CH4 emissions from runoff water of Alaskan mountain glaciers.

Recent studies have observed high methane concentrations in runoff water and the ambient air at various glacier sites, including the Greenland Ice Sheet, the glacier forefield in Svalbard, and the ice cap in Iceland. This study extends these findings to smaller mountain glaciers in Alaska. Methane and carbon dioxide concentrations in the ambient air near the meltwater outlet, fluxes of these gases at the surface of runoff water and riverbank sediments, and dissolved methane content in the runoff water were measured at four glaciers. Three of the four glaciers showed conspicuous signals of methane emissions from runoff water, with the Castner Glacier terminus exhibiting a methane concentration three times higher than background levels, along with elevated dissolved methane levels in the runoff water. This study marks the detection of significant methane emissions from small mountain glacier runoff, contributing to the understanding that mountain glaciers also release methane into the atmosphere.

Protist dynamics in the eastern Tsugaru Strait, Japan from 2010 to 2018: Implications for the relationship between decadal climatology and aquaculture production.

Environmental changes such as seasonality, decadal oscillation, and anthropogenic forcing may shape the dynamics of lower trophic-level organisms. In this study, 9-years (2010-2018) of monitoring data on microscopic protists such as diatoms and dinoflagellates, and environmental variables were analyzed to clarify the relationships between plankton and local/synoptic environmental changes. We found that time-series temperature increased in May, whereas it decreased in August and November. Nutrients (e.g., phosphate) decreased in May, remained unchanged in August, and increased in November from 2010 to 2018. The partial pressure of CO2 increased in May, August, and November over time. It is notable that the change in seawater temperature (-0.54 to 0.32 °C per year) and CO2 levels (3.6-5.7 µatm CO2 per year) in the latest decade in the eastern Tsugaru Strait were highly dynamic than the projected anthropogenic climate change. Protist abundance generally increased or stayed unchanged during the examined period. In August and November, when cooling and decreases in pH occurred, diatoms such as Chaetoceros subgenus Hyalochaete spp. and Rhizosoleniaceae temporally increased from 2010 to 2018. During the study period, we found that locally aquacultured scallops elevated soft tissue mass relative to the total weight as diatom abundance increased, and the relative scallop soft tissue mass was positively related to the Pacific Decadal Oscillation index. These results indicate that decadal climatic forcing in the ocean modifies the local physical and chemical environment, which strongly affects phytoplankton dynamics rather than the effect of anthropogenic climate change in the eastern Tsugaru Strait.

Response of N2O production rate to ocean acidification in the western North Pacific.

Ocean acidification induced by the increase of anthropogenic CO2 emissions has a profound impact on marine organisms and biogeochemical processes.1 The response of marine microbial activities to ocean acidification might play a crucial role in the future evolution of air-sea fluxes of biogenic gases such as nitrous oxide (N2O), a strong greenhouse gas and the dominant stratospheric ozone-depleting substance.2 Here, we examine the response of N2O production from nitrification to acidification in a series of incubation experiments conducted in subtropical and subarctic western North Pacific. The experiments show that, when pH was reduced, the N2O production rate during nitrification measured at subarctic stations increased significantly whereas nitrification rates remained stable or decreased. Contrary to what was previously thought, these results suggest that the effect of ocean acidification on N2O production during nitrification and nitrification rates are likely uncoupled. Collectively these results suggest that, if seawater pH continues to decline at the same rate, ocean acidification could increase the marine N2O production during nitrification in subarctic North Pacific by 185 to 491% by the end of the century.

Will krill fare well under Southern Ocean acidification?

Antarctic krill embryos and larvae were experimentally exposed to 380 (control), 1000 and 2000 µatm pCO2 in order to assess the possible impact of ocean acidification on early development of krill. No significant effects were detected on embryonic development or larval behaviour at 1000 µatm pCO2; however, at 2000 µatm pCO2 development was disrupted before gastrulation in 90 per cent of embryos, and no larvae hatched successfully. Our model projections demonstrated that Southern Ocean sea water pCO2 could rise up to 1400 µatm in krill's depth range under the IPCC IS92a scenario by the year 2100 (atmospheric pCO2 788 µatm). These results point out the urgent need for understanding the pCO2-response relationship for krill developmental and later stages, in order to predict the possible fate of this key species in the Southern Ocean.