Field evaluation of a valved sediment trap

An internally valved sediment trap designed to isolate sinking particulate matter from free‐swimming animals, temporally subsample particle flux, and minimize washout of solid and dissolved material is described. The trap is controlled by a single microprocessor capable of supporting multiple traps as well as other instrumentation on a single array. Test deployments of valved and nonvalved control traps, along with three other conventional cylindrical trap designs, were undertaken during a series of six 1‐week experiments in Dabob Bay, Washington. Treated traps containing biocide‐spiked (HgCl 2 or Formalin) bottom brine layers (80‰ NaCl brine), brine layers alone, and only seawater (untreated) were deployed on multitrap arrays. Fluxes of material >850 µ m in size (almost exclusively large zooplankton) caught in biocide‐ and brine‐treated valved traps were reduced by an average of 88% relative to non‐valved control traps; all other open traps collected >850‐ µ m fluxes equivalent to controls. The type of treatment had a significant effect on the >850‐ µ m mass flux, with Formalin‐treated traps >HgCl 2 ∼ NaCl brine ≫ untreated. Fluxes of <850‐ µ m material were reduced in treated valved traps and averaged 39% less than fluxes caught in VERTEX‐style particle interceptor traps. Organic C: total N ratios were higher in material caught in valved traps than in all other types, primarily due to reduced nitrogen fluxes. Reduced fluxes of the primarily autochthonous biochemicals (pigments, amino acids, and lipids) measured by valved relative to control traps indicate significant exclusion (>80%) of zooplankton <850 µ m from valved traps.