The science of history

According to the oral histories of iwi in the area, D’Urville’s Island’s Lake Moawhitu and Hawke’s Bay’s Lake Whakaki may archive evidence of devasting tsunamis in the past.

Te Herenga Waka—Victoria University of Wellington student Amy Bridges spent her summer using sediment records to try and track these tsunamis and use the scientific record to date when they may have occurred as part of a Summer Research Scholarship.

“I spent my summer with the Lakes380 team at GNS Science, processing sediment core samples and working in the radiocarbon lab, processing samples so they could be tested to work out the age of the material in the sediment,” Amy says. “I looked at over 300 samples throughout the summer!”

“I worked with the Lakes380 team to process samples from both lakes to pick out organic material and pollen samples, which can be used to track the history of what occurred in and around the lake in the past,” Amy says.

Unfortunately, the samples from Lake Whakaki couldn’t be dated as they were mostly made of up reeds and shells, which can’t be dated accurately, Amy says. However, they were able to successfully process the samples from Lake Moawhitu.

The samples Amy investigated from Lake Moawhitu didn’t show any unambiguous evidence of a past tsunami. However, Amy and her Victoria University of Wellington supervisor Dr Jamie Howarth did see some strange results where some of the older organic material had mixed together with younger material.

“While Amy’s diligent work over the summer didn’t yield unambiguous evidence for past tsunami from the lake records, it did provide a valuable pilot study that informs the direction of future work”, says Dr Howarth.

“One way to do this would be to look at the grain sizes in the sample to figure out what processes could have caused this mixing,” Amy says. “It is still possible that a tsunami did occur, so further research focusing on sediment from other parts of the lake could provide more insight.”

Although the results were unclear, Amy says completing her Summer Research Scholarship was still extremely valuable.

“Being immersed in science all summer really made me feel like this is where I’m meant to be,” Amy says. “It was also a great way to gain connections in my field and get into the headspace for a Masters, which is my next step. I had always wanted to work at GNS Science, and I met so many amazing people who I’m still in touch with—it felt like being part of a family.”

“It also showed me that my undergraduate majors—cell and molecular bioscience and physical geography—were actually a good mix, although many people have told me they are an odd combination. I used my physical geography skills on the sediment cores, and then my biology knowledge was very useful in identifying the organic material.”

Amy was inspired to apply for a Summer Research Scholarship after taking part in some research on a similar area during the last year of her undergraduate degree.

Amy also won an award for her research: best poster for Group 1 Science, Engineering, and Health in the Summer Gold Awards. These awards celebrate excellent research by the University’s Summer Research Scholars.

Research on Lake Moawhitu will continue at Te Herenga Waka—Victoria University of Wellington as part of the Lakes380 project. Russleigh Parai (Ngāti Koata, Ngāti Toa) is undertaking a Master’s thesis supervised by Professor Rewi Newham focusing on tuna (eel) populations. He is aiming to uncover the factors underpinning declining numbers in tuna in the lake. Lake Moawhitu is a customary fishing site that has supplied Ngāti Koata, and Ngāti Kuia before them, with a reliable and abundant source of tuna. Successive decades of native vegetation clearance and drainage for pastoral farming have impacted the lake’s condition and that of the adjacent wetland system. Ngāti Koata and the Department of Conservation are working together to enhance Lake Moawhitu, with extensive replanting of the wetland currently in process.