Submerged aquatic vegetation – a nuisance in Finnish lakes ? Lakepromo Biodiversity Seminar in Brighton Anne Tarvainen Ilkka Sammalkorpi Liisa Laitinen Finnish Environment Institute

Contents  Aquatic weed and vegetation situation in Finland  Results from a national inquiry by SYKE in summer 2005  Case studies Lake Ruutinlampi Lake Matalajärvi  Conclusions and research & development needs

Aquatic vegetation overgrowth situation in Finland  Overgrowth of aquatic vegetation is a problem in appr sites (lakes, ponds or bays)  Nuisance species are mainly emergent species (Phragmites australis, Equisetum fluviatile) and floating leafed (Nuphar spp, Nymphea spp.) vegetation  Inquiry in summer 2005 about submerged species Answers from 73 areas (10 bays and 63 lakes, divisions of the lake or ponds)  Inquiry didn’t reach all. Estimate is that appr sites are suffering overgrowth of submerged vegetation

A media favourite  In Finland recreational use of watercourses is extensive especially during the summer. There are summer cottages and most of them are situated next of near to watercourses.  Recreational users of water courses are demanding better circumstances without knowledge of aquatic environment. all aquatic vegetation is considered harmful demand of easy and quick solutions  Problem has been discussed in several newspapers, magazines and TV programs  Grass root level instructions are needed

Inquiry  Sent to Regional environmental centres (13 in Finland) - researchers and lake restoration experts Lake restoration/management actors??? Employment and Economic Development Centres (15 in Finland) -participates restoration projects related to the fish or fisheries Consulting companies Some municipalities Metsähallitus (Finnish Forest and Park Service), Nature Inventory Officers Universities

Geographical distribution of problematic cases

The reported nuisance taxa  From Potamogeton species most common for nuisance were Potamogeton perfoliatus and Potamogeton natas, which are very common in Finland  Aquatic bryophytes were most common in northern and eastern areas of Finland, but also in some areas in the south.  Other species were emergent and floating leafed species

Species involved Canadian waterweed (Elodea canadensis) Rigid hornwort (Ceratophyllum demersum ) Spiked water-milfoil (Myriophyllum spicatum)

Timing of the problem  On several sites reported in inquiry submerged vegetation has caused problems since 1960’s.  Canadian waterweed was brought to Finland 1884 to Botanic Garden in Helsinki. It has been causing problems since it arrival.  In several lakes SAV (submerged aquatic vegetation) has caused problems only since  Interesting was that nuisance caused by Myriophyllum species were reported mainly in

The difficulties caused by excessive SAV Other nuisances Smell Blockage of currents and water exchange

Used restoration methods  Mowing has been the most commonly used method to control aquatic vegetation mainly suitable for emergent species  Harvesters are quite commonly used leaves plant fragments  Seines have successfully used in some small areas potential to develop new practices  Freezing was tested in 1980’s Experiments with Myriophyllum species during the winter in two sites  Also dredging and raising of the water level have been used e.g. in bird lakes  Best results have been achieved repeating restoration methods and combining several restoration methods

Funding the restoration actions  Most common financiers towns or municipalities private persons regional environmental centres local fishing associations some cases also EU funding  Possibilities of sponsor by companies  Voluntary work is essential! Also local participation and community spirit are key factors in successful restoration projects!

Conservational values of the sites  11 of the sites reported in inquiry there were protectorates or threatened plant or bird species were present 10 Natura sites! endangered or near threatened aquatic plants: Potamogeton pusillus, Potamogeton rutilus, Najas tenuissima, Callitriche hermaphroditica and Ranunculus confervoides  12 of sites were important bird sites

Cases  Totally 5 cases  Follow up of vegetation and restoration in summer 2005  Estimation of restoration action efficiency  Some experimental test Lake Kalaton, pH-regulation  Follow up of removed vegetation species composition

Ruutinlampi, Nummi-Pusula  Area 9 ha, maximum depth 1,7 m  Restoration has been launched and carried on by private farmer Aarre Arrajoki  Most common species Elodea canadensis, Nuphar lutea, Potamogeton natans also Ceratophyllum demersum  Internal and external loading  Extensive vegetation causes oxygen depletion during the winter and raises pH even to over 9 in summer  Elodea has been removed with seines and rakes attached to the boat  During the winter lakes has been oxygenated with sludge pump  During the summer 2005 SAV-vegetation was exceptional sparse.

Lake Matalajärvi, Espoo  Surface area 112 ha  A NATURA 2000 target area (Najas tenuissima) and an IBA area for waterfowl protection  Project operated by L. Matalajärvi Association, a volunteer NGO of local stakeholders.  Ceratophyllum d. hampers recreational use and threatens existence of endangered Najas tenuissima.  Funded by the City of Espoo, Kehu association, Uusimaa regional environment centre and sponsored (15 %) by local companies.  Monitoring data of the flora in 1961, 1997 and 2000 (also aerial photographs)  Large layers of fragments of Ceratophyllum were found in areas treated by the harvester  Restoration and follow up continues…

Najas tenuissima  N. tenuissima is one of the most threatened species in Europe and almost all known populations are in southern Finland.  Present populations are known from 18 lakes and one marine estuary.  Nearly 40 % of the present populations are included in the Natura 2000 network.

Research & development needs  Reasons for the he explosion in Combined effects of water level fluctuations, washout, transparency and temperature?  The ecological role of SAV in relation to restoration / management measures and their impact (increased transparency)  Comparison of available removal or control methods development of seines and freezing  Efficiency of methods for removal of SAV – particularly selective removal of Ceratophyllum and Elodea by seining to increase biodiversity Lakes with Najas tenuissima or other endangered SAV species  Identification of naturally productive lakes and considerations of their management need  Information & education to the grass root level and stakeholders  Identification guides to the public