“Tipping Point” to be shown at the San Francisco International Ocean Film Festival

Friday 8 March 2013, 1 pm

“Tipping Point”, France, Laurence Jourdan, 54 min

An intelligent look at the emerging science of ocean acidification, that is shot in dramatic ocean locations from the tropics to the arctic, this film follows scientists on a sensitive, compelling and ultimately hopeful journey, into one of the marine environment’s most imminent challenges. —PW

Diurnal and seasonal variations of carbonate system parameters on Luhuitou fringing reef, Sanya Bay, Hainan Island, South China Sea

The 3-day diurnal dynamics of carbonate system and related parameters on Luhuitou fringing reef of Sanya Bay-adjacent to the South China Sea (SCS) were observed in December of 2009 (early winter), April (spring), July (summer) and November (late-autumn) of 2010. The Luhuitou fringing reef ecosystem was generally dominated by macro and planktonic algae throughout the year except by coralline algae in winter. The system parameters showed distinct diurnal trends in the four seasons. Averaged ranges of diurnal variation for dissolved oxygen and partial pressure of CO₂ (pCO₂) were higher in the autumn, 4.67 mg L⁻¹ and 218.2 μatm, respectively than other seasons. Averaged ranges of diurnal variation for normalized total alkalinity (NTA) was higher in the winter (61.3 μmol kg⁻¹), and lower in the spring (16.0 μmol kg⁻¹). The diurnal variations are mainly controlled by biological activities, especially by the processes of photosynthesis and respiration in the reef ecosystem. In winter, however, calcification and dissolution contributed more to the diurnal variations, compared with the other three seasons. Total alkalinity was largely related to seasonal changes in river inflow rates. Dissolved oxygen, pH, total CO₂ and aragonite saturation also showed seasonal variations. These variations were mainly controlled by the seasonal changes of photosynthesis and respiration, which were mainly affected by changes in benthic community structure, temperature and river inflow rates. The oversaturated pCO₂ in the reef ecosystem with respect to the atmosphere in the winter and summer resulted in CO₂ discharge from the reef ecosystem to the SCS. The whole system served as net source of CO₂ to the atmosphere and the adjacent South China Sea on an annual time scale.

Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction

The boron isotope-pH proxy, applied to mixed-layer planktic foraminifera, has great potential for estimating past CO₂ levels, which in turn is crucial to advance our understanding of how this greenhouse gas influences Earth’s climate. Previous culture experiments have shown that, although the boron isotopic compositions of various planktic foraminifera are pH dependent, they do not agree with the aqueous geochemical basis of the proxy. Here we outline the results of culture experiments on Globigerinoides ruber (white) across a range of pH (∼7.5–8.2) and analysed via multicollector inductively-coupled plasma mass spectrometry (MC-ICPMS), and compare these data to core-top and sediment-trap samples to derive a robust new species-specific boron isotope-pH calibration. Consistent with earlier culture studies, we show a reduced pH dependency of the boron isotopic composition of symbiont-bearing planktonic foraminifera compared to borate ion in seawater. We also present evidence for a size fraction effect in the δ¹¹B of G. ruber. Finally, we reconstruct atmospheric CO₂ concentrations over the last deglacial using our new calibration at two equatorial sites, ODP Site 999A and Site GeoB1523-1. These data provide further grounding for the application of the boron isotope-pH proxy in reconstructions of past atmospheric CO₂ levels.

Distribution of sea urchins living near shallow water CO2 vents is dependent upon species acid–base and ion-regulatory abilities

To reduce the negative effect of climate change on Biodiversity, the use of geological CO₂ sequestration has been proposed; however leakage from underwater storages may represent a risk to marine life. As extracellular homeostasis is important in determining species’ ability to cope with elevated CO₂, we investigated the acid–base and ion regulatory responses, as well as the density, of sea urchins living around CO₂ vents at Vulcano, Italy. We conducted in situ transplantation and field-based laboratory exposures to different pCO₂/pH regimes. Our results confirm that sea urchins have some ability to regulate their extracellular fluid under elevated pCO₂. Furthermore, we show that even in closely-related taxa divergent physiological capabilities underlie differences in taxa distribution around the CO₂ vent. It is concluded that species distribution under the sort of elevated CO₂ conditions occurring with leakages from geological storages and future ocean acidification scenarios, may partly be determined by quite subtle physiological differentiation.

Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, a nutrient source and to mitigate ocean acidification

[1] Chemical weathering is an integral part of both the rock and carbon cycles and is being affected by changes in land use, particularly as a result of agricultural practices such as tilling, mineral fertilization, or liming to adjust soil pH. These human activities have already altered the chemical terrestrial cycles and land-ocean flux of major elements, although the extent remains difficult to quantify. When deployed on a grand scale, Enhanced Weathering (a form of mineral fertilization), the application of finely ground minerals over the land surface, could be used to remove CO₂ from the atmosphere. The release of cations during the dissolution of such silicate minerals would convert dissolved CO₂ to bicarbonate, increasing the alkalinity and pH of natural waters. Some products of mineral dissolution would precipitate in soils or taken up by ecosystems, but a significant portion would be transported to the coastal zone and the open ocean, where the increase in alkalinity would partially counteract “ocean acidification” associated with the current marked increase in atmospheric CO₂. Other elements released during this mineral dissolution, like Si, P or K, could stimulate biological productivity, further helping to remove CO₂ from the atmosphere. On land, the terrestrial carbon-pool would likely increase in response to Enhanced Weathering in areas where ecosystem growth rates are currently limited by one of the nutrients that would be released during mineral dissolution.In the ocean, the biological carbon pumps (which export organic matter and CaCO₃ to the deep ocean) may be altered by the resulting influx of nutrients and alkalinity to the ocean.

[2] This review merges current interdisciplinary knowledge about Enhanced Weathering, the processes involved, and the applicability as well as some of the consequences and risks of applying the method.

Subsurface low pH and carbonate saturation state of aragonite on China side of the North Yellow Sea: combined effects of global atmospheric CO2 increase, regional environmental changes, and local biogeochemical processes

Based upon seven field surveys conducted between May 2011 and January 2012, we investigated pH, carbonate saturation state of aragonite (Ω_arag), and ancillary parameters on the Chinese side of the North Yellow Sea, a western North Pacific continental margin of major economic importance. Subsurface waters were nearly in equilibrium with air in May and June. From July to October, the fugacity of CO₂ (fCO₂) of bottom water gradually increased to 697 ± 103 μatm and pH decreased to 7.83 ± 0.07 due to respiration/remineralization processes of primary production induced biogenic particles. In November and January, bottom water fCO₂ decreased and pH gradually returned to an air-equilibrated level due to cooling enhanced vertical mixing. The corresponding bottom water Ω_arag was 1.74 ± 0.17 (May), 1.77 ± 0.26 (June), 1.70 ± 0.26 (July), 1.72 ± 0.33 (August), 1.32 ± 0.31 (October), 1.50 ± 0.28 (November), and 1.41 ± 0.12 (January). Critically low Ω_arag values of 1.0 to 1.2 were mainly observed in subsurface waters in a salinity range of 31.5–32.5 psu in October and November, accounting for ~ 10% of the North Yellow Sea area. Water mass derived from the adjacent Bohai Sea had a typical water salinity of 30.5–31.5 psu, and bottom water Ω_arag values ranged mostly between 1.6 and 2.4. This study showed that the carbonate system in the North Yellow Sea was substantially influenced by global atmospheric CO₂ increase. The community respiration/remineralization rates in typical North Yellow Sea bottom water mass were estimated at 0.55–1.0 μmol O₂ kg⁻¹ d⁻¹ in warm seasons, leading to seasonal drops in subsurface pH and Ω_arag. Outflow of the Bohai Sea water mass counteracted the subsurface Ω_arag reduction in the North Yellow Sea.

Ken Caldeira – Ocean Acidification IPOC Seminar Part 2 (video)

Ken Caldeira – Ocean Acidification IPOC Seminar Part 1 (video)

Are oysters doomed?

Don’t believe in climate change? Talk to a clam digger.

Behind the counter at Seattle’s Taylor Shellfish Market, a brawny guy with a goatee pries open kumamoto, virginica, and shigoku oysters as easily as other men pop beer cans. David Leck is a national oyster shucking champion who opened and plated a dozen of them in just over a minute (time is added for broken shells or mangled meat) at the 2012 Boston International Oyster Shucking Competition. You have to be quick, these days, to keep up with demand. The oysters here were grown nearby in Taylor’s hundred-year-old beds, but the current hunger for pedigreed mollusks on the half shell stretches to raw bars and markets across the country.