14 research outputs found
Spatial distribution of oxygen-18 and deuterium in stream waters across the Japanese archipelago
The spatial distribution of oxygen and hydrogen isotopic composition
(δ<sup>18</sup>O and δ<sup>2</sup>H) of stream waters across Japan was
clarified with a data set by compiling sample data obtained from 1278 forest
catchments during the summer of 2003. Both δ<sup>18</sup>O and δ<sup>2</sup>H
values showed positive correlations with the mean annual air
temperature and annual evapotranspiration, and negative correlations with
latitude and elevation. Deuterium excess (d-excess) values in stream waters
were higher on the Sea of Japan side, and lower on the Pacific Ocean side,
of the Japanese archipelago. The d-excess in precipitation was generally
higher in winter and lower in summer in Japan. The Sea of Japan side
experiences a great deal of snowfall, and seasonal changes in monthly
precipitation are rather small. In contrast, the Pacific Ocean side
experiences a large amount of rainfall during summer with low levels of
precipitation during the winter. Therefore, the lower d-excess in stream
waters on the Pacific Ocean side reflects summer precipitation, and the
higher values on the Sea of Japan side are affected by delayed recharge from
snowmelt. The isoscapes of stream water connote not only spatially
integrated but also temporally integrated isotope signals of precipitation
and provide a framework for addressing applied hydrological, ecological, or
meteorological research questions at regional scales, such as the effects of
climate change
Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems
Ocean acidification, a complex phenomenon that lowers seawater pH,
is the net outcome of several contributions. They include the dissolution of
increasing atmospheric CO<sub>2</sub> that adds up with dissolved inorganic
carbon (dissolved CO<sub>2</sub>, H<sub>2</sub>CO<sub>3</sub>, HCO<sub>3</sub><sup>−</sup>, and
CO<sub>3</sub><sup>2−</sup>) generated upon mineralization of primary producers (PP) and
dissolved organic matter (DOM). The aquatic processes leading to inorganic
carbon are substantially affected by increased DOM and nutrients via
terrestrial runoff, acidic rainfall, increased PP and algal blooms,
nitrification, denitrification, sulfate reduction, global warming (GW), and
by atmospheric CO<sub>2</sub> itself through enhanced photosynthesis. They are
consecutively associated with enhanced ocean acidification, hypoxia in
acidified deeper seawater, pathogens, algal toxins, oxidative stress by
reactive oxygen species, and thermal stress caused by longer stratification
periods as an effect of GW. We discuss the mechanistic insights into the
aforementioned processes and pH changes, with particular focus on processes
taking place with different timescales (including the diurnal one) in
surface and subsurface seawater. This review also discusses these collective
influences to assess their potential detrimental effects to marine organisms,
and of ecosystem processes and services. Our review of the effects operating
in synergy with ocean acidification will provide a broad insight into the
potential impact of acidification itself on biological processes. The
foreseen danger to marine organisms by acidification is in fact expected to
be amplified by several concurrent and interacting phenomena