Intra- and Interspecific Competition for Nutrients and Light in Diatom Cultures

ABSTRACT

Intra- and interspecific competition of clonal populations of Achnanthidium minutissimum and two potential competitors (Cocconeis Placentula var. lineata and Cymbella cistula) were examined in laboratory experiments. Growth rate of A. minutissimum was compared at low and high initial population densities and when in competition with C. p.lineata or C. cistula. In addition, four treatment combinations of nutrients and light were used. Intraspecific rather than interspecific competitive effects regulated A. minutissimum growth rates. C. p. lineata grew very slowly in cultures. C. cistula grew well in culture, formed stalks, and overgrew A. minutissimum. Facilitation by C. cistula stalks, providing substratum for colonization, may have countered interspecific competition on A. minutissimum.