LOUGH ERNE NUTTALL’S PONDWEED (ELODEA NUTTALLII) Commonly asked questions Lough Erne - Nuttall’s Pondweed (Elodea nuttallii) - Commonly asked questions Contents 1. What is Nuttall’s pondweed? 2. What does it look like? 3. Are there any similar looking species? 4. How can you tell the difference in these species from Nuttall’s pondweed? 5. How did it get here? 6. Why is it only causing problems now? 7. What should boater users do to prepare? What should they do if they encounter weeds? 8. I am a private marina manager in Lough Erne and I would like to control it. Who do I need to contact? 9. Where can I get advice on control options? 10. How does it spread? 11. Where can I get advice on biosecurity measures I can follow to prevent further spread? 12. What is being done? 13. Does it occur at any other sites in Northern Ireland? 14. If I find it at another site where can I report it? 15. Where can I get information on managing the waste weed material? 16. Where can I get additional information on invasive species? 17. Relevant contacts. 1 Lough Erne - Nuttall’s Pondweed (Elodea nuttallii) - Commonly asked questions 1. What is Nuttall’s pondweed? 4. How can you tell the difference in these species from Nuttall’s pondweed? Nuttall’s pondweed is an invasive alien species of aquatic plant (macrophyte) that originates from Canadian pondweed’s (Elodea canadensis) leaves North America. It was first recorded in Northern are arranged in a similar arrangement to Nuttall’s Ireland in 1984 on the west side of Lough Neagh. Its pondweed making it the most difficult to tell apart. preferred habitat is slow flowing water in which it Canadian pondweeds leaves are also arranged in can grow up to a depth of 3 metres. whorls of 3 around the stem. It has been present in NI since the 19th century. The main distinguishing 2. What does it look like? feature of it from Nuttall’s is the individual leaf shape. Canadian pondweed leaves tend to be less recurved than Nuttall’s leaves, they are also quite parallel sided narrowing in the final third to a relatively blunt tip. It is reported as being able to grow in water up to 1.5 – 2 metres in depth. Nuttall’s pondweeds leaves on the other hand tend to narrow gradually from the base of the leaf to a more sharply pointed tip. Image by GB NNS • Leaves are commonly arranged in whorls of 3 around the stem. • Towards the base of the stem leaves maybe arranged in pairs on the stem. • Its preferred habitat is slow flowing water such as those found in lakes and margins of rivers. • It can grow in water up to 3 metres in depth. Image by GB NNS • Leaves may appear to be slightly recurved. • Leaves are widest at the base from which they narrow gradually to a pointed tip. • Leaves can grow up to 3.5cm in length. 3. Are there any similar looking species? Yes. Canadian pondweed (Elodea canadensis) and the curly waterweed (Lagarosiphon major), other invasive aquatic plant species, look very similar. However upon close inspection they differ either in the shape of their leaves or the arrangement of the leaves on the stem. 2 Lough Erne - Nuttall’s Pondweed (Elodea nuttallii) - Commonly asked questions In the water curly waterweed appears to bear a close Nutrient enrichment (Eutrophication) from a range resemblance to Nuttall’s pondweed. It has been of sources, including surrounding land use, is also a present in NI since the 1980s and was introduced significant factor which can exacerbate the growth of from South Africa around the same time as Nuttall’s many aquatic plants by increasing the nutrient food pondweed was introduced from North America. The source available to aquatic plants. main distinguishing features are the curliness of the Typically Nuttall’s pondweed dies back over the leaves, hence the common name (see picture below). winter months and begins growing during the spring A second distinguishing feature is the arrangement months. Evidence has however indicated that the of its leaves which are not arranged in whorls of ice sheets that formed on the Erne system over the threes, as is the case with Nuttall’s pondweed, but winter months has protected the plant to some instead occur randomly around the length of the degree so its usual winter die back did not occur to stem. It can grow in water up to 6 metres in depth. the normal extent. 7. What should boaters do to prepare? What should they do if they encounter weeds? Aquatic weeds may impact on the movement of vessels by fouling propellers and by being drawninto the engine intake causing it to overheat and stop. Masters of craft should clean intake filters and check propellers and engine cooling prior to departure. In the event that a vessel fouls its propeller due to weed, stop the vessel and go astern (reverse) on the engine for a few seconds to see if the propellers clear. If after two or three attempts this proves unsuccessful masters are advised to drop anchor to attend to the problem if possible and if not call their marina operator or hire base for assistance. Under no Image by GB NNS circumstances should someone enter the water to attend to a propeller problem. 5. How did it get here? As an additional preventative measure several The exact method of introduction to the Erne system companies are known to specialise in a range of is unknown. Nuttall’s pondweed was most likely first prop protectors and rope cutter attachments of brought to the UK as an ornamental aquarium / pond varying design that can be attached to the boat plant in the early 1980s. It subsequently could have propeller. These attachments are designed to cut any entered the Erne system through a variety of means ropes or weed which may become snagged by the (pathways and vectors). propeller. These products are widely available from marine suppliers. 6. Why is it only causing problems now? Often it takes time before the impact of an introduced species becomes apparent. For some introduced species this may take several years. Some species can take several years for the population to develop to the point where impacts are observed. In the case of the Erne system the invasion of Zebra mussels (Dreissena polymorpha) in the late 1990s has been identified as a factor that could be exacerbating the Nuttall’s pondweeds growth. This is due to the Zebra mussels filtering the water, making it clearer, enabling the sunlight to penetrate deeper. This enables the plants to occur on the bed of Lough Erne where they previously could not. 1 Lough Erne - Nuttall’s Pondweed (Elodea nuttallii) - Commonly asked questions 8. I am a private marina manager in Lough Erne 9. Where can I get advice on control options? and I want to control it. Who do I need to contact? There are a range of control options available for As Upper Lough Erne has designations of local aquatic plant control. The most suitable control and European importance (Area of Special Scientific options available vary depending on the species of Interest - (ASSI), Special Area of Conservation - (SAC), aquatic plant and site factors (e.g. access). Special Protection Area -(SPA) and as a RAMSAR site) it is important that any control works do not Options currently available include: damage the site or risk further spread of the i. Weed cutting and harvesting ensuring fragments Nuttall’s pondweed. of the plant are removed from the water. This will It is important to protect these sites against any however not be a long term solution and will require activities that would be considered to be potentially repeated cutting and harvesting throughout the damaging to a habitat or habitats or species within growing season for many years. the designated site. Commercial interests, groups and private individuals wanting to undertake control should contact NIEA Conservation, Designations and Protection (CDP) to seek permission (consent). A consent application form can be obtained by contacting CDP at telephone number 028 90 569538 or electronic copy by emailing [email protected] Obtaining consent before undertaking any works in an ASSI is a legal requirement under the Environment Order (NI) 2002. Further information can be found at: http://www.doeni.gov.uk/niea/protected_areas_ home http://www.doeni.gov.uk/niea/index/faqs/desig_ sites.htm ii. Weed cutting and harvesting with additional Additionally anyone planning to carry out control trailing blades. This method aims to not only cut the measures within Lough Erne should also notify DARD plant but also disrupt the fibrous root system and Rivers Agency at their Riverdale offices in Enniskillen tubers of the plant. on 028 66 388529 or by emailing [email protected] as DARD are the registered owners of the bed of Lough Erne. Image by Grainne O’Connor 4 Lough Erne - Nuttall’s Pondweed (Elodea nuttallii) - Commonly asked questions Further advice on aquatic weed control can be obtained via the website www.invasivespeciesireland.com or from the Northern Ireland Environment Agency when seeking consent. Scottish Natural Heritage published a review of methods of control and eradication of Canadian pondweed and Nuttall’s pondweed in 2011. This report is available online at: http://www.snh.gov.uk/publications-data-and- research/publications/search-the-catalogue/ publication-detail/?id=1753 Image by Grainne O’Connor iii. Light exclusion has been trialled at sites such as Lough Corrib and on the Grand Canal and the Barrow Navigation.