Using microbial source tracking to improve water quality in Brighton and Hove
Background
In Spring 2026, Brighton and Hove SeaCheck – an independent citizen science project – used ADAS Biotechnology’s Microbial Source Tracking service to identify sources of E. coli found at bathing spots.
Every week, volunteers at Brighton and Hove SeaCheck sample seawater in Brighton and Hove to test for E. coli – a key indicator of faecal pollution. These test results are posted on their social media channels to update swimmers, fishing groups, and visitors about the local water quality.
Having confirmed E. coli in several seawater samples, the group wanted to understand the cause so they could:
- Better protect swimmers, surfers, paddleboarders, and sea dippers
- Push for better wastewater infrastructure
- Monitor the impact of storm overflow events
- Separate wildlife impacts from human pollution
- Give the wider community scientific insights into water quality
Objectives
The group asked ADAS Biotechnology to carry out Microbial source tracking analysis on collected seawater samples to pinpoint whether the E. coli found was a result of human sewage, agricultural run off, or seagulls.
Actions taken
To establish an initial baseline, the group sent a set of water samples from three locations – the surface water run off (SRO) next to King Alfred Leisure Centre, Brighton Palace Pier, and Sea Lanes – to ADAS Biotechnology for Microbial Source Tracking analysis in January 2026.
After a high level of E. coli was later confirmed at Brighton Palace Pier and King Alfred SRO in February 2026, a second set of water samples was sent.
For each water sample, ADAS Biotechnology carried out Microbial Source Tracking – a DNA amplification technique – to look for three specific DNA markers:
- Human – which would indicate sewage leaks, overflows or aging pipework
- Ruminant/cow – which would indicate agricultural runoff entering waterways
- Seagull – their droppings raise bacteria levels, especially after storms or on busy beaches
Results
The DNA marker for human faecal matter was found in almost all seawater samples submitted for testing.
Ruminant/cow and gull DNA markers were identified too, but at a much lower level – below the threshold for a positive result (below the limit of quantification).
Set 1 – January 2026
Estimation of Contamination per 100 mL on 08 Jan 2026
| Location | E.coli | Human marker | Ruminant marker | Gull marker |
|---|---|---|---|---|
| Sealanes | 230 cfu | 306 gc | Negative | Detected (below the threshold for a positive result) |
| Palace Pier | 339 cfu | 805 gc | Negative | Negative |
| King Alfred SRO | 350 cfu | 794 gc | Negative | Negative |
Set 2 – February 2026
Estimation of Contamination per 100 mL on 3/4 Feb 2026
| Location | E.coli | Human marker | Ruminant marker | Gull marker |
|---|---|---|---|---|
| Palace Pier | 39 cfu | 197 gc | Negative | Negative |
| King Alfred SRO 1 | 1399 cfu | 16553 gc | Negative | 412 gc |
| King Alfred SRO 2 | 95 cfu | Negative | Negative | Negative |
- GC (Genomic copies) = How many DNA copies we detect.
- CFU (Colony-forming units) = A unit of measurement to assess E.coli levels in bathing water. According to UK legislation, 250 cfu per 100ml for coastal waters is ‘Excellent’.
Conclusion
The results indicate that human sewage was the most likely cause of E. coli in seawater at Brighton and Hove in January and February 2026, either as a result of outfalls and/or missed connections.
The differences in DNA marker concentrations between locations suggests that currents and water flow rates have an impact – some locations may be safer than others.
Brighton and Hove Seacheck are working with Southern Water to further investigate these contamination hotspots.
Follow the Brighton and Hove Seacheck team on Instagram to see the latest information on water quality at Brighton and Hove swimming spots.
