EFFECTS OF THE PLANKTONIC PERIOD ON MARINE POPULATION FLUCTUATIONS

Abstract

How and why populations fluctuate and what drives the magnitude of fluctuations are questions that have long intrigued ecologists. Dispersal may dampen population fluctuations through the effect of spreading offspring over heterogeneous habitats. The planktonic period common in many marine organisms, therefore, could dampen population fluctuations through larval dispersal. However, emphasis on the hazards of planktonic life predicts that species that have a longer planktonic period have greater fluctuations in adult populations than species with shorter or no planktonic period. I analyzed the population variation of 570 time series from the literature for intertidal and benthic subtidal marine species and found that time series of adult populations for species with no planktonic period had greater fluctuations than time series for species with a planktonic period (both short and long planktonic period). In addition, there was no difference in fluctuation of adult and recruit time series between species with long and short planktonic periods. The planktonic period did not appear to result in increased population fluctuations, as was widely assumed. Rather, the planktonic period may be acting to decrease population fluctuations, potentially by dispersal. Corresponding Editor: J. E. Duffy.