CampbellReith's Ruth Jones discusses the tentacled lagoon-worm, the proposed translocation of a population on the Isle of Wight and the environmental design criteria necessary to ensure its survival
The adage “out of sight, out of mind” is true in most instances, but not in the case of the tentacled lagoon-worm, Alkmaria romijni.
At less than 5mm long, and present only in the top 1-2cm of sediment, this tiny worm is not easily visible to the naked eye (see image below), but its size belittles its importance. A. romijni is a protected species under Schedule 5 of the Wildlife and Countryside Act 1981, because they are vulnerable to even slight changes to the habitats in which they live.
Populations of the species have been recorded at just 27 sites in the UK and are classified as “scarce”. The worms are found in sheltered estuaries and coastal lagoons, which are habitat types designated as “priority” under the UK biodiversity action plan and listed in Annex I of the Habitats Directive.
River Medina, Isle of Wight
A planning application was submitted to the Isle of Wight Council (IOWC) for the development of Kingston Marine Park – a marine business park comprising the construction of up to 15,000m3 of B1 (offices/light industry), B2 (general industry); and B8 (storage and distribution) floor space for marine use; a 200 tonne hoist dock and holding pontoon; and landscaping (including bunding and habitat creation adjacent to the River Medina).
As part of surveys to inform an environmental impact assessment (EIA), an intertidal and benthic survey was undertaken for the scheme, during which A. romijni was found.
A total of 157 worms were found spread over nine survey stations and control sites along the intertidal foreshore of the River Medina, indicating that this species was not just confined to the proposed development site.
The translocation of A. romijni has been undertaken rarely, although these have been completed successfully. A project at Common Marsh Lagoon on the River Medway in the early 2000s, for example, translocated a relatively small A. romijni population.
A translocation strategy has been developed in consultation with Natural England, the Environment Agency and IOWC to mitigate and compensate for the habitat loss during the construction and operation of the proposed development.
It was suggested that a translocation scheme be adopted to move the A. romijni population to a new proposed habitat compensation site with the same habitat and sediment composition. By implementing appropriate mitigation measures the A. romijni population will not be lost, but moved to a new habitat minimising the potential impact of the development.
The methodology for the translocation at Kingston Marine Park will follow that used on the River Medway development and will use the following environmental criteria to construct the new habitat:
- It will contain a muddy substratum (≥80% silt-clay fraction);
- salinity of around 20 parts per 1,000 ;
- have a depth of up to 1m after the translocation of mud (shallower at the margins); and
- retain at least 60% of its water volume at all states of the tides.
After the translocation has been completed, it has been recommended that the A. romijni in their newly created habitat are not disturbed for a period of at least six months to allow the new lagoon bed to stabilise.
Regular monitoring of salinity, water-level at low tide and the integrity of the lagoon basin will be routinely undertaken to ensure that the lagoon habitat does not degrade following the translocation process.
To determine whether the translocation has been successful, core sampling (approximately six to eight samples) will be undertaken around the lagoon and analysed in laboratory conditions. The monitoring will take place annually, at the same time each year, for three years to confirm the successful colonisation of the receptor site.
The Kingston Marine Park development demonstrates that the EIA process can effectively identify the potential environmental impacts of proposed projects, such as those to the lagoon worm, and incorporate appropriate prevention, mitigation, management and monitoring measures to avoid significant negative impacts.
It also shows that even the smallest creatures can have a big influence on a project, revealing how specialist ecological advice and mitigation measures can often be required.
This article was written as a contribution to the EIA Quality Mark’s commitment to improving EIA practice.
Ruth Jones is an environmental consultant at CampbellReith
