11.1. introduction
11.2 Abundance, distribution and biomass
        11.2.1. Spatial scale
                  11.2.1.1. Horizontal
                  11.2.1.2 Vertical
        11.2.2. Temporal scale
                  11.2.2.1. Days--weeks
                  11.2.2.2. Seasonal
                  11.2.2.3. Environmental correlates
                  11.2.2.4. Swarms
                  11.2.2.5. Biomass
                  11.2.2.6. Assessment of current knowledge and future developments
              11.2.2.7. Summary
11.3. Roles as particle consumers and producers
         11.3.1. Grazing consumers
                    11.3.1.1. Assessment of knowledge and future possibilities
          11.3.2. Particle production, faecal pellets
                    11.3.2.1. Pellet production
                    11.3.2.2. Sinking velocity
11.4. Role in nutrient regeneration:excretion
11.5. Role as prey: links to subsequent trophic levels
11.6. Role as competitors:effects on other zooplankton