extreme disturbance rather than the general level of turbulence.
Nevertheless, turbulence certainly affects some processes. Yen et al. (2008)
using a quasi-spherical, completely enclosed aquarium of 40 cm diameter
and eight pulsing actuators at symmetrical positions have approximately
duplicated typical upper-ocean turbulence in terms of energy dissipation and
eddy dimensions. Indeed, copepods in this apparatus move more or less
independently from water motion up to dissipation rates of 0.1 cm^2 s−3,
above which their motion begins to follow the eddies. The order-of-
magnitude agreement with the results of Caparroy et al. and others is
striking. It can be argued that most turbulence occurs at length scales
(basically eddy diameters) that are large relative to the body sizes of the
mesozooplankton. This argument comes from estimates of the Kolmogorov
length scale, the length at which viscosity effectively damps transfer of
momentum into progressively smaller eddies. However, a plankter of
whatever length within an eddy will be turned over by it, and many of them,
particularly copepods, have preferred orientations but small righting
moment (vertical stability). Thus, turbulence will require recurrent righting
moves regardless of scale, and sufficient eddy motion will make it difficult
to stay oriented.Fig. 7.5 An example of selection by a particle-feeding copepod, female Eurytemora
affinis, from Chesapeake Bay. (a) Particle-size abundance spectra before (dark circles)
and after (open circles) a day of feeding. No particles of about 10 μm equivalent
spherical diameter were removed, and the (b) calculated filtering rate and (c)
ingestion rate spectra reflect that.
(^) (After Richman et al. 1977.)