Never will I look at mud the same..

By Aaron Puckeridge, University of New South Wales

NEVER WILL I LOOK AT MUD THE SAME WAY AGAIN! Did you know that by looking at mud you can find tiny fossilised animals, or even understand past climates? Neither did I. On land, mud has a dark colour from decomposed animal and plant matter, and it is the same in the ocean. In the ocean, dead animals will sink down to the seafloor and accumulate, eventually forming mud. As a marine biologist I have never appreciated how interesting mud can be!

CAPSTAN student samples the mud from the end of the kasten core on RV Investigator as part of his at-sea marine science training
I sample the core catcher of the Kasten core on the stern deck of RV Investigator

Over the last two days onboard RV Investigator, we have been sampling a deep-sea trench in the Great Australian Bight. The seafloor here sits undisturbed by overhead currents, allowing dead animals to accumulate over thousands of years and form mud. Sampling this mud, up to 3000 metres below the surface of the ocean is where the amazing technology onboard the RV Investigator comes into play. High-resolution sonar gives us a 3D image of the seafloor, helping us to select a site to study. Then we lower a large tube to the seafloor and into the seabed to collect a vertical tube of mud, with young mud at the top and old mud deeper down. At a glance, this looks like any old mud, but under the microscope it is almost entirely tiny animals called plankton.

microfossils and biological debris down a microscope observed by CAPSTAN students as part of their at-sea marine science training
Microfossils and other biological debris in the sediments under the microscope.

Over the coming days we will be looking at these tiny plankton fossils to understand how the ocean above the deep-sea trench has changed the in past. Fingers crossed we won’t get seasick while looking down the microscope!

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