high-Mg Calcite Skeleton Research Articles

Calcitic shells in the aragonite sea of the earliest Cambrian

Abstract The initial acquisition of calcium carbonate polymorphs (aragonite and calcite) at the onset of skeletal biomineralization by disparate metazoans across the Ediacaran-Cambrian transition is thought to be directly influenced by Earth's seawater chemistry. It has been presumed that animal clades that first acquired mineralized skeletons during the so-called “aragonite sea” of the latest Ediacaran and earliest Cambrian (Terreneuvian) possessed aragonite or high-Mg calcite skeletons, while clades that arose in the subsequent “calcite sea” of Cambrian Series 2 acquired low-Mg calcite skeletons. Here, contrary to previous expectations, we document shells of one of the earliest helcionelloid molluscs from the basal Cambrian of southwestern Mongolia that are composed entirely of low-Mg calcite and formed during the Terreneuvian aragonite sea. The extraordinarily well-preserved Postacanthella shells have a simple prismatic microstructure identical to that of their modern low-Mg calcite molluscan relatives. High-resolution scanning electron microscope observations show that calcitic crystallites were originally encased within an intra- and interprismatic organic matrix scaffold preserved by aggregates of apatite during early diagenesis. This indicates that not all molluscan taxa during the early Cambrian produced aragonitic shells, weakening the direct link between carbonate skeletal mineralogy and ambient seawater chemistry during the early evolution of the phylum. Rather, our study suggests that skeletal mineralogy in Postacanthella was biologically controlled, possibly exerted by the associated prismatic organic matrix. The presence of calcite or aragonite mineralogy in different early Cambrian molluscan taxa indicates that the construction of calcium carbonate polymorphs at the time when skeletons first emerged may have been species dependent.

High-Mg calcite nanoparticles within a low-Mg calcite matrix: A widespread phenomenon in biomineralization

During the process of biomineralization, organisms utilize various biostrategies to enhance the mechanical durability of their skeletons. In this work, we establish that the presence of high-Mg nanoparticles embedded within lower-Mg calcite matrices is a widespread strategy utilized by various organisms from different kingdoms and phyla to improve the mechanical properties of their high-Mg calcite skeletons. We show that such phase separation and the formation of high-Mg nanoparticles are most probably achieved through spinodal decomposition of an amorphous Mg-calcite precursor. Such decomposition is independent of the biological characteristics of the studied organisms belonging to different phyla and even kingdoms but rather, originates from their similar chemical composition and a specific Mg content within their skeletons, which generally ranges from 14 to 48 mol % of Mg. We show evidence of high-Mg calcite nanoparticles in the cases of six biologically different organisms all demonstrating more than 14 mol % Mg-calcite and consider it likely that this phenomenon is immeasurably more prevalent in nature. We also establish the absence of these high-Mg nanoparticles in organisms whose Mg content is lower than 14 mol %, providing further evidence that whether or not spinodal decomposition of an amorphous Mg-calcite precursor takes place is determined by the amount of Mg it contains. The valuable knowledge gained from this biostrategy significantly impacts the understanding of how biominerals, although composed of intrinsically brittle materials, can effectively resist fracture. Moreover, our theoretical calculations clearly suggest that formation of Mg-rich nanoprecipitates greatly enhances the hardness of the biomineralized tissue as well.

A Review and Meta-Analysis of Potential Impacts of Ocean Acidification on Marine Calcifiers From the Southern Ocean

Understanding the vulnerability of marine calcifiers to ocean acidification is a critical issue, especially in the Southern Ocean (SO), which is likely to be the one of the first, and most severely affected regions. Since the industrial revolution, ~30% of anthropogenic CO2 has been absorbed by the global oceans. Average surface seawater pH levels have already decreased by 0.1 and are projected to decline by ~0.3 by the year 2100. This process, known as ocean acidification (OA), is shallowing the saturation horizon, which is the depth below which calcium carbonate (CaCO3) dissolves, likely increasing the vulnerability of many resident marine calcifiers to dissolution. The negative impact of OA may be seen first in species depositing more soluble CaCO3 mineral phases such as aragonite and high-Mg calcite (HMC). Ocean warming could further exacerbate the effects of OA in these particular species. Here we combine a review and a quantitative meta-analysis to provide an overview of the current state of knowledge about skeletal mineralogy of major taxonomic groups of SO marine calcifiers and to make projections about how OA might affect a broad range of SO taxa. We consider a species' geographic range, skeletal mineralogy, biological traits, and potential strategies to overcome OA. The meta-analysis of studies investigating the effects of the OA on a range of biological responses such as shell state, development and growth rate illustrates that the response variation is largely dependent on mineralogical composition. Species-specific responses due to mineralogical composition indicate that taxa with calcitic, aragonitic, and HMC skeletons, could be at greater risk to expected future carbonate chemistry alterations, and low-Mg calcite (LMC) species could be mostly resilient to these changes. Environmental and biological control on the calcification process and/or Mg content in calcite, biological traits, and physiological processes are also expected to influence species-specific responses.

Control of Deep Currents on Sediment and Cold-Water Coral Distribution on the Northern Manihiki Plateau

High-definition video surveys of remotely operated vehicle (ROV) dives from the NOAA’s Mountains in the Deep 2017 expedition (EX1705) cruise along volcanic ridges and seamounts of the Manihiki Plateau coupled with multibeam bathymetry data and water column profiles, reveal no or minimal sediment cover on the basaltic edifice, but variable amounts of cold-water corals on ferromanganese-encrusted basaltic rocks. Coarse sediment, however, accumulates in crevasses and sedimentary ripples testify the existence of currents in the area. Collectively, these observations illustrate the strong influence of deep currents on the surficial geology and cold-water coral distribution at ~2,000 m water depths. Dive transects along two basaltic seamounts show stark differences of sedimentary features and cold-water coral distribution. On the ridges of “Te Kawhiti” (water depth: 2,089-2,220 m), basaltic slabs, and cold-water corals are far more abundant in comparison to the slope of a mesa in “Te Tuku” (water depth: 2,440-2,495 m). The increased abundance on “Te Kawhiti” is due to the exposure of “Te Kawhiti” to Lower Circumpolar Deep Water that sweeps the summit of the ridges as indicated by frequent ripples observed in between the basaltic rocks. The currents are strong enough to sweep fine-grained sediments away, leaving coarse-grained sediments behind, inducing the formation of ferromanganese crust on the basaltic rocks. Both dive sites are below the high-Mg calcite saturation horizon, and as a result, the cold-water coral community is dominated by Isididae, which can build a high-Mg calcite skeleton in water undersaturated in regards to high-Mg calcite

Elemental systematics of the calcitic skeleton of Corallium rubrum and implications for the Mg/Ca temperature proxy

The high-Mg calcite skeleton of Corallium rubrum was analyzed from living colonies collected from a wide range of depths (15 m to 607 m) and environmental settings in the Mediterranean Sea. An overarching goal was to better understand the calcification process and incorporation of elements into the slow-growing skeleton of both shallow and deep-water specimens, and more specifically, to clarify the veracity of geochemical proxies for reconstructing seawater temperatures. The coral internal structure including growth bands were determined by scanning electronic microscopy (SEM) and petrographic techniques. Trace elements (Li, B, Mg, Sr and Ba) compositions of the coral skeleton were obtained by solution and laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Results show that the skeleton of the deep-water specimens has an internal microstructure similar to shallow-water colonies, with the medullar and the annular zones clearly distinguishable in both shallow and deep-water specimens. In general, the bands of the deep-water samples are very thin and equidistant compared to the irregular banding of the shallow-water specimens. Banding differences relate to the contrasting environmental dynamics, with the shallow-water specimens being exposed to large seasonal fluctuations compared to the relative stable conditions of those inhabiting bathyal depths. The inner medullar and outer annular portions differ in their trace element concentrations: Mg/Ca, Sr/Ca and Li/Ca ratios are higher in the medullar zone and seem to be influenced by growth kinetics, whereas B/Ca and Ba/Ca are similar in both zones and hence unaffected by growth rate. The variability of elemental ratios is lower in the deep-water specimens. Growth bands are highly correlated to Mg/Ca, Sr/Ca and Li/Ca, suggesting common mechanism(s) controlling the incorporation of these elements into the coral skeleton. Mg/Ca ratios were especially depleted in the dark bands. Although the mean Mg/Ca of each specimen is positively correlated to ambient seawater temperature, the intra-annual variations and amplitudes differ and do not correlate to the band widths. These findings suggest that intra- and inter-annual variations of Mg/Ca cannot be used to reconstruct a continuous time-series of long-term seasonal temperature records. However, the mean Mg/Ca composition can serve as a valuable proxy to estimate mean palaeoseawater temperature at a given site within the Mediterranean.

Spatio-temporal variation of skeletal Mg-calcite in Antarctic marine calcifiers.

Human driven changes such as increases in oceanic CO2, global warming, petroleum hydrocarbons and heavy metals may negatively affect the ability of marine calcifiers to build their skeletons/shells, especially in polar regions. We examine spatio-temporal variability of skeletal Mg-calcite in shallow water Antarctic marine invertebrates using bryozoan and spirorbids as models in a recruitment experiment of settlement tiles in East Antarctica. Mineralogies were determined for 754 specimens belonging to six bryozoan species (four cheilostome and two cyclostome species) and two spirorbid species from around Casey Station. Intra- and interspecific variability in wt% MgCO3 in calcite among most species was the largest source of variation overall. Therefore, the skeletal Mg-calcite in these taxa seem to be mainly biologically controlled. However, significant spatial variability was also found in wt% MgCO3 in calcite, possibly reflecting local environment variation from sources such as freshwater input and contaminated sediments. Species with high-Mg calcite skeletons (e.g. Beania erecta) could be particularly sensitive to multiple stressors under predictions for near-future global ocean chemistry changes such as increasing temperature, ocean acidification and pollution.

Ecophysiological response of Jania rubens (Corallinaceae) to ocean acidification

Coralline algae (Rhodophyta) play a key role in promoting settlement of other benthic organisms, being the food source for herbivores, being involved in the stabilization of reef networks, and in carbonate production. They are considered a vulnerable group to ocean acidification due to the potential dissolution of their high-Mg calcite skeleton at lower pH. Nevertheless, different species of coralline algae showed different responses to low-pH/high-pCO2 environment. Here, we studied the physiological response of Jania rubens to the pH condition predicted for the year 2100. We used a natural CO2 vent system as natural laboratory to transplant J. rubens from pH 8.1–7.5 for 3 weeks. Maximal PSII photochemical efficiency showed a significant reduction in transplanted thalli at low pH (7.5-T) compared to other conditions; consistent with that result, also the pigments involved in the light-harvesting spectrum of J. rubens (i.e., chlorophylls, carotenoids, and phycobilins), exhibited a significant decrease under water acidification, highlighting the strong sensitivity of this species to the environmental change. A major understanding of the response of coralline algae at high CO2 will go through the impact of OA on benthic ecosystems in the next future. This contribution is the written, peer-reviewed version of a paper presented at the Conference “Changes and Crises in the Mediterranean Sea” held at Accademia Nazionale dei Lincei in Rome on October 17, 2017.

Boron isotope sensitivity to seawater pH change in a species of Neogoniolithon coralline red alga

The increase in atmospheric carbon dioxide (CO2) observed since the industrial revolution has reduced surface ocean pH by ∼0.1pH units, with further change in the oceanic system predicted in the coming decades. Calcareous organisms can be negatively affected by extreme changes in seawater pH (pHsw) such as this due to the associated changes in the oceanic carbonate system. The boron isotopic composition (δ11B) of biogenic carbonates has been previously used to monitor pH at the calcification site (pHcf) in scleractinian corals, providing mechanistic insights into coral biomineralisation and the impact of variable pHsw on this process. Motivated by these investigations, this study examines the δ11B of the high-Mg calcite skeleton of the coralline red alga Neogoniolithon sp. to constrain pHcf, and investigates how this taxon’s pHcf is impacted by ocean acidification. δ11B was measured in multiple algal replicates (n=4–5) cultured at four different pCO2 scenarios – averaging (±1σ) 409 (±6), 606 (±7), 903 (±12) and 2856 (±54) μatm, corresponding to average pHsw (±1σ) of 8.19 (±0.03), 8.05 (±0.06), 7.91 (±0.03) and 7.49 (±0.02) respectively. Results show that skeletal δ11B is elevated relative to the δ11B of seawater borate at all pHsw treatments by up to 18‰. Although substantial variability in δ11B exists between replicate samples cultured at a given pHsw (smallest range=2.32‰ at pHsw 8.19, largest range=6.08‰ at pHsw 7.91), strong correlations are identified between δ11B and pHsw (R2=0.72, p<0.0001, n=16) and between δ11B and B/Ca (R2=0.72, p<0.0001, n=16). Assuming that skeletal δ11B reflects pHcf as previously observed for scleractinian corals, the average pHcf across all experiments was 1.20 pH units (0.79 to 1.56) higher than pHsw, with the magnitude of this offset varying parabolically with decreasing pHsw, with a maximum difference between pHsw and pHcf at a pHsw of 7.91. Observed relationships between pHsw and calcification rate, and between pHsw and pHcf, suggest that coralline algae exhibit some resilience to moderate ocean acidification via increase of pHcf relative to pHsw in a similar manner to scleractinian corals. However, these results also indicate that pHcf cannot be sufficiently increased by algae exposed to a larger reduction in pHsw, adversely impacting calcification rates of coralline red algae.

Seasonal growth and calcification of a reef-building crustose coralline alga on the Great Barrier Reef

Crustose coralline algae (CCA) play a central role in tropical reef ecology, helping to build and stabilise the reef framework and, due to their high Mg-calcite skeleton, are potential indicators for assessing the impacts of ocean acidification. However, basic information on CCA seasonal growth and calcification is relatively unknown on the Great Barrier Reef (GBR). This study provides seasonal baseline rates of vertical growth, marginal (horizontal) growth and calcification of the abundant CCA species Porolithon onkodes, together with the effect of reduced irradiance on these metrics to better understand the natural variability between CCA living in exposed and shaded areas. Seasonal variation was detected in each of the metrics, with maximum vertical growth and calcification observed in spring and marginal extension in autumn. Annual vertical growth rate was 1.45 mm yr(-1), absolute marginal growth rate (surface area) was 11.12 cm(2) yr(-1), and absolute marginal extension rate (diameter) was 24.66 mm yr(-1). Net calcification, determined using the buoyant weight method (includes secondary calcification deposits) was approximately 2.72 to 3.40 g CaCO3 cm(-2) yr(-1), while gross calcification determined using growth metrics (just newly deposited CaCO3) was 0.43 to 0.59 g CaCO3 cm(-2) yr(-1). Shaded treatments yielded higher growth and gross calcification rates compared to exposed in all seasons except summer. This data provides empirical information necessary to monitor the impacts of future climate change on the GBR and to better understand the response of CCA to manipulative experiments on ocean acidification and warming.

Assessing multi-site δ18O-climate calibrations of the coralline alga Clathromorphum across the high-latitude Northern Hemisphere

An increased number of climate proxy records and more refined interpretation of proxy data are crucial to improve projections of future climate at high latitudes, where internal feedbacks amplify warming and established high-resolution climate archives are especially sparse. Encrusting coralline algae are being developed as a mid- to high-latitude marine climate archive. These long-lived algae form a solid high-Mg calcite skeleton with annual growth bands similar to those of trees and tropical corals. The oxygen isotope ratio of the algal skeleton (δ18Oalg) records local environmental and climatic factors, notably sea surface temperature and seawater δ18O.Here we assess the δ18Oalg–climate relationship in diverse environments across the algal habitat range utilizing two species of coralline algae from the genus Clathromorphum. Clathromorphum is widely distributed from the cold-temperate North Atlantic and Pacific to the Arctic Ocean and has recently yielded numerous climate reconstructions of up to 650years in length. In this study, we calibrate δ18Oalg of four specimens to gridded temperature and salinity data, the latter a proxy for seawater δ18O. These specimens were collected from a variety of algal growth environments across the high-latitude Northern Hemisphere: two specimens from the Aleutian Archipelago, one from the Canadian Arctic, and one from the Gulf of Maine. Low winter temperatures and insolation restrict the months when algae record local climate in the δ18O of their skeletons; we therefore determine these response seasons by correlating monthly temperature and salinity anomalies with annual δ18Oalg anomalies at each site. We then average gridded data over months that correlate significantly (95% confidence interval) for regression with δ18Oalg. While the timing and nature of the climate signal vary across sites, we find significant relationships between δ18Oalg and either temperature or salinity averaged over the response season at three sites. Variation in local climatology among the four sites provides a physical explanation for calibration differences, compounded by uncertainties stemming from the proxy chronology, biological variability, temporal coverage, and sparse historical climate data. This work takes an essential step toward reconstructing high-latitude marine climate patterns with coralline algal δ18O and developing algae proxy system models.

Coralline algae (Rhodophyta) in a changing world: integrating ecological, physiological, and geochemical responses to global change.

Coralline algae are globally distributed benthic primary producers that secrete calcium carbonate skeletons. In the context of ocean acidification, they have received much recent attention due to the potential vulnerability of their high‐Mg calcite skeletons and their many important ecological roles. Herein, we summarize what is known about coralline algal ecology and physiology, providing context to understand their responses to global climate change. We review the impacts of these changes, including ocean acidification, rising temperatures, and pollution, on coralline algal growth and calcification. We also assess the ongoing use of coralline algae as marine climate proxies via calibration of skeletal morphology and geochemistry to environmental conditions. Finally, we indicate critical gaps in our understanding of coralline algal calcification and physiology and highlight key areas for future research. These include analytical areas that recently have become more accessible, such as resolving phylogenetic relationships at all taxonomic ranks, elucidating the genes regulating algal photosynthesis and calcification, and calibrating skeletal geochemical metrics, as well as research directions that are broadly applicable to global change ecology, such as the importance of community‐scale and long‐term experiments in stress response.

Multi-specimen and multi-site calibration of Aleutian coralline algal Mg/Ca to sea surface temperature

Higher latitude oceanic and climatic reconstructions are needed to distinguish natural climate variability from anthropogenic warming in regions projected to experience significant increases in temperature during this century. Clathromorphum nereostratum is a long-lived coralline alga abundant along the Aleutian archipelago that records seasonal to centennial fluctuations in seawater temperatures in its high-Mg calcite skeleton. Thus, C. nereostratum is an important proxy archive to reconstruct past seawater temperature variability in this data-poor subarctic region. Here, we measured magnesium to calcium ratios (Mg/Ca) by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) along the growth axis in six live-collected specimens from three islands in the Aleutian archipelago to assess Mg/Ca reproducibility and to calibrate algal Mg/Ca against modern gridded sea surface temperature (SST) data products. The master Mg/Ca–SST transfer function, determined by averaging the algal Mg/Ca–SST from each island (n=6), resulted in a reconstruction error of ±0.45°C, a 31–46% reduction in error compared to the reconstruction error for a single alga. The master algal-SST record interpolated to monthly and annual resolution significantly varied with gridded SST data products (r2=0.98, p<0.0001, n=517 and r2=.27, p<0.0003, n=44, respectively) for the period from 1960 to 2003. Therefore, coralline algal Mg/Ca-derived SST reconstructions record absolute changes in past SST variability in the Aleutian archipelago. The transfer functions developed here can be applied to Mg/Ca records generated from long-lived specimens of C. nereostratum to reconstruct northern North Pacific and Bering Sea SST variability for the past several hundred years.

Lead concentration and isotopic composition in the Pacific sclerosponge (Acanthochaetetes wellsi) reflects environmental lead pollution

We measured Pb/Ca and Pb isotopes with high resolution in the high-Mg calcite skeleton of a Pacific sclerosponge ( Acanthochaetetes wellsi ) collected from the reef edge off the western coast of Kume Island (East China Sea), to investigate its potential to be used as a proxy for lead contamination in the environment, and atmospheric transportation and fallout over the last few decades. Skeletal Pb/Ca ranged from 58 to 1642 nmol/mol, 10× higher than that of the aragonite skeleton of Pacific corals, and 2.5× higher than that of the aragonite skeletons of Caribbean sclerosponges. The Pb/Ca timeseries recorded from 1967 through 2007 CE correspond to historical changes in atmospheric lead flux in anthropogenic aerosols. Pb isotopes (206Pb/207Pb and 208Pb/207Pb) in the sclerosponge skeleton document that the main source of lead emissions shifted from Japan (1970–1980 CE) to China (1995–2005 CE), as expected from the timing of legislation against the use of leaded gasoline in Japan and China. Our results indicate that the skeleton of the Pacific sclerosponge is a powerful proxy to monitor environmental lead pollution. Applying this methodology to long-living and/or fossil specimens could be useful in determining the interannual variability of atmospheric transport and dynamics over geologic time scales.

Potential of Coralline Algae in Palaeoclimate Reconstruction: Need for Suitable Exploitation in India

Climate parameters of variability and change (natural andanthropogenic) exert considerable influences on all thehuman and natural systems existing on this earth. Theseaspects raise the scientific quest for an understanding ofpalaeoclimate and possible climate dynamics in the future.In the recent past coralline algae has attracted greater focusfrom the palaeoclimate workers across the globe. Thisunderstanding holds critical importance for supporting theneeds of an ever-broadening spectrum of the policy-makersas well as decision-implementing bodies of our society asconsistent efforts are being made to deal with the climateinfluences both at the local as well as global scales. In orderto document the past behavior of the climate systemeffectively, multi-source data is required [1]. Corallinealgae, particularly from the marine realm have the potentialto be one of those sources and have started developing asan excellent proxy for palaeoalgological studies and long-term climate analysis.India is a country rich in both living coralline algae aswell as their fossil counterparts. Fossil coralline algae havebeen recorded from several petroliferous sedimentarybasins of India e.g., Cauvery, Kachchh, Assam Shelf,Andaman-Nicobar and Narmada valley. However, the sci-entific focus has mainly been limited to taxonomic analysis,facies characterization, reconstruction of sedimentaryenvironments, palaeobathymetric zones and ancient shorelines and bars. Till date palaeoclimate studies in India havelargely given impetus to entities like foraminifera, mollusksand bivalves. Unfortunately coralline algae have trailed inthis regard and deserve greater attention as a proxy tool forclimate analysis of the past eras which are a key to thepresent.Coralline algae have a wide coastal distribution in themarine ecosystems right from the neritic to oceanic (epi-pelagic) zones and also possess a wide range of growth-forms, starting from encrusting to lumpy and foliose to thefree-living ones [2], with individual species dependingprimarily on temperature [3]. Coralline algae have a vitalrole in ecosystem management including a diverse rangeof niches [4, 5]. Encrusting coralline algae deposit annualgrowth increments in a high-Mg calcite skeleton and areamongst the longest-living shallow marine organisms.Individual calcified plants can live for several centuries inthe temperate and subarctic oceans. While a large numberof investigations have been successfully applied to obtaingeochemical information pertaining to coralline algalskeletons for reconstructing sea surface temperatures(SST), less attention has been paid till now to employ thegrowth increments as a proxy tool for temperature.According to a recent study, an averaged record of mul-tiple growth increment-width time series of Clathro-morphum compactum specimens across a network of800 km width reveal strong correlations with annualinstrumental SSTs since 1950. Hence, averaging of mul-tiple sclerochronological records of coralline algae canprovide accurate climate information, much like themethods applied in dendrochronology and coral dating.Positive changes in algal growth anomalies record a well-documented regime shift and warming in the northwesternAtlantic during the phase of 1990s. Large positive changesin algal growth anomalies were also present in the 1920sand 1930s and an effective comparison has been madewith that of the 1990s providing the result that the olderimpact may have well exceeded the later one in terms ofmagnitude of warming [6].

Effects of ocean acidification on growth, organic tissue and protein profile of the Mediterranean ­bryo­zoan Myriapora truncata

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 13:251-262 (2011) - DOI: https://doi.org/10.3354/ab00376 Effects of ocean acidification on growth, organic tissue and protein profile of the Mediterranean ­bryo­zoan Myriapora truncata Chiara Lombardi1,*, Silvia Cocito1, Maria Cristina Gambi2, Barbara Cisterna3, Francine Flach3, Paul D. Taylor4, Kim Keltie5, Andrew Freer5, Maggie Cusack6 1ENEA Marine Environment Research Centre, PO Box 224, 19100 La Spezia, Italy 2Laboratory of Functional and Evolutionary Ecology, Stazione Zoologica Anton Dohrn, 80121 Naples, Italy 3Laboratory of Cellular Biology and Neurobiology, Department of Animal Biology, University of Pavia, 27100 Pavia, Italy 4Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK 5Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8TA, UK 6School of Geographical & Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK *Email: chiara.lombardi@enea.it ABSTRACT: The possible effects of ocean acidification on growth, organic tissue and protein profile in the bryozoan Myriapora truncata (Pallas, 1766) were studied in samples transplanted along a gradient of different pH conditions in an area of natural volcanic CO2 vents at Ischia Island (Tyrrhenian Sea, Italy). Living colonies from normal (mean pH 8.10), intermediate (pH 7.83) and low (pH 7.32) pH sites were investigated after intervals of 34, 57 and 87 d of exposure. M. truncata formed new and complete zooids at the normal site, whereas at the intermediate and low pH sites, neither partial nor complete zooids were produced. After 34 d at intermediate and low pH conditions, the organic cuticle which envelops the skeleton increased in thickness when compared to normal colonies, suggesting a protective role against dissolution of the high-Mg calcite skeleton. Significant changes in the protein profile and expression displayed by samples from intermediate and low pH conditions suggest that M. truncata makes an initial attempt to overcome the decrease in pH by up-regulating protein production but eventually, especially in the lowest pH condition, exhausts biochemical energy to maintain this rate of protein production, leading to eventual death. KEY WORDS: Ocean acidification · Bryozoa · Organic tissues · Protein · Growth · Mediterranean Sea · ­Myriapora truncata Full text in pdf format PreviousNextCite this article as: Lombardi C, Cocito S, Gambi MC, Cisterna B and others (2011) Effects of ocean acidification on growth, organic tissue and protein profile of the Mediterranean ­bryo­zoan Myriapora truncata . Aquat Biol 13:251-262. https://doi.org/10.3354/ab00376 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 13, No. 3. Online publication date: October 26, 2011 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2011 Inter-Research.

Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral

High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification technique. The mean δ(26)Mg values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were -0.87‰, -2.57‰, -2.34‰, and -2.43‰, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization. Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 °C to 19.5 °C: 1,000 × ln(α) = -2.63 (±0.076) + 0.0138 (±0.0051) × T(R(2) = 0.82, p < 0.01). The δ(26)Mg values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element partitioning and the calcification rate of biogenic CaCO(3), the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical control on Mg isotope fractionation for high-Mg calcite. On the other hand, δ(26)Mg in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges, and scaphopad, regardless of species differences of samples.

Twentieth century &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C variability in surface water dissolved inorganic carbon recorded by coralline algae in the northern North Pacific Ocean and the Bering Sea

Abstract. The oxygen isotopic composition and Mg/Ca ratios in the skeletons of long-lived coralline algae record ambient seawater temperature over time. Similarly, the carbon isotopic composition in the skeletons record δ13C values of ambient seawater dissolved inorganic carbon. Here, we measured δ13C in the coralline alga Clathromorphum nereostratum to test the feasibility of reconstructing the intrusion of anthropogenic CO2 into the northern North Pacific Ocean and Bering Sea. The δ13C was measured in the high Mg-calcite skeleton of three C. nereostratum specimens from two islands 500 km apart in the Aleutian archipelago. In the records spanning 1887 to 2003, the average decadal rate of decline in δ13C values increased from 0.03‰ yr−1 in the 1960s to 0.095‰ yr−1 in the 1990s, which was higher than expected due to solely the δ13C-Suess effect. Deeper water in this region exhibits higher concentrations of CO2 and low δ13C values. Transport of deeper water into surface water (i.e., upwelling) increases when the Aleutian Low is intensified. We hypothesized that the acceleration of the δ13C decline may result from increased upwelling from the 1960s to 1990s, which in turn was driven by increased intensity of the Aleutian Low. Detrended δ13C records also varied on 4–7 year and bidecadal timescales supporting an atmospheric teleconnection of tropical climate patterns to the northern North Pacific Ocean and Bering Sea manifested as changes in upwelling.

Coralline algal growth-increment widths archive North Atlantic climate variability

Over the past decade coralline algae have increasingly been used as archives of paleoclimate information. Encrusting coralline algae, which deposit annual growth increments in a high Mg-calcite skeleton, are amongst the longest-lived shallow marine organisms. In fact, a live-collected plant has recently been shown to have lived for at least 850 years based on radiometric dating. While a number of investigations have successfully used geochemical information of coralline algal skeletons to reconstruct sea surface temperatures, less attention has been paid to employ growth increment widths as a temperature proxy. Here we explore the relationship between growth and environmental parameters in Clathromorphum compactum collected in the subarctic Northwestern Atlantic. Results indicate that growth-increment widths of individual plants are poorly correlated with instrumental sea surface temperatures (SST). However, an averaged record of multiple growth increment-width time series from a regional network of C. compactum specimens up to 800 km apart reveals strong correlations with annual instrumental SST since 1950. Hence, similar to methods applied in dendrochronology, averaging of multiple sclerochronological records of coralline algae provides accurate climate information. A 115-year growth-increment width master chronology created from modern-collected and museum specimens is highly correlated to multidecadal variability seen in North Atlantic sea surface temperatures. Positive changes in algal growth anomalies record the well-documented regime shift and warming in the northwestern Atlantic during the 1990s. Large positive changes in algal growth anomalies were also present in the 1920s and 1930s, indicating that the impact of a concurrent large-scale regime shift throughout the North Atlantic was more strongly felt in the subarctic Northwestern Atlantic than previously thought, and may have even exceeded the 1990s event with respect to the magnitude of the warming.

Zigzag microstructure in rugose corals: A possible indicator of relative seawater Mg/Ca ratios

Low-Mg calcite (LMC) and high-Mg calcite (HMC) have been identified confidently as original biominerals in different rugose corals. Devonian Tabulophyllum had a LMC skeleton, whereas Pennsylvanian Lophophyllidium had a HMC skeleton. Zigzag microstructure, a diagenetic microstructure in rugose corals, may be related to early migration of Mg2+ ions during transformation of HMC into LMC. Therefore, zigzag microstructure may indicate that the original mineral was HMC even in specimens that subsequently converted to LMC. Stratigraphically, corals with zigzag microstructure are confined to the late Paleozoic, which is coincident with the “aragonite sea” of P.A. Sandberg. Hence, fluctuating Mg/Ca ratios may have directly controlled oscillations in marine carbonate chemistry and the mineral composition of rugose corals so that HMC skeletons (as indicated by zigzag microstructure) formed during intervals with “aragonite seas” and LMC skeletons (e.g., Tabulophyllum ) formed during intervals with “calcite seas.”

Palaeoenvironmental Signals and Growth Rates of Rhodoliths — a Geochemical Approach

Electron microprobe and stable isotope studies were undertaken on Recent rhodolith specimens (coralline red algae) in order to accurately determine their growth rates and palaeotemperature signal. Results show a cyclic variation of the Mg/Ca ratio and an amplitude of the oxygen isotope curve that accurately reflects the sea-surface temperature. Geochemical signals extracted from coral growth bands are commonly used as long term highresolution palaeoenvironmental indicators for reconstructing temperature and salinity variations of surface water masses. The main constraint in using corals is their limited geographical range of distribution, which is confined to tropical and subtropical seas. In order to deduce high resolution geochemical sea surface water signals from nontropical seas, mollusks have been employed by various authors in recent years. This paper introduces rhodoliths as a new organism for palaeoenvironmental analysis of tropical and non-tropical seas. Rhodoliths, which live in the subtidal zone to water depths of 100 m, are defined as nodules and unattached branched growths with a nodular form composed principally of coralline red algae (Bosence, 1983). The High-Mg calcite skeleton can exhibit different growth morphologies which range from spherical to ellipsoidal and can be thickly or thinly branching, with individual branches reaching up to lcm in diameter. Rhodolith morphology is a result of frequent overturning due to water motion (during storms) or biogenic activity (bottom feeding fish, inand epifaunal organisms). Vertical growth rates of coralline red algae are poorly studied but have been reported by various authors to range from 200 gm to 5 ram/year (see Edyvean and Ford (1987) for a compilation of growth rates). We have selected rhodoliths for geochemical studies because (1) they show well developed growth bands, (2) their geographic range spans from tropical to Arctic seas and (3) they exhibit longevity (specimens with an age of several hundred years have been reported; Bosellini and Ginsburg, 1971). This latter will allow us to eventually acquire palaeoenvironmental records dating back further than those derived from molluscan shells. This will have special importance for assessing Arctic records, which, if they are derived from mollusks, do not date back more than a few dozen years. For the present study we collected live (or partially living) specimens of Lithothamnium sp. from the southern Gulf of California, Mexico, where rhodoliths are the second most important carbonate producers after corals. Lithothamnium sp. is most abundant in 2 5 m water depth and individuals with diameters of up to 10 cm have been reported (Foster et al., 1997). For this study we prepared polished thick sections of branches with widths of up to 0.8 cm and lengths of up to 3.5 cm. The COADS SST data set for this site shows an average sea surface temperature range from 19.9-30.8~ however, the geochemical signal could be complicated by nearby seasonal upwelling events. Rhodolith thick sections were element mapped with an electron microprobe for Ca and Mg and individual growth bands were microsampled for stable isotope analysis using a bandwidth of 40 microns and a dril l depth of 60 microns. Complicating factors during the microsampling were the high concavity and slight irregularity of the growth bands and the extremly small sample size (<10 I-tg) that was obtained by drilling along growth bands for a maximum length of 3 mm.