Posts Tagged 'North Pacific'

Quasi‐real‐time and high‐resolution spatiotemporal distribution of ocean anthropogenic CO2

Increasing marine uptake of anthropogenic CO2 (Cant) causes global ocean acidification. To obtain a high‐resolution spatiotemporal distribution of oceanic carbon chemistry, we developed new parameterizations of the seawater total alkalinity (TA), and dissolved inorganic carbon (DIC) from the ocean’s surface to 2000 m depth by using dissolved oxygen (DO), water temperature (T), salinity (S), and pressure (P) data. Using the values of TA and DIC predicted by DO, T, S, and P data derived from autonomous biogeochemical Argo floats (BGC‐Argo), we described the distribution of oceanic Cant in the 2000s in the subarctic North Pacific at high spatiotemporal resolution. The Cant was found about 300 m deeper than during the 1990s; its average inventory to 2000 m was 24.8 ± 10.2 mol m–2, about 20% higher than the 1990s average. Future application of parameterizations to global BGC‐Argo data should allow the detailed global mapping of spatiotemporal distributions of CO2 parameters.

Continue reading ‘Quasi‐real‐time and high‐resolution spatiotemporal distribution of ocean anthropogenic CO2’

Impacts of urban carbon dioxide emissions on sea-air flux and ocean acidification in nearshore waters

Greatly enhanced atmospheric carbon dioxide (CO2) levels relative to well-mixed marine air are observed during periods of offshore winds at coastal sensor platforms in Monterey Bay, California, USA. The highest concentrations originate from urban and agricultural areas, are driven by diurnal winds, and peak in the early morning. These enhanced atmospheric levels can be detected across a ~100km wide nearshore area and represent a significant addition to total oceanic CO2 uptake. A global estimate puts the added sea-air flux of CO2 from these greatly enhanced atmospheric CO2 levels at 25 million tonnes, roughly 1% of the ocean’s annual CO2 uptake. The increased uptake over the 100 km coastal swath is of order 20%, indicating a potentially large impact on ocean acidification in productive coastal waters.

Continue reading ‘Impacts of urban carbon dioxide emissions on sea-air flux and ocean acidification in nearshore waters’

Better regional ocean observing through cross-national cooperation: a case study from the Northeast Pacific

The ocean knows no political borders. Ocean processes, like summertime wind-driven upwelling, stretch thousands of kilometers along the Northeast Pacific (NEP) coast. This upwelling drives marine ecosystem productivity and is modulated by weather systems and seasonal to interdecadal ocean-atmosphere variability. Major ocean currents in the NEP transport water properties such as heat, fresh water, nutrients, dissolved oxygen, pCO2, and pH close to the shore. The eastward North Pacific Current bifurcates offshore in the NEP, delivering open-ocean signals south into the California Current and north into the Gulf of Alaska. There is a large and growing number of NEP ocean observing elements operated by government agencies, Native American Tribes, First Nations groups, not-for-profit organizations, and private entities. Observing elements include moored and mobile platforms, shipboard repeat cruises, as well as land-based and estuarine stations. A wide range of multidisciplinary ocean sensors are deployed to track, for example, upwelling, downwelling, ocean productivity, harmful algal blooms, ocean acidification and hypoxia, seismic activity and tsunami wave propagation. Data delivery to shore and observatory controls are done through satellite and cell phone communication, and via seafloor cables. Remote sensing from satellites and land-based coastal radar provide broader spatial coverage, while numerical circulation and biogeochemical modeling complement ocean observing efforts. Models span from the deep ocean into the inland Salish Sea and estuaries. NEP ocean observing systems are used to understand regional processes and, together with numerical models, provide ocean forecasts. By sharing data, experiences and lessons learned, the regional ocean observatory is better than the sum of its parts.

Continue reading ‘Better regional ocean observing through cross-national cooperation: a case study from the Northeast Pacific’

Seasonal calcification of the coral Acropora digitifera from a subtropical marginal Okinawa reef under ocean acidification

Coral calcification is affected by the decrease in aragonite saturation state (Ωarag) caused by ocean acidification (OA). However, OA effects are modulated by other environmental factors such as seawater temperature, light intensity and nutrients. Considering that in subtropical coral reefs all these factors vary seasonally, it can be hypothesized that the magnitude of OA effects on coral physiology will also vary seasonally. We evaluated the seasonal coral calcification rate of a subtropical reef-building coral under OA conditions. We approached this aim by culturing Acropora digitifera under three different CO2 partial pressure (pCO2) conditions in three different seasons (summer, autumn and winter) under natural light and temperature conditions. Additionally, to predict future coral net G, the year-round seawater carbonate chemistry was measured on the coast of Okinawa Island, and the annual coral CaCO3production amount assessed considering seasonal changes in environmental conditions. Coral A. digitifera net calcification (net G) significantly differed among seasons, and summer net Gwas 1.7 and 2.7 times higher than autumn and winter, respectively. However, the impact of OA did not differ among seasons and the rate of net G decrease per unit Ωarag was 11.1%, 17.4% and 18.7% for summer, autumn and winter, respectively. The regression model indicated that net Gof A. digitifera is primarily affected by temperature, secondly by seawater Ωarag, while light intensity was not selected as an explanatory factor, and there was no interactive effect among the factors. The model predicts that the present annual A. digitifera net G in Okinawa Island reef (present mean annual pCO2: 382 μatm and Ωarag: 3.49) is about 0.3 g CaCO3 cm−2 y−1, and it will decrease by 20% with an increase of 500 μatm seawater pCO2 than the present condition. As reefs in high-latitude regions already have marginal positive net G, further decrease in annual CaCO3 production would be detrimental for the reef under conditions of climate change.

Continue reading ‘Seasonal calcification of the coral Acropora digitifera from a subtropical marginal Okinawa reef under ocean acidification’

Variations in dissolved inorganic carbon species in effluents from large-scale municipal wastewater treatment plants (Qingdao, China) and their potential impacts on coastal acidification

With rapid development of global wastewater treatment plants (WWTPs), acidification and enhanced CO2 release in receiving waters caused by high-CO2 treated wastewater input have raised concerns. Insights into the variations in dissolved inorganic carbon (DIC) species in treated wastewater contribute to understanding the mechanisms of the acidification process. Here, we investigated three large-scale municipal WWTPs that discharged into the coast of Qingdao, China, for variations in effluent DIC species and their control mechanisms. The results showed that the effluent DIC concentrations, with a range of 2554–5718 μmol/L, significantly exceeded the concentration in seawater and mainly increased from winter to spring and decreased from summer to autumn. The effluent DIC and its δ13CDIC showed a good negative correlation. The ratios of effluent DIC to total alkalinity (DIC/TAlk) ranged from 1.00 to 1.24, and the proportions of CO2 in DIC ranged from 0.9 to 19.7%; both sets of values significantly exceeded those in seawater. The proportions of CO32− in DIC were only ~ 0.4%. These features determined that the CO2 concentrations in effluents fluctuated from 3 to 80 times the concentration in seawater, whereas the CO32− concentrations were less than 1/15 of those in seawater. Organic matter degradation and nitrogen removal processes made important contributions to the high effluent CO2 concentrations. The increase in solubility induced by decreased temperature may be the main cause for the higher effluent CO2 concentrations during winter as well as spring months with low effluent temperatures. Correspondingly, the effluent pH values were significantly lower than the seawater pH values and showed a good negative logarithmic correlation with the DIC/TAlk values, reflecting the control of DIC species on the pH values in treated wastewater. Variations in DIC species in treated wastewater can cause changes in the affected region and the degree of the induced acidification in receiving waters.

Continue reading ‘Variations in dissolved inorganic carbon species in effluents from large-scale municipal wastewater treatment plants (Qingdao, China) and their potential impacts on coastal acidification’

Ocean acidification regulates the activity, community structure and functional potential of heterotrophic bacterioplankton in an oligotrophic gyre

Ocean acidification (OA), a consequence of increased global carbon dioxide (CO2) emissions, is considered a major threat to marine ecosystems. Its effects on bacterioplankton activity, diversity and community composition have received considerable attention. However, the direct impact of OA on heterotrophic bacterioplankton is often masked by the significant response of phytoplankton due to the close coupling of heterotrophic bacterioplankton and autotrophs. Here, we investigated the responses of a heterotrophic bacterioplankton assemblage to high pCO2 (790 ppm) treatment in warm tropical western Pacific waters by conducting a microcosm experiment in dark for 12 days. Heterotrophic bacterioplankton abundance and production were enhanced by OA over the first 6 days of incubation, while the diversity and species richness were negatively affected. Bacterioplankton community composition in the high pCO2 treatment changed faster than that in the control. The molecular ecological network analysis showed that the elevated CO2changed the overall connections among the bacterial community and resulted in a simple network under high CO2 condition. Species‐specific responses to OA were observed and could be attributed to the different life strategies and to the ability of a given species to adapt to environmental conditions. In addition, high‐throughput functional gene array analysis revealed that genes related to carbon and nitrogen cycling were positively affected by acidification. Together, our findings suggest that OA has direct effects on heterotrophic bacterioplankton in a low‐latitude warm ocean and may therefore affect global biogeochemical cycles.

Continue reading ‘Ocean acidification regulates the activity, community structure and functional potential of heterotrophic bacterioplankton in an oligotrophic gyre’

Eco-physiological responses of copepods and pteropods to ocean warming and acidification

We compare physiological responses of the crustacean copepod Calanus pacificus and pelagic pteropod mollusk Limacina helicina to ocean temperatures and pH by measuring biomarkers of oxidative stress, antioxidant defences, and the activity of the respiratory electron transport system in organisms collected on the 2016 West Coast Ocean Acidification cruise in the California Current System. Copepods and pteropods exhibited strong but divergent responses in the same habitat; copepods had higher oxygen-reactive absorbance capacity, glutathione-S-transferase, and total glutathione content. The ratio between reduced to oxidised glutathione was higher in copepods than in pteropods, indicating lower oxidative stress in copepods. Pteropods showed higher activities of glutathione reductase, catalase, and lipid peroxidation, indicating increased antioxidant defences and oxidative stress. Thus, the antioxidant defence system of the copepods has a greater capacity to respond to oxidative stress, while pteropods already face severe stress and show limited capacity to deal with further changes. The results suggest that copepods have higher adaptive potential, owing to their stronger vertical migration behaviour and efficient glutathione metabolism, whereas pteropods run the risk of oxidative stress and mortality under high CO2 conditions. Our results provide a unique dataset and evidence of stress-inducing mechanisms behind pteropod ocean acidification responses.

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Ocean acidification in the IPCC AR5 WG II

OUP book