As part of our My Wild City project, The Wildlife Trust for Lancashire, Manchester and North Merseyside has been leading the development of a new Biodiversity Strategy and Action Plan for Manchester.

When developing this strategy with partners it became clear that species records for the city were limited in their number with those available often being old and likely out of date. For example, there were only eight records of toad species across the entire district of Manchester.

I was tasked with undertaking a new pilot in Manchester to look at the viability of using new science-based surveying techniques to address the gap in data associated with pond habitats.

Without accurate and up-to-date records of species populations, it is difficult to apply for funding and write management plans to maximise the conservation of parks and natural areas such as Local Nature Reserves (LNRs) and Sites of Biological Interest (SBIs).

Some species require specific habitats and management practices and not knowing which areas they inhabit may negatively affect the populations. Low records mean it’s also hard to track the spread of invasive species such as terrapins and mink which, without management, can do a lot of damage to the natural ecosystems.

Current species records for ponds in Manchester are mostly based on public sightings through citizen science and basic surveying techniques such as pond dipping which have their downfalls. Pond dipping can be very labour intensive as multiple long surveys need to be done on each site to properly capture as much data as possible, even then there are species that are unlikely to be caught because they are shy or stay away from the shallow pond edge. Especially for sensitive or protected species, such as great crested newts, pond dipping may also be damaging and invasive to the habitat, disturbing the silt and risking injuring the animals.

Environmental DNA (eDNA) is DNA found in cells released from organisms into their environment through things like excretion, shedding and decomposing. The Lancashire Wildlife Trust decided to pilot the use of eDNA surveys as part of our My Wild City project to engage and involve new audiences with nature as well as make recommendations to the wider Manchester Biodiversity Action Group about the viability of using this technique to address the gap in species records for ponds in Manchester.

The eDNA surveys we tried worked by pushing a water sample through a filter to trap traces of eDNA, which we then sent to be tested in a lab with metabarcoding against existing DNA records to identify a comprehensive list of the species present.

As someone who has previously undertaken multiple surveys for pond life on a single pond - this surveying method was much more accessible, safe, and time effective. If budget were available, we could have sampled 20 ponds in the time we had traditionally surveyed one. Collecting a water sample for eDNA is also less invasive than traditional methods and can cover a much broader spectrum of species, for example ‘Vertebrates’ or ‘Macroinvertebrates’ rather than targeting one species.

In the last several years, Natural England has been approving the use of eDNA for testing if ponds contain the highly protected great crested newts, a programme that The Lancashire Wildlife Trust has been involved with in Lancashire. But this single target presence or absence test is a much more basic version of full spectrum testing now available using a database of DNA species records to match to instead.

To test eDNA surveying against other methods we taught students and community groups to survey using traditional sampling as well as eDNA, to then compare the amount and quality of data collected and the disadvantages of different techniques.

We coordinated with a primary school, a secondary school, a group of university students and two park-based community groups to sample six pond sites across the North Manchester area. We chose this area as many of the sites link into the North Manchester Nature Network, a corridor of parks linked for the benefit of wildlife. We also run volunteering sessions on these sites as well as aid with management plans, so it is crucial to know what species we are aiming to protect. To test the different types of surveying available, we also ordered additional tests of macro-invertebrates sequencing on two of the samples.

The results came back after several weeks at the lab and across the six samples they found 35 records of Vertebrates (21 matching species in the database) and 33 taxa of Macro-invertebrates (13 matching species records) between the two sites chosen for further tests. A total of 14 unique fish, four amphibians, 15 birds and two mammals were detected.

In the vertebrate testing, palmate newt was most often identified, and the species present on most sites were common moorhen and eurasian sparrowhawk which were identified in six and four samples, respectively. Lab testing for all samples was successful and they were all considered high-quality samples.

Our eDNA samples identified new species not previously recorded in the area, including species difficult to visually ID on-site without microscopes, for example, specific midge species and smooth versus palmate newts as larvae are very difficult to distinguish in the field. We collected a wide range of species data in a single quick sample whereas to collect the physical data it would need bird surveys, fish netting, pond dipping, and even night surveys in some cases.

On the other hand, it doesn't replace some of the other most reliable surveys. Certain species are harder to test for or just missed especially since DNA only lasts about 7–21 days depending on environmental conditions, for example, we spotted an invasive terrapin during surveying on one of our sites which was not identified in the eDNA results. A few of the results were not identified to species level because of a lack of DNA data or similar genetics, for example, ducks, geese, and swans, expanding this database will therefore lead to more accurate testing in the future.

Some of the records found could also be contamination, the DNA is there but it may have been brought into the pond on birds or fishing gear and not actually be a record of the species living in the pond. Another major con to the eDNA technique is that the results are also not representative of pond population sizes. All records have to therefore be taken with a grain of salt and new species identified should be investigated before they are accepted.

Although eDNA makes a good starting point for studies, it is still crucial that hands-on field surveys are undertaken to confirm results; ideally with volunteers and students where possible to help increase their field skills and knowledge of species ecology which is obviously going to be crucial as a sector if we want people who can also make recommendations around habitat interventions on wetland habitats. 

The trial was essential to understanding not only how the eDNA sampling works but how different groups engage with the project, and we can use this experience to adjust how we plan and run sessions for the most benefit of the groups and the sites.

There is the possibility to expand on this project in the near future, but this will depend on the availability of funding as the kits and lab testing requires capital expenditure. This science-based surveying technique is only going to grow in effectiveness and hopefully cost will reduce as it becomes mainstreamed so this is something that I feel will be critical going forward to help with landscape baselining. 

What can you do to help? Putting a pond, even a small one, in your garden or local green space is one of the biggest improvements you can make to your area’s wildlife, check out our handy guide for advice on how to build a pond.