Effect of cyanobacterium on competition between rotifers: a population growth study

Abstract

We determined the population growth of Plationus patulus and Brachionus havanaensis grown alone or together (1:1 ratio) on different feeds of solely Chlorella, solely Anabaena, or their mixture at a level of 1 × 106 cells mL−1 for all diets. Our results showed that regardless of diet, population densities of B. havanaensis were higher than those of P. patulus. For both rotifer species, Anabaena caused extinction of populations, regardless whether offered alone or in combination with the green alga. In mixed rotifer cultures, the peak densities of P. patulus or B. havanaensis were much lower than when cultured alone. Rate of population increase (r) of P. patulus fed Chlorella was significantly lower (0.12 d−1; p < 0.001) than for B. havanaensis (0.19 d−1) grown under similar conditions. Growth rates of both rotifers fed Anabaena (alone or together with Chlorella) became significantly lower than when fed solely Chlorella. Thus, our results showed that P. patulus and B. havanaensis have similar sensitivities to Anabaena, with both species failing to grow when this cyanobacterium was included in the diet.