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Unraveling the Geomicrobiology of Powell Lake

Posted by Sebastian Haas on August 13, 2019 in News
Sampling on Powell Lake, British Columbia in August of 2016 (Photo by Wayne Lutz)
Sampling on Powell Lake, British Columbia in August of 2016 (Photo by Wayne Lutz)

A new research study conducted by CERC.OCEAN scientists explores the carbon, nitrogen, and sulfur cycles of Powell Lake. This deep, permanently stratified lake in British Columbia contains ancient seawater, trapped in its depths since the end of the last ice age.

Permanently stratified lakes are interesting for biogeochemical cycling as they represent natural laboratories in which elemental cycling along gradually changing environmental conditions can be studied in detail under stable conditions. The deep water of Powell Lake has been out of touch with the atmosphere since the last ice age, with ancient seawater still trapped in the bottom 50m of the water column. This ancient seawater, which has retained about half of its original salt content, is a relic from a time prior to the retreat of the glaciers at the end of the last ice age, when Powell Lake was a fjord connected to the Strait of Georgia (Pacific Ocean). During those 10,000 years of isolation, the water in the bottom 200 meters of the 350-meter-deep water column has been depleted of oxygen as a consequence of microbial degradation of organic matter. In the absence of oxygen, certain groups of microbes have instead produced chemical compounds such as hydrogen sulfide (H2S), ammonium (NH4+) or the greenhouse gas, methane (CH4), as part of their metabolisms. With other groups of microbes consuming these metabolic products, elemental cycles have developed that are independent, or only partly dependent, on oxygen.  

CERC.OCEAN’s comprehensive interdisciplinary study explored Powell Lake’s geomicrobiology, that is the interaction (production and consumption) of environmental microorganisms (bacteria and archaea) with dissolved chemical compounds in the lake water. DNA was extracted from the lake water at different depths, spanning a range of geochemical conditions from oxygenated to highly reducing, and sequenced by several different approaches that revealed the identity (“who” is there?) and the functional capabilities (what are they capable of doing?) of lake water microorganisms. By combining these molecular microbiological approaches with geochemical analyses, the research team documented genetic potential for unusual biogeochemical processes, linked some of them to taxonomic groups of microorganisms (“who” is capable of doing what?), and discovered the molecular traces of novel microbial lineages in the ancient seawater. The broad range of these results also laid the foundation for an even more detailed future study to research a variety of aspects of this fascinating lake.

The study was led by CERC.OCEAN’s PhD Candidate Sebastian Haas under the supervision of Dr. Douglas Wallace, and the multi-disciplinary approach required collaboration with the Molecular Microbiologists Dr. Julie LaRoche and Dr. Dhwani Desai of Dalhousie University’s Biology Department as well as a Physical Oceanographer, Dr. Rich Pawlowicz, of the University of British Columbia).

The peer-reviewed research paper will be published in the journal ‘Environmental Microbiology’ and can be accessed online under the following link: https://onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.14743

To read more about the field work the CERC.OCEAN group has undergone in Powell Lake, click HERE to read about the 2016 trip and HERE to read about the follow-up field work performed in June of 2018.