Phased cell division, specific division rates and other biological observations of Dinophysis populations off the south coast of Ireland
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Specific growth rate
The proportions of viable cells ofDinophysisspp. that were paired (dividing) and recently divided during a cell cycle were measured on populations ofD. acutaandD. acuminataobserved off the south coast of Ireland in July 2007 and July 2009. Both species exhibited phased cell division in 2009 with maximum frequency of division (fmax) 2 h after sunrise. Different patterns of division (timing offmax) were shown by D. acutain 2007, when the population aggregated in a thin layer was transported by a coastal jet flow. High resolution (decimetre-scale) profiles within the thin layer showed large differences in the vertical distribution of biological properties (feeding status, mortality). Values of the specific growth ratemwere compared to estimates derived in similar fashion from observations onDinophysispopulations elsewhere. Different patterns exhibited by the same species in different regions may be attributed to adaptations to latitudinal differences (length of photoperiod). The ...