科研之友
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摘要
Burrowing benthic organisms promote water and solute fluxes across the sediment-water interface. Water and solutes penetrate the burrow walls and are transported into/out of the sediment when organisms flush their burrows with overlying water. Few studies have been done to investigate bioirrigation under shifting environmental conditions. We experimentally quantified bioirrigation by Chironomus plumosus larvae in the laboratory at 3 ranges of O-2 saturation (low, medium, and high O-2 concentrations), 2 temperatures (10 and 20 degrees C), and over different seasons. We measured ventilation activities with O-2 and flow-velocity microsensors, flow velocities during pumping periods with color tracers, pumping rates with conductivity exchange experiments, and rates of advective and diffusive water influx into the sediment by influx assays (NaCl was the tracer in both latter experiments). O-2 saturations <12% extended pumping durations/h, whereas saturations <3% decreased pumping durations to similar to 0. Flow velocities were 2x higher when O-2 saturation was >50% than when it was <10%. Rising temperatures altered larval pumping (higher pumping frequency, lower pumping length) and increased flow velocity. Hence, pumping rate and rates of water influx were significantly higher at 20 than at 10 degrees C. Seasonal variations in bioirrigation occurred despite constant laboratory conditions, i.e., the rate of water influx was significantly higher in spring/summer than in autumn. Our study shows that temporally varying environmental conditions should be considered when evaluating bioirrigation-mediated benthic fluxes across the sediment-water interface.
- 出版日期2012-6
