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David Walsh, PhD

Professor, Biology

David Walsh, PhD
Phone: (514) 848-2424 ext. 3477
Website(s): Visit our lab website

Research interests

Aquatic Microbial Ecology and Evolution
Microorganisms are a diverse component of aquatic ecosystems and their metabolic activities are central to energy, carbon, and nutrient cycling. Our research investigates the biodiversity, metabolic versatility, and evolution of these important aquatic microbes using novel genomics-based molecular approaches. Aquatic ecosystems under investigation include northern oceans, estuaries, and seasonally ice-covered northern lakes. All these ecosystems are impacted by climate change and other anthropogenic perturbations to varying degrees. Our research is coordinated to provide insights into how microbial distributions and activities may be influenced by these environmental pressures, and how changes in microbial distributions and activities may affect aquatic ecosystems as a whole.

Keywords: Microbial ecology and evolution, aquatic microbiology, genomics, metagenomics, Arctic Ocean


PhD (Dalhousie)

Selected publications

SA Kraemer, A Ramachandran, VE Onana, WKW. Li, DA Walsh. (2024) A multiyear time series (2004–2012)of bacterial and archaeal community dynamics in a changing Arctic Ocean. ISME Communications.

RE Garner, SA Kraemer, VE Onana, M Fradette, MP Varin, Y Huot, DA Walsh (2023) A genome catalogue of lake bacterial diversity and its drivers at continental scale. Nature Microbiology, 1-15

T Grevesse, C Guéguen, VE Onana, DA Walsh (2023). Degradation pathways for organic matter of terrestrial origin are widespread and expressed in Arctic Ocean microbiomes. Microbiome 10 (1), 237

Kraemer S.A., Barbosa da Costa N., Oliva A.,Huot Y., Walsh D.A. (2022). A resistome survey across hundreds of freshwater bacterial communities reveals the impacts of veterinary and human antibiotics use. Frontiers in Microbiology.

Garner R.E., Kraemer S.A., Onana V.E., Huot Y., Gregory-Eaves I., Walsh D.A. (2022). Protist Diversity and Metabolic Strategy in Freshwater Lakes Are Shaped by Trophic State and Watershed Land Use on a Continental Scale. mSystems. 7:316

O’Malley M. and Walsh D.A. (2021) Rethinking microbial infallibility in the metagenomics era. FEMS Microbial Ecology 97: fiab092

Ramachandran A. McLatchie, S. and Walsh D.A. (2021) A novel freshwater to marine evolutionary transition revealed within Methylophilaceae bacteria from the Arctic Ocean. mBio 12: e01306-21

Leclerc M., Harrison M.C., Storck V., Planas D., Amyot M., and Walsh D.A. (2021) Microbial diversity and mercury methylation activity in periphytic biofilms at a run-of-river hydroelectric dam and constructed wetlands. mSphere 6: e00021-21

Garner RE, Gregory-Eaves I, Walsh DA. (2020) Sediment Metagenomes as Time Capsules of Lake Microbiomes. MSphere 5:00512-20

Grossart HP, Massana R, McMahon KD, Walsh DA. (2020) Linking metagenomics to aquatic microbial ecology and biogeochemical cycles. Limnology and Oceanography 65:S2

Kraemer S, Ramachandran A, Colatriano D, Lovejoy C, Walsh DA. (2020) Diversity and biogeography of SAR11 bacteria from the Arctic Ocean. The ISME Journal 14:79

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