A bottom water sampler for determining chemical gradients across the water-sediment interface

We developed an inexpensive bottom water sampler that can be operated from a small boat in order to obtain high resolution vertical profiles of dissolved oxygen (DO), chlorophyll, suspended particulate matter (SPM). These vertical profiles allow us to examine bottom resuspension processes and to estimate their benthic fluxes of nutrients across the sediment-water interface in shallow coastal waters. The sampler consists of a 2 m long thick-walled transparent tube with 26 sampling ports at 8-10 cm intervals. Each sampling interval contains a minimum of 300- 370 ml water samples. Test sampling was conducted twice during different tidal phases, and differences in bottom DO, ammonium and SPM were found to be significant between the two tests. Our results suggest that this bottom sampler is essential in order to study sediment-pelagic coupling processes by obtaining high resolution of various parameters in the 2 m water column above the sediment.