BASS Division Talk

Exploring the Limits of Earth’s Habitability by Scientific Ocean Drilling: The Impact of Temperature on Microbial Life and Carbon Flow in Deep Sub-Seafloor Sediments

Speaker: Dr. Verena Heuer

January 14, 2020
Location: ConocoPhillips Auditorium, Gulf Canada Square, 401-9th Ave. S.W. Calgary, AB

12:00pm: Talk Starts


*CSPG members can register for free and track their CPD hours!

The ocean floor is an important interface at which geological, physical, biological and chemical processes interact. Geological processes shape the ocean floor and result in vastly different environments, such as mid-ocean ridges where new ocean floor is formed, subduction zones where old ocean floor is transferred back into the Earth’s interior, cold seeps and hot vents which release fluids and gases from within the ocean floor, and vast areas and volumes of sediment. In these environments, temperature varies widely, and microbial communities are widespread and surprisingly diverse despite energy limitations. Microbial life persists even in Cretaceous sediments down to 2.5 km below the seafloor, and in deeply buried oceanic crust. However, the total amount of subsurface biomass is still a matter of debate, the metabolic activities of deeply buried microbes are barely explored, and factors posing ultimate limits to deep life and the habitability of Earth remain unresolved. 
This lecture will address the role of temperature in deep geosphere-biosphere interactions. It will investigate the impact of temperature on the abundance and activity of microorganisms, on the biotic and abiotic transformation of sedimentary organic matter, and on carbon flow within the ocean floor. Results and technological challenges of recent scientific ocean drilling expeditions in high temperature environments, in particular IODP Expedition 337 Shimokita Deep Coalbed Biosphere and Expedition 370 Temperature Limit of the Deep Biosphere off Cape Muroto, will be discussed. The former was the first scientific ocean drilling expedition to target a deep hydrocarbon reservoir by riser-drilling technology, recovering up to 2.5 km deep, 60°C coal-bearing sediments and associated fluids and gases. The latter aimed to probe the deepest extent of life in ocean-floor sediments, known as the biotic fringe, and applied strict contamination control measures when up to 120°C sediments were retrieved from a 1.2 km deep borehole in the Nankai Trough subduction zone. The lecture will conclude with a discussion of open questions, future challenges and drilling targets within IODP’s Biosphere Frontier Theme.


Verena Heuer has a broad background in Earth Sciences and Geochemistry. She holds a diploma in Geoecology from the University of Bayreuth in Germany, a BSc degree in Chemistry from the University of Canterbury, New Zealand, and a PhD in Geosciences from the University of Bremen in Germany. Since 2004 Dr. Heuer has worked in the Organic Geochemistry Group in Bremen led by Kai Hinrichs as a postdoctoral scholar and tenured research scientist. In this role, she has investigated geosphere-biosphere interactions fuelling microbial life and carbon flow in the deep biosphere. Her investigations build on microbial growth-based methods that exploit information encoded in the stable isotopic composition of microbial substrates, products and metabolites found in sediments. This included contributing to the discovery of intact microbial cells and biogenic methane in coal-bearing sediments down to ~2.5 km depth. Dr. Heuer has participated in more than a dozen sea-going research cruises, including many scientific ocean drilling expeditions. She was co-chief scientist for IODP Expedition 370, the topic of this presentation.