Highlights
- Identification of 37 non-native species with two new to British waters
- Identification of 36 cryptogenic species with four new to the UK
- A variety of sampling techniques is recommended to determine the non-native biota of an area
- The need for baseline data to help establish introduction rates
- Such reviews help assess the effectiveness of biosecurity measures under EU frameworks
Why estuaries?
Estuaries are a hotspot for discovering non-native species, as the species found there are tolerant to different conditions and fluctuations in salinity and temperature. Vectors of introduction include international or recreational shipping, ballast water and aquaculture.
Eradication of marine non-native species once they have become established would be nearly impossible, and although some cause economic or environmental damage, many species are not invasive or damaging to their new environments. Biosecurity measures are in place in many areas with monitoring programmes to provide ongoing data.
The study was collated from routine monitoring surveys and environmental impact studies, as well as literature records, and demonstrate that varied sampling techniques give a comprehensive account of what is in the estuary. The APEM Group BioLabs team identify invasive and non-native species in most projects, either incidentally or as part of the brief.
Dense biofouling on a fender, showing native and non-native species colonising the same habitat.
The importance of sampling methods
Using varied sampling techniques gives the labs team a view of the flora and fauna living in and on the sea bed, the water column, in subtidal and intertidal habitats. Sampling techniques in the Stour and Orwell estuaries included intertidal core sampling, fyke and seine nets, grab sampling, plankton sampling, rapid assessment and trawling.
Rapid assessment surveys are usually carried out by eye at the scene. Other samples are transferred back to the lab, described by Chris as ‘a rock pool in a bucket’:
“Like an explorer, you’re the first person to see that bit of seabed when you open the bucket. There’s always something you’ve never seen before, and always some detective work to follow.”
Nine of the species found in the paper are rated as High Impact under the Water Framework Directive (WFD) and thirteen are listed in the UK Marine Non-Indigenous Species Priority Species List.
The Japanese brush-clawed crab, Hemigrapsus takanoi, collected from the Orwell Estuary, near Ipswich
Ongoing monitoring and assessment
The study suggests that the Stour and Orwell estuaries are among the most invaded regions in northern Europe. This is in part due to strong baseline data going back to at least 1890 for the Stour and Orwell.
With monitoring programmes in other estuaries and local reviews, baseline data on the movement of non-native species will determine a larger picture of hotspots and introduction rates and help assess the effectiveness of biosecurity measures under the EU Water Framework Directive (WFD) and EU Marine Strategy Framework Directive (MSFD).
Watch Chris Ashelby in our webinar ‘Tackling the spread of marine INNS in four steps’ or read his article about how marine invasive and non-native species are found and recognised here. You can also get in contact with Chris and Tim on LinkedIn.
1 Cryptogenic species are those whose origin cannot be demonstrably proven to be native or introduced.
