the revealed changes in general point to a rapid transition to the warmer saltier conditions at the intermediate and deeper levels in the irminger sea and iceland basin at the section latitude in 1997 2006 in particular substantial steady warming and salinification of the iceland scotland overflow water is revealed in both basins the latter result means an abrupt reversal or at least almost a decade long interruption of the long term freshening of this water lasted since the mid 1960s

hydrographic changes in the labrador sea 1960 2005 abstract the labrador sea has exhibited significant temperature and salinity variations over the past five decades the whole basin was extremely warm and salty between the mid 1960s and early 1970s and fresh and cold between the late 1980s and mid 1990s the full column salinity change observed between these periods is equivalent to mixing a 6 m thick freshwater layer into the water column of the early 1970s the freshening and cooling trends reversed in 1994 starting a new phase of heat and salt accumulation in the labrador sea sustained throughout the subsequent years it took only a decade for the whole water column to lose most of its excessive freshwater reinstate stratification and accumulate enough salt and heat to approach its record high salt and heat contents observed between the late 1960s and the early 1970s if the recent tendencies persist the basin s storages of salt and heat will fairly soon likely by 2008 exceed their historic highs the main process responsible for the net cooling and freshening of the labrador sea between 1987 and 1994 was deep winter convection which during this period progressively developed to its record depths it was caused by the recurrence of severe winters during these years and in its turn produced the deepest densest and most voluminous labrador sea water lsw1987 1994 ever observed the estimated annual production of this water during the period of 1987 1994 is equivalent to the average volume flux of about 4 5 sv with some individual annual rates exceeding 7 0 sv once winter convection had lost its strength in the winter of 1994 1995 the deep lsw1987 1994 layer lost communication with the mixed layer above consequently losing its volume while gaining heat and salt from the intermediate waters outside the labrador sea while the 1000 2000 m layer was steadily becoming warmer and saltier between 1994 and 2005 the upper 1000 m layer experienced another episode of cooling caused by an abrupt increase in the air sea heat fluxes in the winter of 1999 2000 this change in the atmospheric forcing resulted in fairly intense convective mixing sufficient to produce a new prominent lsw class lsw2000 penetrating deeper than 1300 m this layer was steadily sinking or deepening over the years following its production and is presently overlain by even warmer and apparently less dense water mass implying that lsw2000 is likely to follow the fate of its deeper precursor lsw1987 1994 the increasing stratification of the intermediate layer implies intensification in the baroclinic component of the boundary currents around the mid depth perimeter of the labrador sea the near bottom waters originating from the denmark strait overflow exhibit strong interannual variability featuring distinct short term basin scale events or pulses of anomalously cold and fresh water separated by warm and salty overflow modifications regardless of their sign these anomalies pass through the abyss of the labrador sea first appearing at the greenland side and then about a year later at the labrador side and in the central labrador basin the northeast atlantic deep water 2500 3200 m originating from the iceland scotland overflow water reached its historically freshest state in the 2000 2001 period and has been steadily becoming saltier since then it is argued that lsw1987 1994 significantly contributed to the freshening density decrease and volume loss experienced by this water mass between the late 1960s and the mid 1990s via the increased entrainment of freshening lsw the hydrostatic adjustment to expanding lsw or both

seawater nutrient and carbonate ion concentrations recorded as p ca ba ca and u ca in the deep sea coral desmophyllum dianthus as paleoceanographic archives deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating but have not been fully investigated for geochemical reconstructions of past ocean conditions here we assess the utility of skeletal p ca ba ca and u ca in the deep sea coral d dianthus as proxies of dissolved phosphate remineralized at shallow depths dissolved barium trace element with silicate type distribution and carbonate ion concentrations respectively measurements of these proxies in globally distributed d dianthus specimens show clear dependence on corresponding seawater properties linear regression fits of mean coral element ca ratios against seawater properties yield the equations p cacoral lmol mol 0 6 0 1 p casw lmol mol 23 18 r 2 0 6 n 16 and ba cacoral lmol mol 1 4 0 3 ba casw lmol mol 0 2 r 2 0 6 n 17 no significant relationship is observed between the residuals of each regression and seawater temperature salinity pressure ph or carbonate ion concentrations suggesting that these variables were not significant secondary dependencies of these proxies four d dianthus specimens growing at locations withoarag 6 0 6 displayed markedly depleted p ca compared to the regression based on the remaining samples a behavior attributed to an undersaturation effect these corals were excluded from the calibration coral u ca correlates with seawater carbonate ion u cacoral lmol mol 0 016 0 003 co 2 3 lmol kg 3 2 0 3 r 2 0 6 n 17 the residuals of the u ca calibration are not significantly related to temperature salinity or pressure scatter about the linear calibration lines is attributed to imperfect spatialtemporal matches between the selected globally distributed specimens and available water column chemical data and potentially to unresolved additional effects the uncertainties of these initial proxy calibration regressions predict that dissolved phosphate could be reconstructed to 0 4 lmol kg for 1 3 1 9 lmol kg phosphate and dissolved ba to 19 nmol kg for 41 82 nmol kg basw carbonate ion concentration derived from u ca has an uncertainty of 31lmol kg for 60 120 lmol kg co 2 3

proteinaceous corals as proxy archives of paleo environmental change abstract high resolution marine data are critical to evaluating anthropogenic impacts on our environment considering the spatial and temporal limitations of direct instrumental measurements proxy data extracted from marine environmental archives are necessary to separate anthropogenic changes from those that would occur naturally the majority of late holocene high resolution environmental reconstructions are derived from marine carbonates including tropical scleractinian corals bivalves crustose coralline algae and sclerosponges however these archives are restricted to the top hundreds of meters of the water column and only preserve environmental variability that is captured by calcium carbonate skeletons at a very few select locations marine sediments archive annual environmental variability in organic and inorganic materials recently additional types of corals are proving to yield information complimentary to these traditional marine archives including cold water scleractinian corals and proteinaceous corals a taxonomically diverse group the proteinaceous corals are broadly defined as those having a branching gross morphology with skeleton comprised at least partly of protein rich organic material they encode characteristics of their food and ambient environment into the chemical and physical composition of their skeleton this environmental encoding combined with their banded skeleton and significant longevity means that proteinaceous corals hold information in their skeleton that helps fill the spatial and temporal gaps in our knowledge of past and present ocean conditions here i review the environmental reconstructions derived from geochemical measurements of the proteinaceous coral skeletons this information is grouped into the mesopelagic environmental variability captured in the skeleton of bamboo corals surface processes captured in the organic skeletons of corals across all ocean depths and environmental variability documented by skeletal radiometric isotopes we include animals from two separate subclasses within the class anthozoa including the parasitic zoanthids that secrete a sclero proteic skeleton since the proteinaceous corals are taxonomically diverse we consider the unique features that define this group of corals including their distribution morphology nutrition and longevity we find that uncertainty surrounding biological parameters limits the precision of reconstructions derived from the calcitic skeleton in contrast analytical effort and cost constrain the number of reconstructions from the organic skeleton through this discussion we provide insights into the uses challenges and directions for future research for this important environmental archive

radiocarbon variability in the western north atlantic during the last deglaciation we present a detailed history of glacial to holocene radiocarbon in the deep western north atlantic from deep sea corals and paired benthic planktonic foraminifera the deglaciation is marked by switches between radiocarbon enriched and depleted waters leading to large radiocarbon gradients in the water column these changes played an important role in modulating atmospheric radiocarbon the deep ocean record supports the notion of a bipolar seesaw with increased northern source deep water formation linked to northern hemisphere warming and the reverse in contrast the more frequent radiocarbon variations in the intermediate deep ocean are associated with roughly synchronous changes at the poles

oxygen and carbon isotope fractionation in calcitic deep sea corals implications for paleotemperature reconstruction abstract inhabiting areas of the ocean where paleoenvironmental records are sparse deep sea corals represent valuable yet largely untapped holocene records of intermediate and deep ocean variability 18o and 13c were analyzed in nine live collected deep sea gorgonian corals isididae and coralliidae in order to further develop the lines paleotemperature method least squares linear regression analysis for full lifespan 18o vs 13c corrected for 18owater and 13cdic was utilized to yield equations of the form y mx b 18o and intercept values were found to be a function of temperature and to approximate calcite 18o equilibrium the corals in this study extend the previously reported calibration hill et al 2011 over a broader range of temperatures from 5 c to 11 2 c when combined with the data from hill et al 2011 a new expression for the relationship between the 18ointercept value and temperature is proposed t c 4 12 0 38 18 o intercept 12 33 0 75 r 2 0 90 p value 0 0001 error estimates are 0 7 c for corals living at cold temperatures 2 c 1 4 c in warmer waters 11 c and 0 5 c at the mean water temperature of the data set 4 6 c the first multi specimen verification of the lines method was performed on three co located bamboo isididae corals and found to give nearly coincident 18o intercepts detailed intraspecimen sampling reveals 18o and 13c isotopic variability within coeval portions of the skeleton in one specimen lines method analysis was utilized on multiple samples taken from the same temporal increment of the skeleton yielding multiple 18o intercepts calculated temperatures using the calibration proposed here describe a temperature range of 7 9 to 10 3 c which approaches the temperature range of 11 1 0 7 c at the coral collection location

the middle devonian basins of western norway sedimentary response to large scale transtensional tectonics abstract the devonian basins of western norway were formed during late to post orogenic extension of overthickened caledonian crust the basins are situated in the hanging wall of the extensional nordfjord sogn detachment zone nsdz and display extensional half graben geometries in sections parallel to the local direction of principal extension based on overall facies configurations paleocurrent patterns and intrabasinal structures we infer an anticlockwise rotation of the syndepositional extension direction from nw se in the south solund basin to wsw ene in the north hornelen basin the axes of folds that are roughly parallel to the local extension direction are rotated correspondingly the kvamshesten basin is located between the solund and hornelen basins sedimentological and structural data show evidence of an early southeastwards tilt direction followed by a more eastwards tilt and associated e w flowing paleodrainage correspondingly nw se trending folds and reverse faults are superposed by e w trending ones at low to intermediate stratigraphic levels the variations in apparent tilt direction for the basins together with variations in intrabasinal structure is interpreted to reflect an anticlockwise rotation of the regional syndepositional strain field the above observations and inferences indicate that the devonian basins in western norway formed in a strain field dominated by regional transtension accommodated by extension along the nsdz and sinistral strike slip along orogen parallel shear zones and faults to the north of the basins alternatively nw directed extension preceded the introduction of a sinistral strike slip component the models are in accordance with recent work carried out in the footwall of the nsdz and illustrates the tectono sedimentary response to a complex interplay between extension and strike slip that appears to have been fundamental in the late stage disintegration of the caledonian orogen

the southern ocean s role in carbon exchange during the last deglaciation changes in the upwelling and degassing of carbon from the southern ocean form one of the leading hypotheses for the cause of glacial interglacial changes in atmospheric carbon dioxide we present a 25 000 year long southern ocean radiocarbon record reconstructed from deep sea corals which shows radiocarbon depleted waters during the glacial period and through the early deglaciation this depletion and associated deep stratification disappeared by 14 6 ka thousand years ago consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a southern ocean ventilation event given this evidence for carbon exchange in the southern ocean we show that existing deep ocean radiocarbon records from the glacial period are sufficiently depleted to explain the 190 per mil drop in atmospheric radiocarbon between 17 and 14 5 ka

correlation of boron isotopic composition with ultrastructure in the deep sea coral lophelia pertusa implications for biomineralization and paleo ph using the crpg cnrs cameca 1270 ion microprobe facility we have measured boron isotopic compositions b 11 b 10 in different ultrastructural components of the deep sea aragonitic scleractinian coral lophelia pertusa we observe a systematic difference in b isotopic composition between the early mineralization zone emz and adjacent fibrous skeleton in emz the measured delta 11 b values are consistently low fibrous aragonite is characterized by systematically higher delta 11 b values but also displays b isotopic heterogeneity associated with specific growth bands in the calyx wall the magnitude of the observed b isotopic variations cannot be explained by changes in environmental conditions and is likely caused by biological processes involved in the biomineralization of new skeleton i e vital effects the observed b isotopic variations are opposite to the predictions of geochemical models for vital effects these models are based on the idea that stable isotopic fractionations including c and o in coral skeleton are driven by changes in ph of the fluid from which the skeleton is presumed to precipitate our data indicate that ph variations are not responsible for the observed stable isotopic fractionations geochemical models therefore do not provide an adequate framework within which to understand coral skeletal formation without a better understanding of these processes the use of b isotopic composition to reconstruct paleo ph variations in the oceans must be considered problematic at least as far as lophelia pertusa is concerned

bamboo coral ba ca calibration of a new deep ocean refractory nutrient proxy abstract it is poorly understood how intermediate water masses are affected by decadal scale climate via biogeochemical cycling export production and changes in circulation ventilation to this end a geochemical nutrient proxy from deep sea bamboo corals would provide decadal to centennial scale records of deep and intermediate water nutrient dynamics seawater barium basw has a nutrient like distribution in the water column similar to silicate so ba ca records in foraminifera shallow water surface corals and other deep sea corals have been used to trace refractory nutrients here we present the first calibration of a nutrient proxy from skeletal barium preserved in the calcitic internodes of deep sea bamboo corals collected from intermediate water depths a calibration was calculated from a broadly distributed suite of isidella and keratoisis corals spanning a silicate and basw gradient n 33 corals 300 2800 m ba ca b a m b o o c o r a l mol mol 0 079 0 008 ba sw nmol kg 4 205 0 870 r 2 0 77 n 33 the strong linear correlation between ba cabamboo coral and basw suggests that coral ba ca is a reliable recorder of seawater barium and therefore silicate we find a distribution coefficient dba for ba cabamboo coral of 1 3 0 2 similar to that of other corals surface and deep sea dwelling and inorganic calcium carbonate precipitation experiments dba 1 2 1 5 this suggests that ba incorporation is primarily driven by cationic substitution in bamboo corals and holds promise as a globally applicable refractory nutrient proxy we find interannual decadal scale variability in a ba cabamboo coral timeseries from a california margin coral san juan seamount 1295 m these data suggest that additional high resolution ba cabamboo coral records may reveal a connection between regional scale intermediate water biogeochemistry and low latitude surface ocean atmospheric climate