Day 12 Why we pursue science: Christian Halverson

By October 6th, 2017

Air filter

After the last couple of days excitement about the wreck, and long nights ensuring sediment grabs and plankton recorders are being placed out, it is time to get down to why this voyage has such an unusual title—Natural iron fertilisation of the oceans around Australia: Linking terrestrial dust and bushfires to marine biogeochemistry. Morgane, a wonderful French scientist based at the University of Tasmania, is working on trace elements in aerosols and trace elements found in ocean water.

If you are a keen gardener, or have an interest in human health, you will appreciate what trace elements are. These elements are found in tiny amounts but living things still require them as nutrients to ensure certain aspects of their biology works in the most efficient way. Morgane has talked with us on a couple of occasions about iron’s role in the oceans. Though often very high in soils on land, iron that makes its way into the oceans is not very soluble. In fact, very few trace elements are soluble. Yet phytoplankton and marine plants need it for forming chlorophyll and undertaking photosynthesis.

Her work is to sample the air, passing it through a filtration system that is incredibly clean. The particles are left on filter paper that, to be honest, at the end looks as clean as when it was placed into the filter pump in the first place. She works in the aerosol sampling lab right in the bow. It is well air conditioned for a constant cool temperature but she has to deal with the pitching vessel the whole time. This area bounces around a lot more than most of the other areas on Investigator. The equipment is set up semi-permanently as she has done around four voyages sampling air and ocean water. The air comes in from the mast at the bow that only functions when the wind is driving straight in. Sea water is taken from the drop keel only when extended below the gondola holding the GSM sonars. Even rain water is collected in a super clean bucket by Morgane standing in the rain…no kidding.

Why so clean? We are dealing with the smallest of quantities, parts per billion. This is an iron ship, with steel piping, just a hint of wind or water that is travelling close to the hull could pick up traces from the ship, or even exhaust from the engines, and not the environment. Even your hair or a fleck of dust will ruin the experiment completely. Back at a lab at the university the filter paper samples will have the purest of water passed through them to extract the trace elements on the paper— often less than 10 percent of the trace elements. The rest is not soluble, and if not soluble, it won’t normally be readily available for living organisms. The remainder is still used and biological systems are mimicked to extract just a little more.

We travelled past smoky bush fires around northern NSW, and there was hope, in an odd way, that the volcano in Bali might emit natural trace elements. If these trace elements could be detected, it could add huge amounts of knowledge to an area of the planet we know so little about. Dust storms are common, sometimes they fall in the ocean and cause a plankton bloom, other times the same sorts of dust storms don’t cause blooms at all, and almost no one knows why, or has done work on this in the Southern Hemisphere. This really is cutting edge science, and it might just help us to understand why dumping a huge amount of iron ore into the oceans will not cause the planktonic blooms that can geoengineer a solution to climate change. What it might lead to is a greater understanding of the important but dynamic interplay of the atmosphere and the oceans. Who would have thought that Eric’s birds are doing OK because the same element that makes our car makes chlorophyll function?