Dwarf Stonewort (Nitella tenuissima)
Key Details
| Taxonomic Groups: | Non-vascular plant (incl. chromists) > stonewort > Stonewort |
| Red List Status: | (Not Relevant) [(not listed)(nr)] |
| D5 Status: | |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Nitella tenuissima |
| UKSI Recommended Authority: | (Desv.) Kütz. |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | (not listed) |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Provisional England CR, Britain EN (Stewart & Lansdown 2021, Stewart 2022). Last seen 2000 at Wicken Fen and 1961 at Foulden Common. Not seen for longer period elsewhere in East Anglian fens, principally Cambridge/Ely area and Upper Waveney/Little Ouse Fens. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | At Wicken Fen has appeared from time to time following clearance /disturbance (in recent times about every 20 years). Evidence at Wicken Fen and elsewhere indicate that spores remain viable for decades so that habitat restoration has the potential to be effective even when the species has not been seen for a significant period. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | Yes |
| Justification: | At Wicken Fen and sites outside England, the species has appeared in several different locations within sites, suggesting a resource of viable spores much wider than the locations known. Pond creation/clearance and ditch clearance in the areas around where it is/was historically known could result in its appearance. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 6. Recovery solutions trialled |
| Recovery potential/expectation: | Medium-high |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Although the species has not been seen in England for over 20 years, there is a good probability that favourable management could result in its reappearance - See answers to Q2 and Q3 |
Key Actions
Key Action 1
Proposed Action: Creation of pools and ditch clearance. Requirements are open substrates in shallow scrapes in up to 50 cm max. with firm peat/marl base and calcareous water. Pools can be temporary or semi-permanent but in more permanent water the build up of soft silt and competing vegetation is less favourable.
Action targets: 7. Best approach adopted at appropriate scales
Action type: Habitat management
Duration: 1 year
Scale of Implementation: ≤ 5 sites
High priority sites: Wicken Fen, Lopham Fen, Foulden Common
Comments: Some suitable pools have been created in the part of Lopham Fen where previously recorded but Nitella tenuissima has not appeared. No current proposals at Wicken Fen or Foulden Common
Key Action 2
Proposed Action: Survey of Great Fen Project areas with historic records to identify if any suitable habitat created and if the species has appeared. The species was lost from the target sites when they were drained but there could still be viable spores in the soil that could reappear if suitable conditions created. During restoration work the possibility of suitable open conditions in pools are particularly likely due to disturbance activities. See Action 1 for details of preferred habitat.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Status survey/review
Duration: 1 year
Scale of Implementation: ≤ 5 sites
High priority sites: Bottisham Fen, Burwell Fen, St. Edmunds Fen
Comments: Also addresses SRC steps 4 & 5. Although not seen for over a century in these sites, the oospores are known to be long-viable
Key Action 3
Proposed Action: Reprofiling of Wicken Lode to create areas of shallow shelf. The current profile of Wicken Lode is steep-sided with no shallow habitat for this species. When last seen there (in 1992) it seemed to be restricted to fallen blocks which stuck up into shallower water.
Action targets: 7. Best approach adopted at appropriate scales
Action type: Habitat management
Duration: 1 year
Scale of Implementation: 1 site
High priority sites: Wicken Fen
Comments: Species has been abundant in Wicken Lode in the past but the current profile seems unsuitable. After initial reprofiling, there may need subsequent maintenance of form.
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.