Rate of Iceland Sea acidification from time series measurements (update)

The Iceland Sea is one part of the Nordic Seas. Cold Arctic Water prevails there and the deep-water is an important source of North Atlantic Deep Water. We have evaluated time series observations of measured pCO₂ and total CO₂ concentration from discrete seawater samples during 1985–2008 for the surface and 1994–2008 for deep-water, and following changes in response to increasing atmospheric carbon dioxide. The surface pH in winter decreases at a rate of 0.0024 yr⁻¹, which is 50% faster than average yearly rates at two subtropical time series stations, BATS and ESTOC. In the deep-water regime (>1500 m), the rate of pH decline is a quarter of that observed in surface waters. The surface seawater carbonate saturation states (Ω) are about 1.5 for aragonite and 2.5 for calcite, about half of levels found in subtropical surface waters. During 1985–2008, the degree of saturation (Ω) decreased at an average rate of 0.0072 yr⁻¹ for aragonite and 0.012 yr⁻¹ for calcite. The aragonite saturation horizon is currently at 1710 m and shoaling at 4 m yr⁻¹. Based on this rate of shoaling and on the local hypsography, each year another 800 km² of seafloor becomes exposed to waters that have become undersaturated with respect to aragonite.

VIRTUALURCHIN interactive tutorials

Gametes of sea urchins yield exceptional experiences in the classroom; teachers and students alike are riveted by being able to observe fertilization, cell division and embryonic development. The gametes are easy to use, the developmental stages are readily seen with the microscope and the rapidity of fertilization and early cell divisions allows the student to ask questions and obtain answers within the bounds of a normal classroom schedule. The utility of urchins for inquiry-based science is unrivaled.

Ocean acidification in WAMC Northeast Public Radio (audio)

Guests NOAA Ocean Chemist Richard Feely and Filmmakers Sven Huseby and Barbara Ettinger answer questions about ocean acidification. Alan Chartock hosts.

Effects of long-term high CO2 exposure on two species of coccolithophores

The physiological performance of two coccolithophore species, Emiliania huxleyi and Coccolithus braarudii, was investigated during long-term exposure to elevated pCO2 levels. Mono-specific cultures were grown over 152 (E. huxleyi) and 65 (C. braarudii) generations while pCO2 was gradually increased to maximum levels of 1150 μatm (E. huxleyi) and 930 μatm (C. braarudii) and kept constant thereafter. Rates of cell growth and cell quotas of particulate organic carbon (POC), particulate inorganic carbon (PIC) and total particulate nitrogen (TPN) were determined repeatedly throughout the incubation period. Increasing pCO2 caused a decrease in cell growth rate of 9% and 29% in E. huxleyi and C. braarudii, respectively. In both species cellular PIC:TPN and PIC:POC ratios decreased in response to rising pCO2, whereas no change was observed in the POC:TPN ratios of E. huxleyi and C. braarudii. These results are consistent with those obtained in shorter-term high CO2 exposure experiments following abrupt pertubations of the seawater carbonate system, indicating that for the strains tested here i) a gradual CO2 increase does not alleviate CO2/pH sensitivity, and ii) observed CO2 sensitivities are persistent over multiple generations.

Strain-specific responses of Emiliania huxleyi to changing seawater carbonate chemistry (update)

Four strains of the coccolithophore E. huxleyi (RCC1212, RCC1216, RCC1238, RCC1256) were grown in dilute batch culture at four CO2 levels ranging from ~200 μatm to ~1200 μatm. Growth rate, particulate organic carbon content, and particulate inorganic carbon content were measured, and organic and inorganic carbon production calculated. The four strains did not show a uniform response to carbonate chemistry changes in any of the analysed parameters and none of the four strains displayed a response pattern previously described for this species. We conclude that the sensitivity of different strains of E. huxleyi to acidification differs substantially and that this likely has a genetic basis. We propose that this can explain apparently contradictory results reported in the literature.

Ocean acidification teaching module

The Ocean Carbon and Biogeochemistry Program has assembled a teaching module about ocean acidification for grades 5-12 containing two lab experiments and one classroom demonstration. In the first experiment, students test the pH of numerous household liquids, including artificial seawater. In the second experiment, students bubble seawater and other natural waters with their breath to simulate accelerated ocean acidification, and they use the skills gained from the first lab to interpret their results. In the demonstration, teachers soak seashells in weak acid to simulate the possible physical consequences of ocean acidification on mollusks. The kit is designed to be as low-cost and adaptable as possible; most supplies can be purchased at a local supermarket or pet store. The kit includes teacher setup checklists and recipes for each lab, student handouts, student worksheets with data tables and synthesis questions, a teacher’s answer key, and links to additional teaching and background materials. Finally, U.S. national science education standards supported by this kit are listed.

Global and local forcing of Early Toarcian seawater chemistry: A comparative study of different paleoceanographic settings (Paris and Lusitanian basins)

The Early Toarcian was characterized by two large perturbations to the carbon cycle: a positive trend associated with increased organic matter burial and ocean anoxia, and a pronounced negative carbon isotope excursion (CIE). We contrast the geochemical evolution in the carbonate phases of two successions: one from the Paris Basin (Sancerre core, comprising black shales), the other from the Lusitanian Basin (Peniche section with very minor lithological expression of bottom water anoxia). Our aim was to identify whether these carbon cycle perturbations were related, and differentiate between the common (global) versus regional expressions of the biogeochemical response and ocean chemistry. Our results highlight contrasts in timing of different phases of anoxia in both locations through the widely documented negative CIE. Widespread anoxic conditions were not a necessary prerequisite for generating a pronounced CIE, as required by the recycling (so-called “Küspert”) model. The production of carbonate simultaneously dropped during the δ¹³C negative shift in both locations, likely in response to lowered seawater saturation rate induced by substantial absorption of CO₂ from the atmosphere. The recovery interval was accompanied by a rapid reestablishment of seawater alkalinity, and primary and carbonate productivity in epicontinental seas, as evidenced by high δ¹³C and Sr/Ca, in contrast with the more open ocean regime in the Lusitanian Basin. Our results confirm that parallels can be draw between the ocean productivity response and feedback during the Toarcian CIE and the PETM. Both events are characterized by ocean acidification and reduced pelagic calcification followed by a peak in nearshore coccolith productivity, which could have helped the recovery from the perturbation.

CRISP Report: Acidification and Coral Reefs

The increase in atmospheric carbon dioxide is leading to an increase in dissolved CO2 in the oceans, leading to another increase in hydrogen ions and therefore a relative acidification, although the pH still remains slightly alkaline. In addition, this will also lead to fewer available carbonate ions. This concentration contributes to the transformation of calcium ions from a solid state (calcium carbonate) to a liquid state. Thus, the calcification rate will similarly decrease in all carbonate skeletal organisms, including corals. The risk of such a drop in calcium carbonate saturation is that dissolution factors, combined with mechanical destruction and bioerosion, will reverse coral reef construction and start fragmentation of the structure. It is generally thought that the concentration of atmospheric carbon dioxide, currently of 386 ppm, should not exceed 450-500 ppm to avoid this situation. However, according to IPCC scenarios, such values will be reached in less than a century. More research is required to determine the effects of increasing seawater acidification on more coral species, specifically through physiological studies on corals and their symbiotic zooxanthellae to establish the potential adaptability of some species. This report is available in English, French and Spanish.

Seawater near Japan growing acidic / 23 years of data show CO2-influenced drop in pH level; effect on sea life unclear

Waters near Japan are becoming less alkaline, and the change is so sudden that if the pace of acidification keeps up, it could threaten the ecosystem in 100 years, according to researchers studying the phenomenon.

Ocean water is mildly alkaline by nature, but when the amount of carbon dioxide in seawater increases, the water becomes less alkaline. On the pH scale, ocean water is usually about 8.1, which is alkaline. Depending on location, however, seawater alkalinity is getting closer to the neutral figure of 7.

The drop in alkaline levels is believed to be caused by CO2, the amount of which in the atmosphere has surged due to large consumption of fossil fuels, among other factors.

A group of scientists, led by Takashi Midorikawa of the Meteorological Research Institute in Tsukuba, Ibaraki Prefecture, has checked the pH readings of surface seawater off the Kii Peninsula at 30 degrees north latitude that have been made since 1986. They have found that the pH has dropped by 0.04 during this period, a considerable change. Such ocean acidification has been observed elsewhere as well, such as off Hawaii.

From laboratory manipulations to Earth system models: scaling calcification impacts of ocean acidification (update)

The observed variation in the calcification responses of coccolithophores to changes in carbonate chemistry paints a highly incoherent picture, particularly for the most commonly cultured “species”, Emiliania huxleyi. The disparity between magnitude and potentially even sign of the calcification change under simulated end-of-century ocean surface chemical changes (higher pCO₂, lower pH and carbonate saturation), raises challenges to quantifying future carbon cycle impacts and feedbacks because it introduces significant uncertainty in parameterizations used for global models. Here we compile the results of coccolithophore carbonate chemistry manipulation experiments and review how ocean carbon cycle models have attempted to bridge the gap from experiments to global impacts. Although we can rule out methodological differences in how carbonate chemistry is altered as introducing an experimental bias, the absence of a consistent calcification response implies that model parameterizations based on small and differing subsets of experimental observations will lead to varying estimates for the global carbon cycle impacts of ocean acidification. We highlight two pertinent observations that might help: (1) the degree of coccolith calcification varies substantially, both between species and within species across different genotypes, and (2) the calcification response across mesocosm and shipboard incubations has so-far been found to be relatively consistent. By analogy to descriptions of plankton growth rate vs. temperature, such as the “Eppley curve”, which seek to encapsulate the net community response via progressive assemblage change rather than the response of any single species, we posit that progressive future ocean acidification may drive a transition in dominance from more to less heavily calcified coccolithophores. Assemblage shift may be more important to integrated community calcification response than species-specific response, highlighting the importance of whole community manipulation experiments to models in the absence of a complete physiological understanding of the underlying calcification process. However, on a century time-scale, regardless of the parameterization adopted, the atmospheric pCO₂ impact of ocean acidification is minor compared to other global carbon cycle feedbacks.