Working Group I contribution to the IPCC Fifth Assessment Report – expert and government review of the second order draft

Working Group I (WGI) of the Intergovernmental Panel on Climate Change (IPCC) is pleased to announce that the Second Order Draft of the WGI contribution to the IPCC Fifth Assessment Report (AR5), Climate Change 2013: The Physical Science Basis is now available for Expert and Government Review from 5 October – 30 November 2012. In order to review the Second Order Draft, you are invited to submit a completed registration form provided below. For additional information, please see the Introduction to the Expert Review of IPCC Working Group I AR5 Draft Reports.

Small changes in pH have direct effects on marine bacterial community composition: a microcosm approach

As the atmospheric CO₂ concentration rises, more CO₂ will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15–8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments.

Ocean fertilization for geoengineering: a review of effectiveness, environmental impacts and emerging governance

Dangerous climate change is best avoided by drastically and rapidly reducing greenhouse gas emissions. Nevertheless, geoengineering options are receiving attention on the basis that additional approaches may also be necessary. Here we review the state of knowledge on large-scale ocean fertilization by adding iron or other nutrients, either from external sources or via enhanced ocean mixing. On the basis of small-scale field experiments carried out to date and associated modelling, the maximum benefits of ocean fertilization as a negative emissions technique are likely to be modest in relation to anthropogenic climate forcing. Furthermore, it would be extremely challenging to quantify with acceptable accuracy the carbon removed from circulation on a long term basis, and to adequately monitor unintended impacts over large space and time-scales. These and other technical issues are particularly problematic for the region with greatest theoretical potential for the application of ocean fertilization, the Southern Ocean. Arrangements for the international governance of further field-based research on ocean fertilization are currently being developed, primarily under the London Convention/London Protocol.

Near-future ocean acidification causes differences in microbial associations within diverse coral reef taxa

Microorganisms form symbiotic partnerships with a diverse range of marine organisms and can be critical to the health and survival of their hosts. Despite the importance of these relationships, the sensitivity of symbiotic microbes to ocean acidification (OA) is largely unknown and this needs to be redressed to adequately predict marine ecosystem resilience in a changing climate. We adopted a profiling approach to explore the sensitivity of microbes associated with coral reef biofilms and representatives of 3 ecologically important calcifying invertebrate phyla (corals, foraminifera and crustose coralline algae (CCA)) to OA. The experimental design for this study comprised four pHs consistent with current IPCC predictions for the next few centuries (pH_NIST 8.1, 7.9, 7.7, 7.5); these pH/pCO₂ conditions were produced in flow through aquaria using CO₂ bubbling. All reduced pH/increased pCO₂ treatments caused clear differences in the microbial communities associated with coral, foraminifera, CCA and reef biofilms over six weeks, while no visible signs of host stress were detected over this period. The microbial communities of coral, foraminifera, CCA and biofilms were significantly different between pH 8.1 (pCO₂=464 μatm) and pH 7.9 (pCO₂=822 μatm), a concentration likely to be exceeded by the end of the present century. This trend continued at lower pHs/higher pCO₂. 16S rRNA gene sequencing revealed variable and species-specific changes in the microbial communities with no microbial taxa consistently present or absent from specific pH treatments. The high sensitivity of coral, foraminifera, CCA and biofilm microbes to OA conditions projected to occur by 2100 is a concern for reef ecosystems and highlights the need for urgent research to assess the implications of microbial shifts for host health and coral reef processes.

Measurement of benthic photosynthesis and calcification in flowing-through seawater with stable carbonate chemistry

Estimation of photosynthetic or calcification rates of benthic organisms under stable seawater chemistry is important to fathom their capacity of CO₂ fixation under constant or controlled levels of pCO₂ and acidity of seawater. The flowing-through system, introduced here, can hold large individuals or colonies and maintain the carbonate chemical parameters stable while photosynthetic or calcification rate is measured based on the assimilation pipe inlet and outlet differences in dissolved O₂ concentrations or total alkalinity. The data obtained with this system for macroalgae showed constancy over time under controlled conditions, resulting in higher photosynthetic rates compared with those measured in a closed mode, which caused significant changes in the carbonate system (decreased pCO₂ and DIC and increased pH). When the method was applied to measurements of calcification based on the changes in total alkalinity, reliable data were obtained for both coralline algae and oysters. In addition, it can also be applied to measure respiration of both macrophyte and animals and to test the effects of increased pCO₂ and current speeds when these factors are controlled under either laboratory or field conditions while exposed to natural solar radiation.

Impact of medium-term exposure to elevated pCO2 levels on the physiological energetics of the mussel Mytilus chilensis

This study evaluated the impact of medium-term exposure to elevated pCO₂ levels (750–1200 ppm) on the physiological processes of juvenile Mytilus chilensis mussels over a period of 70 d in a mesocosm system. Three equilibration tanks filled with filtered seawater were adjusted to three pCO₂ levels: ∼380 (control), ∼750 and ∼1200 ppm by bubbling air or an air–CO₂ mixture through the water. For the control, atmospheric air (with aprox. 380 ppm CO₂) was bubbled into the tank; for the 750 and 1200 ppm treatments, dry air and pure CO₂ were blended to each target concentration using mass flow controllers for air and CO₂. No impact on feeding activity was observed at the beginning of the experiment, but a significant reduction in clearance rate was observed after 35 d of exposure to highly acidified seawater. Absorption rate and absorption efficiency were reduced at high pCO₂ levels. In addition, oxygen uptake fell significantly under these conditions, indicating a metabolic depression. These physiological responses of the mussels resulted in a significant reduction of energy available for growth (scope for growth) with important consequences for the aquaculture of this species during medium-term exposure to acid conditions. The results of this study clearly indicate that high pCO₂ levels in the seawater have a negative effect on the health of M. chilensis. Therefore, the predicted acidification of seawater associated with global climate change could be harmful to this ecologically and commercially important mussel.

Ocean acidification increases the toxicity of contaminated sediments

Ocean acidification (OA) may alter the behaviour of sediment-bound metals, modifying their bioavailability and thus toxicity. We provide the first experimental test of this hypothesis with the amphipod Corophium volutator. Amphipods were exposed to two test sediments, one with relatively high metals concentrations (Σ_metals 239 mg kg⁻¹) and a reference sediment with lower contamination (Σ_metals 82 mg kg⁻¹) under conditions that mimic current and projected conditions of OA (390 to 1140 μatm pCO₂). Survival and DNA damage was measured in the amphipods, while the flux of labile metals was measured in the sediment and water column using Diffusive Gradients in Thin-films. The contaminated sediments became more acutely toxic to C. volutator under elevated pCO₂ (1140 μatm). There was also a 2.7-fold increase in DNA damage in amphipods exposed to the contaminated sediment at 750 μatm pCO₂, as well as increased DNA-damage in organisms exposed to the reference sediment, but only at 1140 μatm pCO₂. The projected pCO₂ concentrations increased the flux of nickel (Ni) and zinc (Zn) to labile states in the water column and pore water. However, the increase in metal flux at elevated pCO₂ was equal between the reference and contaminated sediments or, occasionally, greater from reference sediments. Hence, the toxicological interaction between OA and contaminants could not be explained by effects of pH on metal speciation. We propose that the additive physiological effects of OA and contaminants will be more important than changes in metal speciation in determining the responses of benthos to contaminated sediments under OA. Our data demonstrate clear potential for near-future OA to increase the susceptibility of benthic ecosystems to contaminants. Environmental policy should consider contaminants within the context of changing environmental conditions. Specifically, sediment metals guidelines may need to be re-evaluated to afford appropriate environmental protection under future conditions of OA.

A bi-partisan move to save Washington shellfish

Gov. Gregoire’s ocean acidification panel is wrapping up its recommendations for deterring an oyster apocalypse and lawmakers aren’t wasting any time.

Lawmakers will introduce a new bill to tackle Washington’s ocean acidification troubles prior to the upcoming state legislative session in January, according to state Sen. Kevin Ranker (D-Orcas Island).

Ocean acidification (video)

OSU to co-host forum in Tillamook on ocean acidification, low oxygen

A public forum on Tuesday, Oct. 23, in Tillamook will explore the current and potential future impacts of two emerging phenomena along the Oregon coast – increasing ocean acidity and seasonal incidence of low-oxygen waters, or “hypoxia.”

A series of speakers will present the latest research at the free community event, “Demystifying Coastal Hypoxia & Ocean Acidification,” which begins at 6:30 p.m. at Tillamook Bay Community College Room 214/215. A panel discussion will follow, focusing on what individuals, communities, government agencies and others can do to reduce and manage potential impacts ocean acidification and hypoxia, both globally and locally.