Trench nutrient cycling with Ronnie N. Glud

Author: Thomas Linley
Published: Sun 03 Aug 2025
Episode Link: https://www.deepseapod.com

In this episode…

Welcome back to the Deep-Sea Podcast, your punk take on all things deep sea! Join Dr. Thom Linley and Professor Alan Jamieson as they dive into the latest from the abyssal plain and beyond.

Deep Sea News Highlights: We kick things off with a rethinking of the deep-sea boundary! Professor Alan Jamieson discusses his recent "food for thought" paper that challenges the long-held 200-meter definition, arguing for a more scientifically relevant boundary of 1,000 meters. Find out why this seemingly arbitrary line might be doing "a lot of damage" to our understanding and attitude towards the deep sea.

Also in the news, get ready for updates on:

A new story map on mesophotic reefs following the Deepwater Horizon spill in the Gulf of Mexico.

An exciting project charting shipwrecks in the Great Lakes using cutting-edge ROV technology for 3D modelling.

The discovery of a deep-sea limpet named after a One Piece character, found at an astonishing 6 kilometres deep!

How Earth's deep-sea microbes are being used to model potential life on Jupiter's moon Europa.

Groundbreaking research on a new bioplastic that vanishes by over 80% in extreme deep-sea conditions, offering hope for sustainable solutions.

Guest Interview: Nutrient cycling in the hadal trenches (6 to 11 km) and the crucial role they play in global element cycling. Professor Ronnie N. Glud, a leading biochemist and Director of the Danish Centre for Hadal Research (HADAL), talks us through how the trenches, once thought to be barren, are actually "dynamic deep-sea hotspots with intensified microbial activity and diversity". Learn about:

How hadal trenches act as "depocenters" for organic material, leading to microbial activity that's 2 to 6 times higher than in adjacent abyssal sites.

The surprising diversity of microbial "generalists" that easily adapt to the immense pressure and low temperatures, aided by viruses that facilitate "horizontal gene transfer".

The return of full anaerobic diagenetic processes (like sulphate reduction and anammox) in trench sediments, making them significant sinks for fixed nitrogen.

The role of marine snow and seismic activity in efficiently transporting organic matter and, surprisingly, pollutants like PCBs and heavy metals to these remote depths.

Why these trenches are not isolated environments but are highly connected to surface ocean processes, even responding to climate-driven changes in primary production.

We also have a surprise blobfish guest!

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Thanks again for tuning in; we’ll deep-see you next time!

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