Published 27 May 2012
The ocean absorbs a large portion of the CO2 that we release into the atmosphere from our power plants and tail pipes. But when it gets there that CO2 makes the water more acidic and less hospitable for some creatures, like shellfish. In Puget Sound some shellfish hatcheries have already lost millions of oyster larvae because of exposure to acidic water.
Ocean acidification has scientists and policymakers in the Northwest concerned. Washington Governor Chris Gregoire has convened a panel on Ocean Acidification, which met this week. Ashley Ahearn reports.
Continue reading ‘Algae and Puget Sound acidification linked (audio)’
Ocean acidification poses multiple challenges for coral reefs on molecular to ecological scales, yet previous experimental studies of the impact of projected CO2 concentrations have mostly been done in aquarium systems with corals removed from their natural ecosystem and placed under artificial light and seawater conditions. The Coral–Proto Free Ocean Carbon Enrichment System (CP-FOCE) uses a network of sensors to monitor conditions within each flume and maintain experimental pH as an offset from environmental pH using feedback control on the injection of low pH seawater. Carbonate chemistry conditions maintained in the −0.06 and −0.22 pH offset treatments were significantly different than environmental conditions. The results from this short-term experiment suggest that the CP-FOCE is an important new experimental system to study in situ impacts of ocean acidification on coral reef ecosystems.
Kline D. I., Teneva L., Schneider K., Miard T., Chai A., Marker M., Headley K., Opdyke B., Nash M., Valetich M., Caves J. K., Russell B. D., Connell S. D., Kirkwood B. J., Brewer P., Peltzer E., Silverman J., Caldeira K., Dunbar R. B., Koseff J. R., Monismith S. G., Mitchell B. G., Dove S. & Hoegh-Guldberg O., 2012. A short-term in situ CO2 enrichment experiment on Heron Island (GBR). Scientific Reports 2:413. Article.
Coastal ocean acidification is expected to interfere with the physiology of marine bivalves. In this work, the effects of acidification on the physiology of juvenile mussels Mytilus galloprovincialis were tested by means of controlled CO2 perturbation experiments. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain 2 reduced pH levels: −0.3 and −0.6 pH units as compared with the control seawater. After 78 d of exposure, we found that the absorption efficiency and ammonium excretion rate of juveniles were inversely related to pH. Significant differences among treatments were not observed in clearance, ingestion and respiration rates. Coherently, the maximal scope for growth and tissue dry weight were observed in mussels exposed to the pH reduction ΔpH = −0.6, suggesting that M. galloprovincialis could be tolerant to CO2 acidification, at least in the highly alkaline coastal waters of Ria Formosa (SW Portugal).
Continue reading ‘Tolerance of juvenile Mytilus galloprovincialis to experimental seawater acidification’
Coccolithophores are an important component of the Earth system, and, as calcifiers, their possible susceptibility to ocean acidification is of major concern. Laboratory studies at enhanced pCO2 levels have produced divergent results without overall consensus. However, it has been predicted from these studies that, although calcification may not be depressed in all species, acidification will produce “a transition in dominance from more to less heavily calcified coccolithophores” [Ridgwell A, et al., (2009) Biogeosciences 6:2611–2623]. A recent observational study [Beaufort L, et al., (2011) Nature 476:80–83] also suggested that coccolithophores are less calcified in more acidic conditions. We present the results of a large observational study of coccolithophore morphology in the Bay of Biscay. Samples were collected once a month for over a year, along a 1,000-km-long transect. Our data clearly show that there is a pronounced seasonality in the morphotypes of Emiliania huxleyi, the most abundant coccolithophore species. Whereas pH and CaCO3 saturation are lowest in winter, the E. huxleyi population shifts from <10% (summer) to >90% (winter) of the heavily calcified form. However, it is unlikely that the shifts in carbonate chemistry alone caused the morphotype shift. Our finding that the most heavily calcified morphotype dominates when conditions are most acidic is contrary to the earlier predictions and raises further questions about the fate of coccolithophores in a high-CO2 world.
Continue reading ‘Predominance of heavily calcified coccolithophores at low CaCO3 saturation during winter in the Bay of Biscay’
Ocean Acidification (OA) has been an important research topic for a decade. Scientists have focused on how the predicted 56% decline in the seawater carbonate ion () concentration will dramatically impair the ability of calcifiers, ranging from coccolithophores to shellfish, to form calcium carbonate (CaCO3) structures, and the implications of the reduced carbonate saturation state (Ω) for increased dissolution of such structures. However, most published OA studies have overlooked a fundamental issue: most calcifying organisms do not rely on carbonate from seawater to calcify; they use either bicarbonate () or metabolically-produced CO2. The ability of important primary (corals, coralline seaweeds and coccolithophores) and secondary (mollusks) producers to modify their local carbonate chemistry suggests that the primary threat to them from OA is by dissolution rather than impaired calcification. Here, we draw on calcification research from an era before OA and combine it with recent studies that question the source of the carbonate ion, to provide new insights into how OA might affect calcifying organisms. Organismal modification of local carbonate chemistry may enable calcifiers to successfully form calcareous structures despite OA.
Continue reading ‘Before ocean acidification: calcifier chemistry lessons’
The California Current System (CCS) is expected to experience the ecological impacts of ocean acidification (OA) earlier than most other ocean regions because coastal upwelling brings old, CO2-rich water relatively close to the surface ocean. Historical inorganic carbon measurements are scarce, so the progression of OA in the CCS is unknown. We used a multiple linear regression approach to generate empirical models using oxygen (O2), temperature (T), salinity (S), and sigma theta (σθ) as proxy variables to reconstruct pH, carbonate saturation states, carbonate ion concentration ([CO32−]), dissolved inorganic carbon (DIC) concentration, and total alkalinity (TA) in the southern CCS. The calibration data included high-quality measurements of carbon, oxygen, and other hydrographic variables, collected during a cruise from British Columbia to Baja California in May–June 2007. All resulting empirical relationships were robust, with r2 values >0.92 and low root mean square errors. Estimated and measured carbon chemistry matched very well for independent data sets from the CalCOFI and IMECOCAL programs. Reconstructed CCS pH and saturation states for 2005–2011 reveal a pronounced seasonal cycle and inter-annual variability in the upper water column. Deeper in the water column, conditions are stable throughout the annual cycle, with perennially low pH and saturation states. Over sub-decadal time scales, these empirical models provide a valuable tool for reconstructing carbonate chemistry related to ocean acidification where direct observations are limited. However, progressive increases in anthropogenic CO2 content of southern CCS water masses must be carefully addressed to apply the models over longer time scales.
Continue reading ‘Robust empirical relationships for estimating the carbonate system in the southern California Current System and application to CalCOFI hydrographic cruise data (2005–2011)’