Characterization of intermittency in zooplankton behaviour in turbulence
- 259 Downloads
We consider Lagrangian velocity differences of zooplankters swimming in still water and in turbulence. Using cumulants, we quantify the intermittency properties of their motion recorded using three-dimensional particle tracking velocimetry. Copepods swimming in still water display an intermittent behaviour characterized by a high probability of small velocity increments, and by stretched exponential tails. Low values arise from their steady cruising behaviour while heavy tails result from frequent relocation jumps. In turbulence, we show that at short time scales, the intermittency signature of active copepods clearly differs from that of the underlying flow, and reflects the frequent relocation jumps displayed by these small animals. Despite these differences, we show that copepods swimming in still and turbulent flow belong to the same intermittency class that can be modelled by a log-stable model with non-analytical cumulant generating function. Intermittency in swimming behaviour and relocation jumps may enable copepods to display oriented, collective motion under strong hydrodynamic conditions and thus, may contribute to the formation of zooplankton patches in energetic environments.
KeywordsTopical Issue: Multi-scale phenomena in complex flows and flowing matter
- 10.U. Frisch, Turbulence: The legacy of A. N. Kolmogorov. (Cambridge University Press, Cambridge, UK 1995).Google Scholar
- 17.F.G. Schmitt, in Nonlinear Science, Complexity edited by A.C.J. Luo, L. Dai, H.R. Hamidzadeh (World Scientific.Google Scholar
- 24.N.A. Malik, T. Dracos, D.A. Papantoniou, Exp. Fluids 15, 279 (1993).Google Scholar
- 25.J. Willneff, A. Gruen, in Proceedings of the 9th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery. Honolulu, HI, USA.Google Scholar
- 28.P.K. Yeung, S.B. Pope, B.L. Sawford, J. Turbul. 7, (2006) DOI:10.1080/14685240600868272.
- 30.C.W. Gardiner, Handbook of stochastic methods, 3rd edition (Springer, Berlin, 2004).Google Scholar
- 31.W. Feller, An introduction to probability theory and its applications 3rd edition (John Wiley & Sons, New York, 1971).Google Scholar
- 32.G. Samorodnitsky, M.S. Taqqu, Stable non-Gaussian random processes (Chapman & Hall/CRC, New York, 1994).Google Scholar