Archive for February, 2014

Reminder: Scientists, contribute to the OA-ICC data compilation on the biological response to ocean acidification!

Numerous papers report the effects of ocean acidification on marine organisms and communities, but it has been difficult to compare the results since the carbonate chemistry and ancillary data are often reported in different units and scales, and calculated using different sets of constants.

In response to this problem, a data compilation on the biological response to ocean acidification initiated by the EU projects EUR-OCEANS and EPOCA has been resumed in the framework of the International Atomic Energy Agency (IAEA) project “Ocean Acidification International Coordination Centre (OA-ICC)”.

If you are a scientist publishing on the biological response to ocean acidification, you will likely be contacted in the future. The OA-ICC thanks you in advance for sharing your data, it is a great way to get more cited!

Continue reading ‘Reminder: Scientists, contribute to the OA-ICC data compilation on the biological response to ocean acidification!’

Acidification in the Sea of Japan between 1965 and 2011

Oceans absorb approximately 26% of carbon dioxide emitted to the atmosphere owing to fossil fuel burning, cement production and clearing of forests. Consequently, the pH value of seawater may be decreasing at a rate not seen for at least the last 30 million years. As is well known, such ocean acidification significantly impacts the ability of many major marine organisms (e.g., calcareous phytoplankton) to build their outer shells as well as inner skeletal structures, subsequently reducing the growth and survival of early life stages of some species.

The rate of acidification is generally diminished with an increasing depth. Slowing down the thermohaline circulation due to global warming could reduce the pH in the deep oceans. The effect of deep oceans acidification has not been discussed. As a miniature ocean with its own deep and bottom water formations, the Sea of Japan provides an insight into how future global warming can alter the deep oceans acidification.

The data collected between 1965 and 2011 from the Sea of Japan have been archived by the Japan Meteorological Agency (JMA). To compare with the observed data, we considered three factors which affect ocean acidification: (1) global warming; (2) penetration of anthropogenic CO2 and (3) reduced ventilation. The observed data shows that the acidification rates have the maximum of -0.00236 pH units yr-1 at a depth of 300m. The rates increase from -0.00129 pH units yr-1 at 1000m to -0.00303 pH units yr-1 at 2500m. In our estimation, the acidification rate due to (1) global warming only affects the upper 100m seawater; (2) penetration of anthropogenic CO2 in the Sea of Japan is faster than that of the open ocean at the same depth, owing to the younger Sea of Japan water; (3) reduced ventilation has accumulated more CO2 and acid by the decomposition of organic matter. This factor is more effective than anthropogenic CO2 penetration. To sum up the three factors above, the estimated rates at the depths below 1500m are similar to those observed rates.

Our result shows that the effect of reduced ventilation should be considered in the ocean acidification studies. The ocean ecosystem could be impacted earlier and more severely than only considering the penetration of anthropogenic CO2.
Continue reading ‘Acidification in the Sea of Japan between 1965 and 2011’

Virtual labs as context for learning – continuities and contingencies in student activities

While sceptics have been little convinced about the beneficial consequences that would follow from the introduction of IT in school, technophiles have continued to make claims about how such resources will contribute to solving pedagogical problems of various kinds, including changing the role of the teacher (cf., e, g., Postman, 1979; Selwyn, 1999). (…)

The aim of the present study is to explore virtual labs as a context for learning about ocean acidification. In particular, we are interested in the activities that evolve when students engage in virtual lab work. Our question concerns what the consequences are for interaction and knowledge-sharing between students in such contexts. (…)
Continue reading ‘Virtual labs as context for learning – continuities and contingencies in student activities’

Carbon biogeochemistry of the eastern Bering Sea shelf

The uptake of anthropogenic carbon dioxide (CO2) has caused perturbations to marine biogeochemistry in recent years, including decreasing ocean pH and carbonate mineral saturation states (Ω). Collectively termed ocean acidification (OA), these conditions hinder the growth of calcium carbonate shells and effectively reduce habitat for some marine calcifiers. Given that the Bering Sea is one of the world’s most productive marine ecosystems and supports both commercial fishing industries and subsistence communities, it is integral to understand its susceptibility to OA.

Here, new observations of the organic and inorganic carbon systems are used to identify mechanisms leading to CO2 accumulation and sub-regional enhancement of vulnerability to OA processes. Chapter 1 describes the state of knowledge of OA in this area, highlighting two regions where low Ω conditions are consistently observed: near the coast, and over the northern shelf. Chapter 2 describes net heterotrophic processes near the coast, in conjunction with low bottom water Ω. Chapter 3 examines this heterotrophy in more detail, showing that focused deposition of organic matter and its subsequent respiration. Chapters 4 and 5 focus on very low Ω values observed over the northern shelf. In combination with natural respiration processes, anthropogenic CO2 was shown to cause low Ω and seasonal dissolution of carbonate minerals in Chapter 4. Chapter 5 illustrates how sea ice cover inhibits the flux of CO2 from the surface ocean to the atmosphere, which raises the inventory of CO2 in the water column.

These results are synthesized in Chapter 6. Low-Ω conditions and areas of carbonate mineral dissolution will continue to expand as anthropogenic CO2 accumulates in shelf waters in the coming decades, further reducing viable habitat for key calcifiers. Model projections of future surface water conditions indicate that average Ω over the Bering Sea shelf will drop below the observed natural variability by 2100, with average conditions favoring carbonate mineral dissolution in surface waters by 2150. Presently, episodic events will cause regions of the Bering Sea to be undersaturated in Ω, which could have significant and cascading impacts throughout the Pacific-Arctic region.
Continue reading ‘Carbon biogeochemistry of the eastern Bering Sea shelf’

Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium

To predict effects of climate change and possible feedbacks, it is crucial to understand the mechanisms behind pCO2 responses of biogeochemically relevant phytoplankton species. Previous experiments on the abundant N2-fixer Trichodesmium demonstrated strong pCO2 responses, which were attributed to an energy reallocation between its carbon and nitrogen acquisition. Pursuing this hypothesis, we manipulated the cellular energy budget by growing Trichodesmium erythraeum IMS101 under different pCO2 levels (180, 380, 980 and 1400 µatm) and nitrogen sources (N2 and NO3). Subsequently, biomass production and the main energy-generating processes (photosynthesis and respiration) and energy-consuming processes (N2-fixation and carbon acquisition) were measured. While oxygen fluxes and chlorophyll fluorescence indicated that energy generation and its diurnal cycle was neither affected by pCO2 nor nitrogen source, cells differed in production rates and composition. Elevated pCO2 increased N2-fixation and organic carbon and nitrogen contents. The degree of stimulation was higher for nitrogenase activity than for cell contents, indicating a pCO2 effect on the transfer efficiency from N2 to biomass. pCO2-dependent changes in the diurnal cycle of N2-fixation correlated well with carbon affinities, confirming the interactions between nitrogen and carbon acquisition. Regarding effects of the nitrogen source, production rates were enhanced in NO3 grown cells, which we attribute to the higher N retention and lower ATP demand compared to N2-fixation. pCO2 effects on carbon affinity were less pronounced in NO3 users than N2-fixers. Our study illustrates the necessity to understand energy budgets and fluxes under different environmental conditions for explaining indirect effects of rising pCO2.
Continue reading ‘Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium’

The effects of rising ocean temperature and pCO2 on the physiology and growth of giant kelp, Macrocystis pyrifera, and grazing by purple urchins, Strongylocentrotus purpuratus

As climate change rapidly alters the world’s oceans, marine life will have to acclimate and/or adapt to warmer and more acidic conditions. While there is a growing body of literature on the individual effects of elevated temperature and CO₂ on marine biota, few studies have examined the synergistic effects of these factors, especially regarding how they impact species interactions. In coastal environments of temperate latitudes, forests of kelp (large brown seaweeds in the Order Laminariales) provide habitat and food for numerous species, support enhanced biodiversity, and provide important ecosystem services. Consequently, impacts to these important ecosystem engineers can have disproportionately large effects on coastal ecosystem functioning. To determine how climate change might impact kelp forest ecosystems, I examined two of the more conspicuous and ecologically important kelp forest species, namely the giant kelp, Macrocystis pyrifera, and the purple sea urchin, Strongylocentrotus purpuratus. First, I performed three separate experiments in order to determine the effects of elevated temperature and pCO₂ on M. pyrifera growth and photosynthetic performance. In my first experiment I cultured M. pyrifera meristematic tissues under three pCO₂ levels (500, 1000, 1500 matm CO₂) and examined how this impacted their growth, steady-state photosynthetic oxygen evolution, and changes in their tissue carbon:nitrogen ratios. In my second experiment, I used a fully factorial design with two temperatures (12°C and 15°C) and two pCO₂ levels (500 matm and 1500 matm CO₂), and examined how these impacted kelp growth, steady-state photosynthetic carbon uptake, and tissue carbon:nitrogen ratios. In my third experiment, I used the same fully factorial design (12°C and 15°C; 500 matm and 1500 matm CO₂), but examined changes in kelp photosynthetic pigment composition and carbonic anhydrase activity (an estimate of their ability to use HCO3 – in photosynthesis). Counter to my expectations, elevating only pCO₂ in the water had no effect on kelp growth rates, photosynthesis or tissue carbon:nitrogen ratios in either of the first two experiments. In contrast, in the second experiment, elevating only seawater temperature resulted in a significant reduction in both photosynthesis and growth, and an increase in tissue carbon:nitrogen ratios. However, when seawater temperature and pCO₂ were increased together, the kelps exhibited significant increases in photosynthesis and growth relative to the other treatments This suggested that rising ocean temperatures may interact with rising pCO₂ to elicit responses that are different than when either of these factors is increased by itself. In my third experiment, elevating pCO₂ in the water significantly reduced carbonic anhydrase activity, suggesting a reduction in HCO₃ –based photosynthesis (i.e. a down regulation of carbon concentrating mechanisms) and an increase in CO₂-based photosynthesis. In contrast, elevating temperature and/or CO₂ alone had littleto- no impact on photosynthetic pigment concentrations. Following the experiments on M. pyrifera, I then examined how climate change will impact the interactions between S. purpuratus and M. pyrifera. Here, I cultured these two species separately under both “present day” conditions (i.e. 12°C and 500 matm CO₂) and “future” conditions (i.e. 15°C and 1500 matm CO₂) for three months. During this period, urchins were fed kelp from either their own water conditions or the alternate conditions, resulting in a fully factorial design with four treatment combinations (urchins held under either present day or future conditions being fed kelps grown under either present day or future conditions). My results indicate that urchins held under future conditions exhibited reduced feeding and growth rates, and smaller gonads than urchins held under present day conditions regardless of the conditions in which their food was grown. In contrast, urchins held under present day conditions and fed kelp grown under future conditions showed higher feeding and growth rates compared to similar urchins fed kelps grown under present day conditions. Together, my data suggest that M. pyrifera may benefit physiologically from a warmer, more acidic (i.e. higher pCO₂) ocean while S. purpuratus will likely be impacted negatively. Given that S. purpuratus can exert a strong deterministic influence on M. pyrifera distribution and abundance, changes to either of their populations that might arise from climate change can alter how they interact and thus have serious consequences for many coastal environments.
Continue reading ‘The effects of rising ocean temperature and pCO2 on the physiology and growth of giant kelp, Macrocystis pyrifera, and grazing by purple urchins, Strongylocentrotus purpuratus’

Effects of ocean acidification on the early developmental stages of the horned turban, Turbo cornutus

To estimate the impact of CO2-driven ocean acidification on the early life stages of gastropods, the effects of increased partial pressure of seawater carbon dioxide (pCO2) (800–2,000 μatm) on the early developmental stages and larval shell length of the commercially important gastropod, the horned turban snail, Turbo cornutus were investigated. Increase in experimental seawater pCO2 had an increasingly negative impact on the early developmental rate; the proportion of embryos or larvae displaying retarded development increased at higher pCO2. The proportion of embryos that developed to the 4-cell stage at 2 h after fertilization decreased linearly with increasing pCO2. At ~1,000 μatm pCO2, retarded development was observed in ~50 % of larvae. No embryos developed to the 4-cell stage at 2,000 μatm pCO2 within 2 h of fertilization. A similar trend continued until 24–26 h after fertilization; the proportion of larvae attaining veliger stage by 24–26 h also decreased with increasing pCO2. The shell length of T. cornutus veligers decreased gradually as seawater pCO2 increased, but markedly decreased in seawater under nearly unsaturated and unsaturated conditions (≤1.04) of the aragonite saturation state (Ω aragonite). The results indicate that increased pCO2 seawater has a progressive and acute effect on embryonic and larval T. cornutus, and imply that the extended early developmental period and/or the downsized larval shell produced by ocean acidification will have a negative impact on survival, settlement and recruitment well into the future.
Continue reading ‘Effects of ocean acidification on the early developmental stages of the horned turban, Turbo cornutus’

Elevated pCO2 exposure during fertilization of the bay scallop Argopecten irradians reduces larval survival but not subsequent shell size

Ocean acidification, characterized by elevated partial pressure of CO2 (pCO2), generally has negative effects on early life stages of invertebrates. We tested the idea that fertilization is a critical CO2 exposure stage for the bay scallop Argopecten irradians by determining the effects on bay scallops of exposure to high CO2 (pCO2 ~2600 ppm, pH ~7.30) from fertilization to 7 d old. To assess the possibility of persistent effects of exposure during fertilization, further treatments included switches from high CO2 to ambient CO2 (pCO2 ~480 ppm, pH ~7.96) and from ambient CO2 to high CO2 at 2 h post-fertilization. Survival of larvae decreased significantly when they were fertilized in high CO2. A switch in CO2 conditions 2 h post-fertilization did not change this effect, suggesting that the critical exposure window for this survival effect is within the first 2 h. In contrast, CO2 conditions during fertilization did not affect larval shell size, but the switch treatments showed that exposure to high CO2 after 2 h post-fertilization decreased shell size, indicating that the exposure window for a size effect was later in development, possibly during shell calcification. Finally, a shell deformity was seen in scallops with continuous exposure to high CO2 and those switched from ambient CO2 to high CO2 at 2 h post-fertilization. Decreased survival during fertilization and smaller larval shell size due to ocean acidification could ultimately reduce the population size of this commercially important bivalve, which has already seen dramatic population decline due to loss of juvenile habitat.
Continue reading ‘Elevated pCO2 exposure during fertilization of the bay scallop Argopecten irradians reduces larval survival but not subsequent shell size’

Subsurface pH and carbonate saturation state of aragonite on the Chinese side of the North Yellow Sea: seasonal variations and controls (update)

Based upon eight field surveys conducted between May 2011 and May 2012, we investigated seasonal variations in pH, carbonate saturation state of aragonite (Ωarag), and ancillary data on the Chinese side of the North Yellow Sea, a western North Pacific continental margin of major economic importance. Subsurface waters were CO2-undersaturated in May and nearly in equilibrium with atmospheric CO2 in June. From July to October, the fugacity of CO2 (fCO2) of bottom water gradually increased from 438 ± 44 μatm to 630 ± 84 μatm, and pHT decreased from 8.02 ± 0.04 to 7.88 ± 0.06 due to local aerobic remineralization of primary-production-induced biogenic particles. The subsurface community respiration rates in summer and autumn were estimated to be from 0.80 to 1.08 μmol-O2 kg−1 d−1 within a relatively high salinity range of 31.63 to 32.25. From November to May in the next year, however, subsurface fCO2 gradually decreased and pH increased due to cooling and water column ventilation. The corresponding bottom water Ωarag was 1.85 ± 0.21 (May), 1.79 ± 0.24 (June), 1.75 ± 0.27 (July), 1.76 ± 0.29 (August), 1.45 ± 0.31 (October), 1.52 ± 0.25 (November), and 1.41 ± 0.12 (January). Extremely low Ωarag values (from 1.13 to 1.40) were observed mainly in subsurface waters within the high salinity range of 31.63 to 32.25, which covered a major fraction of the study area in October and November. Of the China seas, the North Yellow Sea represents one of the systems most vulnerable to the potential negative effects of ocean acidification.
Continue reading ‘Subsurface pH and carbonate saturation state of aragonite on the Chinese side of the North Yellow Sea: seasonal variations and controls (update)’

Acidic water blamed for West Coast scallop die-off

9550862Nanaimo-based Island Scallops has shut down its processing plant and laid off a third of its workforce.

Ten million scallops that have died in the waters near Qualicum Beach due to rising ocean acidity are the latest victims in a series of marine die-offs that have plagued the West Coast for a decade.

Human-caused carbon dioxide emissions in the atmosphere are being absorbed by the ocean and may have pushed local waters through a “tipping point” of acidity beyond which shellfish cannot survive, according to Chris Harley, a marine ecologist at the University of B.C.
Continue reading ‘Acidic water blamed for West Coast scallop die-off’


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Ocean acidification in the IPCC AR5 WG II

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