ABSTRACT: The Optical Plankton Counter (OPC) was used to count individual animals in situ, and to produce a one-dimensional spatial-series from which gap relationships could be quantified at the millimeter scale and above, using a Distance to Next Encounter (DNE) technique. Both DNE and one-dimensional neighbor analyses indicated that zooplankton distributions in all transects were significantly (p < 0.0001) aggregated into patches. Within patches, zooplankton were effectively (r² ~= 0.94) randomly distributed, resulting in important implications for some of the newer foraging models concerning zooplankton. The DNE frequency distributions all exhibited a distinct pattern that would not be expected from single Poisson distribution, indicating patchiness at the meter scale. This allowed calculation of various statistics used to describe in situ patchiness such as: relative percentage of a transect occupied by patches (79 to 89%) and gaps, estimates of patch size (~2 m diameter), and patch densities (7000 to 14000 organisms m^-3).

KEY WORDS: Plankton · Zooplankton · Patchiness · Gaps · Transect

Published in MEPS Vol. 171 (1998) on October 1
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998