Loss of buoyancy control in the copepod Calanus finmarchicus

Jonathan H Cohen; Kim S Last; Jack Waldie; David W Pond

doi:10.1093/plankt/fbz036

Loss of buoyancy control in the copepod Calanus finmarchicus

J Plankton Res. 2019 Sep;41(5):787-790. doi: 10.1093/plankt/fbz036. Epub 2019 Oct 14.

Authors

Jonathan H Cohen¹, Kim S Last², Jack Waldie², David W Pond^{2

3}

Affiliations

¹ School of Marine Science and Policy, University of Delaware, 700 Pilottown Road, Lewes, DE, 19958, USA.
² Scottish Association for Marine Sciences, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK.
³ Institute of Aquaculture, University of Stirling, Stirlingshire, FK9 4LA, UK.

Abstract

A mechanism is demonstrated that could explain large-scale aggregations of lipid-rich copepods in the surface waters of marine environments. Laboratory experiments establish that changes in salinity and temperature induce lipid-mediated buoyancy instability that entrains copepods in surface waters. Reduced hydrostatic pressure associated with forced ascent of copepods at fjordic sills, shelf breaks and seamounts would also reduce the density of the lipid reserves, forcing copepods and particularly those in diapause to the surface. We propose that salinity, temperature and hydrodynamics of the physical environment, in conjunction with the biophysical properties of lipids, explain periodic high abundances of lipid-rich copepods in surface waters.

Keywords: depth regulation; lipid phase transition; pressure; salinity; temperature.