Archive for July, 2011

CBD notification on ocean acidification expert meeting

The Convention for Biological Diversity has released an “Invitation to CBD Expert Meeting to Develop a Series of Joint Expert Review Processes to Monitor and Assess the Impacts of Ocean Acidification on Marine and Coastal Biodiversity”, 19-20 October 2011, Montreal, Canada.

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The influence of increased temperature and carbon dioxide levels on the benthic/sea ice diatom Navicula directa

Polar oceans are very susceptible to increased levels of atmospheric CO2 and may act as the world’s largest sink for anthropogenic CO2. Simultaneously, as atmospheric CO2 increases, sea surface temperature rises due to global warming. These two factors are important in regulating microalgal ecophysiology, and it has been suggested that future global changes may significantly alter phytoplankton species composition. This study aims to investigate potential consequences of global change in terms of increased temperature and CO2 enrichment on the benthic/sea ice diatom Navicula directa. In a laboratory experiment, the physiological response to elevated temperature and partial pressure of CO2 (pCO2) was investigated in terms of growth, photosynthetic activity and photosynthetic pigment composition. The experiment was performed under manipulated levels of pCO2 (380 and 960 ppm) and temperature (0.5 and 4.5°C) to simulate a change from present levels to predicted levels during a worst-case scenario by the year 2100. After 7 days of treatment, no synergetic effects between temperature and pCO2 were detected. However, elevated temperature promoted effective quantum yield of photosynthesis (∆F/Fm) and increased growth rates by approximately 43%. Increased temperature also resulted in an altered pigment composition. In addition, enrichment of CO2 appeared to reduce specific growth rates of N. directa. Even though growth rates were only reduced by approximately 5%, we hereby report that increased pCO2 levels might also have potential negative effects on certain diatom strains.

Continue reading ‘The influence of increased temperature and carbon dioxide levels on the benthic/sea ice diatom Navicula directa’

Physiological energetics of juvenile clams Ruditapes decussatus in a high CO2 coastal ocean

Effects of coastal ocean acidification, other than calcification, were tested on juvenile clams (Ruditapes decussatus) during a controlled CO2 perturbation experiment. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain two reduced pH levels: -0.4 and -0.7 pH units as compared with the control seawater. After 87 days of exposure, we found that the acidification conditions tested in this experiment significantly reduced the clearance, ingestion and respiration rates, and increased the ammonia excretion rate of R. decussatus seeds. Reduced ingestion combined with increased excretion is generally associated with a reduced energy input, which will likely contribute to a slower growth of the clams in a future high CO2 coastal ocean. These results emphasize the need for management policies to mitigate the adverse effects of global change on aquaculture, which is an economically relevant activity in most coastal areas worldwide.

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OCB PI ocean acidification workshop report released

The full meeting report for the OCB OA PI workshop, held March 22-24, 2011, has been released.

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Interactive comment on “Ocean acidification: setting the record straight” by A. J. Andersson and F. T. Mackenzie

Andersson and Mackenzie (2011) cite our talk on “Carbonate sediments on Antarctic shelves and implications for a mechanism to buffer Ocean Acidification in the Southern Ocean” at the ASLO Aquatic Sciences Meeting in San Juan, Puer to Rico, in February 2011 (Hauck et al., 2011) as an example for investigating possible buffering effects by CaCO3 dissolution of shelf sediments.

We agree with the authors in their recommendations that the points “evidence of a buffer effect“ (when the seawater is already undersaturated with respect to CaCO3 ), “kinetics“, and “physical mixing“ should be considered in studies addressing a possible buffer effect. We would like to add another step (Step Zero), which has to happen even before these considerations: proper quantification of how much CaCO3 is available in the region considered and identification of the mineral composition (aragonite, calcite, magnesium rich calcites). This very first step is what we presented at the ASLO Meeting (Hauck et al., 2011).

Continue reading ‘Interactive comment on “Ocean acidification: setting the record straight” by A. J. Andersson and F. T. Mackenzie’

Ocean acidification – Category 1: the molecular basis of ocean acidification effects on calcification in zooxanthellate corals

Sponsor: National Science Foundation
Dates: September 2010 – August 2011

Project Description

Ocean acidification (the decrease in seawater pH) is driven by the increase in atmospheric CO2. This is expected to have a dramatic effect on organisms that precipitate calcium carbonate. Coral reefs are formed and maintained by calcifying organisms, particularly reef-building corals. Current predictions are that coral species will be negatively impacted; however the limited number of available measurements exhibit significant variability for reasons that are not understood. This is critically important as coral reef ecosystems hold significant cultural and economic values both nationally and internationally. This program is therefore focused on the molecular basis for calcification in corals in order to understand how corals will respond to ocean acidification in the next century.

Continue reading ‘Ocean acidification – Category 1: the molecular basis of ocean acidification effects on calcification in zooxanthellate corals’

The ionic strength dependence of lead (II) carbonate complexation in perchlorate media

Lead speciation in many aqueous geochemical systems is dominated by carbonate complexation. However, direct observations of Pb2+ complexation by carbonate ions are few in number. This work represents the first investigation of the equilibrium “equation 1” over a range of ionic strength. Through spectrophotometric observations of formation at 25 °C in NaHCO3–NaClO4 solutions, “equation 2” formation constants of the form “equation 3” were determined between 0.001 and 5.0 molal ionic strength. Formation constant results were well represented by the equation: “equation 4”.

This result, combined with previous critical assessments of formation constants for the equilibrium “equation 5”, was used to estimate the ionic strength dependence for the equilibrium “equation 6”: “equation 7”.

where “equation 8”. The carbonate complexation constants produced in this study, combined with previous complexation constants for formation of PbII chloride and hydroxide species, were used to predict formation constants for mixed-ligand species Pb(CO3)Cl- , Pb(OH)Cl0 , and Pb(CO3)OH- Formation constant estimates for the system “equation 9” were then used to assess PbII speciation in seawater. In the absence of complexation by organics, approximately 1.9% of the total lead in surface seawater (S = 35, t =25 °C, pH not, vert, similar 8.2 (free H+ concentration scale)) is present as free hydrated Pb2+. Carbonate complexes, “equation 10” and Pb(CO)3Cl–, are predominant forms of PbII in seawater at high pH, and lead chloride complexes are predominant species at low pH. For pH > 7.7 the sum concentration of “equation 11”, Pb(CO3)Cl-, PbOH+, and Pb(OH)Cl0 in seawater exceeds the sum concentration of Pb2+, PbCl+, “equation 12”, and “equation 13”

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New insights from coral growth band studies in an era of rapid environmental change

The rapid formation of calcium carbonate coral skeletons (calcification) fuelled by the coral-algal symbiosis is the backbone of tropical coral reef ecosystems. However, the efficacy of calcification is measurably influenced by the sea’s physico-chemical environment, which is changing rapidly. Warming oceans have already led to increased frequency and severity of coral bleaching, and ocean acidification has a demonstrable potential to cause reduced rates of calcification. There is now general agreement that ocean warming and acidification are attributable to human activities increasing greenhouse gas concentrations in the atmosphere, and the large part of the extra carbon dioxide (the main greenhouse gas) that is absorbed by oceans. Certain massive corals provide historical perspectives on calcification through the presence of dateable annual density banding patterns. Each band is a page in an environmental archive that reveals past responses of growth (linear extension, skeletal density and calcification rate) and provides a basis for prediction of future of coral growth. A second major line of research focuses on the measurement of various geochemical tracers incorporated into the growth bands, allowing the reconstruction of past marine climate conditions (i.e. paleoclimatology). Here, we focus on the structural properties of the annual density bands themselves (viz. density; linear extension), exploring their utility in providing both perspectives on the past and pointers to the future of calcification on coral reefs. We conclude that these types of coral growth records, though relatively neglected in recent years compared to the geochemical studies, remain immensely valuable aids to unravelling the consequences of anthropogenic climate change on coral reefs. Moreover, an understanding of coral growth processes is an essential pre-requisite for proper interpretation of studies of geochemical tracers in corals.

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Response of larval barnacle proteome to CO2-driven seawater acidification

The majority of benthic marine invertebrates have a complex life cycle, during which the pelagic larvae select a suitable substrate, attach to it, and then metamorphose into benthic adults. Anthropogenic ocean acidification (OA) is postulated to affect larval metamorphic success through an altered protein expression pattern (proteome structure) and post-translational modifications. To test this hypothesis, larvae of an economically and ecologically important barnacle species Balanus amphitrite, were cultured from nauplius to the cyprid stage in the present (control) and in the projected elevated concentrations of CO2 for the year 2100 (the OA treatment). Cyprid response to OA was analyzed at the total proteome level as well as two protein post-translational modification (phosphorylation and glycosylation) levels using a 2-DE based proteomic approach. The cyprid proteome showed OA-driven changes. Proteins that were differentially up or down regulated by OA come from three major groups, namely those related to energy-metabolism, respiration, and molecular chaperones, illustrating a potential strategy that the barnacle larvae may employ to tolerate OA stress. The differentially expressed proteins were tentatively identified as OA-responsive, effectively creating unique protein expression signatures for OA scenario of 2100. This study showed the promise of using a sentinel and non-model species to examine the impact of OA at the proteome level.

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Physiological effects of hypercapnia in the deep-sea bivalve Acesta excavata (Fabricius, 1779) (Bivalvia; Limidae)

The option of storing CO2 in subsea rock formations to mitigate future increases in atmospheric CO2 may induce problems for animals in the deep sea. In the present study the deep-sea bivalve Acesta excavata was subjected to environmental hypercapnia corresponding to conditions reported from natural CO2 seeps. Effects on acid-base status and metabolic rate were related to time of exposure and subsequent recovery. During exposure there was an uncompensated drop in both hemolymph and intracellular pH. Intracellular pH returned to control values, while extracellular pH remained significantly lower during recovery. Intracellular non-bicarbonate buffering capacity of the posterior adductor muscle of hypercapnic animals was significantly lower than control values, but this was not the case for the remaining tissues analyzed. Oxygen consumption initially dropped by 60%, but then increased during the final stages of exposure, which may suggest a higher tolerance to hypercapnia than expected for a deep-living species.

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Ocean acidification in the IPCC AR5 WG II

OUP book