Archive for January, 2013

Effects of sea-water acidification on fertilization and larval development of the oyster Crassostrea gigas

Oceans face a serious change to their natural biogeochemical cycle due to the rapid absorption of CO2 generated by human activities. Ocean acidification is the common term used to describe the decrease of seawater pH caused by the absorption of atmospheric CO2. To evaluate the effects of ocean acidification, we focused on the larval stage of bivalves, which produce a fragile calcareous skeletal structure, very sensitive to changes in seawater chemistry. In this context, we investigated sperm motility, fertilization rate and larval viability (survival, growth and abnormalities) of the Pacific oyster, Crassostrea gigas, a commercially important bivalve, in a controlled CO2 perturbation experiment. The carbonate chemistry of seawater was manipulated by diffusing pure CO2, to attain two reduced pH levels (ΔpH = − 0.4 and ΔpH = − 0.7) which were compared to unmanipulated seawater. The results show high sensitivity of C. gigas veliger larvae to low values of pH, as reflected by a decrease in survival and growth rates, as well as an increased frequency of prodissoconch abnormalities and protruding mantle. Moreover, results also show that sperm motility, fertilization rate, and hatching success, were negatively influenced by acidification. The exposure to ΔpH = − 0.7 had a higher impact on the fertilization and larval viability than ΔpH = − 0.4. The results suggest that the reproductive success and the biological mechanisms for calcification may be prematurely interrupted and disturbed when C. gigas veliger larvae are exposed to an acidified environment which may reduce their viability and compromise settlement and future abundances of this species.

Continue reading ‘Effects of sea-water acidification on fertilization and larval development of the oyster Crassostrea gigas’

CO2-induced ocean acidification impairs calcification in the tropical urchin Echinometra viridis

Atmospheric carbon dioxide (pCO2) has risen from approximately 280 to 400 ppm since the Industrial Revolution, due mainly to the combustion of fossil fuels, deforestation, and cement production. It is predicted to reach as high as 900 ppm by the end of this century. Ocean acidification resulting from the release of anthropogenic CO2 has been shown to impair the ability of some marine calcifiers to build their shells and skeletons. Here, we present the results of ocean acidification experiments designed to assess the effects of an increase in atmospheric pCO2 from ca. 448 to 827 ppm on calcification rates of the tropical urchin Echinometra viridis. Experiments were conducted under the urchin’s winter (20 °C) and summer (30 °C) water temperatures in order to identify seasonal differences in the urchin’s response to ocean acidification. The experiments reveal that calcification rates decreased for urchins reared under elevated pCO2, with the decline being more pronounced under wintertime temperatures than under summertime temperatures. These results indicate that the urchin E. viridis will be negatively impacted by CO2-induced ocean acidification that is predicted to occur by the end of this century. These results also suggest that impact of CO2-induced ocean acidification on urchin calcification will be more severe in the winter and in cooler waters.

Continue reading ‘CO2-induced ocean acidification impairs calcification in the tropical urchin Echinometra viridis’

Follow BIOACID on Facebook and Twitter!

You can now follow BIOACID, and the ongoing mesocosm experiments in Kristineberg in Sweden, on Facebook and Twitter.

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Unikt forskningsprojekt om försurning (video; in Swedish)

I ett unikt forskningsprojekt som inleddes under torsdagen utanför Lysekil i Bohuslän ska försurningen av våra hav studeras. Tio enorma plastprovrör ska sättas ut, och där ska forskarna studera plankton och fisklarver under fem månader.

Continue reading ‘Unikt forskningsprojekt om försurning (video; in Swedish)’

Pigga plankton i sura hav (video; in Swedish)

Video in Swedish on the BIOACID mesocosm experiment currently taking place in Sweden.

Continue reading ‘Pigga plankton i sura hav (video; in Swedish)’

Försurningen i havet kartläggs (video; in Swedish)

Tio jättelika plasttorn ska inom kort sättas ut i Gullmarsfjorden. Det blir startskottet för en fem månaders forskarstudie i syfte att se försurningens effekter på havet.

I de 20 meter långa plaströren, som ska sticka upp ett par meter ovanför vattenytan, ska det bland annat finnas djurplankton. Genom att tillsätta olika halter av koldioxid ska forskarna se hur de påverkas vid olika surhetsgrader.

Det är världens hittills största experiment i sitt slag.

Continue reading ‘Försurningen i havet kartläggs (video; in Swedish)’

Ocean acidification and sea scallops: predicting impacts of climate change

Project Status: This project began in January, 2012 and is projected to be completed in December, 2015

We are supporting the development of an integrated model to forecast impacts of ocean acidification on the Atlantic sea scallop fishery. The model will (1) predict ocean acidification trends, (2) determine effects on sea scallop populations and landings and (3) project impacts to the fishery and regional economy.

Continue reading ‘Ocean acidification and sea scallops: predicting impacts of climate change’

Ocean acidification shows negligible impacts on high-latitude bacterial community structure in coastal pelagic mesocosms (update)

The impact of ocean acidification and carbonation on microbial community structure was assessed during a large-scale in situ costal pelagic mesocosm study, included as part of the EPOCA 2010 Arctic campaign. The mesocosm experiment included ambient conditions (fjord) and nine mesocosms with pCO2 levels ranging from ~145 to ~1420 μatm. Samples for the present study were collected at ten time points (t–1, t1, t5, t7, t12, t14, t18, t22, t26 to t28) in seven treatments (ambient fjord (~145), 2 × ~185, ~270, ~685, ~820, ~1050 μatm) and were analysed for “small” and “large” size fraction microbial community composition using 16S RNA (ribosomal ribonucleic acid) amplicon sequencing. This high-throughput sequencing analysis produced ~20 000 000 16S rRNA V4 reads, which comprised 7000 OTUs. The main variables structuring these communities were sample origins (fjord or mesocosms) and the community size fraction (small or large size fraction). The community was significantly different between the unenclosed fjord water and enclosed mesocosms (both control and elevated CO2 treatments) after nutrients were added to the mesocosms, suggesting that the addition of nutrients is the primary driver of the change in mesocosm community structure. The relative importance of each structuring variable depended greatly on the time at which the community was sampled in relation to the phytoplankton bloom. The sampling strategy of separating the small and large size fraction was the second most important factor for community structure. When the small and large size fraction bacteria were analysed separately at different time points, the only taxon pCO2 was found to significantly affect were the Gammaproteobacteria after nutrient addition. Finally, pCO2 treatment was found to be significantly correlated (non-linear) with 15 rare taxa, most of which increased in abundance with higher CO2.

Continue reading ‘Ocean acidification shows negligible impacts on high-latitude bacterial community structure in coastal pelagic mesocosms (update)’

Response of Nodularia spumigena to pCO2 – Part 2: Exudation and extracellular enzyme activities (update)

The filamentous and diazotrophic cyanobacterium Nodularia spumigena plays a major role in the productivity of the Baltic Sea as it forms extensive blooms regularly. Under phosphorus limiting conditions Nodularia spumigena have a high enzyme affinity for dissolved organic phosphorus (DOP) by production and release of alkaline phosphatase. Additionally, they are able to degrade proteinaceous compounds by expressing the extracellular enzyme leucine aminopeptidase. As atmospheric CO2 concentrations are increasing, we expect marine phytoplankton to experience changes in several environmental parameters, including pH, temperature, and nutrient availability. The aim of this study was to investigate the combined effect of CO2-induced changes in seawater carbonate chemistry and of phosphate deficiency on the exudation of organic matter, and its subsequent recycling by extracellular enzymes in a Nodularia spumigena culture. Batch cultures of Nodularia spumigena were grown for 15 days under aeration with low (180 μatm), medium (380 μatm), and high (780 μatm) CO2 concentrations. Obtained pCO2 levels in the treatments were on median 315, 353, and 548 μatm CO2, respectively. Extracellular enzyme activities as well as changes in organic and inorganic compound concentrations were monitored. CO2 treatment–related effects were identified for cyanobacterial growth, which in turn influenced the concentration of mucinous substances and the recycling of organic matter by extracellular enzymes. Biomass production was increased by 56.5% and 90.7% in the medium and high pCO2 treatment, respectively, compared to the low pCO2 treatment. In total, significantly more mucinous substances accumulated in the high pCO2 treatment, reaching 363 μg Xeq L−1 compared to 269 μg Xeq L−1 in the low pCO2 treatment. However, cell-specific rates did not change. After phosphate depletion, the acquisition of P from DOP by alkaline phosphatase was significantly enhanced. Alkaline phosphatase activities were increased by factor 1.64 and 2.25, respectively, in the medium and high compared to the low pCO2 treatment. We hypothesise from our results that Nodularia spumigena can grow faster under elevated pCO2 by enhancing the recycling of organic matter to acquire nutrients.

Continue reading ‘Response of Nodularia spumigena to pCO2 – Part 2: Exudation and extracellular enzyme activities (update)’

Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change (update)

We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity (AT) from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite). The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC) and particulate organic carbon (POC) fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq. yr−1, primarily from PIC dissolution (46%) and ammonification (33%). Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1and alkalinity efflux by 4.8 Teq. yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC, alkalinity and nutrient fluxes under variable scenarios of ocean productivity and chemistry, but also provides insights into the underlying processes.

Continue reading ‘Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change (update)’

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Ocean acidification in the IPCC AR5 WG II

OUP book