A Teeny Tiny Trip to Queenstown: An Above-Average Day in the Life of the WAI Microplastics Summer Scholar
By Alice Gilbert (WAI Summer Scholar).
My day started early, I was up before the sunrise and excited to go sample microplastics at Lake Hayes, Lake Wakatipu, and Moke Lake (on the way to Glenorchy). I had the truck packed in record time, and was soon crossing the Crown Range, with the No Such Thing as a Fish podcast playing in the background. Today’s episode covered everything from flatworm penis fencing to how humans could technically be considered worms because we’re vaguely tube-shaped and don’t poop out of our mouths. A solid start to the day.
For those who don’t know me, I’m Alice, a freshwater ecology student at the University of Otago, and I’m WAI’s Microplastics Summer Scholar for 2025.
This summer, my research focuses on whether hydrogen peroxide digestion is necessary in WAI’s community science method for microplastic sampling. Peroxide digestion removes organic matter from microplastic samples, making it easier to differentiate microplastics from other fibres and debris. But is it actually improving accuracy?
That’s what I aim to find out — first by gathering samples from a range of sites around the Central Lakes area, to compare a range of different organic matter contents. Hydrogen peroxide is expensive and poses safety risks, so eliminating it could simplify the process for community groups — provided it doesn’t significantly alter the accuracy of microplastic counts.
My first stop was Lake Hayes — Te Wai Whakaata o Hākitekura. Having worked the past three summers for Mana Tāhuna doing catchment restoration, I’ve spent hundreds of hours here and always enjoy seeing how the native plantings are progressing.
I set up my gear by the Mill Creek inflow, using the table from my Honda CR-V (yes, I brought that in the WAI Hilux). While taking turbidity measurements, I noticed a large shape moving beneath the surface. At first, I thought it was an unusually big trout, but its dark bronze colour, wide pectoral fins, and crosshatched looking scales told a different story — it was a grass carp.
Last semester during my invasion ecology class, we had heard about lake invasives from Associate Research Professor Marc Schallenberg. One of the species mentioned were grass carp, a large herbivorous course fish, which can cause significant ecological harm in lakes and rivers due to their tendency to consume large amounts of aquatic vegetation.
Professor Schallenberg had mentioned a positive eDNA result for grass carp in Lake Hayes, indicating the presence of the invasive fish in the catchment. While grass carp can be legally stocked (with a permit) for aquatic weed control, part of the permit requires containment. The assumption had been that their presence was limited to golf course ponds upstream — not the lake itself. Grass carp have the potential to cause significant damage to the lakes native macrophyte beds (aquatic plants), so an incursion is not only an issue for the permit holder, but also an issue for the health of the lake.
I decided to flick a text to Professor Schallenberg.
“98% sure I just saw a massive grass carp in Lake Hayes.”
He responded faster than I had expected.
“Could it have been an eel? There are some big eels in there.”
I may not be an expert, but I was a little hurt by his lack of trust in my fish ID skills. I clarified why I was sure that it was a grass carp not an eel, and Dr Schallenberg said he’d pass the info to his contact at DOC.
Frustrated by this discovery, it took me longer than expected to finish up at Lake Hayes, and I delayed myself further by stopping in at the Mana Tāhuna office to say hello. I then headed into Queenstown to sample Lake Wakatipu – Whakatipu Waimāori.
I had intended to sample near the Horn Creek inflow; however, I didn’t consider how the volume of people around would affect my ability to get the truck close to the site. Having circled the nearby streets an embarrassing number of times (and briefly considering the old ‘leave the hazards on’ trick), I resigned myself to squelching down the main street in my waders, trundling my cart full of sampling gear across the cobbles.
In the midst of sampling, I received a call from Professor Schallenberg’s contact at DOC. After discussing my sighting, we confirmed that it was a grass carp — the only other remotely similar fish would be a goldfish (also a pest), and those aren’t exactly known for their dark bronze hue. He reported the grass carp sighting internally to the DOC database, and I later reported it through the MPI pest hotline.
As I wrapped up, I was intercepted by locals asking about solar flares (which are not in my field of expertise) and had a lovely chat with an American couple who then gifted me homemade lip balm as thanks for answering all their questions.
My last stop was Moke Lake (Punamāhaka, or Waikāmāhaka), where the late afternoon sun made my dark-coloured waders feel like a questionable life choice. At this point I was tired and wanted to avoid attention, so I dragged my sampling gear down the gravel track away from the busiest area; although the rattling of glassware in my cart ensured that everyone noticed me anyway.
I was eager to work quickly, but the soft sediment made things tricky — even the smallest movement stirred up debris, forcing me to wait for it to settle before collecting samples. After another hour and a half of careful work, I trundled my cart back along the path (enduring more side-eyes from passersby), packed up my gear, and started the drive back.
After half an hour of sitting in traffic trying to get through Queenstown I could hear my stomach grumbling, so I stopped at a friend’s house in Arrowtown for dinner before continuing the drive back over the hill to the WAI office. Unpacking the truck in the dark, I made the discovery that one of the sample jars had cracked during the drive, leaking into the bottom of a cardboard box. Unfortunately, I only found this out as I lifted the box out of the truck…. luckily, only two broke but that was not how I planned to end my night.
Despite the heat, delays, and an unexpected pest fish sighting, I managed to complete my sampling mission for the day. Science is rarely straightforward, and sometimes (most times) things don’t go to plan. But if nothing else, I now have a newfound appreciation for the unpredictability of fieldwork — and for cushioning my sample jars, just in case.
This blog was written by WAI Summer Scholar Alice Gilbert.
‘A Teeny-Tiny Truth’ is a research project that investigates microplastics in our fresh water, while empowering our community to participate and drive change.
WAI Wānaka run citizen science sessions, collecting and testing water samples and creating learning opportunities for the community. As part of this initiative, we have released two citizen science guides for sampling microplastics in water. One for communities, the other for schools.