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Abstract:
Coastal zones are important source regions for a variety of trace gases including
halocarbons and sulphur-bearing species. While salt-marshes, macroalgae and phytoplankton
communities have been intensively studied, little is known about trace gas
fluxes in seagrass 5 meadows. Here we report results of a newly developed dynamic flux
chamber system that can be deployed in intertidal areas over full tidal cycles allowing
for high time resolved measurements. The trace gases measured in this study included
carbon dioxide (CO2), methane (CH4) and a variety of hydrocarbons, halocarbons and
sulphur-bearing compounds. The high time resolved CO2 and CH4 flux measurements
10 revealed a complex dynamic mediated by tide and light. In contrast to most previous
studies our data indicate significantly enhanced fluxes during tidal immersion relative to
periods of air exposure. Short emission peaks occured with onset of the feeder current
at the sampling site.
We suggest an overall strong effect of advective transport processes to explain the
15 elevated fluxes during tidal immersion. Many emission estimates from tidally influenced
coastal areas still rely on measurements carried out during low tide only. Hence, our
results may have significant implications for budgeting trace gases in coastal areas.
This dynamic flux chamber system provides intensive time series data of community
respiration (at night) and net community production (during the day) of shallow coastal 20 systems.
