Are distinct morphotypes of the genera Anabaena and Aphanizomenon a response to environmental variation in boreal and arctic lakes in Finland?
Lepistö, Liisa; Holopainen, Anna-Liisa
Monitoring data from Finnish boreal and arctic lakes was used to study the morphological variation (phenotypes) of Anabaena and Aphanizomenon (Nostocales) in relation to different environmental conditions. Altogether 18 morphotypes were identified in the used data. Correspondence analysis (CCA) revealed three main groups which were distinguished by water transparency, the amount of humic substances and the nutrient concentration. This study showed that morphotypes of Anabaena and Aphanizomenon are specialized in different environments. In particular, Anabaena lemmermannii was found to concentrate in large, oligotrophic, clear water lakes, whereas Anabaena flos-aquae was clustered in small lakes having a moderate high total nitrogen concentration. Furthermore, Anabaena lemmermannii was the most frequently recorded species in this study, however in low densities, and occurred only occasionally in lakes with abundant Aphanizomenon. The genus Aphanizomenon occurred in humic, large and nutrient rich lakes. Our study underlines the need for further monitoring of cyanobacteria using morphological methods combined with phylogenetics and toxin analyses. Anabaena lemmermannii and A. flos-aquae, as individual species, and the genus Aphanizomenon in its entirety should be identified even more in details. These studies will yield precise information on taxa typical of different waters, and in turn provide tools to enable measures for the successful restoration of lakes.