Paper No. 12
Presentation Time: 11:10 AM
CLIMATE, HYDROLOGY, AND PROXY RECORDS OF CLIMATE
In order to investigate how lake and wetland hydrologic processes
act as filters of climate signals recorded in sediments, we have been monitoring
two nearly identical wetlands in close proximity (< 50 m). Both wetlands
reside under the same climate, terrain, and the bulk of their water is
received from snowmelt and spring rains, but they have different interactions
with the groundwater. One wetland (P8) currently functions as a through-flow
basin; recharging and discharging the groundwater on opposite ends.
The second wetland (P1) receives a small amount of groundwater and primarily
loses water through evaporation and secondarily to groundwater. P1 and
P8 exhibit different water d18O,
DIC d13C, and ostracode species assemblages.
The d18O and DIC d13C
are higher for P1 (d18O -3.5 vs
-6.1 for P8, DIC d13C -4.6 vs -9.6
for P8) because of the longer residence time and the cumulative effect
of photosynthetic activity. Ostracodes are small invertebrates sensitive
to temperature, alkalinity/Ca ratio, and physical hydrology. Species such
as Cypridopsis vidua and Potamocypris unicaudata are common
to both P1 and P8, but Candona decora, Candona distincta
and Notrodromas monicha, the species that prefer groundwater discharge
sites, are only found abundantly in P8. Thus even in these small
wetlands with their simple hydrology relative to larger systems, hydrologic
processes are modifying the climate signal as measured by proxies such
as ostracode shell d18O and species
assemblage before they are stored in the sediment. Such modification may
not be easily discernible in a sedimentary paleoclimate record.