growth and high resolution paleoenvironmental signals of rhodoliths coralline red algae a new biogenic archive we investigated rhodoliths coralline red algae from a subtropical locality in the gulf of california lithothamnium crassiusculum and a subarctic locality in newfoundland lithothamnium glaciale for their potential as paleoenvironmental archives using microanalytical geochemical techniques to measure variations in 18o mg and ca rhodoliths are potentially well suited as recorders of shallow water paleoenvironmental signals because they 1 have worldwide distribution from the tropics to polar regions 2 are long lived from decades to centuries and 3 display well developed growth bands our results indicate that rhodolith growth bands preserve ultrahigh resolution records of paleoceanographic paleoclimatic change and likely constitute an important new archive for reconstructing the paleoenvironmental history of littoral neritic areas in which these algae are found the 18o content of individually sampled rhodolith growth bands ranges from 2 4 to 4 6 in l crassiusculum and from 3 2 to 0 3 in l glaciale in both cases the range of 18o values suggests a slightly lower amplitude of variation in sea surface temperature than that actually measured in the ocean at the two study sites both l crassiusculum and l glaciale show a negative offset from isotopic equilibrium electron microprobe analysis of magnesium and calcium in growth bands reveals cyclic variations with values ranging between 7 7 18 5 mol mgco3 in l glaciale and 13 2 22 5 mol mgco3 in l crassiusculum in addition electron microprobe element maps highlight individual growth bands provide a powerful approach to study rhodolith formation and indicate that the specimens we analyzed have vertical growth rates of 250 450 m yr

evaluation of the biogeochemical controls on b ca of globigerinoides ruber white from the oceanic flux program bermuda a b s t r a c t boron to calcium b ca ratios in planktonic foraminifera is suggested to be a proxy for the surface oceanic carbonate system the reliability of the proxy has been questioned due to conflicting reports from culture and sediment calibrations on the influence of temperature on b ca to assess this issue b ca and mg ca ratios and 18 ow ere measured in tests of the symbiont bearing surface dwelling planktonic foraminifer globigerinoides ruber white collected by the oceanic flux program ofp time series sediment traps located approximately 75 km se of bermuda b ca ratios in the 300 400 m size fraction of g ruber were approximately 10 20 higher than those in the 200 300 m size fraction in contrast mg ca ratios and 18 ov alues do not exhibit any relationship to test size which indicates that the size effect observed for b ca is not due to differences in depth habitat but to vital effects seasonal variation in the b ca ratio was similar in both size fractions and ranged by 20 30 mol mol this range is larger than that predicted by seasonal variations in seawater b oh hco the proposed boron species incorporated into planktonic foraminiferal calcite and indicates that b ca in g ruber is influenced by an additional variable s the seasonal cycle of b ca in g ruber white was more strongly correlated with light intensity than with temperature both observations suggest that the presence of symbionts in g ruber and seasonal variability in their photosynthetic activity act to modify the internal ph during calcification by up to 0 2u nits relative to ambient seawater 2014 elsevier b v all rights reserved

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

reconstructing greenland ice sheet runoff using coralline algae the greenland ice sheet gris contains the largest store of fresh water in the northern hemisphere equivalent to 7 4 m of eustatic sea level rise but its impacts on current past and future sea level ocean circulation and european climate are poorly understood previous estimates of gris melt from 26 yr of satellite observations and temperature driven melt models over 48 yr show increasing melt trends there are however no runoff data of comparable duration with which to validate the relationship between the spatial extent of melting and runoff or temperature based runoff models further longer runoff records are needed to extend the melt pattern of greenland to centennial timescales enabling recent observations and trends to be put into a better historical context we have developed a new gris runoff proxy by extracting information on relative salinity changes from annual growth bands of red coralline algae we observed significant negative relationships between historic runoff relative salinity and marine summer temperature in sondre stromfjord greenland we produce the first reconstruction of runoff from a section of the gris that discharges into sondre stromfjord over several decades 1939 2002 and record a trend of increasing reconstructed runoff since the mid 1980s in situ summer marine temperatures followed an equivalent trend we suggest that since a d 1939 atmospheric temperatures have been important in forcing runoff these results show that our technique has significant potential to enhance understanding of runoff from large ice sheets as it will enable melt reconstruction over centennial to millennial timescales

evidence of early flandrian tidal surges in lower strathearn scotland detailed stratigraphic palaeobotanical diatom and pollen and radiometric evidence from a sequence of buried estuarine deposits buried peat and overlying estuarine carse deposits at wester rhynd in lower strathearn suggests the occurrence of two brief marine incursions between the abandonment by the sea of a buried estuarine flat probably the low buried beach at about 8765 75 bp and c 8500 bp the first incursion shortly after 8565 85 bp caused bottom living marine diatoms to be thrown without clastic material onto the rapidly accumulating terrestrial peat the second bracketed by dates of 8485 80 and 8510 85 bp deposited an extremely thin 1 mm layer of fine sand that interrupts an otherwise unbroken buried peat succession covering the period 8765 75 to 7710 70 bp the marine diatom lithostratigraphic and 14c evidence together are consistent with a storm storm surge or tsunami origin for these events which are recognised principally from the diatom evidence having left no mark in the pollen record

a record of mining and industrial activities in new caledonia based on trace elements in rhodolith forming coralline red algae abstract we investigate the ability of coralline red algae to record historical nickel mining activity that occurred between the early 1960s and 1981 in the coulee river watershed southwest new caledonia laser ablation inductively coupled plasma mass spectrometry la icpms was used to determine high resolution sub annual variations of trace metal ratios mn ca fe ca ni ca and co ca in three 45 years old free living forms of the rhodolith coralline red alga sporolithon durum from ricaudy reef in the inner lagoon of new caledonia 15 km from the coulee river mouth we find increased mn ca and fe ca ratio values track the intensity of mining in the coulee river catchment whereas ni ca ratio values appear more sensitive to the ore type saprolite versus laterite that were targeted during two separate stages of mining activity mn ca fe ca and ni ca decrease following the cessation of mining in 1981 but did not reach current values until 10 years after that date surprisingly co ca variations do not correlate with mining activity but rather increase steadily through the record period we argue this relates to nickel refining and smelting activity over the past half century our results further suggest that the local inter annual rainfall variability may influence the metal concentrations recorded in the rhodoliths during the period of intense mining activity but the link between metal uptake and rainfall is not entirely clear for the entire growth period of the rhodoliths

evidence from sites in western ireland of late holocene changes in coastal environments the presence of sand layers interleaved with biogenic material in coastal sedimentary sequences from back barrier areas has often been used as evidence of storm surge or tsunami action during the holocene this paper discusses such stratigraphies from two adjacent sites in western ireland in order to assess the validity of this inference detailed examination of the sand layers indicates that while some of the sand beds at one of the sites were deposited by overwash other processes including aeolian deposition and fluvial reworking of aeolian sediments were also important in sand redistribution in the back barrier areas in these cases local controls including site drainage characteristics barrier morphology and available sediment supply appear to have been important in site evolution a regional signal of storm frequency was not detected

coralline algae are global palaeothermometers with bi weekly resolution abstract high resolution palaeoclimate data are required for the holocene to resolve differences recorded by current proxies the pole to pole distribution of rhodoliths coralline algae with their annual and sub annual calcite bands make these attractive candidates for such a role these bands contain climate information in the form of elemental traces in situ temperature ist was recorded at two rhodolith beds for 1 5 years the concentrations of mgco 3 and srco 3 mol deposited in lithothamion glaciale and phymatolithon calcareum over this 18 month period were determined using electron and ion microprobes highly significant linear relationships exist between mg sr and ist as well as sea surface temperature calibration between mg concentration and ist was used to obtain a 2 year temperature profile from a subfossil rhodolith thallus indicating half the seasonal peak to peak temperature amplitude earlier during the holocene than the present day both slow growing species 1 allowed sampling resolutions of 23 year 1 which is equivalent to 1 reading every 2 weeks sub monthly mg and sr records in rhodoliths make them unique globally distributed palaeothermometers which may help refine regional climate histories during the holocene

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

late holocene sea levels in ireland the course of irish sea levels during the late holocene is not well known yet it is an understanding of this period that will prove crucial in the definition and management of future sea level changes the coastline of ireland embraces wide environmental and glacio isostatic contrasts which serve and to some extent control sea level events at both local and regional scales making definitive resolution of relative sea level changes difficult in the southwest the picture is of inexorable relative sea level rise studies in co kerry show a gradual submergence of terrestrial facies by estuarine and in places marine materials pollen and diatom studies together with 14c dates suggest a decreasing rate of relative sea level rise in the last 2500 years often associated with geomorphological changes sites on the south coast of ireland confirm the evidence from the southwest in cork harbour recent relative sea level rise since 2100 bp was responsible for marginal land submergence while elsewhere rising water levels appear to have caused rapid barrier migrations and coast erosion palaeoenvironmental evidence from this region suggests a distinctive pattern of sea level change associated with sedimentary and or crustal dynamics which is not encountered elsewhere in northwest europe the overall rate of relative sea level change on the south and southwest coasts falls between 0 6 and 1 1 mm year over the last 5000 years in the north there is a clear east to west variation in relative sea level trends following an isostatically controlled peak 3 to 1 m od between 6500 bp east and 3500 bp west falling sea levels from 3500 to 1500 bp have been followed by a general slow rise although there are still local anomalies to this pattern most noticeably at malin head where sea level is currently falling at 2 4mm year relative sea level signatures in ireland differ markedly between the north and south coasts furthermore geomorphological and ecological contexts of this rise vary from east to west providing a complex all ireland framework for future investigations

the evolution of pco2 ice volume and climate during the middle miocene abstract the middle miocene climatic optimum 17 15 ma mco is a period of global warmth and relatively high co2 and is thought to be associated with a significant retreat of the antarctic ice sheet ais we present here a new planktic foraminiferal 11b record from 16 6 to 11 8 ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to co2 these new data demonstrate that the evolution of global climate during the middle miocene as reflected by changes in the cyrosphere was well correlated to variations in the concentration of atmospheric co2 what is more within our sampling resolution 1 sample per 300 kyr there is no evidence of hysteresis in the response of ice volume to co2 forcing during the middle miocene contrary to what is understood about the antarctic ice sheet from ice sheet modelling studies in agreement with previous data we show that absolute levels of co2 during the mco were relatively modest 350 400 ppm and levels either side of the mco are similar or lower than the pre industrial 200 260 ppm these new data imply the presence of either a very dynamic ais at relatively low co2 during the middle miocene or the advance and retreat of significant northern hemisphere ice recent drilling on the antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the ais did occur during the middle miocene but the complete loss of the ais was unlikely consequently it seems that ice volume and climate variations during the middle miocene probably involved a more dynamic ais than the modern but also some component of land based ice in the northern hemisphere

mid and late holocene environmental change in western ireland new evidence from coastal peats and fossil timbers with particular reference to relative sea level change the results of radiocarbon dating and dendrochronological investigations of timbers mainly pine and oak preserved in coastal peats on the atlantic coast of mid western ireland are reported these

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

geologic evidence for earthquakes during the past 2000 years along the copalis river southern coastal washington evidence for several prehistoric earthquakes is present in deposits less than 2000 years old that crop out at the copalis river estuary 47 07 2 n 124 09 7 w the deposits show that land subsided decimeters into the intertidal zone on as many as three occasions and that sand vented while the land underwent little or no subsidence on another occasion the evidence for earthquake induced subsidence consists of buried marsh and forest soils that evince sudden estuarine submergence attended on at least one occasion by a landward directed surge of sandy water this combination of submergence and surge implies subsidence and tsunami exposed evidence for subsidence and tsunami along the copalis river is strong for a time within a few decades of 300 years ago moderate for a time 1400 1900 years ago and weak subsidence or lacking tsunami for an intermediate time also about 1400 1900 years ago the history of sudden submergence and tsunami in the past 2000 years at the copalis river estuary resembles that shown by buried soils farther south in coastal washington at grays harbor and willapa bay the history can be explained most simply by great mw of 8 or 9 thrust earthquakes at the boundary between the juan de fuca and north america plates with one or two earthquakes occurring 1400 1900 years ago and another close to 300 years ago the evidence for earthquake induced venting along the copalis river consists of sand intrusions and vented sand volcanoes the sand rose through muddy estuarine deposits at least 3 m thick entraining these deposits in fragments as much as 0 3 m long intrusion occurred at one or more times in the past 2000 years and at least some of the venting occurred 900 1300 years ago the sand bodies do not imply artesian flow of flood pressured groundwater because the sand vented forcefully and infrequently through a lowland that probably lacked natural levees the earthquake implied by the venting of sand 900 1300 years ago could have come from a source below above or at the boundary between the juan de fuca and north america plates if from the subducted juan de fuca plate the implied earthquake was farther west or larger than the largest earthquakes within that plate during the past 100 years evidence permitting a source within the north america plate includes a fault scarp an uplifted tideflat and landslides near puget sound dating from the interval 700 1700 years ago a plate boundary source would explain buried soils whose estuarine submergence and burial imply coseismic subsidence for parts of coastal washington in the interval 600 1300 years ago however stratigraphy shows that little or no coseismic subsidence occurred along the copalis river during the venting 900 1300 years ago if a plate boundary earthquake struck coastal washington 900 1300 years ago the earthquake produced a different distribution of land level change than did the plate boundary earthquakes inferred for 1400 1900 and 300 years ago

pedogenic and geomorphic evolution of a buried dune palaeocatena at magilligan foreland northern ireland abstract field description and laboratory analyses of a complex stratigraphy recently exposed near magilligan point have elucidated the late holocene evolution of magilligan foreland n ireland a marine beach ridge palaeocatena passes northwards into a penecontemporaneous aeolian dune palaeocatena both include soils and peat filled depressions and are overlain by an aeolian dune sand a second dune sand is confined to the south of magilligan foreland the thickness of the decalcified zone of the palaeocatena varies from 0 4 m near the crest of the palaeodune to 2 m below its slopes the palaeodune core exhibits large scale cross stratification enclosing unusual small scale reverse flow cross stratified sets d 90 90 depletion values indicate similar weathering intensities in the palaeocatena and in the overlying sand but deeper weathering in the former a mineral stability sequence has been constructed and unweathered sand identified which indicates the original composition of the magilligan deposits inter profile differences in weathering rates are attributed to variations in local environments

characteristics and development of soils at magilligan foreland northern ireland with emphasis on dune and beach sand soils summary evidence obtained from 34 soil pits has established the characteristics and development of soils at magilligan foreland northern ireland soil development sequences for the calcareous dune and beach sand areas are outlined although age estimates for each stage cannot be established with certainty dune soils begin as raw sands and under stable conditions progress to sand pararendzinas and then to brown calcareous sands the beach soil sequence is raw alluvial soils rendzina like alluvial soils brown calcareous alluvial soils humus podzols brown calcareous alluvial soils the podzols have reverted to brown calcareous alluvial soils as a result of agricultural activities during the past 1 200 years these sequences are more detailed than those previously identified for british coastal sands

multi proxy evidence for holocene lake level and salinity changes at an loch mor a coastal lake on the aran islands western ireland abstract curves for holocene lake levels and salinity changes are presented for an loch mor a small oligohaline lake on the aran islands off the west coast of ireland based on palaeoecological investigations of a 12 m long lake sediment core new insights are also provided into holocene sea level change in the galway bay region particular emphasis has been placed on the ostracod fauna both past and present salinity and lake level changes were reconstructed from the fossil ostracod assemblages based on the known tolerances of individual species and on the assemblages as a whole additional evidence was provided by other proxies including strontium isotope ratios derived from ostracod shells and other carbonates plant macrofossil and pollen analyses and sedimentological changes the early holocene pre boreal i e 11 5 10 ka was characterised by low lake levels and slightly elevated salinity values probably the result of high evapotranspiration and low precipitation rather than elevated sea levels early holocene plant and animal migration to the island does not seem to have been impeded but relative sea levels were not necessarily so low below 40 m a s l that landbridges were present to the mainland between ca 10 and 8 5 ka relatively high lake levels prevailed at 8 3 and 7 5 ka minor fluctuations lowering of the lake level occurred that are assumed to relate to early holocene abrupt events beginning at 7 05 ka lake levels declined sharply a general trend towards rising lake levels started at ca 6 4 ka and accelerated at ca 5 6 ka as runoff increased as a result of neolithic clearances at ca 4 8 ka lake levels began to rise once again probably in response to changes in rainfall and or evapotranspiration and runoff lower lake levels during the first half of the 1st millennium ad were probably a response to decreased runoff as a result of a drier climate coupled with regeneration of woody vegetation the sharpest rise in both lake levels and salinity began during the ninth century ad which is attributed to a rapid rise in relative sea level

mineralogy and geochemistry of a marine sequence gulf of salerno italy abstract within the context of a multidisciplinary study aiming at the paleoenvironmental and paleoclimatic reconstruction in the last 28 000 yr of the southern tyrrhenian sea west mediterranean area geochemical and mineralogical investigations were performed on sea sediments of a 6 17 m long core collected in the gulf of salerno southern italy 14 42 24 e 40 28 92 n at 292 m bsl the mineralogy of the sedimentary sequence was controlled by climatic changes fluvial discharge processes and hydrodynamic conditions that occurred in the southern tyrrhenian sea during the last glacial post glacial transition notable was the occurrence of detrital mineral phases quartz calcite dolomite clay minerals volcanic glass pumice sanidine clinopyroxene biotite and leucite in response to terrigenous input through intensive periods of precipitation runoff and sele river discharge changes in the clay mineral assemblage during the holocene from 9500 to 6000 yr bp indicate increasing precipitation in the source area pyrite and barite crystallization related to biogeochemical cycles were found to affect chemical conditions of the sedimentary environment irregular crystals of analcime were produced by alteration of the ad 79 vesuvius eruption pumice the distribution of major and trace elements between stratigraphic layers was influenced by mineralogy concentrations of redox sensitive elements fe mn zn ni cu largely depended on organic matter and sulphur whereas for most of the others a key role was played by clay minerals enhanced ba content was found at the 320 and 160 cm levels increased pb content was observed at the surface bcr sequential extraction showed that cu and pb in the sediments were prevalently associated with oxidizable components primarily sulphides zn ni and mn were strongly bound to residual mineral phases likely of volcanic origin fe was found mainly associated with easily reducible oxide phases and as pyrite

the storegga slides evidence from eastern scotland for a possible tsunami abstract the second storegga slide on the continental slope off western norway has been dated at between 8000 and 5000 yrs b p a prominent sand layer in flandrian holocene deposits along the coast of eastern scotland and dated at approximately 7000 yrs b p may have been deposited by a tsunami generated by the slide the altitude and stratigraphy of the layer allow estimates to be made of the magnitude of the earthquake which initiated the slide

assessment of temporal changes in coastal sand dune environments using the log hyperbolic grain size method three cores 9 m long recovered from late holocene coastal sand dunes in northumberland north eastern england were examined stratigraphically and dated by the infrared stimulated luminescence irsl method to the time period between the medieval warm period mwp 900 1200 ad and little ice age lia 1550 1800 ad grain size variability and caco 3 content were determined at 10 mm intervals throughout parts of the cores the sahara computer program was used to plot the log hyperbolic distribution lhd of grain size spectra from different stratigraphic levels and estimate the lhd s statistical components core samples plot variously in the depositional and erosional domains of the hyperbolic chi vs xi shape triangle which describes components of sediment sorting depositional and erosional phases discriminated within the lhd s shape triangle cannot readily be resolved from core stratigraphies or correlated between cores irsl dates from single cores show a clustering about the period 1430 1540 between the dated horizons dunes accreted at 0 02 0 05 m year 1 enabling the timing of excursions in and to be estimated these excursions which can be resolved to the subannual level between the dated horizons may be related to deposition by episodic storms or storm surges in the north sea region which is supported by historical documentary evidence this innovative use of the lhd method and its derived statistics can be used successfully to describe temporal trends in coastal depositional environments and identify likely storm events in dune sediment records

high resolution subsurface gpr imaging and sedimentology of coastal ponds maine u s a implications for holocene back barrier evolution ground penetrating radar gpr transects and sediment cores have been used to examine the basement morphology stratig raphy and environmental history of maritime ponds along the pen insular coast of maine silver lake lily pond and north pond are shallow 3 m water bodies bordered by steep bedrock ridges in the north east and west and sandy barriers to the south the bedrock basins of the ponds are formed in metasedimentary rocks surrounded by resistant pegmatitic intrusions a dense network of gpr traverses obtained over the ice covered silver lake reveals a series of prominent wavy parallel and basin fill reflector geometries terminating against the bedrock or grading into the barrier sediments and interpreted as organic lake bottom facies the transparent units represent sand rich horizons mostly eolian in origin convex up structures found both on the surface and within the basin fill sequence are interpreted as pre served parts of coastal dunes the present study indicates that fresh water conditions prevailed since at least 4 6 ka with an initial sedi mentation rate of 1 7 mm yr the position of this unit below the con temporary sea level suggests presence of a welded barrier by that time radar profiles taken along the shores of lily pond a small water body behind the sand dune barrier indicate a significantly larger areal extent of the pond in the past a succession of organic deposits over lying a pleistocene glaciomarine unit indicates progressive inundation of the paleo lagoon by rising sea level saltwater peat seaward of lily pond was buried by washover sands about 1 2 ka and a narrow pond existed here prior to dredging and artificial infilling of its eastern part in the 1950s 60s the organic and eolian units are absent in the north pond where sedimentary fill consists of glaciomarine clay overlain by marine sands a proposed three stage model of pond evolution along an embayed coastline consists of 1 organic accumulation in an up land depression during lower sea level 2 predominantly washover or tidal deposition in a lagoon stage 2a or blocked coastal pond stage 2b during initial transgression and 3 mainly eolian and organic de position behind a prograded or aggraded barrier future accelerated rise in relative sea level and inadequate sediment supply will cause many back barrier ponds to reenter stage 2 of the proposed model

coralline algal mg o bond strength as a marine pco2 proxy past ocean acidification recorded in the geological record facilitates the understanding of rates and influences of contemporary pco 2 enrichment most ph reconstructions are made using boron however there is some uncertainty associated with vital effects and isotopic fractionation here we present a new structural proxy for carbonate chemistry mg o bond strength in coralline algae coralline algae were incubated in control 380 matm pco 2 moderate 750 matm pco 2 and high 1000 matm pco 2 acidification conditions for 24 months raman spectroscopy was used to determine skeletal mg o bond strength there was a positive linear relationship between pco 2 concentration and bond strength mediated by positional disorder in the calcite lattice when accounting for seasonal temperature the structural preservation of the carbonate chemistry system in coralline algal high mg calcite represents an alternative approach to reconstructing marine carbonate chemistry significantly it also provides an important mechanism for reconstructing historic atmospheric co 2 concentrations