Science Centres: Oceans

Myriad applications for isotope analysis

NIWA’s New Wave micromill is used to prepare microsamples for chemical and isotopic analysis. Complex structures can be sampled with submicron stage resolution and positional accuracy. Pictured clockwise top to bottom are: speleothem (being milled), bamboo coral sections, a galaxid otolith, a pair of pilchard otoliths.

NIWA is the leading institute in New Zealand doing high resolution analysis of stable isotopes in carbonates to identify environmental change over timescales of tens to thousands of years. We use these techniques on materials as diverse as planktonic shells, fish earbones, and limestone structures in caves.

The work may be technical, but it brings wide benefits, providing detailed records of past ocean/climate change, improving data for climate modelling, and helping predict the response of the ocean to climate change.

Planktonic foraminifera are single-celled organisms about the size of a grain of sugar. Isotopic analysis on these, and on deepsea corals and brachiopods, tells us much about how the marine climate has changed in the past, including relatively abrupt changes in ocean circulation.

Locked inside speleothems, including stalactites and stalagmites, is a historical record of heavy rain seeping into caves. Isotope analysis here helps define risk assessment models (e.g., for tropical cyclones) and improves understanding of climate changes.

Stable isotopes in coastal fauna such as paua shells provide a picture of local climate variability and help us estimate paua age and growth rate; information vital for assessing the sustainability of these coastal fisheries.

Isotope analysis of fish otoliths (earbones) is clarifying the life histories of some significant commercial species.

NIWA has conducted isotope analysis for national and international clients, including the Ministry of Fisheries, University of Auckland, University of Waikato, University of Otago, Victoria University, GNS Science, CSIRO (Australia), and UMR Geosciences (France).