Science Centres: Aquatic Biodiversity and Biosecurity

We are nearing the end of the first year of a four-year FRST programme on groundwater ecosystems. This research aims for better understanding of the natural ecosystems of cave and gravel aquifers. These systems are important water sources for humans, but also support a unique assemblage of animals.

Glowworm food

Glowworm feeding threads. [Photo: Waitomo Glowworm Caves.]

As part of this programme, we recently completed a preliminary survey of aquatic invertebrates in Waitomo Stream. These invertebrates provide the main food supply for glowworms, which use bioluminescence to attract their prey. Despite being key to a multi-million dollar tourist operation at Waitomo Glowworm Caves, suprisingly little is known about glowworm ecology or their invertebrate prey.

Our surveys showed healthy populations of mayflies and caddisflies, both within the caves and upstream. This pilot study will help the caves’ Environmental Advisory Group to design an appropriate long-term monitoring programme to track glowworm food supply. The programme will also provide educational materials to add value to the tourist experience of the caves.

Coins contaminate natural treasure

Aranui Caves. [Photo: Waitomo Glowworm Caves.]

One important objective of the Groundwater Ecosystems programme is to identify tourism impacts in cave systems. We recently investigated the environmental impacts of coins deposited in Aranui Cave, in collaboration with Waitomo Glowworm Caves management.

Aranui is one of three principal tourist caves around Waitomo and is renowned for its spectacular cave formations. For generations, visitors have thrown coins into a small rimstone pool in the cave. We recently found extremely high levels of copper and nickel in the wishing well pool compared with a reference site. Levels were orders of magnitude higher than sediment quality guidelines, and were likely to be highly toxic to aquatic life. Our biological sampling showed that only micro-organisms were present in the main pool, with lower diversity than in reference pools.

NIWA has since assisted DoC and the cave management company to clean up the pool, removing contaminated sediments and 1.7 kg of coins, some dating back to the 1940s. NIWA will continue monitoring contaminant levels and will assist in educating tourists to spend their money in town, not in the pool.

Our future Waitomo research will focus on comparing invertebrate communities, their biodiversity, and ecosystem structure across a gradient of tourism levels, from lightly visited to heavily visited caves.