The Ōtokia Creek and Marsh Habitat Trust of Brighton, Dunedin, have always known their little creek was special. Environmental DNA (eDNA) has given them an opportunity to showcase some of the biodiversity.
Fed by craggy bush streams and pastural runlets, Ōtokia Creek winds down gullies and valleys behind the small coastal town of Brighton, about 18 kilometres south-west of Dunedin. The trickles eventually dissipate into a vast marshland cut with wide channels before entering the Pacific Ocean at Brighton Beach.
Ōtokia Creek has been previously described as a “dead muddy little ditch”, but a group of locals know it more intimately; they say it is teeming with life from birds and fish to insects. Now they have eDNA results to prove it.
Matthew York has been playing in the creek for “30 odd years”, having grown up on the shaggy semi-rural coastline next to the creek. For the past six years he has been using his own water monitoring unit to investigate flow, water temperature, turbidity and clarity, pH, conductivity, phosphate and nitrate – physical and chemical parameters that together help to build up a picture of waterway health.
The water monitoring unit supplied and maintained by Matthew York.
About a year ago, Matthew York gathered with a group of locals to form the Ōtokia Creek and Marsh Habitat Trust, in response to a proposal for a new landfill nearby that would encroach onto the catchment area for the creek. The Trust administers pest control, sycamore removal and restoration planting along the creek and marshlands, and is constructing a nursery to raise more plants. It’s aim is to restore and protect the habitats of the creek and marsh for the many native species who call it home, and to support members of their community to get involved and enjoy the area.
The Trust has been amazed by the willingness of the local community to pitch in. Groups of 15 to 20 people turn up for planting days, and they have received donations of up to 200 trees. They have recently worked with Wildlands Restoration Services to formulate a strategic biodiversity plan to guide their restoration efforts.
A group of volunteers and members of the Ōtokia Creek and Marsh Habitat Trust gathered at a tree planting morning.
A young helper.
The eDNA sample was taken from a patch of creek shaded in bush cover in late autumn. When the results arrived, Matthew York said that he spent three hours Googling the different species to learn about them. “I was pleasantly surprised”, he said, “there was a whole range of things I wasn’t aware were living in the creek.”
There were also many species that were expected, as visual surveys had been part of the Trust’s ongoing monitoring programme. These surveys have spotted short and long-fin eels, kōkopu, fresh water shrimp, and giant bullies living in the stream and marsh. The marsh also provides a habitat for water birds, including the critically threatened black stilt/kakī, royal spoonbills, mallard ducks, oyster catchers/tōrea, white herons, pied stilt/poaka and paradise ducks.
“A benefit of the eDNA test is that it is indisputable compared to a civilian undertaking visual monitoring” says Matthew York. In this case, the results have been able to validate what the group knew was present, but also turn up some pleasant surprises. The redfin bully was captured in this genetic snapshot, as well as long and shortfin eels/tuna, giant and banded kōkopu, bellbird (korimako/makomako), goldfinch and mallard duck.
The Trust has made the eDNA results publicly available on the Wai Tūwhera o te Taiao map.
Find out about the redfin bully
Explore the map - Wilderlab website
Ōtokia Creek and Marsh Habitat Trust sample results - Wilderlab website
For the Ōtokia Creek and Marsh Habitat Trust, having this evidence under their belt has proven helpful when engaging with councils and the wider community. Its members are looking into funding extra samples to dig deeper, with plans to collect eDNA at sites every two kilometres up the creek. Using the flow data collected at the water monitoring station, they have worked out that it would take the water 24 hours to flow two kilometres, and plan to sample at these intervals to get a good snapshot of the full creek.
As the creek and marsh continue to be nurtured by these proactive locals, we look forward to seeing how it goes.
If you would like to contribute a story, photos, art, or reflections for this e-pānui, please get in touch with our Science Communicator at eDNA@epa.govt.nz