As part of the Upper Itchen Initiative, River Action Project Chairman Charles Watson used eDNA to survey aquatic macroinvertebrates in three Hampshire chalk streams.

Despite having no previous ecological training, Charles collected the samples himself and sent them to the NatureMetrics lab for analysis, quickly and safely. The results revealed significant differences in macroinvertebrate diversity between sites with different suspected levels of pollution.

The River Itchen and its tributaries form part of an important chalk stream network, and local conservation groups and charities had raised concerns about the impact of businesses in the area.

With limited resources for formal surveys, the group needed a cost-effective, accessible way to collect data on macroinvertebrate communities across the landscape. The aim was to characterise the ecological impact of industrial activity on the Itchen and build an evidence base for conservation action.

After a single online training session, Charles collected eDNA samples across three separate chalk streams.

In our lab, we analysed the samples using our eDNA macroinvertebrate metabarcoding pipeline. This targets aquatic insects, including pollution-sensitive groups such as mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera).

The results were delivered in an easy-to-understand report, highlighting significant differences in macroinvertebrate diversity between sites with different suspected levels of pollution.

Highlights of the report included:

• A total of 339 taxa were detected, belonging to 17 orders, 54 families and 187 genera. This included midges (Diptera: Chironomidae), which are extremely challenging to identify using conventional morphology and are therefore often overlooked or lumped into a single taxon in surveys.
• The most abundant groups by sequence read count were flies (Diptera) and mayflies (Ephemeroptera). Other important groups such as stoneflies (Plecoptera) and caddisflies (Trichoptera) were also detected. Freshwater shrimp (Gammarus) were notably absent, as this analysis focuses on aquatic insects.
• The most abundant species by sequence reads was the large dark olive (Baetis rhodani).

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After just one online training session, a non-specialist gathered robust, multi-site biodiversity data – showing that eDNA can lower the barrier to evidence-based conservation. The results gave River Action and local groups a scientifically credible dataset to support their case for tackling industrial pollution in one of England’s most ecologically important chalk stream networks.