https://doi.org/10.1140/epjp/s13360-022-02455-7
Regular Article
Copepod swimming activity and turbulence intensity: study in the Agiturb turbulence generator system
1
Université de Lille, CNRS, Univ. Littoral Côte d’Opale, UMR 8187 - LOG - Laboratoire d’Océanologie et de Géosciences, 62930, Wimereux, France
2
Université de Lille, Unité de Mécanique de Lille - J. Boussinesq, ULR 7512, 59000, Lille, France
3
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, 361102, Xiamen, China
4
SMSE-Mingguang Joint Research Center for Advanced Palygorskite Materials, SJTU, 239400, Mingguang, China
b
francois.schmitt@log.cnrs.fr
Received:
2
December
2021
Accepted:
5
February
2022
Published online:
21
February
2022
Copepods of the species Acartia tonsa have been placed in a laboratory generated turbulent flow system, called Agiturb, characterized by Taylor-scale-based Reynolds numbers from 130 to 360. Trajectories of alive and dead copepods, and of polystyrene spherical particles of size 600 
m, have been measured in the dark with infrared lights, using a high speed camera at 1200 fps. Using adequate filtering, horizontal velocity and acceleration measurements have been performed. The velocity probability density functions (PDF) of dead copepods are very close to the one of material particles of the same size. The PDFs of alive and dead copepods are different for low Reynolds numbers, and become superposed for Reynolds numbers larger than 160. On the contrary, the PDFs of accelerations of alive and dead copepods are also different for medium values of the Reynolds number, and become superposed for Reynolds numbers larger than 270. This shows that copepods’ swimming behaviour occurs and is detectable under moderate turbulence, and not for high intensity turbulence. This gives information about the so called optimal turbulence levels for Acartia tonsa copepods and shows that when turbulence is of too high intensity, these copepods have no specific behavior.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022
