Mineralogy of Arctic bryozoan skeletons in a global context

Facies (2009) 55489ndash500

DOI 101007s10347-009-0179-3

ORIGINAL ARTICLE

Mineralogy of Arctic bryozoan skeletons in a global context

P Kuklinski middot P D Taylor

Received 12 November 2008 Accepted 22 January 2009 Published online 24 February 2009copy Springer-Verlag 2009

Abstract Bryozoans are major carbonate producers insome ancient and Recent benthic environments includingparts of the Arctic Ocean Seventy-six species of bryozoansfrom within the Arctic Circle have been studied using XRDto determine their carbonate mineralogies and the Mgcontent of the calcite The majority of species were foundto be calcitic only four having bimineralic skeletons thatcombined calcite and aragonite and none being entirelyaragonitic In almost all species the calcite was of the low-(lt4 mol MgCO3) or intermediate-Mg (4ndash1199 molMgCO3) varieties Previous regional studies of bryozoanbiomineralogy have found higher proportions of biminera-lic andor aragonitic species in New Zealand and the Medi-terranean with a greater number of calcitic speciesemploying intermediate- and high-Mg calcite The Antarc-tic bryozoan fauna however has a similar mineralogicalcomposition to the Arctic The lesser solubility of low-Mgcalcite compared to both Mg calcite and aragonite in coldpolar waters is most likely responsible for this latitudinalpattern However it is unknown to what extent environ-mental factors drive the pattern directly through eliciting anecophenotypic response from the bryozoans concerned orthe pattern reXects genetic adaptations by particular bryo-zoan clades

Keywords Carbonate mineralogy middot Arctic middot Bryozoans

Introduction

Bryozoa are colonial suspension-feeding aquatic inverte-brates (Ryland 1970) Most of the gt6000 living species ofbryozoans secrete calcareous skeletons Locally they arepresent in great abundance within benthic communities andcontribute large amounts of biogenic sediment to the seaXoor (eg Wass et al 1970 Bone and James 1993 papersin James and Clarke 1997) Bryozoan-rich deposits arerecorded from the Ordovician to the present day across allclimatic zones from the tropics (eg Pray 1958 Ettensohnet al 1986) to the poles (eg Taviani et al 1993 Bader andSchaumlfer 2005 Rogala et al 2007) Throughout the post-Pal-aeozoic however the calcareous skeletons of bryozoanshave been most abundant as sediment producers in coolerwaters outside the tropics (Taylor and Allison 1998) Coolwater bryozoan-rich carbonates may also include molluscsto constitute a grain association termed lsquobryomolrsquo (Nelson1988)

Existing data on the skeletal mineralogy of bryozoans indi-cates that about two-thirds of analysed species have calciticskeletons (Smith et al 2006) Of the remainder approxi-mately half are aragonitic and half are bimineralic the lattercombining calcite and aragonite in diVerent layers of the skel-eton All unequivocal aragonitic and bimineralic speciesbelong to the Cheilostomata the dominant order of bryozoansin modern seas Cyclostomes the other modern bryozoanswith biomineralized skeletons are all apparently calcitic Bio-mineralized skeletons evolved independently in cyclostomesand cheilostomes from soft-bodied ancestors in the Ordovi-cian and Jurassic respectively The Mg content within bryo-zoan calcite varies widely from low (lt4 mol MgCO3) tohigh (gt12 mol MgCO3) (Bone and James 1993 Smith et al2006) Some of this variability occurs within species whereassome is interspeciWc (Smith et al 1998)

P Kuklinski (amp)Institute of Oceanology Polish Academy of Sciences ul Powstancow Warszawy 55 81 712 Sopot Polande-mail kukiiopangdapl

P Kuklinski middot P D TaylorNatural History Museum Cromwell Road London SW7 5BD UK

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490 Facies (2009) 55489ndash500

The large mineralogical and geochemical spectrumexhibited by bryozoans (Smith et al 2006) makes them agood group for investigating the diVerential eVects of oce-anic acidiWcation and increase in seawater temperaturecaused by global warming The rise in atmospheric CO2

over the past century has led to greater CO2 uptake by theoceans increasing hydrogen ions (H+) and causing oceanicacidiWcation Along with a concomitant decrease in carbon-ate ions (CO3

2iexcl) this has changed the saturation state of theoceans with respect to calcium carbonate (CaCO3) miner-als Decreased carbonate saturation state can be predicted tolead to reduced calciWcation rates a shift towards organ-isms that secrete calcite (which is less soluble than arago-nite) and competitive advantages for those organismswithout calciWed skeletons (Kleypas et al 1999 Riebesellet al 2000 Fabry 2008)

Of all organisms inhabiting shallow seas the impact ofacidiWcation is likely to be most severe for species secretingcalcareous skeletons (Raven et al 2005) among which bry-ozoans are a major example However compared to suchgroups as molluscs there are few studies of bryozoan min-eralogy (Poluzzi and Sartori 1975 Borisenko and Gontar1991 Smith et al 1998) Smith et al (2006) surveyed pub-lished data Wnding that carbonate mineralogy was knownfor only about 6 of living species There are only twoareas (Mediterranean and New Zealand) where large num-bers of bryozoans have been studied mineralogically Toassess the vulnerabilities of diVerent species to climatechange and to understand bryozoan diagenesis we desper-ately need more information on the skeletal mineralogy andchemistry of the numerous species that inhabit shallowwaters especially in areas most inXuenced by climatechange

In this study we investigate the skeletal mineralogy ofbryozoans from the Arctic the most rapidly warmingregion on Earth (Schiermeier 2007 IPCC 2007) Here bry-ozoans are one of the most species-rich benthic groups thatsecrete carbonate skeletons (Henrich et al 1992 Andruleitet al 1996) However knowledge of the skeletal mineral-ogy and geochemistry of Arctic bryozoans is woefullyinadequate Indeed the 1183 individual mineralogicalanalyses tabulated by Smith et al (2006) for bryozoansincluded data from only 24 Arctic species This represents7 of the biomineralizing bryozoan species in the Arctic(Kluge 1975) In the only study to date of polar bryozoans(Borisenko and Gontar 1991) species from the Arctic andAntarctic were found to be almost entirely calcitic As theirstudy focused mostly on the Antarctic and covered only afraction of the over 300 species of Arctic bryozoans it isdiYcult to draw Wrm conclusions about the mineralogy ofArctic bryozoan species

Several studies of organisms secreting calcareousskeletons have shown that lower seawater temperatures

correlate with secretion of calcite skeletons with low-magnesium content over more soluble high-magnesiumcalcite or aragonite skeletons eg in gastropods (Taylorand Reid 1990) or serpulids (Lowenstam 1954a)Because both aragonite and high-magnesium calcite areappreciably more soluble in cold water (Mucci 1983Davis et al 2000) we here hypothesise that the Arcticbryozoan fauna will contain a higher proportion of spe-cies with low-Mg calcite (LMC) skeletons than faunasfrom warmer waters This hypothesis is tested by com-paring our new data on Arctic bryozoans with publisheddata from warmer temperate zones of the MediterraneanSea and New Zealand We also hypothesise that trendswill be evident both within- and between-speciestowards lower amounts of aragonite and lower levels ofMg in calcite towards higher latitudes (lower sea watertemperatures)

Study area

The Arctic Ocean is an almost land-locked sea surroundingthe North Pole There are several diVerent deWnitions of theArctic including the widely used yet impractical climate-based boundary at the 10degC July isotherm For the purposeof this study we use the Arctic Circle (66deg33N) as theboundary of the Arctic which is the approximate limit ofthe midnight sun and the polar night

The Arctic Ocean has the widest continental shelf ofall the oceans It represents raquo50 of the area and extendsin some cases as far as 1210 km seaward The continen-tal shelf encloses a deep basin with an average depth ofabout 3600 m The marine environment of the ArcticOcean is characterized by a relatively narrow range inannual temperatures often near the freezing point of sea-water which is slightly below zero degrees (Andersonet al 1994) Vast areas of the Arctic Ocean are covered byice However there is considerable seasonal and regionalvariation in ice cover ranging from 70 pound 106 km2 inSeptember to 154 pound 106 km2 in March (Parkinson et al1999) Because of continuous darkness in the winter andcontinuous daylight in the summer there is high season-ality in primary productivity with the greatest abundanceof phytoplankton in the summer (Sakshaug 2003) All ofthese environmental factors have implications for ecolog-ical conditions in the Arctic For example species rich-ness on the Arctic shelves is generally lower than intemperate or tropical shelf regions (Gray 2002) Yet themarine life of the Arctic Ocean is highly adapted in itshistory ecology and physiology to the extreme andhighly seasonal conditions of the environment (eg Thielet al 1996 Clarke 1998 Kuklinski and Porter 2004Kuklinski and Taylor 2006)

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Facies (2009) 55489ndash500 491

Materials and methods

Material

Bryozoans used for mineralogical analysis in this studywere alive when collected and obtained from various loca-tions ranging from northern Norway to Greenland Spits-bergen and the Siberian coast (Kara Laptev Sea) (seeAppendix) Some of these areas (northern Norway WestSpitsbergen) can be considered as sub-Arctic climaticallydue to the inXuence of a warm current (gt3degC) originatingfrom the Gulf Stream (Loeng 1991 Rudels et al 1994)

Many of the bryozoan species analysed here are Arcticendemics They were identiWed using the monograph ofKluge (1975) the taxonomy being updated from morerecent publications when necessary All of the bryozoanscome from shelf depths ranging from 1 to 210 m (seeAppendix) A total of 149 analyses were made of 76 bryo-zoan species (Appendix) representing over 20 of the esti-mated diversity of bryozoans recorded from the ArcticSeven species are cyclostomes the remaining 69 cheilosto-mes The species analysed come from 55 diVerent bryozoangenera

Sample preparation and mineralogical analysis

Bryozoans colonize various substrates both abiotic (egrocks) and biotic (eg shells algae) As shell substrateshave their own mineralogies particular care was takenwhen sampling bryozoans from these substrates Encrustingbryozoans were dissected oV their substrates and only colo-nies with clean basal surfaces were used for analysis Colo-nies were also carefully examined for the presence ofepibionts (eg foraminifera) which were removed in orderto avoid mineralogical contamination Whenever possibleseveral unbleached colonies were used for each species inorder to identify anomalous values resulting from contami-nants

Mineralogical analyses were undertaken using a high-precision Nonius XRD-PSD with a position-sensitivedetector (PSD) This instrument allows repeatable analysesto be made rapidly Small samples of bryozoan skeletons(lt1 g) were powdered and analysed to determine the pre-dominant biomineral estimate the proportions of calciteand aragonite in bimineralic species and the Mg content inthe calcite of calcitic and bimineralic skeletons Theamount of each polymorph in bimineralic species wasdetermined by Wtting peak intensities compared to standardpatterns generated from 100 aragonite and 100 calciteThe error associated with this method is estimated to be 2based on test samples of known aragonite proportion Inorder to calculate Mol MgCO3 we measured the positionof the d104 peak assuming a linear interpolation between

CaCO3 and MgCO3 This composition information is accu-rate to within 2 provided the diVraction angles are wellcalibrated for the instrument pure Si was used as the instru-ment calibration standard in this case Computations wereundertaken using Nonius GUFI software Species withentirely calcitic skeletons were divided into low-Mg calcite(lt4 mol MgCO3) (LMC) intermediate-Mg calcite (4ndash1199 mol MgCO3) (IMC) and high-Mg calcite (cedil12mol MgCO3) (HMC) (see Bone and James 1993)

Whenever possible we examined mineralogical vari-ability within species between locations Mineralogical var-iation within colonies from distal branch tips to colonybases was also investigated for four species with erect colo-nies

Comparison with other regions

In order to compare our data with results from other regionswe used published literature Few comprehensive studies ofbryozoan mineralogy have been published and there arenone for the tropics Our comparisons are therefore limitedto two temperate and one polar region the MediterraneanSea (Poluzzi and Sartori 1975) New Zealand (Smith et al1998) and the Antarctic (Borisenko and Gontar 1991) Allof these studies used a similar methodology (XRD-PSD) tothat employed here Proportions of species with calciticaragonitic and bimineralic skeletons from these regionswere calculated and compared with our new data from theArctic Mg contents of bryozoan calcite were also com-pared as ratios of LMC IMC and HMC In some casespublished analyses of Mg contents were presented as wtMgCO3 These were transformed to mol MgCO3 (seeSmith and Nelson 1993 Fig 5) Whenever more than oneindividual of a given species was analysed the mean valuewas used for our summary calculations Analysis of vari-ance (ANOVA) followed by log(x + 1) data transformation(to improve normality and homogeneity) was used toexplore the statistical signiWcance of the observed patterns

Results

Arctic bryozoans

The great majority of Arctic bryozoan species (96) werefound to have calcitic skeletons generally with low magne-sium content (see Appendix) Among 76 species analysedonly three were found to be bimineralic (4) and none ara-gonitic (Fig 1) The average mol MgCO3 in the calcite ofall species analysed was found to be 40 with 43 ofspecies secreting LMC 57 of species IMC and noneHMC (Fig 1) No evidence was found for two phases ofcalcite having diVerent contents of Mg in any of the species

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492 Facies (2009) 55489ndash500

analysed All except two of the cyclostomes had monomi-neralic LMC skeletons and the average mol MgCO3 wasfound to be 34 which is slightly lower than that of thecheilostomes

Among the four erect species where skeletal mineralogywas compared between the bases and tips of the branchesthree showed a decrease of mol MgCO3 towards the tipsie from older to younger parts of colonies (Fig 2) This isconsistent with the secretion of calcite containing higherlevels of Mg as zooids in the colony age

Two Arctic species (Harmeria scutulata and Cystisellasaccata) exhibited signiWcant diVerences in mol MgCO3

among sampling localities in the Arctic (Fig 3) There wasno clear relationship between water temperature and molMgCO3 in H scutulata For example water temperaturesare lower in Hornsund fjord than in Isfjorden but individu-als from Hornsund fjord had higher levels of mol MgCO3

in their skeletons (Fig 3) On the other hand C saccatafrom the colder Laptev Sea had lower mol MgCO3 intheir skeletons than individuals from warmer waters ofWest Spitsbergen (Fig 3)

Other regions

Mediterranean sea

Of the 94 Mediterranean species analysed by Poluzzi andSartori (1975) 55 (59) were calcitic eight (9) arago-nitic and 31 (32) bimineralic (Fig 1) The average molMgCO3 in the calcite of all Mediterranean species analysedwas found by these authors to be 75 with 7 of speciesbeing LMC 92 IMC and 1 HMC (Fig 1)

New Zealand

The 49 bryozoan species from New Zealand waters investi-gated by Smith et al (1998) comprised 32 (65) that werecalcitic no aragonitic forms and 17 (35) bimineralic(Fig 1) They found the average mol MgCO3 in thecalcite for all species analysed to be 61 with 21 ofspecies being LMC 79 IMC and none HMC (Fig 1)

Antarctica

Of the 21 Antarctic species analysed by Borisenko andGontar (1991) 20 (95) were calcitic one (5) aragoniticand none bimineralic (Fig 1) They found the averagemol MgCO3 in the calcite for all species analysed to be

Fig 1 Comparative mineralogy and Mg geochemistry of bryozoanfaunas from the Arctic Mediterranean New Zealand and Antarctic

Fig 2 Mean values (sectstandard error) of mol MgCO3 from colonybases to tips in four erect bryozoan species from the Arctic Theincrease in mol MgCO3 proximally towards the colony base in threeof these species suggests secretion of calcite richer in Mg as the zooidsgrow older (sample sizes are in brackets)

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Facies (2009) 55489ndash500 493

19 with all of the species falling into the LMC category(Fig 1)

Latitudinal patterns

Mean mol MgCO3 is statistically signiWcantly diVerent(F(3224) = 4785 P lt 0001) between the Arctic Mediter-ranean New Zealand and Antarctic bryozoan faunas(Fig 4) Both Arctic and Antarctic bryozoan faunas aredominantly calcitic whereas Mediterranean and NewZealand bryozoan faunas contain higher proportions ofbimineralic species (32 and 35 respectively) as well asgreater amounts of MgCO3 in the calcite when comparedto the polar faunas In contrast to all other regions whichlack of species with entirely aragonitic skeletons 9 ofthe Mediterranean bryozoan species have completely ara-gonitic skeletons

Discussion

This study reveals Arctic bryozoan species to have predom-inantly calcitic skeletons a high proportion with LMC cor-roborating the results found in a less comprehensive studyof Arctic bryozoans (Borisenko and Gontar 1991) Arcticbryozoan mineralogy is rather homogeneous across all ana-lysed species and resembles that of Antarctic bryozoans(Fig 1) despite the very diVerent taxonomic compositionof Arctic and Antarctic bryozoan faunas In contrastwarmer-water bryozoans from lower latitudes exhibitgreater mineralogical diversity and a larger range of Mg inthe calcite (Fig 1) For example bryozoans from temperateseas around New Zealand (Smith et al 1998) have a muchhigher proportion of species with bimineralic skeletons andthe range of Mg in their calcite is greater than that observedin the Arctic (Figs 1 4 Appendix) An even more markedcontrast is evident between the Arctic and the Mediterra-nean where in addition to the broader range of Mg valuesand high proportion of IMC some species have entirelyaragonitic skeletons (Poluzzi and Sartori 1975)

Not withstanding the lack of data on tropical bryozoanfaunas over a global scale a latitudinal pattern in bryozoanskeletal mineralogy is evident high latitude cold-waterfaunas contain a large proportion of species having LMCskeletons while lower-latitude warmer-water faunas tendto have higher levels of Mg in the calcite and also containbimineralic and aragonitic species that are rare or absent athigh latitudes A key question is the extent to which thispattern is under biological or environmental control Whileit is believed that the skeletal mineralogy of many organ-isms is primarily biologicallytaxonomically controlled(eg octocoralsmdashBayer and Macintyre 2001 stylasteridhydrocoralsmdashCairns and Macintyre 1992 gastropodsmdashTaylor and Reid 1990) numerous investigations haveshown how environmental factors including temperatureand seawater chemistry can aVect the chemical and mineral

Fig 3 Mean values (sectstandard error) of mol MgCO3 in Harmeria scutulata (left) and Cystisella saccata (right) from diVerent Arctic localities (H Hornsund fjord I Isfjorden sample sizes are in circles)

Fig 4 Mean values (sectstandard error) of mol MgCO3 of bryozoanfaunas from the Arctic Mediterranean New Zealand and Antarctic(sample sizes are in circles)

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composition of the skeleton (eg Lowenstam 1954a Dodd1967 Checa et al 2007) For example some gastropodspecies (Cohen and Branch 1992) show a pattern ofincreasing calcite at higher latitudes Chave (1954) foundpositive correlations between Mg levels in calcite and sea-water temperatures in several groups of marine organismsincluding foraminifera corals echinoderms crustaceansand calcareous algae While Cairns and Macintyre (1992)found no consistent correlation between carbonate poly-morph or magnesium content in stylasterids as a groupthey did Wnd that species secreting calcitic skeletons wererestricted to waters colder than 13degC

For bryozoans both Lowenstam (1954b) and Ruckerand Carver (1969) found a temperature-related trend withinpopulations of the bimineralic bryozoan Schizoporella uni-cornis the proportion of aragonite in the skeleton increas-ing with seawater temperature However the conclusionsof these two studies were based on analyses of sampleswithout replication and there are doubts about the correctidentiWcation of the species (S Tompsett pers commDecember 2008) Therefore the results have to be treatedwith caution Lombardi et al (2008) studied the bimineraliccheilostome Pentapora and found higher levels of arago-nite in a population from the Ligurian Sea than one fromcolder waters oV Britain Kuklinski and Taylor (2008) com-pared congeneric species across a latitudinal transect toshow that there is a shift towards aragonitic and bimineralicskeletons from the Arctic into lower latitudes Howeveramong the New Zealand bryozoans analyzed by Smithet al (1998) mineralogical patterns in relation to meanwater temperature were found to be weak

Secretion of calcite by marine organisms inhabitinglow-temperature waters is not an absolute physiologicalnecessity as there are many polar molluscs and hydrozoanswith fully aragonitic skeletons (Carter 1980 Cairns andMacintyre 1992) Indeed present-day marine waters have aMgCa molar ratio of 52 close to the point in whichinorganic carbonates are composed entirely of aragonite(Stanley and Hardie 1998) implying that aragonite biomin-eralization may be in greater equilibrium with ambientconditions that calcite biomineralization even in coldwaters Checa et al (2007) were able to show in laboratoryexperiments that the chemistry of seawater aVects not onlythe chemical composition (Mg-content) of the calcitesecreted but also determines the polymorph of calciumcarbonate formed by bivalves calcitic species precipitatedaragonite in Mg-enriched seawater Similar responses tochanging MgCa ratios have been documented among scle-ractinian corals (Ries et al 2006) and calcareous algae(Ries 2005) cultured in the laboratory

Latitudinal trends found in molluscan biomineralogyhave been interpreted to reXect adaptation against greatershell dissolution in colder waters calcite being less vulner-

able to dissolution due to its lower solubility in seawater(Mucci 1983) Based on the characteristics of calcite andaragonite (calcite being less dense harder with perfectcleavage less costly to produce and less soluble than arago-nite) Carter (1980 see also Carter et al 1998) suggestedseveral adaptive advantages of secreting calcite in bivalves(1) more rapid secretion of large shells (2) more energeti-cally eYcient shell secretion (3) enhancement of fracturerepair and (4) reduction in shell dissolution Some or all ofthese factors may also apply to Arctic bryozoans explain-ing the dominance of species with low-Mg calcite skele-tons The short period of food availability for Arcticbryozoans perhaps places a premium on the eYcient use ofenergy in biomineralization compared to bryozoans livingat lower latitudes

The observed lower Mg content in younger parts of thecolony (growth tips) in three out of four analysed Arcticspecies (Fig 2) is consistent with the Wndings of Smithet al (1998) from New Zealand and Poluzzi and Sartori(1975) from the Mediterranean Sea As noted by Smithet al (1998) this may reXect environmental or diageneticmechanisms The recent study of Schaumlfer and Bader (2008)showed a clear trend towards higher levels of Mg in theskeleton of the bryozoan C sinuosa in summer than in win-ter implying a strong environmental control However thesimultaneous secretion of LMC in the primary layer andIMC in the secondary layer of C sinuosa under the sameenvironmental conditions indicates biological control of theprocess Furthermore the lack of any trend in Mg contentalong branches of Adeonellopsis sp collected from NewZealand found by Wejnert and Smith (2008) supports thehypothesis that change in Mg content during colonydevelopment is under biological control rather than beingdependent on environmental factors related to seasonality(eg temperature) Taken together these studies indicatecomplexities in the variation of Mg contents in bryozoanskeletons

The high proportion of calcitic bryozoans with relativelylow Mg contents at polar latitudes may aVect diagenesisrelative to lower latitudes where bryozoans have higher Mgcontents and increasingly more aragonite is present (egJames et al 2005) Dissolution of aragonite and its repre-cipitation as calcite has been recognized as one of the maindriving forces in meteoric diagenesis (James and Choquette1983) The less-soluble skeletons of polar bryozoans withrelatively low Mg levels will not provide a signiWcantsource of cement Modern polar carbonate sediments domi-nated by bryozoans may therefore be poorly cementedCombined with the low growth rates of cold-water bryozo-ans which results in low carbonate productivity and slowrates of accumulation (Smith 2007) poor cementationshould bias against the survival in the geological record ofbryozoan limestones from high latitudes

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Conclusions

Arctic bryozoans secrete skeletons predominantly com-posed of calcite with low and intermediate levels of Mgsupporting our initial hypothesis based on the higher solu-bilities of aragonite and HMC in cold waters In contrastbryozoans from warmer waters have skeletons exhibiting awider diversity of mineralogy and Mg geochemistry withmany aragonitic and bimineralic species The most persua-sive though untested explanation for the relative largeproportion of species with low-Mg calcite skeletons in theArctic is as an adaptation against dissolution (but cfHarper 2000) aragonite and high-Mg calcite being moreprone to dissolution in cold polar waters than in warmerwaters at lower latitudes The mineralogy of Arctic bry-ozoans has implications for diagenesis while preservationof individual bryozoan skeletons may be enhancedbecause of their mineralogy low productivity and rates ofcarbonate deposition together with the paucity of bryo-zoan aragonite that can be dissolved to provide cementmay act against the survival of polar bryozoan carbonatesin the rock record

With progressive oceanic acidiWcation and the concomi-tant decrease in carbonate saturation state bryozoan specieswith aragonitic bimineralic and HMC skeletons will beaVected Wrst However the low overall number of specieswith such skeletal compositions in the Arctic will mean thatthe impact of acidiWcation caused by climate change islikely to be less than in lower latitudes

Acknowledgments We would like to thank Caroline Kirk and Gor-don Cressey for help with XRD and mineralogical data analysis Theauthors would also like to thank Bjorn Berning and an anonymous re-viewer for comments leading to an improved manuscript The studyhas been completed thanks to the Wnancial support to from the EU pro-grammes BRYOARC and DYNARC as well as a grant from the Pol-ish Ministry of Science and Higher Education (NN304 270434) to PK

Appendix

Mineralogy and mole percentage of Mg in the skeletons ofthe Arctic bryozoan species analysed for this study Allspecies belong to the order Cheilostomata except for thoseindicated by an asterisk which are Cyclostomata (namdashdata not available)

Species name Locality Latitude Longitude Depth (m) Aragonite Mol MgCO3

Amphiblestrum trifolium (Wood 1844) Spitsbergen 77degN 15degE na 0 447

Arctonula arctica (Sars 1851) Spitsbergen 76deg57N 15deg55E 12 0 0

Bidenkapia spitsbergensis (Bidenkap 1897) Spitsbergen 77degN 15degE na 0 146

BuVonellaria arctica (Berning and Kuklinski 2008) Spitsbergen 78deg59N 10deg58E 12 0 744

Bugulopsis peachi (Busk 1851) Chukchi Sea na na na 0 341

Callopora craticula (Alder 1856) Spitsbergen 78deg595N 11deg589E 10 0 01


Callopora smitti (Kluge 1946) Spitsbergen 76deg40N 15deg40E na 0 382

Carbasea carbasea (Ellis and Solander 1786) Spitsbergen 76deg57N 15deg55E 12 0 713

Cauloramphus sp Laptev Sea 74deg300N 137deg050E 22 0 092

Cauloramphus intermedius (Kluge 1962) Spitsbergen 76deg57N 15deg55E 12 0 426

Celleporina nordenskjoldi (Kluge 1929) Laptev Sea 74deg300N 137deg050E 22 0 249

Celleporina surcularis (Packard 1863)mdashbase Spitsbergen 79deg010N 11deg318E raquo200 0 484

Celleporina surcularis (Packard 1863)mdashtip Spitsbergen 79deg010N 11deg318E raquo200 0 392

Celleporella hyalina (Linnaeus 1767) Spitsbergen 78deg11N 15deg08E 12 0 0

Celleporella hyalina (Linnaeus 1767) Greenland 73deg20N 54deg20W 11ndash36 0 0



Cheilopora sincera (Smitt 1867) Laptev Sea 74deg245N 131deg013E 30 0 378



Cribrilina annulata (Fabricius 1780) Northern Norway 69deg49N 19deg00E 1 0 682

Cribrilina annulata (Fabricius 1780) Spitsbergen 76deg57N 15deg55E 12 0 651

Cribrilina cryptooecium (Norman 1903) Northern Norway 69deg49N 19deg00E 1 0 457



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Cribrilina spitzbergensis (Norman 1903) Spitsbergen 78deg59N 10deg58E 210 0 382

Cylindroporella tubulosa (Norman 1868) Spitsbergen 76deg57N 15deg55E 12 0 498

Cylindroporella tubulosa (Norman 1868) Spitsbergen 78deg10N 14deg40E raquo100 0 409


Cystisella saccata (Busk 1856) Spitsbergen 77degN 15degE na 0 645

Cystisella saccata (Busk 1856) Laptev Sea 74deg299N 139deg413E 25 0 539


Cystisella saccata (Busk 1856)mdashbase Spitsbergen 78deg10N 14deg40E raquo100 0 389

Cystisella saccata (Busk 1856)mdashtip Spitsbergen 78deg10N 14deg40E raquo100 0 406

Cystisella saccata (Busk 1856)mdashbase Spitsbergen 77degN 15degE na 0 58


Cystisella saccata (Busk 1856)mdashbase Laptev Sea 74deg300N 137deg050E 22 0 348

Cystisella saccata (Busk 1856)mdashtip Spitsbergen 77degN 15degE na 0 604

Cystisella saccata (Busk 1856)mdashtip Laptev Sea 74deg300N 137deg050E 22 0 313

Dendrobeania fruticosa (Packard 1863) Spitsbergen 78deg595N 11deg589E 10 0 532

Dendrobeania murrayana (Johnston 1847) Spitsbergen 76deg57N 15deg55E 6 0 317

Doryporella spathulifera (Smitt 1868) Spitsbergen 79deg32N 18deg46E 20 0 197

Einhornia arctica (Borg 1931) Spitsbergen 79deg03N 11deg39E 10 0 447


Escharella sp Spitsbergen 76deg57N 15deg55E 6 0 419


Escharoides jacksoni (Waters 1900) Laptev Sea na na na 0 433

Eucratea loricata (Linnaeus 1758) Spitsbergen 76deg57N 15deg55E 6 0 638


Eucratea loricata (Linnaeus 1758) Laptev Sea na na na 0 59

Eucratea loricata (Linnaeus 1758) Laptev Sea 73deg299N 131deg399E 25 0 382


Flustra nordenskjoldi (Kluge 1929) Bering Sea na na na 0 331

Flustra serrulata (Busk 1878) Laptev Sea 75deg489N 134deg232E 43 0 597



Harmeria scutulata (Busk 1855) Spitsbergen 78deg11N 15deg08E 12 0 139




Harmeria scutulata (Busk 1855) Greenland 73deg20N 54deg20W 11ndash36 0 109



Harmeria scutulata (Busk 1855) Northern Norway 69deg49N 19deg00E 1 0 535



Heteropora pelliculata (Waters 1879) Bering Sea na na na 0 126

Hincksipora spinulifera (Hincks 1889) Spitsbergen 78deg59N 10deg58E 210 0 696


Hincksipora spinulifera (Hincks 1889) Spitsbergen 79deg32N 18deg46E na 0 631

Hippodiplosia ussowi (Kluge 1908) Barents Sea na na na 0 59

Hippoporella hippopus (Smitt 1867) Spitsbergen 79deg32N 18deg46E 20 0 648

Hippoporella hippopus (Smitt 1867) Spitsbergen 78deg10N 14deg40E raquo100 0 426



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Facies (2009) 55489ndash500 497

Hippothoa arctica (Kluge 1906) Spitsbergen 78deg59N 10deg58E 210 0 0


Hippothoa expansa (Dawson 1859) Spitsbergen 78deg59N 10deg58E 210 0 054

Hornera lichenoides (Linneaus 1758) Spitsbergen na na na 0 501

Idmidronea atlantica (Forbes in Johnston 1847) Spitsbergen 77degN 15degE na 0 331

Lepraliodes nordlandica (Nordgaard 1905) Spitsbergen 78deg59N 10deg58E 210 1037 484

Lepraliodes nordlandica (Nordgaard 1905) Spitsbergen na na na 816 74

Lepraliella contigua (Smitt 1868) Spitsbergen 79deg32N 18deg46E 20 0 682

Lichenoporid sp Spitsbergen 78deg11N 15deg08E 12 0 252



Microporella klugei (Kuklinski and Taylor 2008) Spitsbergen 78deg11N 15deg08E 12 0 638

Microporella klugei (Kuklinski and Taylor 2008) Spitsbergen 78deg10N 14deg40E raquo100 0 378


Microporella arctica (Norman 1903) Spitsbergen 78deg595N 11deg589 10 0 43

Myriapora orientalis (Kluge 1929) Bering Sea na na na 0 075

Myriapora subgracilis (drsquoOrbigny 1852)mdashbase Spitsbergen na na na 0 416

Myriapora subgracilis (drsquoOrbigny 1852)mdashtip Spitsbergen na na na 0 327

Myriozoella costata (Kluge 1962) Spitsbergen 78deg59N 10deg58E 210 0 453




Myriozoella crustacea (Smitt 1868) Spitsbergen 76deg57N 15deg55E 12 0 286

Oncousoecia canadensis (Osburn 1933) Spitsbergen 78deg59N 10deg58E 210 0 576

Pachyegis princeps (Norman 1903) Spitsbergen 77degN 15degE na 721 887

Pachyegis princeps (Norman 1903) East-Spitsbergen na na na 1739 699

Pachyegis princeps (Norman 1903) Spitsbergen na na na 891 682

Parasmittina ldquotrispinosardquo (Johnston 1838) Spitsbergen 78deg59N 11deg58E 10 1057 679

Parasmittina ldquotrispinosardquo (Johnston 1838) Spitsbergen 79degN 11degE na 0 447


Porella proboscidea (Hincks 1888) Spitsbergen 78deg59N 10deg58E na 0 163

Porella sp Spitsbergen na na na 0 747

Posterula sarsi (Smitt 1867)mdashbase Spitsbergen 78deg59N 10deg58E 210 0 87

Posterula sarsi (Smitt 1867)mdashtip Spitsbergen 78deg59N 10deg58E 210 0 556PseudoXustra birulai (Kluge 1929) Kara Sea na na na 0 453PseudoXustra solida (Stimpson 1854) Kara Sea na na na 0 382PseudoXustra solida (Stimpson 1854) Kara Sea na na na 0 467

Raymondcia bella (Busk 1860) Spitsbergen 78deg59N 10deg58E 210 1176 808

Raymondcia bella (Busk 1860) Spitsbergen 79deg32N 18deg46E na 1287 744

Raymondcia rigida (Lorenz 1886) Spitsbergen 79deg018N 11deg498E 10 0 682



Reteporella beaniana (King 1846) Northern Norway 71degN 25degE na 0 569

Reteporella cellulosa (Linneaus 1767) Spitsbergen 78deg59N 10deg58E 210 0 47

Rhamphostomella costata (Lorenz 1886) Spitsbergen 79deg018N 11deg498E 10 0 358

Rhamphostomella costata (Lorenz 1886) Spitsbergen na na na 0 317

Rhamphostomella costata (Lorenz 1886) Greenland 73deg20N 54deg20W 11ndash36 0 18

Rhamphostomella plicata (Smitt 1868) Spitsbergen 77degN 15degE na 0 392

Schizoporella pachystega Kluge 1929 Spitsbergen 78deg10N 14deg40E raquo100 0 569


123

498 Facies (2009) 55489ndash500

References

Anderson LG Bjork G Holby O Jones EP Kattner G KoltermannKP Lijeblad B Lindegren R Rudels B Swift J (1994) Watermasses and circulation in the Eurasian Basin results from theOden 91 expedition J Geophys Res 993273ndash3283 doi10102993JC02977

Andruleit H Freiwald A Schaumlfer P (1996) Bioclastic carbonate sedi-ments on the southwestern Svalbard shelf Mar Geol 134163ndash182 doi1010160025-3227(96)00044-8

Bader B Schaumlfer P (2005) Bryozoans in polar latitudes Arctic andAntarctic bryozoan communities and facies Denisia 16263ndash282

Bayer FM Macintyre IG (2001) The mineral component of the axiaand holdfasts of some gorgonacean octocorals (CoelenterataAnthozoa) with special reference to the family Gorgoniidae ProcBiol Soc Wash 114309ndash345

Bone Y James NP (1993) Bryozoans as carbonate sediment producerson the cool Lacepede Shelf southern Australia Sediment Geol86247ndash271 doi1010160037-0738(93)90025-Z

Borisenko YA Gontar VI (1991) Skeletal composition of cold-waterbryozoans (in Russian) Biol Morya 180ndash90

Cairns SD Macintyre IG (1992) Phylogenetic implications of calciumcarbonate mineralogy in the Stylasteridae (Cnidaria Hydrozoa)Palaios 796ndash107 doi1023073514799

Carter JG (1980) Environmental and biological controls of bivalveshell mineralogy and microstructure In Rhoads DC Lutz RA(eds) Skeletal growth of aquatic organisms Plenum Press NewYork pp 69ndash114

Carter JG Barrera E Tevesz MJS (1998) Thermal potential and min-eralogical evolution in the Bivalvia (Mollusca) J Paleontol72991ndash1010

Chave KE (1954) Aspects of the biogeochemistry of magnesium 1Calcareous marine organisms J Geol 62266ndash283

Checa AG Jimenez-Lopez C Rodriguez-Navarro A Machado JP(2007) Precipitation of aragonite by calcite bivalves in Mg-en-riched marine waters Mar Biol (Berl) 150819ndash827 doi101007s00227-006-0411-4

Clarke A (1998) Temperature and energetics an introduction to coldocean physiology In Poumlrtner H-O Playle RC (eds) Cold oceanphysiology Society for Experimental Biology Seminar SeriesCambridge University Press Cambridge pp 3ndash30

Cohen AL Branch GM (1992) Environmentally controlled variation inthe structure and mineralogy of Patella granularis shells from thecoast of southern Africa implications for palaeotemperatureassessments Palaeogeogr Palaeoclimatol Palaeoecol 9149ndash57doi1010160031-0182(92)90031-Y

Davis KJ Dove PM De Yoreo JJ (2000) The role of Mg2+ as an impu-rity in calcite growth Science 2901134ndash1137 doi101126science29054941134

Dodd JR (1967) Magnesium and strontium in calcareous skeletons areview J Paleontol 411313ndash1329

Ettensohn FR et al (1986) Paleoecology and paleoenvironments of thebryozoan-rich Sulphur Well Member Lexington Limestone (Mid-dle Ordovician) central Kentucky Southeast Geol 26199ndash219

Fabry VJ (2008) Marine calciWers in a high-CO2 ocean Science3201020ndash1022 doi101126science1157130

Schizoporella pachystega (Kluge 1929) Spitsbergen 78deg59N 10deg58E 210 0 58

Schizoporella perforata (Kluge 1952) Spitsbergen 78deg59N 10deg58E 210 0 498

Schizoporella stylifera (Levinsen 1887) Spitsbergen 78deg59N 10deg58E 210 0 784

Scrupocellaria arctica (Busk 1855) Spitsbergen na na na 0 341

Scrupocellaria orientalis (Kluge 1955) Spitsbergen 76deg57N 15deg55E 12 0 293SecuriXustra securifrons (Pallas 1766) Spitsbergen 79deg01N 11deg49E raquo50 0 648

Semibugula birulai (Kluge 1929) Chukchi Sea na na na 0 0

Septentriopora karasi (Kuklinski and Taylor 2006) Spitsbergen 76deg57N 15deg55E 12 0 457

Smittina minuscula (Smitt 1868) Spitsbergen 79deg03N 11deg39E na 0 375


Stomachetosella cruenta (Busk 1854) Spitsbergen 78deg595N 11deg589E 10 0 686



Tegella arctica (drsquoOrbigny 1853) Spitsbergen 78deg595N 11deg589E 10 0 443


Tegella arctica (drsquoOrbigny 1853) Greenland 73deg20N 54deg20W 11ndash36 0 0

Tegella cf unicornis (Fleming 1828) Laptev Sea 74deg298N 134deg032E 30 0 044



Tricellaria ternata (Ellis and Solander 1786) Spitsbergen 78deg595N 11deg589E 10 0 228


Tricellaria ternata (Ellis and Solander 1786) Spitsbergen 78deg15N 13deg55E na 0 385

Tubulipora fructuosa (Gostilovskaya 1955) White Sea na na na 0 109

Tubulipora soluta (Kluge 1946) Kara Sea na na na 0 402

Umbonula littoralis (Hastings 1944) Northern Norway 69deg49N 19deg00E 1 0 692


123

Facies (2009) 55489ndash500 499

Gray JS (2002) Species richness of marine soft sediments Mar EcolProg Ser 244285ndash297 doi103354meps244285

Harper EM (2000) Are calcitic layers an eVective adaptation againstshell dissolution in the Bivalvia J Zool (Lond) 251179ndash186doi101111j1469-79982000tb00602x

Henrich R Hartmann M Reitner J Schaumlfer P Freiwald A SteinmetzS Dietrich P Thiede J (1992) Facies belts and communities of theArctic Vesterisbanken Seamount (Central Greenland Sea) Facies2771ndash104 doi101007BF02536805

IPCC (2007) Climate change 2007 The intergovermental panel on cli-mate change 4th assessment report Last accessed February 92009 wwwipccch

James NP Choquette PW (1983) Diagenesis 9 Limestones the mete-oric diagenetic environment Geosci Can 11161ndash194

James NP Clarke JDA (eds) (1997) Cool-water carbonates SEPMSpecial Publication vol 56 pp 1ndash440

James NP Bone Y Kyser TK (2005) Where has all the aragonitegone Mineralogy of Holocene neritic cool-water carbonatessouthern Australia J Sediment Res 75454ndash463 doi102110jsr2005035

Kleypas JA Buddemeier RW Archer D Gattuso J-P Langdon C Op-dyke BN (1999) Geochemical consequences of increased atmo-spheric carbon dioxide on coral reefs Science 284118ndash120doi101126science2845411118

Kluge GA (1975) Bryozoa of the northern seas of the USSR AmerindPublishing Co New Delhi

Kuklinski P Porter J (2004) Alcyonidium disciforme Smitt 1871 anexceptional Arctic bryozoan J Mar Biol Assoc U K 84267ndash275doi101017S0025315404009130h

Kuklinski P Taylor PD (2006) Unique life history strategy in a suc-cessful Arctic bryozoan Harmeria scutulata J Mar Biol Assoc UK 861035ndash1046 doi101017S0025315406014019

Kuklinski P Taylor PD (2008) Are bryozoans adapted for living in theArctic In Hageman SJ Key MM Winston JE (eds) BryozoanStudies 2007 Proceedings of the 14th International BryozoologyAssociation Conference Boone North Carolina 1ndash8 July 2007Virginia Museum of Natural History Memoir Special Publica-tion Number vol 15 pp 101ndash110

Loeng H (1991) Features of the physical oceanographic conditions ofthe Barents Sea In Sakshaug E Hopkins CCE Oritsland NA(eds) Proceedings of the Pro Mare Symposium on Polar MarineEcology Trondheim 12ndash16 May 1990 Polar Res vol 10 pp 5ndash18

Lombardi C Cocito S Hiscock K Occhipinti-Ambrogi A Setti MTaylor PD (2008) InXuence of seawater temperature on growthbands mineralogy and carbonate production in a bioconstruction-al bryozoan Facies 54333ndash342 doi101007s10347-008-0143-7

Lowenstam HA (1954a) Environmental relations of modiWcation com-positions of certain carbonate secreting marine invertebrates ProcNatl Acad Sci USA 4039ndash48 doi101073pnas40139

Lowenstam HA (1954b) Factors aVecting the aragonitecalcite ratios incarbonate secreting marine organisms J Geol 62284ndash322

Mucci A (1983) The solubility of calcite and aragonite in seawater atvarious salinities temperatures and one atmosphere total pres-sure Am J Sci 283780ndash799

Nelson CS (1988) An introductory perspective on non-tropical shelfcarbonates Sediment Geol 603ndash12 doi1010160037-0738(88)90108-X

Parkinson CL Cavalieri DJ Gloersen P Zwally HL Comiso JC(1999) Arctic sea ice extents areas and trends 1978ndash1996 JGeophys Res 10420837ndash20856 doi1010291999JC900082

Poluzzi A Sartori R (1975) Report on the carbonate mineralogy ofBryozoa Documents des Laboratoires de Geacuteologie de la Faculteacutedes Sciences de Lyon Hors Srie vol 3 pp 193ndash210

Pray LC (1958) Fenestrate bryozoan core facies Mississippian bio-herms southwestern United States J Sediment Petrol 28261ndash273

Raven FRS et al (2005) Ocean acidiWcation due to increasing atmo-spheric carbon dioxide The Royal Society Report 1205 60 pp

Riebesell U Zondervan I Rost B Tortell PD Zeebe RE Morel FM(2000) Reduced calciWcation of marine plankton in response toincreased atmospheric CO2 Nature 407364ndash367 doi10103835030078

Ries JB (2005) Aragonite production in calcite seas eVect of seawaterMgCa ratio on calciWcation and growth of the calcareous algaPenicillus capitatus Paleobiology 31445ndash458 doi1016660094-8373(2005)031[0445APICSE]20CO2

Ries JB Stanley SM Hardie LA (2006) Scleractinian corals producecalcite and grow more slowly in artiWcial Cretaceous seawaterGeology 34525ndash528 doi101130G226001

Rogala B James NP Reid CM (2007) Deposition of polar carbonatesduring interglacial highstands on an early Permian shelf Tasma-nia J Sediment Res 77587ndash606 doi102110jsr2007060

Rucker JB Carver RE (1969) A survey of the carbonate mineralogy ofcheilostome Bryozoa J Paleontol 43791ndash799

Rudels B Jones EP Anderson LG Kattner G (1994) On the interme-diate depth waters of the Arctic Ocean In Johannessen OMMuench RD Overland JE (eds) The Polar Oceans and their rolein shaping the global environment Am Geophys UnionWashington DC pp 33ndash46

Ryland JS (1970) Bryozoans Hutchinson LondonSakshaug E (2003) Primary and secondary production in the Arctic

seas In Stein R Macdonald RW (eds) The organic carbon cyclein the Arctic Ocean Springer Berlin Heidelberg New York pp57ndash81

Schaumlfer P Bader B (2008) Geochemical composition and variability inthe skeleton of the bryozoans Cellaria sinuosa (Hassall) biolog-ical versus environmental control In Hageman SJ Key MMWinston JE (eds) Bryozoan Studies 2007 Proceedings of the14th International Bryozoology Association Conference BooneNorth Carolina 1ndash8 July 2007 Virginia Museum of Natural His-tory Memoir Special Publication Number vol 15 pp 269ndash279

Schiermeier Q (2007) The new face of the Arctic Nature 446133ndash135 doi101038446133a

Smith AM (2007) Age growth and carbonate production by erect rigidbryozoans in Antarctica Palaeogeogr Palaeoclimatol Palaeoecol25686ndash98 doi101016jpalaeo200709007

Smith AM Nelson CS (1993) Mineralogical carbonate geochemicaland diagenetic data for modern New Zealand bryozoans Depart-ment of Earth Sciences University of Waikato OccasionalReport No 17 pp 1ndash71

Smith AM Nelson CS Spencer GH (1998) Skeletal carbonate miner-alogy of New Zealand bryozoans Mar Geol 15127ndash46doi101016S0025-3227(98)00055-3

Smith AM Key MM Gordon DP (2006) Skeletal mineralogy of bry-ozoans taxonomic and temporal patterns Earth Sci Rev 78287ndash306 doi101016jearscirev200606001

Stanley SM Hardie LA (1998) Secular oscillations in the carbonatemineralogy of reef-building and sediment-producing organismsdriven by tectonically forced shifts in seawater chemistry Palae-ogeogr Palaeoclimatol Palaeoecol 1443ndash19 doi101016S0031-0182(98)00109-6

Taviani M Reid DE Anderson JB (1993) Skeletal and isotopic com-position and paleoclimatic signiWcance of Late Pleistocene car-bonates Ross Sea Antarctica J Sediment Petrol 6384ndash90

Taylor JD Reid DG (1990) Shell microstructure and mineralogy of theLittorinidae ecological and evolutionary signiWcance Hydrobio-logia 193199ndash215 doi101007BF00028077

Taylor PD Allison PA (1998) Bryozoan carbonates in space and timeGeology 26459ndash462 doi1011300091-7613(1998)026lt0459BCTTASgt23CO2

Thiel H Poumlrtner HO Arntz WE (1996) Marine life at low tempera-turesmdasha comparison of polar and deep-sea characteristics In

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500 Facies (2009) 55489ndash500

Uiblein F Ott J Stachowitsch M (eds) Deep-sea and extremeshallow-water habitats aYnities and adaptations Biosystematicsand Ecology Series vol 11 pp 183ndash219

Wass RE Conolly JR MacIntyre RJ (1970) Bryozoan carbonate sandcontinuous along southern Australia Mar Geol 963ndash73doi1010160025-3227(70)90080-0

Wejnert KE Smith AM (2008) Within-colony variation in skeletalmineralogy of Adeonellopsis sp (Cheilostomata Bryozoa) fromNew Zealand NZ J Mar Freshwater Sci 42389ndash395

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490 Facies (2009) 55489ndash500

The large mineralogical and geochemical spectrumexhibited by bryozoans (Smith et al 2006) makes them agood group for investigating the diVerential eVects of oce-anic acidiWcation and increase in seawater temperaturecaused by global warming The rise in atmospheric CO2

over the past century has led to greater CO2 uptake by theoceans increasing hydrogen ions (H+) and causing oceanicacidiWcation Along with a concomitant decrease in carbon-ate ions (CO3

2iexcl) this has changed the saturation state of theoceans with respect to calcium carbonate (CaCO3) miner-als Decreased carbonate saturation state can be predicted tolead to reduced calciWcation rates a shift towards organ-isms that secrete calcite (which is less soluble than arago-nite) and competitive advantages for those organismswithout calciWed skeletons (Kleypas et al 1999 Riebesellet al 2000 Fabry 2008)

Of all organisms inhabiting shallow seas the impact ofacidiWcation is likely to be most severe for species secretingcalcareous skeletons (Raven et al 2005) among which bry-ozoans are a major example However compared to suchgroups as molluscs there are few studies of bryozoan min-eralogy (Poluzzi and Sartori 1975 Borisenko and Gontar1991 Smith et al 1998) Smith et al (2006) surveyed pub-lished data Wnding that carbonate mineralogy was knownfor only about 6 of living species There are only twoareas (Mediterranean and New Zealand) where large num-bers of bryozoans have been studied mineralogically Toassess the vulnerabilities of diVerent species to climatechange and to understand bryozoan diagenesis we desper-ately need more information on the skeletal mineralogy andchemistry of the numerous species that inhabit shallowwaters especially in areas most inXuenced by climatechange

In this study we investigate the skeletal mineralogy ofbryozoans from the Arctic the most rapidly warmingregion on Earth (Schiermeier 2007 IPCC 2007) Here bry-ozoans are one of the most species-rich benthic groups thatsecrete carbonate skeletons (Henrich et al 1992 Andruleitet al 1996) However knowledge of the skeletal mineral-ogy and geochemistry of Arctic bryozoans is woefullyinadequate Indeed the 1183 individual mineralogicalanalyses tabulated by Smith et al (2006) for bryozoansincluded data from only 24 Arctic species This represents7 of the biomineralizing bryozoan species in the Arctic(Kluge 1975) In the only study to date of polar bryozoans(Borisenko and Gontar 1991) species from the Arctic andAntarctic were found to be almost entirely calcitic As theirstudy focused mostly on the Antarctic and covered only afraction of the over 300 species of Arctic bryozoans it isdiYcult to draw Wrm conclusions about the mineralogy ofArctic bryozoan species

Several studies of organisms secreting calcareousskeletons have shown that lower seawater temperatures

correlate with secretion of calcite skeletons with low-magnesium content over more soluble high-magnesiumcalcite or aragonite skeletons eg in gastropods (Taylorand Reid 1990) or serpulids (Lowenstam 1954a)Because both aragonite and high-magnesium calcite areappreciably more soluble in cold water (Mucci 1983Davis et al 2000) we here hypothesise that the Arcticbryozoan fauna will contain a higher proportion of spe-cies with low-Mg calcite (LMC) skeletons than faunasfrom warmer waters This hypothesis is tested by com-paring our new data on Arctic bryozoans with publisheddata from warmer temperate zones of the MediterraneanSea and New Zealand We also hypothesise that trendswill be evident both within- and between-speciestowards lower amounts of aragonite and lower levels ofMg in calcite towards higher latitudes (lower sea watertemperatures)

Study area

The Arctic Ocean is an almost land-locked sea surroundingthe North Pole There are several diVerent deWnitions of theArctic including the widely used yet impractical climate-based boundary at the 10degC July isotherm For the purposeof this study we use the Arctic Circle (66deg33N) as theboundary of the Arctic which is the approximate limit ofthe midnight sun and the polar night

The Arctic Ocean has the widest continental shelf ofall the oceans It represents raquo50 of the area and extendsin some cases as far as 1210 km seaward The continen-tal shelf encloses a deep basin with an average depth ofabout 3600 m The marine environment of the ArcticOcean is characterized by a relatively narrow range inannual temperatures often near the freezing point of sea-water which is slightly below zero degrees (Andersonet al 1994) Vast areas of the Arctic Ocean are covered byice However there is considerable seasonal and regionalvariation in ice cover ranging from 70 pound 106 km2 inSeptember to 154 pound 106 km2 in March (Parkinson et al1999) Because of continuous darkness in the winter andcontinuous daylight in the summer there is high season-ality in primary productivity with the greatest abundanceof phytoplankton in the summer (Sakshaug 2003) All ofthese environmental factors have implications for ecolog-ical conditions in the Arctic For example species rich-ness on the Arctic shelves is generally lower than intemperate or tropical shelf regions (Gray 2002) Yet themarine life of the Arctic Ocean is highly adapted in itshistory ecology and physiology to the extreme andhighly seasonal conditions of the environment (eg Thielet al 1996 Clarke 1998 Kuklinski and Porter 2004Kuklinski and Taylor 2006)

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Facies (2009) 55489ndash500 491


Material










Results

Arctic bryozoans


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Other regions

Mediterranean sea


New Zealand


Antarctica




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Discussion





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Conclusions




Appendix





























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References











































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Material










Results

Arctic bryozoans


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Other regions

Mediterranean sea


New Zealand


Antarctica




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Discussion





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Conclusions




Appendix





























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References











































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Other regions

Mediterranean sea


New Zealand


Antarctica




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Discussion





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Conclusions




Appendix





























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References











































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Discussion





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Conclusions




Appendix





























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Mineralogy of Arctic bryozoan skeletons in a global context

Documents

Transcript of Mineralogy of Arctic bryozoan skeletons in a global context