Download "Land-Coastal Interactions: Carbon and Organic Matter Cycling"

Initiative for Coastal Climate
Change Research
Carbon and Organic Matter Cycling in Coastal Virginia:
Connections Between Chesapeake Bay
and its Surrounding Watershed
Jim Bauer
Liz Canuel
Department of Physical Sciences
VIMS
Rivers transport to the oceans
the products of rock weathering
and terrestrial biomass production,
both as solutes and particles,
via the hydrologic cycle
Major C Reservoirs and Fluxes in Fluvial Systems
Sedimentary
Rocks
(Internal modification)
Estuaries
(Internal modification)
& Marshes
Æ How will changes in the balance between allochthonous and autochthonous inputs
of C and OM (and the inherent reactivity of each) to rivers and coastal waters affect:
- biogeochemical cycles (nutrients, O2, etc.)
- ecosystem structure and function (e.g., microbial vs. grazer-based)
From Richey, J.E. (2004) Pathways of atmospheric CO2 through fluvial systems. In: Field
and Raupach, eds., “The Global Carbon Cycle”, SCOPE, Island Press, pp. 329-340.
Virginia’s exceptionally long
tidal shoreline provides nearly
10,000 linear miles of interface
over which materials from land
can exchange via rivers and
groundwater with estuarine,
bay, and other coastal waters.
This, along with the relatively
small water volume in the Bay,
allows for significantly
greater impacts by land on
Va. coastal waters than other
coastal regions of the U.S.
What Kinds of Changes Have Already Occurred
in the Chesapeake Bay?
From Zimmerman and Canuel (2000) Marine Chemistry 69: 117-137 and (2002) Limnol. Oceanogr. 47: 1084-1093.
Dominant Land Uses in the
Chesapeake Bay Watershed
- control variations in allochthonous inputs
From www.whrc.org
Long-Term Changes in River Water
Inputs to Chesapeake Bay
Æ Implications for materials transported by rivers, e.g., nutrients sediments, etc. and
their impacts on ecological and geological processes in the Bay and along the coast
http://md.water.usgs.gov/monthly/bay.html
Predicted Habitat Losses in Chesapeake
Bay Over the Next ~100 years
From National Wildlife Federation (2008) Sea-Level Rise and Coastal
Habitats of the Chesapeake Bay: A Summary.
http://www.nwf.org/sealevelrise/pdfs/NWF_ChesapeakeReportFINAL.pdf
Losses of Terrestrial Organic C
(globally, soils contain ~2x as much C and atmosphere or vegetation)
Æ Due to enhanced DOC mobilization? Respiration? Both?
Changes in soil organic carbon contents across England and Wales between 1978 and 2003.
a) Carbon contents in the original samplings, and b) rates of change calculated from the changes
over the different sampling intervals. Values at sites that were not resampled were calculated
from their original organic carbon contents using equation (1). The changes were negative in all
but 8% of the sites.
From Bellamy et al. (2005) Carbon losses from all soils across
England and Wales 1978–2003. Nature 437: 245-248.
Elevated CO2
Ambient CO2
DOC Mobilization from Soils – CO2 Effects
From Freeman et al (2004) Export of dissolved organic carbon from peatlands under
elevated carbon dioxide levels. Nature 430: 195-198.
DOC Mobilization from Soils – Hydrologic Effects
drought
non-drought
From Freeman et al (2004) Export of dissolved organic carbon from peatlands under
elevated carbon dioxide levels. Nature 430: 195-198.
Changes in Inorganic C Export from the Mississippi
Discharge and Alk
Export
Alk Export and Land Cover
From Raymond and Cole (2003) Increase in the export of alkalinity from North America’s
largest river. Science 301, 88-91. Data from U.S.G.S. databases
For the majority of (freshwater) aquatic ecosystems, including rivers and estuaries:
Respiration (R) >> Gross Primary Production (GPP)
pCO2 in World Rivers
atmosphere
From Cole and Caraco (2001) Carbon in catchments: connecting terrestrial
carbon losses with aquatic metabolism. Mar. Freshwater Res. 52: 101-110.
Long-term monitoring of river-estuary C and OM pools
Δ
- Hudson River as an example
From Findlay (2005) Increased carbon transport in the Hudson River: unexpected consequence of changes in
nitrogen deposition? Frontiers in Ecology and the Environment 3: 133-137.
Anthropogenic Organic C Input Estimates
- the Hudson watershed as an example
Gasoline + oil use:
≅ 2.4 x 1012 moles C y-1
Atmospheric:River
annual OC fluxes ≅ 0.5-1
(OCatm is ~10-60% fossil)
vs.
River OC flux:
≅ 1.3 x 1010 moles C y-1
*
*
From: NRC (2003) Oil in the sea III: inputs, fates and effects, National Academies Press; Hildemann et al. (1994)
Environ. Sci. Technol. 28: 1565; Tanner et al. (2004) Aerosol Sci. Technol. 38: 133; Wakeham et al. (2004)
Environ. Sci. Technol. 38: 431 (for Lake Washington).
Emerging climate change issues for
coupled land-coastal ocean carbon cycling
Initiative for Coastal
Climate Change Research
1) Basic need for more information on river/estuarine C and OM pools,
allochthonous/autochthonous inputs, processing, etc. (Richey 2004, SCOPE)
Æ both historically and present-day
2) Long-term time-series studies and monitoring for assessment of change
Æ and need to do more with existing large datasets
3) Better assessment of local- and regional-scale climate change impacts
Æ can we delineate “natural” and “altered” systems and processes?
all necessary to better constrain inputs, fates and fluxes of C
and OM for both regional and global coastal fluxes & budgets,
how changing quantities and quality of OM control ecosystemlevel processes, other elemental cycles, etc.