Labyrinth of doom: A device to minimize the “swimmer” component in sediment trap collections

Abstract

A simple device used to discriminate between “swimmers” and “nonswimmers” in sediment trap collections has been developed. It consists of a series of funnels which concentrate passively sinking material into a central collection tube, whereas swimmers are distributed randomly between the inner and outer collection tubes. The degree to which swimmer/nonswimmer fractionation is achieved depends on the number and spacing of funnels and the ratio of inner to outer collection tube areas. Although inner collection tube samples contain a few swimmers, there are considerably fewer than are collected in cod ends without this device. Furthermore, outer tube contents are devoid of passively sinking material providing a “pure swimmer” fraction which can be compared to inner collection tube contents. This device has been successfully deployed on many occasions in traps of the Soutar (conical) and Knauer (cylindrical) type as part of the VERTEX program in the NE Pacific.