Underwater observations of gelatinous zooplankton: Sampling problems, feeding biology, and behavior1

Abstract

Observations by SCUBA divers on the distribution and biology of gelatinous zooplankton have stimulated speculations about the structure of tropical oceanic ecosystems. The gelatinous group represents one of four apparent strategies for survival in pelagic animals. Conventional plankton collection probably does not sample these organisms accurately due to their patchy distribution, fragility, and escape responses. Many gelatinous plankters filter feed using mucous structures; these mechanisms are important because of their efficiency in collecting particulate material, and because mucus is a source of organic aggregates in the sea. Such aggregates are often large, irregularly distributed, and of complex composition; these properties are rarely discerned by conventional sampling gear. The aggregates contribute considerable spatial heterogeneity to a seemingly homogeneous environment. An entire category of pelagic animals lives in association with these floating substrates. The diversity and trophic complexity of epipelagic plankton communities have been underestimated by previous investigators.