We describe a completely randomizable flow-through outdoor mesocosm for climate change and ecotoxicology studies that was built with inexpensive materials. The 16 raceway tanks allow up to 6× water renewal per hour, avoiding changes in natural abiotic seawater conditions. We use an open-source hardware board (Arduino) that was adapted to control heaters and an innovative CO2 injection system. This system reduced seawater pH up to −0.9 units and increased temperature up to +6°C in three treatments and a control. Treatments can be continuously compared with the control and vary according to diel fluctuations, thus following the diel range observed in the sea. The mesocosm facility also includes an integrated secondary system of 48 aquaria for ecotoxicology studies. We validated the reproducibility and relevance of our experimental system by analyzing the variation of the total DNA of the microbial community extracted from corals in three elevated temperature scenarios during a 40-day experiment. We also present data from temperature, acidification, and copper contamination trials, which allowed continuous, reliable, and consistent treatment manipulations.
Posts Tagged 'methods'
A novel marine mesocosm facility to study global warming, water quality, and ocean acidification
Published 7 October 2015 Science ClosedTags: chemistry, field, mesocosms, methods
Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements
Published 29 September 2015 Science ClosedTags: Antarctic, chemistry, field, methods, South Atlantic
The oceans are a major sink for anthropogenic atmospheric carbon dioxide, and the uptake causes changes to the marine carbonate system and has wide ranging effects on flora and fauna. It is crucial to develop analytical systems that allow us to follow the increase in oceanic pCO2 and corresponding reduction in pH. Miniaturised sensor systems using immobilised fluorescence indicator spots are attractive for this purpose because of their simple design and low power requirements. The technology is increasingly used for oceanic dissolved oxygen measurements.
We present a detailed method on the use of immobilised fluorescence indicator spots to determine pH in ocean waters across the pH range 7.6–8.2. We characterised temperature (−0.046 pH/°C from 5 to 25 °C) and salinity dependences (−0.01 pH/psu over 5–35), and performed a preliminary investigation into the influence of chlorophyll on the pH measurement. The apparent pKa of the sensor spots was 6.93 at 20 °C. A drift of 0.00014 R (ca. 0.0004 pH, at 25 °C, salinity 35) was observed over a 3 day period in a laboratory based drift experiment. We achieved a precision of 0.0074 pH units, and observed a drift of 0.06 pH units during a test deployment of 5 week duration in the Southern Ocean as an underway surface ocean sensor, which was corrected for using certified reference materials. The temperature and salinity dependences were accounted for with the algorithm, R=0.00034−0.17·pH+0.15·S2+0.0067·T−0.0084·S·1.075R=0.00034−0.17·pH+0.15·S2+0.0067·T−0.0084·S·1.075.
This study provides a first step towards a pH optode system suitable for autonomous deployment. The use of a short duration low power illumination (LED current 0.2 mA, 5 μs illumination time) improved the lifetime and precision of the spot. Further improvements to the pH indicator spot operations include regular application of certified reference materials for drift correction and cross-calibration against a spectrophotometric pH system. Desirable future developments should involve novel fluorescence spots with improved response time and apparent pKa values closer to the pH of surface ocean waters.
Micromotor-based biomimetic carbon dioxide sequestration: towards mobile microscrubbers
Published 25 September 2015 Science ClosedTags: methods, mitigation
We describe a mobile CO2 scrubbing platform that offers a greatly accelerated biomimetic sequestration based on a self-propelled carbonic anhydrase (CA) functionalized micromotor. The CO2 hydration capability of CA is coupled with the rapid movement of catalytic micromotors, and along with the corresponding fluid dynamics, results in a highly efficient mobile CO2 scrubbing microsystem. The continuous movement of CA and enhanced mass transport of the CO2 substrate lead to significant improvements in the sequestration efficiency and speed over stationary immobilized or free CA platforms. This system is a promising approach to rapid and enhanced CO2 sequestration platforms for addressing growing concerns over the buildup of greenhouse gas.
Micro-CT analysis of the Caribbean octocoral Eunicea flexuosa subjected to elevated pCO2
Published 21 September 2015 Science ClosedTags: biological response, corals, growth, laboratory, methods, morphology, North Atlantic
Rising anthropogenic carbon dioxide has resulted in a drop in ocean pH, a phenomenon known as ocean acidification (OA). These acidified waters have many ramifications for diverse marine biota, especially those species which precipitate calcium carbonate skeletons. The permanence of coral reef ecosystems is therefore closely related to OA stress as habitat-forming corals will exhibit reduced calcification and growth. Relatively little is known concerning the fate of other constituent taxa which may either suffer concomitant declines or be competitively favoured in acidified waters. Here, we experimentally (49 d) test the effects of next century predictions for OA (pH = 7.75, pCO2 = 1081 µatm) vs. near-present-day conditions (pH = 8.01, pCO2 = 498 µatm) on the common Caribbean octocoral Eunicea flexuosa. We measure linear extension of this octocoral and use a novel technique, high-resolution micro-computed tomography, to measure potential differences in the morphology of calcified internal skeletal structures (sclerites) in a 2 mm apical section of each branch. Despite the use of highly accurate procedures, we found no significant differences between treatments in either the growth of E. flexuosa branches or the structure of their sclerites. Our results suggest a degree of resilience to OA stress and provide evidence that this octocoral species may persist on Caribbean coral reefs, despite global change.
Mussel shells of Mytilus edulis as bioarchives of the rare earth elements and yttrium distribution in seawater and the potential impact of pH and temperature on the partitioning behaviour
Published 11 September 2015 Science ClosedTags: individualmodeling, methods, modeling, paleo
Mussel shells are potential bioarchives of proxies for changes of the physico-chemical conditions in the bivalve’s habitat. One such proxy is the distribution of the Rare Earths and Yttrium (REY) in seawater, as REY speciation in seawater is sensitive to pH and temperature variations, due to the impact of these parameters on the activity of CO32− in seawater. We present a new protocol for sample preparation and determination of REY concentrations in bivalve shells, that includes sample treatment with NaOCl followed by REY separation and preconcentration. The data obtained was further used to calculate REY partition coefficients between shells of M. edulis and ambient seawater, and acquired results were then used in the investigation of the potential effects of pH and temperature on REY partitioning.
Shells of M. edulis mussels from the North Sea show consistent shale-normalized (“SN”) REY patterns that increase from the light REY to the middle REY and decrease from the middle REY to the heavy REY. Despite being different to the general seawater REYSN pattern, the shells still display distinct REY features of seawater such as a negative CeSN anomaly and small positive YSN and GdSN anomalies. Apparent partition coefficients for the REY between the shell and seawater (appDREYshell/seawater) are low and decrease strongly from the light REY (4.04 for La) to the heavy REY (0.34 for Lu). However, assuming that only the free REY3+ are incorporated into the shell, appDREY3+shell/seawater values are higher and rather similar for all REY (102.46 for La; 113.44 for Lu), but show a slight maximum at Tb (199.18). Although the impact of vital effects i.e. REY speciation in a mussel’s extrapallial fluid from which the carbonate minerals precipitate, cannot be quantified yet, it appears that M. edulis shells are bioarchives of some REY features of seawater.
We modelled the REYSN patterns of a hypothetical mussel shell at pH 8.2 and 7.6 and at temperatures of 25 and 5 °C assuming that only REY3+ are incorporated into the carbonate’s crystal lattice. The results suggest that with lower pH, REY concentrations in a shells increase, but with little effect on the shape of the REYSN patterns, while a temperature change has an impact on the REYSN pattern, but only minor effects on REY concentrations.
A new method for calibrating a boron isotope paleo-pH proxy using massive Porites corals
Published 9 September 2015 Science ClosedTags: chemistry, methods, paleo
The boron isotope ratio (δ11B) of marine biogenic carbonates can reconstruct pH and pCO2 of seawater, and potentially CO2 concentration in the atmosphere. To date, δ11B-pHSW calibration has been proposed via culturing experiments, where calcifying organisms are cultured under artificially acidified seawater. However, in scleractinian corals, reconstructed pH values using culture-based calibrations do not agree well with actual observations of seawater CO2 chemistry. Thus, another approach is needed to establish a more reliable calibration method. In this study, we established field-based calibrations for Chichijima and Tahiti, both located in subtropical gyres where surface seawater is close to CO2 equilibrium. We suggest a new approach to calibration of δ11B-pH in which the long-term δ11B variation of massive Porites corals is compared with the decreasing pH trend (i.e., ocean acidification) that has occurred since the Industrial Revolution. This calibration will offer a new avenue for studying seawater CO2 chemistry using coral δ11B in diverse settings, such as upwelling regions, coral reefs, and coastal areas. This article is protected by copyright. All rights reserved.
An automated procedure for laboratory and shipboard spectrophotometric measurements of seawater alkalinity: Continuously monitored single-step acid additions
Published 21 August 2015 Science ClosedTags: chemistry, field, methods
Building on the spectrophotometric procedure of Yao and Byrne (1998), an automated analysis system has been developed for laboratory and shipboard measurements of total alkalinity at a rate of 6 samples per hour. The system is based on single-point hydrochloric acid (HCl) titrations of seawater samples of a known volume with bromocresol purple as an indicator. The titration is continuously monitored using visible spectroscopy to guide the titration rate according to the real-time pH of the samples. Each titration is terminated just below the equivalence point to achieve a precision and accuracy near 1 μmol kg− 1.
Bryozoans in climate and ocean acidification research: A reappraisal of an under-used tool
Published 20 August 2015 Science ClosedTags: biological response, bryozoa, methods, paleo, review
Bryozoans are colonial animals that are widely distributed in marine benthic environments and play an important role in temperate and cold-water oceanic shelves as habitat providers. Morphologically and mineralogically diverse, bryozoans are important carbonate producers with an extensive fossil record, which makes them good indicators in environmental and (paleo) environmental research. Existing data, though insufficient, suggests that bryozoans can become a valuable tool in investigating present-day climate change. This paper reviews the major characteristics of bryozoans, their function in shallow oceanic areas worldwide, and their potential as proxy organisms in climate and ocean acidification research.
Red coralline algae and climate change: growth, magnesium concentration variability and the development of a new palaeoclimate proxy
Published 20 August 2015 Science ClosedTags: algae, biological response, growth, laboratory, methods, morphology, multiple factors, North Atlantic, paleo, temperature
Past ocean acidification recorded in the geological record facilitates the understanding of rates and influences of contemporary pCO2 enrichment. High resolution proxies of pCO2 and pH can be used to reconstruct components of the palaeocarbonate system. At present, most pH reconstructions are made using boron isotopes, however, there is some uncertainty associated with vital effects and isotopic fractionation. In addition to contemporary ocean acidification, marine organisms currently experience thermal stress associated with increasing atmospheric temperatures. Here we present a study of the influences of multiple stressors on the growth and structure of a marine carbonate, predicted to occur within this century, and a novel structural proxy for carbonate chemistry; Mg-O bond strength in coralline algae. Free living Lithothamnion glaciale algae were incubated in control (380ppm pCO2), moderate acidification (750ppm pCO2) and high acidification (1000ppm pCO2) at ambient and enhanced (+2°C) temperature conditions for 24 months. Coralline algae growth (linear extension) was highly dependent on temperature, with +2°C samples experiencing significantly reduced growth. No significant correlation was found between pCO2 and growth, indicating L. glaciale’s ability to acclimatize. Relative magnesium concentration and Mg-O bond strength within the high-Mg skeleton cyclically over an annual cycle. For all seasons there was a positive linear relationship between pCO2 concentration and bond strength mediated by positional disorder of the calcite lattice. Structural preservation of the carbonate chemistry system in coralline algal high Mg calcite represents an alternative approach to reconstructing marine carbonate chemistry parameters based on skeletal structure rather than chemistry.
A toolbox for secondary quality control on ocean chemistry and hydrographic data
Published 17 August 2015 Science ClosedTags: chemistry, methods
High quality, reference measurements of chemical and physical properties of seawater are of great importance for a wide research community, including the need to validate models and attempts to quantify spatial and temporal variability. Whereas data precision has been improved by technological advances, the data accuracy has improved mainly by the use of certified reference materials (CRMs). However, since CRMs are not available for all variables, and use of CRMs does not guarantee bias-free data, we here present a recently developed Matlab toolbox for performing so-called secondary quality control on oceanographic data by the use of crossover analysis. This method and how it has been implemented in this toolbox is described in detail. This toolbox is developed mainly for use by sea-going scientists as a tool for quickly assessing possible bias in the measurements that can—hopefully—be remedied during the expedition, but also for possible post-cruise adjustment of data to be consistent with previous measurements in the region. The toolbox, and reference data, can be downloaded from the Carbon Dioxide Information Analysis Center (CDIAC): http://cdiac.ornl.gov/ftp/oceans/2nd_QC_Tool_V2/.
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Assessing the impact of diagenesis on δ11B, δ13C, δ18O, Sr/Ca and B/Ca values in fossil planktic foraminiferal calcite
Published 13 August 2015 Science ClosedTags: biological response, chemistry, methods, paleo, protists
The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test, biasing any resulting paleoenvironmental reconstruction. The δ11B of planktic foraminiferal calcite is a promising ocean pH-proxy but the effect of diagenesis is still poorly known. Here we present new δ11B, δ13C, δ18O, Sr/Ca and B/Ca data from multiple species of planktic foraminifera from time-equivalent samples for two low latitude sites: clay-rich Tanzanian Drilling Project (TDP) Site 18 from the Indian Ocean containing well-preserved (‘glassy’) foraminifera and carbonate-rich Ocean Drilling Program (ODP) Site 865 from the central Pacific Ocean hosting recrystallized (‘frosty’) foraminifera. Our approach makes the assumption that environmental conditions were initially similar at both sites so most chemical differences are attributable to diagenesis. Planktic foraminiferal δ18O and δ13C records show offsets in both relative and absolute values between the two sites consistent with earlier findings that these isotopic ratios are strongly influenced by diagenetic alteration. Sr/Ca and B/Ca ratios in planktic foraminiferal calcite are also offset between the two sites but there is little change in the relative difference between surface and deep dwelling taxa. In contrast, δ11B values indicate no large differences between well-preserved and recrystallized foraminifera suggesting that despite extensive diagenetic alteration the δ11B of biogenic calcite appears robust, potentially indicative of a lack of free exchange of boron between pore fluids and the recrystallizing CaCO3. Our finding may remove one potential source of uncertainty in δ11B based pH reconstructions and provide us with greater confidence in our ability to reconstruct pH in the ancient oceans from at least some recrystallized foraminiferal calcite. However, further investigations should extend this approach to test the robustness of our findings across a range of taphonomies, ages and burial settings.
Contextualizing the impact of ocean acidification on veliger growth for three commercially important bivalve molluscs
Published 12 August 2015 Science ClosedTags: biological response, methods, mollusks, morphology, review
The impact of ocean acidification on the growth rate of bivalve veligers for three commercially important species (Crassostrea gigas, Crassostrea virginica and Mytilus edulis) has been assessed experimentally for the last decade. Based on the results correlating an increase in pCO2 with a reduction in growth rate, these studies have concluded that ocean acidification will have a strong impact on veligers. This study reassesses these results in the context of temperature dependant growth curves derived from historical benchmarks of veliger growth rates. Most of the ocean acidification data points fall within the confidence interval identified by the historical data. This study concludes that in terms of shell growth, ocean acidification exerts a minimal influence on maximum shell length. The differences in experimental methodologies are compared, and the different metrics used to relate ocean acidification to growth are discussed. Recommendations are included for future research and governmental action towards ocean acidification.
Stable carbon isotope fractionation of organic cyst-forming dinoflagellates: Evaluating the potential for a CO2 proxy
Published 12 August 2015 Science ClosedTags: biological response, growth, laboratory, methods, paleo, phytoplankton, primary production
Over the past decades, significant progress has been made regarding the quantification and mechanistic understanding of stable carbon isotope fractionation (13C fractionation) in photosynthetic unicellular organisms in response to changes in the partial pressure of atmospheric CO2 (pCO2). However, hardly any data is available for organic cyst-forming dinoflagellates while this is an ecologically important group with a unique fossil record. We performed dilute batch experiments with four harmful dinoflagellate species known for their ability to form organic cysts: Alexandrium tamarense, Scrippsiella trochoidea, Gonyaulax spinifera and Protoceratium reticulatum. Cells were grown at a range of dissolved CO2 concentrations characterizing past, modern and projected future values (∼5–50 μmol L−1), representing atmospheric pCO2 of 180, 380, 800 and 1200 μatm. In all tested species, 13C fractionation depends on CO2 with a slope of up to 0.17‰ (μmol L)−1. Even more consistent correlations were found between 13C fractionation and the combined effects of particulate organic carbon quota (POC quota; pg C cell−1) and CO2. Carbon isotope fractionation as well as its response to CO2 is species-specific. These results may be interpreted as a first step towards a proxy for past pCO2 based on carbon isotope ratios of fossil organic dinoflagellate cysts. However, additional culture experiments focusing on environmental variables other than pCO2, physiological underpinning of the recorded response, testing for possible offsets in 13C values between cells and cysts, as well as field calibration studies are required to establish a reliable proxy.
Evaluating the utility of B/Ca ratios in planktic foraminifera as a proxy for the carbonate system: A case study of Globigerinoides ruber
Published 12 August 2015 Science ClosedTags: biological response, chemistry, field, laboratory, methods, protists, sediment
B/Ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system. However, the carbonate system controls on B/Ca ratios are not straightforward, with Δ[ inline image] ([ inline image]in situ – [ inline image]at saturation) correlating best with B/Ca ratios in benthic foraminifera, rather than pH, inline image, or inline image (as a simple model of boron speciation in seawater and incorporation into CaCO3 would predict). Furthermore, culture experiments have shown that in planktic foraminifera properties such as salinity and [B]sw can have profound effects on B/Ca ratios beyond those predicted by simple partition coefficients. Here, we investigate the controls on B/Ca ratios in G. ruber via a combination of culture experiments and core-top measurements, and add to a growing body of evidence that suggests B/Ca ratios in symbiont-bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions. We find that while B/Ca ratios in culture experiments covary with pH, in open ocean sediments this relationship is not seen. In fact, our B/Ca data correlate best with [ inline image] (a previously undocumented association) and in most regions, salinity. These findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite. Regardless, our results underscore the need for caution when attempting to interpret B/Ca records in terms of the ocean carbonate system, at the very least in the case of mixed-layer planktic foraminifera.
Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured Arctica islandica (update)
Published 11 August 2015 Science ClosedTags: chemistry, methods, paleo
Ocean acidification, the decrease in ocean pH associated with increasing atmospheric CO2, is likely to impact marine organisms, particularly those that produce carbonate skeletons or shells. Therefore, it is important to investigate how environmental factors (seawater pH, temperature and salinity) influence the chemical compositions in biogenic carbonates. In this study we report the first high-resolution strontium (87Sr / 86Sr and δ88 / 86Sr) and boron (δ11B) isotopic values in the aragonite shell of cultured Arctica islandica (A. islandica). The 87Sr / 86Sr ratios from both tank water and shell samples show ratios nearly identical to the open ocean, which suggests that the shell material reflects ambient ocean chemistry without terrestrial influence. The 84Sr–87Sr double-spike-resolved shell δ88 / 86Sr and Sr concentration data show no resolvable change throughout the culture period and reflect no theoretical kinetic mass fractionation throughout the experiment despite a temperature change of more than 15 °C. The δ11B records from the experiment show at least a 5‰ increase through the 29-week culture season (January 2010–August 2010), with low values from the beginning to week 19 and higher values thereafter. The larger range in δ11B in this experiment compared to predictions based on other carbonate organisms (2–3‰) suggests that a species-specific fractionation factor may be required. A significant correlation between the ΔpH (pHshell − pHsw) and seawater pH (pHsw) was observed (R2 = 0.35), where the pHshell is the calcification pH of the shell calculated from boron isotopic composition. This negative correlation suggests that A. islandica partly regulates the pH of the extrapallial fluid. However, this proposed mechanism only explains approximately 35% of the variance in the δ11B data. Instead, a rapid rise in δ11B of the shell material after week 19, during the summer, suggests that the boron uptake changes when a thermal threshold of > 13 °C is reached.
Incentivizing innovation for the oceans and beyond
Published 7 August 2015 Science ClosedTags: chemistry, methods
For over a decade, XPRIZE has been the leader in incentivized global prize competitions. Historically, such competitions have radically changed the world by spurring the rapid innovation of technologies to address societal challenges. XPRIZE currently has four active global competitions, including the $2 million Wendy Schmidt Ocean Health XPRIZE to develop accurate, robust, and affordable pH sensors to improve our understanding of ocean acidification. This addresses the grand challenge of the overwhelming lack of data on our oceans. Innovations are expected to emerge from this competition that could be adapted to other ocean sensors, including portability, ease of deployment and recovery, solutions to address power and biofouling limitations, and data recovery using modern software and wireless capabilities. This competition is part of the XPRIZE Ocean Initiative, which is a suite of five ocean XPRIZE competitions that, over 10 years, will award millions of dollars to innovators who can solve some of the grand challenges facing the ocean. Collectively, these ocean-focused prizes aim to achieve the XPRIZE vision of a healthy, valued, and understood ocean.
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Simultaneous determination of δ11B and B/Ca ratio in marine biogenic carbonates at nanogram level
Published 5 August 2015 Science ClosedTags: chemistry, methods, paleo
In this study we introduce a new in situ technique which allows the determination of the boron isotopic composition and B/Ca ratios simultaneously at the nanogram level using a combination of optical emission spectroscopy and multiple ion counting MC ICP-MS with laser ablation. This technique offers a new application in the paleo-field of oceanography and climatology since small samples like e.g. single foraminiferal shells can be analyzed. The simultaneous determination of the boron isotopic composition and B/Ca ratios provides two independent proxies which allow the reconstruction of the full carbonate system. To test the new technique we performed measurements on the cultured, benthic foraminifer Amphistegina lessonii. Our results yielded an average boron isotopic composition δ11B = 18.0 ± 0.83‰ (SD) with an average internal precision of 0.52‰ (RSE). The boron concentration was 53 ± 7 μg/g (SD). These results agree with the range reported in the literature. The reconstructed mean pH value is in excellent agreement with the measured pH of the seawater in which the foraminifers grew.
The analysis of a foraminifer consumed approximately 1200 ng calcium carbonate containing ca. 0.06 ng boron. Compared to bulk analytical methods, this new technique requires less material and reduces the time for sample preparation.
Ocean acidification and marine microorganisms: responses and consequences
Published 5 August 2015 Science ClosedTags: abundance, biological response, BRcommunity, community composition, methods, nitrogen fixation, otherprocess, physiology, phytoplankton, primary production, prokaryotes, review
Ocean acidification (OA) is one of the global issues caused by rising atmospheric CO2. The rising pCO2 and resulting pH decrease has altered ocean carbonate chemistry. Microbes are key components of marine environments involved in nutrient cycles and carbon flow in marine ecosystems. However, these marine microbes and the microbial processes are sensitive to ocean pH shift. Thus, OA affects the microbial diversity, primary productivity and trace gases emission in oceans. Apart from that, it can also manipulate the microbial activities such as quorum sensing, extracellular enzyme activity and nitrogen cycling. Short-term laboratory experiments, mesocosm studies and changing marine diversity scenarios have illustrated undesirable effects of OA on marine microorganisms and ecosystems. However, from the microbial perspective, the current understanding on effect of OA is based mainly on limited experimental studies. It is challenging to predict response of marine microbes based on such experiments for this complex process. To study the response of marine microbes towards OA, multiple approaches should be implemented by using functional genomics, new generation microscopy, small-scale interaction among organisms and/or between organic matter and organisms. This review focuses on the response of marine microorganisms to OA and the experimental approaches to investigate the effect of changing ocean carbonate chemistry on microbial mediated processes.
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Coralline red algae: a proxy in climate and ocean acidification studies
Published 4 August 2015 Science ClosedTags: algae, biological response, chemistry, methods, paleo, review
Coralline red algae (Corallinaceae, Rhodophyta) play a major role in the ecology and structure of photic hard bottoms as well as many soft bottoms throughout the world oceans. As major calcifying organisms widely distributed in shallow marine systems and with an extensive fossil record, they can be used as an ideal proxy in environmental and (paleo)climate studies. This paper aims to be a short overview of the major characteristics of corallines as major important carbonate producers in shallow coastal marine areas worldwide and its value as a proxy in climate and ocean acidification research.
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Ocean acidification has different effects on the production of DMS and DMSP measured in cultures of Emiliania huxleyi and a mesocosm study: a comparison of laboratory monocultures and community interactions
Published 23 July 2015 Science ClosedTags: biogeochemistry, biological response, BRcommunity, field, laboratory, mesocosms, methods, phytoplankton, primary production
The human-induced rise in atmospheric carbon dioxide since the industrial revolution has led to increasing oceanic carbon uptake and changes in seawater carbonate chemistry, resulting in lowering of surface water pH. In this study we investigated the effect of increasing pCO2 on concentrations of volatile biogenic dimethylsulphide (DMS) and its precursor dimethylsulphoniopropionate (DMSP), through monoculture studies and community pCO2 perturbation. DMS is a climatically important gas produced by many marine algae: it transfers sulphur into the atmosphere and is a major influence on biogeochemical climate regulation through breakdown to sulphate and formation of subsequent cloud condensation nuclei (CCN). Overall, production of DMS and DMSP by the coccolithophore Emiliania huxleyi strain RCC1229 was unaffected by growth at 900 µatm pCO2, but DMSP production normalised to cell volume was 12% lower at the higher pCO2 treatment. These cultures were compared with community DMS and DMSP production during an elevated pCO2 mesocosm experiment with the aim of studying E. huxleyi in the natural environment. Results contrasted with the culture experiments and showed reductions in community DMS and DMSP concentrations of up to 60% and 32% respectively at pCO2 up to 3000 µatm, with changes attributed to poorer growth of DMSP-producing nanophytoplankton species, including E. huxleyi, and potentially increased microbial consumption of DMS and dissolved DMSP at higher pCO2. DMS and DMSP production differences between culture and community likely arise from pH affecting the inter-species responses between microbial producers and consumers.
