Description of a new submersible filter-pump apparatus for sampling plankton

A low-volume submersible filter-pump apparatus was designed for the collection of zooplankters and other aquatic organisms in all aquatic ecosystems, particularly rivers and power plant cooling lakes. The device combines the best features of pumps and tow net samplers by enclosing both pump and filter into a submersible unit that functions conveniently in a continuous and simultaneous operation. Compared to conventional tow net samplers, the Waite-O'Grady filter pump collected greater numbers of rotifers and immature copepods per unit volume and fewer numbers of mature copepods, while the capture rate of cladocerans was virtually the same. The filter-pump apparatus can be easily modified for the sampling of a variety of other aquatic organisms including macroinvertebrate drift, ichthyoplankton, and net phytoplankton.