What lives in the river

A community project is using environmental DNA (eDNA) to identify native and exotic species in the Manawatū River. Elaine Fisher reports.

In Environment14 Minutes

The secrets of what lives in and around the headwaters of the Manawatū River may soon be revealed thanks to a project involving local hapū, school children, a dairy farming family and scientists.

Local iwi have built a whare at the top of the Manawatu River catchment with interpretive panels explaining the history of the area and the work being done to restore the mauri of the awa.

Funded through Our Land and Waters Rural Professionals Fund, the nine-month-long project involves collecting water samples and using environmental DNA (eDNA) to identify native and exotic species of fauna and flora which live in or near the river. As living things move through their environment, they leave behind small fragments of genetic material referred to as eDNA. By filtering this material out of water, it is possible to gain insights into the types of organisms living in an area. And, according to one of the scientists involved, Amy Gault of Wilderlab NZ, the samples often uncover previously undetected inhabitants and go beyond what can be found with visual survey methods.

“In a location elsewhere in New Zealand, by using eDNA we have detected the presence of the ancient fish Lamprey (Geotria australis) which had not been found despite 15 years of monitoring of that waterway. The eDNA gave strong signals and when searchers went higher up in the river, they found a small pocket habitat where an adult lamprey was residing under a log.

“In another case, eDNA picked up evidence of fernbirds in an area they were not thought to inhabit, meaning the birds could get the protection they needed.”

Amy says eDNA sampling kits provided by Wilderlab are easy to use, even by children.

“They are a useful tool, especially for areas which logistically are harder to monitor, because the testing casts a ‘wider net’ upstream of a sampling site. This can also be valuable for monitoring rare and cryptic species which can be difficult to find and identify, particularly those in vulnerable or fragile habitats.”

These are the kind of results those involved in the latest project, called  “Using eDNA to identify taonga species” hope eDNA will reveal. The project is an extension of work begun four years ago by Penelope and Blair Drysdale of Te Miro dairy farm at the headwaters of the Manawatū River in the Ruahine Ranges, and Te Kāuru Eastern Manawatū River Hapū Collective, to restore 18 hectares of retired land along the river.

The latest project’s team includes Te Miro Farm, Te Kāuru, Arapera Paewai of Taiao Ora Contracting, Adrian Cookson of AgResearch, and Shaun Wilkinson and Amy Gault of Wilderlab NZ. Sampling for eDNA testing began in December and will be repeated in January, March and May.

The aim is to use the scientific evidence of eDNA to help understand the health of the water and the taonga species it supports. The project will compare eDNA from farmland, and a culturally significant headwater site, to understand the ecosystem changes as the awa (river) travels through different landscapes.

The results will enable farmers to see where wildlife and farmed animals are contributing to eDNA, provide a method to detect positive change in future, and provide communities with a way to connect more deeply with their awa and its ecosystem.

The headwaters of the 180-kilometre-long Manawatū River is sacred and Arapera Paewai says for generations local hapū have lived alongside the river which was an important source of food and means of travel.

“We have been collecting and retelling stories of the awa as a way of reconnecting with it for a long time. In 2010 Te Kāuru created an action plan to improve water quality including riparian plantings near the river’s source.

“We were looking for opportunities to work alongside landowners in restoration work and the relationship with Te Miro Farm happened almost organically and has gone from strength to strength in a short period of time. Ultimately, we are all trying to improve the awa and build relationships, showing other areas how much can be achieved by working together.”

Te Kāuru Eastern Manawatū River Hapū Collective is based in Dannevirke. Its aims are; ‘to have the Manawatū River returned to its original calling as a source of regional pride and mana; to have the Manawatū catchment and waterways  returned to a healthy condition; and to ensure that sustainable use of the land and water continues to underpin the economic prosperity of the region”.

Improving water quality and the environment around the river, as it passes through their 200ha farm, was among the first goals for Penelope and Blair when they bought Te Miro Farm just under five years ago.

“The river margins were degraded with weeds and heavily grazed. We were really fortunate to be put in touch with Arapera who came out and walked the river with us. From there our relationship blossomed and the project to restore and enhance the Manawatū River began and is still going on.

“It’s a never-ending project in which each party has similar values and visions which include involving local schools. It is special that people from all walks of life come out and work together to achieve a mutual vision.”

So far more than 30,000 native trees have been planted along the awa, by local hapū groups and students from Norsewood and Districts School who will also be part of the eDNA project. A further 10,000 eco-sourced native tree seedlings await planting in the new Te Miro farm nursery, a focal point for community engagement with the ongoing project.

For Adrian, the eDNA project is a further extension of water quality work he has been involved in with Arapera, Te Kāuru and more recently Te Miro Farm which, close to its source, is the first dairy farm on the Manawatū River.

“In the last year and a half we have been doing regular water quality sampling near the headwaters and where the river flows in and exits Te Miro Farm to get an idea of E. coli in the bush and into and out of the farm to show the impact of farming on the river.

“At this stage we believe dairy farming is having only a minor impact on the E. coli counts because of the farm management, effluent containment systems and the retirement and planting of riparian margins.”

Results from eDNA testing will show the biodiversity of life in and around the river and Adrian says it’s an exciting tool for engaging children.

“The samples will bring a lot more clarity for students about the birds, animals, fish, trees and plants living around the awa and may help translate where pollution is coming from and ways to improve water quality.”

Te Miro Farm is well on the way to gaining organic certification for its land and 320-cow herd.

“They are cross-bred cows which are milked once a day. The contour is not typical dairy country. It is steep to rolling hilly country and we have retired around 38ha of wetland and swampy areas and planted them in native species,” Penelope says.

Today the Manawatū River has a reputation as being extremely polluted by run-off from farms and wastewater discharges from the towns and cities through which it passes. Those involved in the discovery and recording of what lives in and around its headwaters, and improving the water quality there, hope others will be inspired to follow their lead and restore the river to its natural state.

Perfect for diversity

Excellent’ is the ranking from the eDNA analysis of the headwaters of the Manawatu River as it runs through Te Miro Farm.

“When we were out taking the eDNA samples (late last year), the team really noticed the beautiful clarity of the water at even the lowest farm site (shown in the Wheel of Life diagram), something which is unfortunately not very common in pastoral waterways,” Wilderlab NZ scientist Amy Gault says.

“This also meant that the boulder habitat in the stream was perfect to support a large diversity of organisms to comfortably live in. Pair this with the bush shading and thick riparian boundaries, it wasn’t too surprising to see that the eDNA ranks it as an ‘Excellent’ site.”

The results of the eDNA sampling are displayed in a Wheel of Life diagram and Amy explains that the Wilderlab’s ecological health index, the taxon-independent community index (TICI), works in a similar way to the commonly used Macroinvertebrate Community Index (MCI).

“Except it works with ‘indicator sequences’ instead of indicator macroinvertebrate taxa. The TICI scores from the five sampling sites, from the upper reserve site down to the lower farm site, showed only small variations in ecological health, a real testament to the mahi that Te Miro Farm have been doing to protect the stretch of awa that flows through their farm.

“The TICI includes information from across the tree of life, allowing it to give a more holistic lens into the water health than other indices which only consider a handful of organisms.

“Importantly, it includes a lot of information from the base of the ecosystem such as various microeukaryotes, bacteria, and other ciliates. These often-misunderstood groups are often only talked about in a negative way, but the world is becoming a lot more accepting as we continue to learn just how diverse these groups are and how many of which are actually indicators of healthier waterways.”

There were really strong DNA signals of the treasured dwarf galaxias (Galaxias divergens), kōura/freshwater crayfish (Paranephrops planifrons) and both longfin and shortfin tuna/eels (Anguilla dieffenbachia and australis) at all of the sites. There was also a large number of native macroinvertebrate taxa, including several mayfly and caddisfly species which are known to be good indicators of healthy waterways, Amy said.

“The eDNA results picked up the presence of two species of rats, red deer, and brushtail possums, which are all known to be pests in the area. It also detected DNA from pig, sheep and cattle, which is neither uncommon nor worrisome given the farmed population in the near vicinity.”