This sea week Our Changing World joins Dr. Kim Currie on the Munida transect time-series - a long running investigation of how the chemistry of the oceans off New Zealand is changing.

Six times a year, for the last 23 years, Dr. Kim Currie has made the same boat journey, for the same reason - to collect valuable ocean chemistry data.

As Kim knows, sometimes good science takes time.

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The Munida transect time series, named after the research vessel it started on, has been running since 1998. Back then, we didn't know about ocean acidification - how the ocean's chemistry is changing as it absorbs carbon dioxide from the atmosphere.

When she started the study, Kim was interested in how New Zealand oceans were involved in the movement of carbon between the land, sea and air. So, she picked a 65 km transect line off the coast of Dunedin, one that crosses an interesting area where subantarctic and subtropical water masses meet, and she began to collect data.

Today, Kim follows this same transect line six times a year and gathers data in the same careful, consistent manner. While the boat steams along, Kim collects a myriad of surface ocean chemistry measurements, as well as water samples for later carbon content analysis.

There is a lot of natural variation in something as dynamic as the South Pacific Ocean. Only because of Kim's careful data collection over a long period have they been able to tease out the trend that shows that the pH of the open ocean is indeed dropping, as a result of the oceans absorbing more carbon dioxide.

For Kim collaboration is key. Collaboration with the global science community to ensure that data is collected the same way and therefore comparable. Collaboration across New Zealand to establish a New Zealand Ocean Acidification Observing Network to investigate coastal changes. And collaboration with staff and students at the University of Otago to maximise the use of the research vessel and the time at sea.

This New Zealand Seaweek, listen as Claire Concannon climbs aboard the University of Otago's research vessel the Polaris II to learn more about this globally important study and to find out about the wide range of other research happening along the way.

Thanks to Dr Kim Currie of NIWA, University of Otago students Erik Johnson, Hannah Heynderickx, Jordon Sparrow, Nico Daudt and Oscar Thomas, University of Otago research technician Judith Murdoch, and to Graeme Loh.

To learn more:

- Listen to this Our Changing World episode about ocean acidification from April 2021…

Go to this episode on rnz.co.nz for more details