A new chamber design for measuring community metabolism in a Michigan stream

We designed an open-ended community metabolism chamber to simultaneously measure surface and hyporheic metabolism. Our chamber design eliminated reaeration, compartmentalized metabolism, maintained ambient conditions and included hyporheic respiration. We compared results from our hyporheic chamber to results obtained from: (1) closed benthic community metabolism chambers constructed as recommended by Bott et al. (1978), and (2) whole-stream metabolism techniques as modified by Marzolf et al. (1994). Simultaneous comparisons of all three procedures were made for a 35 m riffle section of Augusta Creek, a 3rd-order Michigan stream, in July 1997 and repeated in July 1998. Simultaneous comparisons of all three procedures were also made for a 30 m sandy run section of Augusta Creek in September 1997, and repeated in September 1998. Our hyporheic chamber estimates for community respiration (CR24) were similar to those obtained using the whole-stream metabolism procedure but were considerably higher than estimates obtained using the closed benthic chambers in three of the four experiments. These data suggest that our chamber design provided estimates of community metabolism which included both benthic and hyporheic respiration. The chamber incorporates several positive aspects of both closed chambers and the whole-stream method. This new method can be replicated, eliminates the need for a reaeration coefficient, ambient conditions are better approximated since it remains an open system, and it appears to provide more realistic estimates of whole-stream metabolism compared to the traditional chamber approach.