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Keywords:

  • Dinophyceae;
  • flagella;
  • cell motility;
  • nitrate

Summary

The mobility of dinophytes allows them to migrate dielly, in a vertically stratified environment, between deeper regions where concentrations of nutrients (principally nitrate) are higher but light low, and less deep regions with lower nutrient concentrations but more light. When there is a substantial (several metres) depth range in which dinophytes can grow but, at any given depth, growth is restricted by both nitrate and light availability, vertical migration from a deeper station at night to a less deep station during the day could increase the availability of light and nitrate to a dinophyte cell over a complete light-dark cycle.

Cost-benefit analysis shows that the benefits of migration (increased acquisition of photons and nitrate relative to non-migratory cells) could very substantially exceed the costs (the energy and nitrogen required to produce and operate the flagella apparatus and any additional nitrate or photon-harvesting machinery which may be required as a result of migration). It is therefore concluded that, in some habitats, vertical migration could increase the growth rates of dinophytes. The occurrence of such increases under natural conditions, and their selective significance, await further investigation.