Invasive Species Week

Pacific Oyster (Crassostrea gigas) reef in Langstone Harbour.

Invasive and Non-Native Species in Langstone Harbour

Langstone Harbour is an ecological treasure, home to thriving marine life, diverse seabird populations, and underwater landscapes shaped by centuries of maritime history.  But beneath its surface lies a growing challenge: invasive and non-native species (INNS) – organisms introduced from outside the region that disrupt natural ecosystems and threaten native biodiversity.

One of the leading initiatives raising awareness of the challenge of INNS is Project Portunus, a citizen science project led by the Nautical Archaeology Sub-Aqua Club, a branch of the British Sub-Aqua Club.

What are INNS?

INNS are species that did not originate in Langstone Harbour, such as the Pacific Oyster.  Non-native refers to any plant, animal, or microorganism that has been brought, intentionally or accidentally, into an environment where it does not naturally occur.  However, not all non-native species cause harm – approximately 10% will become invasive.  A species only becomes invasive once it starts to disrupt the environment, economy, or human health.  The Pacific Oyster, for example, was introduced to the UK for aquaculture and has spread widely throughout the Solent.

Some common pathways for their introduction to the marine environment include:

🚢Hull fouling – slow moving vessels travelling between places can unknowingly transport marine organisms attached to hulls.

🚧Coastal and marine infrastructure – facilities such as docks, piers, seawalls, moorings, and pontoon can provide stepping stones and colonisation surfaces for species during spread.  A lack of natural predators and grazers on artificial structures encourages establishment.

🌿Habitat restoration – moving plants, substrate, organisms, and seawater can accidentally introduce non-natives in their juvenile stages, sometimes invisible to the naked eye.

Once non-native species establish themselves, they can outcompete native organisms, alter seabed ecosystems, and disrupt food webs.

Project Portunus: Citizen Science in Action

Named after the Roman god of harbours and a genus of crab, Project Portunus is an initiative dedicated to exploring, recording, and documenting the underwater environment of Langstone and Chichester Harbours.  The project was part-funded by the Solent Forum’s Natural Environment Group, established to manage the threats facing Solent European Marine Sites.  Volunteer divers, trained in underwater surveying, are working to:

🔬Identify and track invasive species, collecting data to support conservation efforts.

⚓Document the marine environment, including native and non-native species.

🌿Support habitat restoration, providing valuable insights into changing ecological conditions.

Alongside dives, the Project team have been undertaking shoreline surveys of key areas in Langstone.  During the March spring tides, intertidal surveys have revealed 17 non-native species at The Kench, four of which have never been recorded in Langstone Harbour before.  These records are available on iNaturalist for public viewing.  If you come across something unusual in the coastal environment, you can log it on iNaturalist where experts can review and identify species.

GB Non-Native Secretariat

The GB Non-Native Secretariat (GBNNS) website hosts an incredible amount of information on INNS in Britain. There are a number of events taking place this week for those interested in NNS! It also hosts information for water users on how they can stop the spread, using Check, Clean, Dry.

The Solent Forum and partners have developed a biosecurity portal for people working and living in the Solent, with details on pathways of spread, specific marine invasive species, and a biosecurity action plan for the Eastern harbours.