Sporulation and the development of planktonic blue-green algae in two Salopian meres

Abstract

Factors affecting akinete formation and the survival of planktonic bluegreen algal populations after the formation of 'water blooms’ were investigated in two eutrophic kataglacial lakes. It is considered that the induction of sporulation may be due to extreme conditions at the water surface during the summer to which the algal bloom is exposed, rather than to nutrient, especially orthophosphate, deficiency. It has not been shown conclusively that akinetes constitute an overwintering stage of the planktonic algal life cycle, or that akinetes germinate in the spring to produce the inoculum for subsequent vegetative growth. Comparisons of planktonic, sedimenting and benthic algal material indicate that germination shortly after maturation may provide the greater part of the overwintering planktonic vegetative populations. Population sizes and life cycles appear to be influenced by the physical factors which control the stability of the water column.