Formation of Micropatches by Zooplankton-Driven Microturbulences

The distribution and behavior of tintinnids Stenosernella nucula have been measured in situ within a microlayer formed by 39 million individuals⋅liter–1 with an optical particle counting- and imaging-system. The parallel propulsions of the many animals add up and drive strong downwelling water currents. Preliminary results for swimming-speeds, -directions and organism-distributions are presented. Probably due to gyrotaxis (Kessler, 1985, 1986) or some unknown bio/physical processes the organisms are focused into their self-generated velocity profile. Similar phenomena have been described for very dense plankton cultures as “bioconvection” (Childress et al., 1975a, 1975b; Platt, 1961; Plesset and Winet, 1974; Plesset et al., 1975). The micropatches are 2–4 mm wide and 8–340 mm deep with organism concentrations up to 215 million tintinnids⋅liter–1. The flows form small convection cells similar to Langmuir- or Benard-cells with distances between the patches of 8–30 mm. At the edge of the downwelling areas water velocity increases from near zero to 2–3 mm per s over a vertical distance of less than 1 mm resulting in considerable shear. Some ecological consequences of these microturbulences and microdistributions for predator-prey relationships and particle transports in eutrophic estuaries are discussed

In situ investigations on the respiration and behaviour of the eelpout Zoarces viviparus under short-term hypoxia

Respiration and activity of eelpouts Zoarces viviparus L. were measured in an underwater respiration chamber in Kiel Bay (Germany) under short-term hypoxia. Respiration and swimming activity both declined almost continuously with decreasing oxygen saturation..

Video systems for in situ studies of zooplankton

A variety of survey instruments and systems designed for measuring the behavior of individual zooplankton have been built around video technology. Systems designed for studying behavior are already producing remarkable observations of biological interactions in situ. If the survey tools under development achieve their potential, they will surpass the spatial and temporal resolution of conventional sampling methods, reduce the amount of human effort required for data processing, and also collect taxonomic information that is not available from acoustic devices or the Optical Plankton Counter. This paper (i) describes a variety of video systems for studying zoo plankton in situ; (ii) discusses common design considerations and technical challenges; and (iii) compares the present and future capabilities of video devices with other methods of studying zooplankton in situ