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Submerged aquatic vegetation – a nuisance in Finnish lakes ? Lakepromo Biodiversity Seminar in Brighton 26.-28.20.2005 Anne Tarvainen Ilkka Sammalkorpi.

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Presentation on theme: "Submerged aquatic vegetation – a nuisance in Finnish lakes ? Lakepromo Biodiversity Seminar in Brighton 26.-28.20.2005 Anne Tarvainen Ilkka Sammalkorpi."— Presentation transcript:

1 Submerged aquatic vegetation – a nuisance in Finnish lakes ? Lakepromo Biodiversity Seminar in Brighton 26.-28.20.2005 Anne Tarvainen Ilkka Sammalkorpi Liisa Laitinen Finnish Environment Institute

2 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

3 Aquatic vegetation overgrowth situation in Finland  Overgrowth of aquatic vegetation is a problem in appr. 1 000 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. 100-300 sites are suffering overgrowth of submerged vegetation

4 A media favourite  In Finland recreational use of watercourses is extensive especially during the summer. There are 450 000 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

5 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

6 Geographical distribution of problematic cases

7 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

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

9 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 2000.  Interesting was that nuisance caused by Myriophyllum species were reported mainly in 2001-2004.

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

11 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 2005-2006 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

12 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!

13 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

14 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

15 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.


17 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…

18 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.


20 Research & development needs  Reasons for the he explosion in 2002-2004. 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


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