Increasingly, ecologists are being called upon to
demonstrate how ecological interactions are modified by human disturbances, and
what the consequences are for ecosystem services. �As a prime example, streams of the
northeastern United States
are experiencing increasing baseline salinities as a result of road deicer
runoff.� Preliminary studies have shown
increases of microbial respiration on leaf litter in response to heightened
chloride levels.� Organic debris dams in
streams can serve as regions of high microbial processing, which are critical
to ecosystem function.� We investigated
the influence of heightened chloride and dissolved organic carbon (DOC) levels
similar to those observed in urban streams to identify responses of microbial
respiration rates in sub-debris dam sediments.�
A dark-bottle biological oxygen demand study was conducted utilizing
sub-debris dam sediments collected from forested, urban and restored-urban
streams from within the Baltimore
metropolitan region.� Sediments were
treated with elevated chloride (1500 mg/l), a DOC inoculum, in a full factorial
design.� Within sites, the effect of
chloride was variable, but generally reduced rates of microbial
respiration.� This interacted with DOC
addition, but DOC caused a predictable increase in respiration rates.� Results suggest that increasing loads of road
salt deicer to streams could alter the capacity for carbon to be metabolized
within sediments, with the effective amount of change depending on the
ecological condition of the stream receiving such surface runoff.