-
Biophysical controls on organic carbon fluxes in fluvial networks.pdf
-
Metabolism of terrestrial organic carbon in freshwater ecosystems is responsible for a large amount of carbon dioxide outgassing to the atmosphere, in contradiction to the conventional wisdom that terrestrial organic carbon is recalcitrant and contributes little to the support of aquatic metabolism. Here, we combine recent findings from geophysics, microbial ecology and organic geochemistry to show geophysical opportunity and microbial capacity to enhance the net heterotrophy in streams, rivers and estuaries. We identify hydrological storage and retention zones that extend the residence time of organic carbon during downstream transport as geophysical opportunities for microorganisms to develop as attached biofilms or suspended aggregates, and to metabolize organic carbon for energy and growth. We consider fluvial networks as meta-ecosystems to include the acclimation of microbial communities in downstream ecosystems that enable them to exploit energy that escapes from upstream ecosystems, thereby increasing the overall energy utilization at the network level.
Located in
Resources
/
Climate Science Documents
-
Density stratification in an estuary with complex geometry: Driving processes and relationship to hypoxia on monthly to inter-annual timescales
-
The density field in Narragansett Bay (NB), a northeast U.S. estuary with complex geometry that suffers hypoxia, is described and related to driving factors using monthly means from time series observations at 9 sites during late spring to early fall 2001–2009. Stratification (deep-shallow density difference) is dominated by salinity and strongest (4–7 kg m␣3 in late spring) near rivers in the north and east. Shallow horizontal density gradients are about 0.2 kg m␣3 km␣1; deep densities have minor spatial and seasonal variations. Geographic structure in density, and its inter-annual anomalies, is weaker than expected based on the complex geometry and large size relative to the internal deformation radius. Inter-annual variability is primarily driven by river flow and weakly influenced by winds, contrasting nearby systems (Chesapeake Bay, Long Island Sound), likely due to reduced fetch and/or unfavorable alignment with prevailing winds. Stratification response to river flow follows 2/3 power scaling despite that the theory omits important NB attributes (complex geometry, depth-varying horizontal gradients). Contrasting other systems (Delaware Bay, San Francisco Bay), horizontal gradients are at least as responsive to river forcing as theoretical 1/3 power scaling; depth-dependent horizontal gradients or finite basin constraint of intrusion length may be responsible. Bay-wide inter-annual variations in seasonal hypoxia correlate with late spring stratification, though stratification peaks in the north and east with hypoxia most severe in the north and west. Long-term response of stratification, and thus its role in hypoxia, to climate-driven increases in river flow and temperatures will be dominated by the former.
Located in
Resources
/
Climate Science Documents
-
Enhanced poleward moisture transport and amplified northern high-latitude wetting trend
-
Observations and climate change projections forced by greenhouse gas emissions have indicated a wetting trend in northern high latitudes, evidenced by increasing Eurasian Arctic river discharges (1–3). The increase in river discharge has accelerated in the latest decade and an unprecedented, record high discharge occurred in 2007 along with an extreme loss of Arctic summer sea-ice cover (4–6). Studies have ascribed this increasing discharge to various factors attributable to local global warming effects, including intensifying precip- itation minus evaporation, thawing permafrost, increasing greenness and reduced plant transpiration7–11. However, no agreement has been reached and causal physical processes remain unclear. Here we show that enhancement of poleward atmospheric moisture transport (AMT) decisively contributes to increased Eurasian Arctic river discharges. Net AMT into the Eurasian Arctic river basins captures 98% of the gauged climatological river discharges. The trend of 2.6% net AMT increase per decade accounts well for the 1.8% per decade increase in gauged discharges and also suggests an increase in underlying soil moisture. A radical shift of the atmospheric circulation pattern induced an unusually large AMT and warm surface in 2006–2007 over Eurasia, resulting in the record high discharge.
Located in
Resources
/
Climate Science Documents
-
Pensacola and Perdido Bays Estuary Program
-
Pensacola and Perdido Bays Estuary Program serves as a trusted source for residents, businesses, industry, and the community on issues relating to preserving, restoring, improving and maintaining the natural habitat and ecosystem of the bays, estuaries and watersheds of Pensacola and Perdido Bays.
PPBEP strives to achieve a healthy and collaborative environment by:
1. Elevating and increasing the importance, awareness and understanding of environmental quality.
2. Employing rigorous, unbiased and scientifically sound science to inform and guide decisions, policies, and initiatives.
3. Funding programs and projects that protect the environment, increase ecological resilience.
4. Building a network of inclusive, multi-stakeholder partnerships that takes into account factors affecting the environment, the economy, and the community-at-large for the benefit of improving the quality of life for all.
Located in
LP Members
/
Organizations Search
-
St. Andrew and St. Joseph Bays Estuary Program
-
The St. Andrew Bay Watershed in the central Florida Panhandle covers 1,156 square miles that includes the interconnected estuary system of both St. Andrew Bay (West, North, and East bays) and St. Joseph Bay. This gem of an estuary and watershed is one of the most biologically diverse bays in North America and the only watershed in Northwest Florida located entirely in the state of Florida.
Located in
LP Members
/
Organizations Search
