Archive for January, 2013

Effect of increased pCO2 on the planktonic metabolic balance during a mesocosm experiment in an Arctic fjord (update)

The effect of ocean acidification on the balance between gross community production (GCP) and community respiration (CR) (i.e., net community production, NCP) of plankton communities was investigated in summer 2010 in Kongsfjorden, west of Svalbard. Surface water, which was characterized by low concentrations of dissolved inorganic nutrients and chlorophyll a (a proxy of phytoplankton biomass), was enclosed in nine mesocosms and subjected to eight pCO2 levels (two replicated controls and seven enhanced pCO2 treatments) for one month. Nutrients were added to all mesocosms on day 13 of the experiment, and thereafter increase of chlorophyll a was provoked in all mesocosms. No clear trend in response to increasing pCO2 was found in the daily values of NCP, CR, and GCP. For further analysis, these parameters were cumulated for the following three periods: phase 1 – end of CO2 manipulation until nutrient addition (t4 to t13); phase 2 – nutrient addition until the second chlorophyll a minimum (t14 to t21); phase 3 – the second chlorophyll a minimum until the end of this study (t22 to t28). A significant response was detected as a decrease of NCP with increasing pCO2 during phase 3. CR was relatively stable throughout the experiment in all mesocosms. As a result, the cumulative GCP significantly decreased with increasing pCO2 during phase 3. After the nutrient addition, the ratios of cumulative NCP to cumulative consumption of NO3 and PO4 showed a significant decrease during phase 3 with increasing pCO2. The results suggest that elevated pCO2 influenced cumulative NCP and stoichiometric C and nutrient coupling of the plankton community in a high-latitude fjord only for a limited period. However provided that there were some differences or weak correlations between NCP data based on different methods in the same experiment, this conclusion should be taken with caution.

Continue reading ‘Effect of increased pCO2 on the planktonic metabolic balance during a mesocosm experiment in an Arctic fjord (update)’

Ocean acidification – can corals cope?

Sat. Feb. 2, Dr. Martin Tresguerres of the Scripps Institution of Oceanography will speak by nat’l conference call to Citizens Climate Lobby (CCL) meeting in Lakeville, on the topic of “Ocean Acidification – Can Corals Cope?”

Prof. Tresguerres will speak on global warming’s evil twin – ocean acidification, which could lead to a collapse of the marine food chain.

Continue reading ‘Ocean acidification – can corals cope?’

Ocean acidification monitors coming to Alaska (audio)

Alaska will soon have a monitoring system for rising levels of acidity in the ocean. The state Legislature provided $2.7 million to set up a network of buoy sensors along the coast. Scientists got an update on ocean acidification yesterday at the Alaska Marine Science Symposium in Anchorage.

Continue reading ‘Ocean acidification monitors coming to Alaska (audio)’

Response of bacterioplankton activity in an Arctic fjord system to elevated pCO2: results from a mesocosm perturbation study (update)

The effect of elevated seawater carbon dioxide (CO2) on the activity of a natural bacterioplankton community in an Arctic fjord system was investigated by a mesocosm perturbation study in the frame of the European Project on Ocean Acidification (EPOCA). A pCO2 range of 175–1085 μatm was set up in nine mesocosms deployed in the Kongsfjorden (Svalbard). The activity of natural extracellular enzyme assemblages increased in response to acidification. Rates of β-glucosidase and leucine-aminopeptidase increased along the gradient of mesocosm pCO2. A decrease in seawater pH of 0.5 units almost doubled rates of both enzymes.

Heterotrophic bacterial activity was closely coupled to phytoplankton productivity in this experiment. The bacterioplankton community responded to rising chlorophyll a concentrations after a lag phase of only a few days with increasing protein production and extracellular enzyme activity. Time-integrated primary production and bacterial protein production were positively correlated, strongly suggesting that higher amounts of phytoplankton-derived organic matter were assimilated by heterotrophic bacteria at increased primary production. Primary production increased under high pCO2 in this study, and it can be suggested that the efficient heterotrophic carbon utilisation had the potential to counteract the enhanced autotrophic CO2 fixation. However, our results also show that beneficial pCO2-related effects on bacterial activity can be mitigated by the top-down control of bacterial abundances in natural microbial communities.

Continue reading ‘Response of bacterioplankton activity in an Arctic fjord system to elevated pCO2: results from a mesocosm perturbation study (update)’

High heat flow and ocean acidification at a nascent rift in the northern Gulf of California

The prevailing tectonic setting in the Gulf California suggests the presence of an undetermined number of short spreading centres with associated hydrothermal systems. However, to date, active seafloor spreading phenomena have been documented in only three of the eight tectonically active basins. Here we report heat flow values as high as 15,436 mW m−2 in two of the northernmost basins of the Gulf of California, providing evidence of intense hydrothermal activity associated with the transition from continental rifting to seafloor spreading. The mean heat flow for the Wagner and Consag basins area is 1,875 mW m−2, more than 15 times higher than the mean value for oceanic crust (105.4 mW m−2). Additional evidence for vigorous hydrothermal circulation and a shallow heat source includes intense gas discharge (CO2 and CH4), widespread low pH (average 7.7), locally high 222Rn concentrations in the bottom water and a high extent of organic matter maturation in the sediments.

Continue reading ‘High heat flow and ocean acidification at a nascent rift in the northern Gulf of California’

Interactive comment on “Ocean acidification increases photosynthate translocation in a coral–dinoflagellates symbiosis” by P. Tremblay et al.

This is not a full review, just an open comment providing some suggestions on this interesting manuscript.

– The title and first paragraph of the introduction set the experiments in the context of anthropogenic ocean acidification and the abstract concludes “this decrease might have important consequences for the survival of corals under an acidification stress”. Yet, the perturbation used, pH of 7.2 and pCO2 of almost 4000 atm, are not relevant in this context. Barry et al. (2011) provide guidelines on the experimentaldesign of ocean acidification perturbation experiments. I suggest that the title, abstract and introduction should be revised in order to avoid misleading the readership.

Continue reading ‘Interactive comment on “Ocean acidification increases photosynthate translocation in a coral–dinoflagellates symbiosis” by P. Tremblay et al.’

BIOS Explorer 2013 – ocean acidification (video)

Continue reading ‘BIOS Explorer 2013 – ocean acidification (video)’

Oceans at risk, a culture at stake

We have seen many significant changes to Washington’s landscape, climate and waters in our lifetime. We have watched with dismay as habitat, salmon runs, and shellfish beds have been lost. Ocean acidification is the most recently recognized of these changes, a serious and immediate threat to our marine resources, one that has developed at an alarming and unprecedented rate.

Salmon and shellfish are at the very core of the Tulalip Tribes’ and other first nations’ culture. More than just traditional food staples and economic health are at risk here. Our very culture is at stake. These Northwest icons and many other marine species and thousands of Washington jobs are in jeopardy and need our protection.

Continue reading ‘Oceans at risk, a culture at stake’

Survival of the fittest: ocean acidification produces winners and losers

As atmospheric carbon dioxide levels continue to increase, the ocean absorbs more carbon dioxide. This absorption comes at a cost, since it makes the ocean more acidic. An acid ocean will affect all marine species, but the potential severity of these effects is the subject of debate.

Most research on ocean acidification has focused on the response of pooled groups of animals. A recent study published in the journal PLoS ONE by a research team at Macquarie University has examined the responses of individual animals. They used the common purple sea urchin (Heliocidaris erythrogramma) to test if some individuals benefit from a more acidic ocean.

Continue reading ‘Survival of the fittest: ocean acidification produces winners and losers’

Benthic interactions in a high CO2-world

The Baltic Sea is a physically diverse habitat with a generally low species diversity. The blue mussel Mytilus edulis is widely distributed in the benthic macrozoobenthos of the Western Baltic, the main predators of which are the common sea star Asterias rubens and the shore crab Carcinus maenas. Any environmental stress influencing the predator-prey interactions between these species has the potential to shape the entire ecosystem. The current increase in atmospheric pCO2 causes a concurrent increase in the acidification of seawater and can thus pose such an environmental stress. In coastal habitats and specifically the Baltic Sea, the decrease of seawater pH can be much more pronounced than in the open ocean. In order to estimate possible interaction shifts in the macrozoobenthos under conditions of seawater acidification, this work investigates the effect of an increase in water pCO2 on the predators A. rubens and C. maenas and their consumption of M. edulis. The results of three different own studies show an impact of increased seawater pCO2 around 3500 μatm on growth and mussel consumption in adult sea stars and a seawater pCO2 of around 1200 μatm to impact growth, mussel consumption, scope for growth and righting response of juvenile A. rubens. Mussel sizes consumed, metabolism, NH4+-excretion and calcification were, however, not impacted by an increase in seawater acidification and coelomic pH not regulated by means of active bicarbonate accumulation. Crabs were impacted in metabolism, NH4+-excretion, O:N-ratio and metabolic energy loss at a seawater pCO2 of about 3500 μatm. Mussel consumption was only impacted at a pCO2 of 3500 μatm, over intermediate time spans (10 weeks), but not over a longer (six month) time span. Hemolyph pH was regulated to remain at control levels by active bicarbonate accumulation at intermediate (10 week) time spans over all levels of seawater acidification, while hemolymph pH followed the non-bicarbonate buffer line at the intermediate (around 1200 μatm) level and was only regulated at the high (around 3500 μatm) treatment level over the long (six month) time span. Moulting intervals, growth, mussel sizes consumed, carapace thickness, stability, dry weight and calcification were not influenced by seawater acidification These results indicate a change in feeding pressure on the blue mussel M. edulis under future high levels of seawater acidification. Further, A. rubens appears stronger impacted by seawater acidification than C. maenas and juvenile A. rubens even stronger than adult specimen. I conclude that seawater acidification has the potential to reshape the benthic ecosystem of the Western Baltic. This work therefore helps to understand ecosystem responses to environmental stress and contributes to making predictions on future species distributions in the Baltic Sea.

Continue reading ‘Benthic interactions in a high CO2-world’

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Ocean acidification in the IPCC AR5 WG II

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