ABSTRACT: A design for an in situ video camera for plankton observations is presented. A light weight aluminium rig supports a video camera with an opposing stroboscope which produces dark field images of plankton >0.3 mm. In the present configuration the camera can be used down to 100 m and provides video images of 10 to 40x magnification when viewed on a 14' (ca 35 cm) monitor. Video recordings from the field show moderate aggregations of small copepods to the subsurface fluorescence maximum and at times indications of horizontal patchiness. The large copepod Calanus finmarchicus was found to aggregate 5 m below the fluorescence maximum at night. In comparisons with a traditional WP-2 plankton net, the video camera provided similar length frequency distributions while abundance estimates from video recordings were 10 to 20% higher than net estimates. It is concluded that the presented video camera offers excellent observations of the pelagic environment at an affordable cost.

KEY WORDS: Fine-scale distribution · Copepods · Gelatinous plankton · Marine snow

Published in MEPS Vol. 164 (1998) on April 9
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998