Future pCO2 Research Articles

Ocean acidification and warming scenarios increase microbioerosion of coral skeletons

Biological mediation of carbonate dissolution represents a fundamental component of the destructive forces acting on coral reef ecosystems. Whereas ocean acidification can increase dissolution of carbonate substrates, the combined impact of ocean acidification and warming on the microbioerosion of coral skeletons remains unknown. Here, we exposed skeletons of the reef-building corals, Porites cylindrica and Isopora cuneata, to present-day (Control: 400 μatm - 24°C) and future pCO2 -temperature scenarios projected for the end of the century (Medium: +230 μatm - +2°C; High: +610 μatm - +4°C). Skeletons were also subjected to permanent darkness with initial sodium hypochlorite incubation, and natural light without sodium hypochlorite incubation to isolate the environmental effect of acidic seawater (i.e., Ωaragonite <1) from the biological effect of photosynthetic microborers. Our results indicated that skeletal dissolution is predominantly driven by photosynthetic microborers, as samples held in the dark did not decalcify. In contrast, dissolution of skeletons exposed to light increased under elevated pCO2 -temperature scenarios, with P. cylindrica experiencing higher dissolution rates per month (89%) than I. cuneata (46%) in the high treatment relative to control. The effects of future pCO2 -temperature scenarios on the structure of endolithic communities were only identified in P. cylindrica and were mostly associated with a higher abundance of the green algae Ostreobium spp. Enhanced skeletal dissolution was also associated with increased endolithic biomass and respiration under elevated pCO2 -temperature scenarios. Our results suggest that future projections of ocean acidification and warming will lead to increased rates of microbioerosion. However, the magnitude of bioerosion responses may depend on the structural properties of coral skeletons, with a range of implications for reef carbonate losses under warmer and more acidic oceans.

Impact of ocean acidification on escape performance of the king scallop, Pecten maximus, from Norway

The ongoing process of ocean acidification already affects marine life, and according to the concept of oxygen and capacity limitation of thermal tolerance, these effects may be intensified at the borders of the thermal tolerance window. We studied the effects of elevated CO2 concentrations on clapping performance and energy metabolism of the commercially important scallop Pecten maximus. Individuals were exposed for at least 30 days to 4 °C (winter) or to 10 °C (spring/summer) at either ambient (0.04 kPa, normocapnia) or predicted future PCO2 levels (0.11 kPa, hypercapnia). Cold-exposed (4 °C) groups revealed thermal stress exacerbated by PCO2 indicated by a high mortality overall and its increase from 55 % under normocapnia to 90 % under hypercapnia. We therefore excluded the 4 °C groups from further experimentation. Scallops at 10 °C showed impaired clapping performance following hypercapnic exposure. Force production was significantly reduced although the number of claps was unchanged between normocapnia- and hypercapnia-exposed scallops. The difference between maximal and resting metabolic rate (aerobic scope) of the hypercapnic scallops was significantly reduced compared with normocapnic animals, indicating a reduction in net aerobic scope. Our data confirm that ocean acidification narrows the thermal tolerance range of scallops resulting in elevated vulnerability to temperature extremes and impairs the animal’s performance capacity with potentially detrimental consequences for its fitness and survival in the ocean of tomorrow.

Appropriate pCO2 treatments in ocean acidification experiments

Experiments in which organisms are reared in treatments simulating current and future pCO2 concentrations are critical for ocean acidification (OA) research. The majority of OA exposure experiments use average atmospheric pCO2 levels as a baseline treatment. We conducted an ecoregion-scale analysis of global carbon chemistry datasets. For many locales, atmospheric pCO2 levels are not an appropriate characterization of marine carbon chemistry. We argue that atmospheric pCO2 should be disregarded when setting baseline treatment conditions and experimental design should rely on measurements of carbon chemistry in a study subject’s habitat. As carbon chemistry conditions vary with space and time, we suggest using a range of pCO2 values as a control rather than a single value. We illustrate this issue with data on the habitat of Euphausia pacifica, which currently lives in waters with a pCO2 around 900 μatm, a concentration much higher than the current global atmospheric mean.

Effects of ocean acidification on different life-cycle stages of the kelp Laminaria hyperborea (Phaeophyceae)

Abstract Our objective for this study was to evaluate the influence of preindustrial and expected future atmospheric CO2 concentrations (280 μatm and 700 μatm pCO2, respectively) on different life-cycle stages of the kelp Laminaria hyperborea from Helgoland (Germany, North Sea). Zoospore germination, gametogenesis, vegetative growth, sorus formation and photosynthetic performance of vegetative and fertile tissue were examined. The contribution of external carbonic anhydrase (exCA) to C-supply for net-photosynthesis (net-PS) and the Chla- and phlorotannin content were investigated. Female gametogenesis and vegetative growth of sporophytes were significantly enhanced under the expected future pCO2. rETR(max) and net-PS of young vegetative sporophytes tended to increase performance at higher pCO2. The trend towards elevated net-PS vanished after inhibition of exCA. In vegetative sporophytes, phlorotannin content and Chla content were not significantly affected by pCO2.

Effect of elevated pCO2 on the production of dimethylsulphoniopropionate (DMSP) and dimethylsulphide (DMS) in two species of Ulva (Chlorophyceae)

Concentrations of the secondary algal metabolite dimethylsulphoniopropionate (DMSP) and its breakdown product, the climate-active trace gas dimethylsulphide (DMS), are sensitive to changes in pCO2. Data on the response of marine macroalgae to future pCO2 levels are lacking. Here we report the first measurements of DMSP and DMS production in two species of chlorophyte macroalgae (Ulva lactuca and U. clathrata). Laboratory cultures were grown in pH–stated medium that received pulses of CO2 to create pCO2 conditions ranging from ambient (432 μatm) to future (1514 μatm). Intracellular concentration of DMSP remained unaffected in both species (101 ± 21 and 69 ± 20 mmol g−1 FW in U. lactuca and U. clathrata, respectively) but significant differences in extracellular production of DMSP and DMS were observed for U. lactuca: Whilst production of total DMSP (the sum of external DMSP and DMS) was different between replicated experiments, the percentage of total DMSP produced throughout each experiment increased significantly by up to 65% with increasing pCO2 to 1514 μatm. In contrast, DMS production decreased from 0.4 to 0.25 nmol g−1 FW h−1. This decrease was not a linear function of pCO2 but an almost 50% step-wise loss of DMS production was indicated between 635 and 884 μatm, a pCO2 predicted for the next 100 years. Since Ulva spp. form massive harmful blooms (‘green tides’) that can occur free-floating and faraway (>100 km) from the coast, they may provide a locally significant source of DMS to the remote marine boundary layer.

Dynamics of extracellular enzyme activities in seawater under changed atmospheric pCO2: a mesocosm investigation

As part of the PeECE II mesocosm project, we investigated the effects of pCO2 levels on the initial step of heterotrophic carbon cycling in the surface ocean. The activities of microbial extracellular enzymes hydrolyzing 4 polysaccharides were measured during the development of a natural phytoplankton bloom under pCO2 conditions representing glacial (190 µatm) and future (750 µatm) atmospheric pCO2. We observed that (1) chondroitin hydrolysis was variable throughout the pre-, early- and late-bloom phases, (2) fucoidanase activity was measurable only in the glacial mesocosm as the bloom developed, (3) laminarinase activity was low and constant, and (4) xylanase activity declined as the bloom progressed. Concurrent measurements of microbial community composition, using denaturing-gradient gel electrophoresis (DGGE), showed that the 2 mesocosms diverged temporally, and from one another, especially in the late-bloom phase. Enzyme activities correlated with bloom phase and pCO2, suggesting functional as well as compositional changes in microbial communities in the different pCO2 environments. These changes, however, may be a response to temporal changes in the development of phytoplankton communities that differed with the pCO2 environment. We hypothesize that the phytoplankton communities produced dissolved organic carbon (DOC) differing in composition, a hypothesis supported by changing amino acid composition of the DOC, and that enzyme activities responded to changes in substrates. Enzyme activities observed under different pCO2 conditions likely reflect both genetic and population-level responses to changes occurring among multiple components of the microbial loop.

Effects of increased pCO2 and temperature on the North Atlantic spring bloom. I. The phytoplankton community and biogeochemical response

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 388:13-25 (2009) - DOI: https://doi.org/10.3354/meps08133 Effects of increased pCO2 and temperature on the North Atlantic spring bloom. I. The phytoplankton community and biogeochemical response Yuanyuan Feng1,8, Clinton E. Hare1, Karine Leblanc1,9,10, Julie M. Rose1,11, Yaohong Zhang1, Giacomo R. DiTullio2, Peter A. Lee2, Steven W. Wilhelm3, Janet M. Rowe3,12, Jun Sun4, Nina Nemcek5, Celine Gueguen5,13, Uta Passow6, Ina Benner6, Christopher Brown7, David A. Hutchins1,8,* 1College of Marine and Earth Studies, University of Delaware, 700 Pilottown Road, Lewes, Delaware 19958, USA 2Hollings Marine Laboratory, College of Charleston, 331 Fort Johnson Road, Charleston, South Carolina 29412, USA 3Department of Microbiology, University of Tennessee, 1414 West Cumberland Ave, Knoxville, Tennessee 37996, USA 4Key Laboratory of Marine Ecology and Environmental Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China 5Department of Earth and Ocean Science, The University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada 6Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27568, Germany 7Earth System Science Interdisciplinary Center, University of Maryland Research Park (M-Square), 5825 University Research Ct, Ste 4001, College Park, Maryland 20740, USA 8Present address: Department of Biological Sciences, University of Southern California, 3616 Trousdale Parkway, Los Angeles, California 90089, USA 9Present address: Aix-Marseille Université, CNRS, LOB-UMR 6535, Laboratoire d’Océanographie et de Biogéochimie, OSU/Centre d’Océanologie de Marseille, 163 Avenue de Luminy, 13288 Marseille Cedex 09, France 10Present address: CNRS (CNRS/INSU), UMR 6535, Campus de Luminy Case 901, 163 Avenue de Luminy, 13288 Marseille Cedex 09, France 11Present address: Biology Department, MS #32, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA 12Present address: Department of Biological Sciences, The University of Nebraska, 204 Morrison Center Lincoln, Nebraska 68583-0900, USA 13Present address: Department of Chemistry, Trent University, 1600 West Bank Drive, Peterborough, Ontario K9J 7B8, Canada *Corresponding author. Email: dahutch@usc.edu ABSTRACT: The North Atlantic spring bloom is one of the largest annual biological events in the ocean, and is characterized by dominance transitions from siliceous (diatoms) to calcareous (coccolithophores) algal groups. To study the effects of future global change on these phytoplankton and the biogeochemical cycles they mediate, a shipboard continuous culture experiment (Ecostat) was conducted in June 2005 during this transition period. Four treatments were examined: (1) 12°C and 390 ppm CO2 (ambient control), (2) 12°C and 690 ppm CO2 (high pCO2), (3) 16°C and 390 ppm CO2 (high temperature), and (4) 16°C and 690 ppm CO2 (‘greenhouse’). Nutrient availability in all treatments was designed to reproduce the low silicate conditions typical of this late stage of the bloom. Both elevated pCO2 and temperature resulted in changes in phytoplankton community structure. Increased temperature promoted whole community photosynthesis and particulate organic carbon (POC) production rates per unit chlorophyll a. Despite much higher coccolithophore abundance in the greenhouse treatment, particulate inorganic carbon production (calcification) was significantly decreased by the combination of increased pCO2 and temperature. Our experiments suggest that future trends during the bloom could include greatly reduced export of calcium carbonate relative to POC, thus providing a potential negative feedback to atmospheric CO2 concentration. Other trends with potential climate feedback effects include decreased community biogenic silica to POC ratios at higher temperature. These shipboard experiments suggest the need to examine whether future pCO2 and temperature increases on longer decadal timescales will similarly alter the biological and biogeochemical dynamics of the North Atlantic spring bloom. KEY WORDS: Ocean acidification · Global change · Carbon dioxide · Temperature · Coccolithophores · Diatoms · Calcification · North Atlantic bloom Full text in pdf format PreviousNextCite this article as: Feng Y, Hare CE, Leblanc K, Rose JM and others (2009) Effects of increased pCO2 and temperature on the North Atlantic spring bloom. I. The phytoplankton community and biogeochemical response. Mar Ecol Prog Ser 388:13-25. https://doi.org/10.3354/meps08133 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 388. Online publication date: August 19, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Testing the effect of CO2 concentration on the dynamics of marine heterotrophic bacterioplankton

To date no study exists that directly addresses changes in dynamics of heterotrophic bacteria in surface waters in relation to partial pressure of CO 2 (pCO2). Therefore, we studied the effect of changes in pCO2 on bacterial abundance and activities by using mesocosms with different pCO2 levels (;190, ;370, and ;700 ppmV, representing past, present-day, and future atmospheric pCO2, respectively). Abundance of total bacteria did not differ with increasing pCO2 throughout the whole study period, whereas bacterial protein production (BPP) was highest at highest pCO2. This effect was even more pronounced for cell-specific production rates, especially those of attached bacteria, which were up to 25 times higher than those of free bacteria. During the breakdown of the bloom, however, the abundance of both free and attached bacteria was significantly increased with pCO 2. Differences in bacterial growth rate (m) were smaller than those of BPP, but both m and BPP of attached bacteria were elevated under high pCO2. Averages of total protease as well as a- and b-glucosidase activities were highest at elevated pCO 2 levels, but a statistically significant dependence on pCO 2 was only evident for protease activity. There is a measurable but indirect effect of changes in pCO2 on bacterial activities that are mainly linked to phytoplankton and presumably particle dynamics.

Is atmospheric CO2 a selective agent on model C3 annuals?

Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene and is projected to increase from 36 to 70 Pa CO2 before the end of the 21st century. High pCO2 often increases the growth and reproduction of C3 annuals, whereas low pCO2 decreases growth and may reduce or prevent reproduction. Previous predictions regarding the effects of high and low pCO2 on C3 plants have rarely considered the effects of evolution. Knowledge of the potential for evolution of C3 plants in response to CO2 is important for predicting the degree to which plants may sequester atmospheric CO2 in the future, and for understanding how plants may have functioned in response to low pCO2 during the Pleistocene. Therefore, three studies using Arabidopsis thaliana as a model system for C3 annuals were conducted: (1) a selection experiment to measure responses to selection for high seed number (a major component of fitness) at Pleistocene (20 Pa) and future (70 Pa) pCO2 and to determine changes in development rate and biomass production during selection, (2) a growth experiment to determine if the effects of selection on final biomass were evident prior to reproduction, and (3) a reciprocal transplant experiment to test if pCO2 was a selective agent on Arabidopsis. Arabidopsis showed significant positive responses to selection for high seed number at both 20 and 70 Pa CO2 during the selection process. Furthermore, plants selected at 20 Pa CO2 performed better than plants selected at 70 Pa CO2 under low CO2 conditions, indicating that low CO2 acted as a selective agent on these annuals. However, plants selected at 70 Pa CO2 did not have significantly higher seed production than plants selected at 20 Pa CO2 when grown at high pCO2. Nevertheless, there was some evidence that high CO2 may also be a selective agent because changes in development rate and biomass production during selection occurred in opposite directions at low and high pCO2. Plants selected at high pCO2 showed no change or reductions in biomass relative to control plants due to a decrease in the length of the life cycle, as indicated by earlier initiation of flowering and senescence. In contrast, selection at low CO2 resulted in an average 35% increase in biomass production, due to an increase in the length of the life cycle that resulted in a longer period for biomass accumulation before senescence. From the Arabidopsis model system we conclude that some C3 annuals may have produced greater biomass in response to low pCO2 during the Pleistocene relative to what has been predicted from studies exposing a single generation of C3 plants to low pCO2. Furthermore, C3 annuals may exhibit evolutionary responses to high pCO2 in the future that may result in developmental changes, but these are unlikely to increase biomass production. This series of studies shows that CO2 may potentially act as a selective agent on C3 annuals, producing changes in development rate and carbon accumulation that could not have been predicted from single-generation studies.