Search

Interspecifically induced phytoplankton colony formation, which is accompanied by increased particle size and sedimentation, plays important roles in enhancing anti-predation capability and alleviating competition among photosynthetic organisms. Induced morphological changes may indirectly affect the structure of food webs and thus influence ecosystem functions. In this study, the effects of microcystin-LR (MC-LR) on colony formation of Chlorella vulgaris under induction by the submerged macrophyte Potamogetom crispus were evaluated. The growth of C. vulgaris was significantly inhibited under P. crispus stress (10g FW L−1), and the adverse influences of extracts were considerably greater than those of exudates. In addition, the cell numbers per colony and colony proportion of C. vulgaris were significantly increased with the presence of P. crispus extracts. However, in contrast to our expectation, the addition of MC-LR exerted no significant effects on the growth and morphological changes of C. vulgaris under P. crispus induction. The present research results provide additional knowledge on interspecific interactions between submerged macrophyte and green algae in the eutrophic cyanotoxin-contaminated ecosystems. [ABSTRACT FROM AUTHOR]

In eutrophic freshwater lakes, cyanobacteria and green algae are in succession due to abiotic factors. Allelochemical interaction also exists. In this study, we indicated that filtrates of Microcystis aeruginosa can influence the growth rate and photosynthetic pigments of the target alga named Chlorella vulgaris. We also determined the morphological appearance and colony formation of green alga C. vulgaris that were induced by chemicals associated with a competitor cyanobacterium named M. aeruginosa. However, microcystins (MCs) were not the active substances in this study. The morphology changes and growth of C. vulgaris affected by M. aeruginosa filtrates were dependent on the initial cultivation density of the target algae and the cultivation phase of M. aeruginosa. We also assumed that the morphology changes were defensive strategies utilised by C. vulgaris to resist M. aeruginosa. The temporary stress of M. aeruginosa was favourable to the growth of C. vulgaris. By contrast, the continuous induction of colony formation by M. aeruginosa in the field inhibited the growth of C. vulgaris. The present results provided new insights into the interaction between algae and theoretical basis for algae succession in the field. Pascal Laffaille takes great interests in fish ecology, especially focusing on the responses of fish populations and communities to anthropogenic disturbance. His current studies are aimed to propose management action plans. [ABSTRACT FROM AUTHOR]