Seawater carbonate chemistry and biological processes of coral Acropora muricata during experiments and observations in La Saline fringing reef, La Reunion Island, western Indian Ocean, 2011

The effect of decreasing aragonite saturation state (Omega Arag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440-340 µatm), Omega Arag (1.4-4.0), and dissolved inorganic carbon (DIC) concentrations (2,100-1,850 µmol/kg). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in Omega Arag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 µmol/kg (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to Omega Arag at BR. When normalized to NP, calcification was linearly related to Omega Arag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low Omega Arag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased Omega Arag (increased pCO2) whatever the nutrient loading.

Seawater carbonate chemistry and protein and chlorophyll a content per nubbin of Acropora muricata during observations of La Saline fringing reef, La Reunion Island, western Indian Ocean, 2011

The effect of decreasing aragonite saturation state (Omega Arag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440-340 µatm), Omega Arag (1.4-4.0), and dissolved inorganic carbon (DIC) concentrations (2,100-1,850 µmol/kg). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in Omega Arag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 µmol/kg (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to Omega Arag at BR. When normalized to NP, calcification was linearly related to Omega Arag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low Omega Arag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased Omega Arag (increased pCO2) whatever the nutrient loading.

(Table 1) Geographical location and nutrient composition of saline lake sediments (SLS) and nearby adjacent biological soil crusts (BSC) identified as potential dust sources

While microbial communities of aerosols have been examined, little is known about their sources. Nutrient composition and microbial communities of potential dust sources, saline lake sediments (SLS) and adjacent biological soil crusts (BSC), from Southern Australia were determined and compared with a previously analyzed dust sample. Multivariate analyses of fingerprinting profiles indicated that the bacterial communities of SLS and BSC were different, and these differences were mainly explained by salinity. Nutrient concentrations varied among the sites but could not explain the differences in microbial diversity patterns. Comparison of microbial communities with dust samples showed that deflation selects against filamentous cyanobacteria, such as the Nostocales group. This could be attributed to the firm attachment of cyanobacterial filaments to soil particles and/or because deflation occurs mainly in disturbed BSC, where cyanobacterial diversity is often low. Other bacterial groups, such as Actinobacteria and the spore-forming Firmicutes, were found in both dust and its sources. While Firmicutes-related sequences were mostly detected in the SLS bacterial communities (10% of total sequences), the actinobacterial sequences were retrieved from both (11-13%). In conclusion, the potential dust sources examined here show highly diverse bacterial communities and contain nutrients that can be transported with aerosols. The obtained fingerprinting and sequencing data may enable back tracking of dust plumes and their microorganisms.

Table 2 & Appendix A. Properties of operations injecting CO2 into saline aquifers

The experience from CO2 injection at pilot projects (Frio, Ketzin, Nagaoka, US Regional Partnerships) and existing commercial operations (Sleipner, Snøhvit, In Salah, acid-gas injection) demonstrates that CO2 geological storage in saline aquifers is technologically feasible. Monitoring and verification technologies have been tested and demonstrated to detect and track the CO2 plume in different subsurface geological environments. By the end of 2008, approximately 20 Mt of CO2 had been successfully injected into saline aquifers by existing operations. Currently, the highest injection rate and total storage volume for a single storage operation are approximately 1 Mt CO2/year and 25 Mt, respectively. If carbon capture and storage (CCS) is to be an effective option for decreasing greenhouse gas emissions, commercial-scale storage operations will require orders of magnitude larger storage capacity than accessed by the existing sites. As a result, new demonstration projects will need to develop and test injection strategies that consider multiple injection wells and the optimisation of the usage of storage space. To accelerate large-scale CCS deployment, demonstration projects should be selected that can be readily employed for commercial use; i.e. projects that fully integrate the capture, transport and storage processes at an industrial emissions source.