PS 50-173 - Uncovering the mystery of harmful algal bloom seasonal dynamics in Canadian boreal lakes

Background/Question/Methods

Cyanobacteria are the Earth’s oldest photoautotrophs and provided the level of oxygen we currently have today. However, when they overgrow and form a bloom, they cause ecological degradation and sometimes they produce toxins that become life threatening. This phenomenon is “harmful algal blooms” and is linked with eutrophication, and water temperature rising in boreal lakes. Recent observations showed some unusual occurrence of harmful algal blooms under the ice cover which contradicts the fact that higher temperature always influence the bloom formation. This study aims to better understand the dynamic of harmful algal blooms in boreal lakes by identifying the specific driving factors responsible for cyanobacterial development based on seasonal variation from lakes of Abitibi-Témiscamingue (Quebec, Canada). We hypothesize that, cyanobacterial bloom formation and development are due to higher temperature in lake water and high nutrients availability in the lake during winter. Our experimental design is composed by two different types of boreal lakes: Lake Fortune and Lake Beauchamp. We are identifying phytoplankton community composition and cyanobacterial species in those communities in each month starting from June 2021 to May 2022. Also, cyanotoxin concentrations will be estimated. Finally, RNA analyses will be carried out to determine the cyanobacterial cell activity.

Results/Conclusions

According to our preliminary results, Lake Fortune experienced cyanobacterial bloom mainly from 5 main species namely, Aphanizomenon, Dolichospermum, Limnothrix, Pseudanabaena. Between the month of July to October, Planktothrix showed an increasing trend (7 times). We also find the correlation of cyanobacterial cell count with dissolved organic carbon and chlorophyll a. The outcomes of the project can contribute to the goal of controlling life threatening and toxicity producing cyanobacteria. Additionally, it will contribute to develop a comprehensive knowledge and tool for improving water quality for MRC Abitibi region.