Using maths to unlock underwater mysteries

A University of Queensland scientist is using mathematics, and a motley crew of tiny sea creatures known as zooplankton, to unlock some of the ocean’s biggest mysteries.

Professor Anthony Richardson, from UQ’s School of Mathematics and Physics and CSIRO Oceans and Atmosphere, says that zooplankton – despite being tiny – can offer great data on the state of our oceans, and could help us answer big questions in fields such as food security and climate change.

UQ's Professor Anthony J. Richardson. Image: Patrick Hamilton.

UQ's Professor Anthony J. Richardson. Image: Patrick Hamilton.

“Zooplankton range from microscopic organisms to large species, such as krill and jellyfish, and are the most numerous animals on the planet,” Professor Richardson said.

“In fact, every litre of seawater contains on average three or four zooplankton individuals, and there are 1.35 billion trillion litres water in the ocean – that’s a lot of creatures – probably more than the total number of insects on Earth.

“But despite this abundance, there remain large gaps in our understanding of the role of zooplankton in our oceans – particularly how they affect food webs and transfer energy up to fish.”

“Knowing more about the diversity of species, and where they’re located, can help us build mathematical models to better understand them, our oceans, and the ecological processes that sustain us.”

Professor Richardson and his colleagues are currently refining a model to work out the role zooplankton play in transferring energy and carbon through the marine food web, and how this might be altered with climate change.

“To understand more about the role of zooplankton, we need to build models of entire marine ecosystems,” Professor Richardson said.

“So, as part of the Integrated Marine Observing System (IMOS), the UQ St Lucia Campus runs a plankton sampling program around Australia.

“Monthly samples of plankton are collected and taken back to the lab for analysis, which help inform authorities about which marine areas are best to protect, while giving us the data we need for mathematical modelling.“UQ mathematics students have developed a size-spectrum model of zooplankton and the marine ecosystem, from phytoplankton to fish.

“This modelling approach uses body size of plankton to estimate their individual processes, such as their metabolic rate, how fast they grow, and what size prey they eat.

“Modelling can tell us how fisheries could change in the face of climate change, in fact, our model suggests declines in fisheries in the future in unsuspecting places that weren’t previously predicted.

“And zooplankton are critical in sequestering carbon in the deep ocean, so this data also helps reveal whether our oceans are coping – or not – in the face of rising emissions.”

“Answering these big questions is extremely challenging – we can’t study every organism – but that’s the beauty of mathematical analysis, as it gives us the tools we need to make informed assumptions ocean trends more widely.”

The common small copepod Paracalanus aculeatus (about 1 mm in length).

The copepod Subeucalanus pileatus (2 mm in length).