Phytoplankton Assemblages As a Criterion in the Ecological Classification of Lakes in Finland
Total Page:16
File Type:pdf, Size:1020Kb
BOREAL ENVIRONMENT RESEARCH 11: 35–44 ISSN 1239-6095 Helsinki 20 February 2006 © 2006 Phytoplankton assemblages as a criterion in the ecological classification of lakes in Finland Liisa Lepistö1), Anna-Liisa Holopainen2), Heidi Vuoristo1) and Seppo Rekolainen1) 1) Finnish Environment Institute, P.O. Box 140, FI-00251 Helsinki, Finland 2) Karelian Research Institute, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland; and North Karelian Environment Centre, P.O. Box 69, FI-80101 Joensuu, Finland Received 17 May 2004, accepted 28 June 2005 (Editor in charge of this article: Johanna Mattila) Lepistö, L., Holopainen, A.-L., Vuoristo, H. & Rekolainen, S. 2006: Phytoplankton assemblages as a criterion in the ecological classification of lakes in Finland. Boreal Env. Res. 11: 35–44. Implementation of the Water Framework Directive requires the formulation of lake types and classification of the lakes within each type using biological quality elements. In this study phytoplankton was used to test the lake typology of 32 non-impacted lakes belonging to eight of the ten lake types described in the preliminary Finnish typology. Phytoplankton did not accurately define these types, as only five lake groups were clustered in the DCA ordination analysis. The ecological status was preliminarily established for 23 impacted lakes using total phytoplankton biomass and the number of taxa. Impacted oligo-humic lakes were tentatively classified to a lower ecological status than in the general water qual- ity classification carried out in the 1990s. Even more variation was observed when assess- ing the ecological status of humic impacted lakes. The number of taxa, on the other hand, appeared to overestimate the ecological status of the lakes, obviously due to the prelimi- nary boundary classes used in this study. Introduction et al. 1992, Willén 2002). The occurrence of individual species may vary widely, so that the Key issues in the implementation of the Water dominant species at different stages of succes- Framework Directive (European Union 2000) sion will not always be the same (e.g. Lepistö for lakes are formulating lake types, and clas- 1999). Seasonally the mean population densi- sifying the lakes within each type using bio- ties may vary over 2–9 orders of magnitude logical quality elements, e.g. phytoplankton. The depending on the trophic state (Reynolds 1984, composition of a phytoplankton assemblage is Holopainen et al. 2003). These complex interac- known to depend not only on water quality, tions and rapid changes in phytoplankton bio- physical factors and lake basin size, but also mass and species composition should be taken on biological factors such as specific growth into account when assessing biological quality and loss rates among the algae, parasitism, pre- in lakes. Phytoplankton assemblages have not dation and competition. Phytoplankton assem- previously been included in the parameters when blages with short renewal times are not constant, considering the general water quality classifica- partly due to their different developmental time tion in Finland (Vuoristo 1998), although even scales (Hutchinson 1967, Reynolds 1984, Fee slight human impact affects the phytoplankton 36 Lepistö et al. • BOREAL ENV. RES. Vol. 11 a total of 55 Finnish lakes (Fig. 1) was used in this study. Phytoplankton biomass and compo- sition were estimated by microscopy using the Nordic variant of Utermöhl technique (Olrik et al. 1998). The complete set of lakes was divided into two parts: non-impacted lakes (i.e. refer- ence lakes) with no or only minor anthropogenic alterations, and impacted lakes. The criteria of the division of the lakes were based on water quality, land use and point source loading data. The preliminary division was made by expert judgment in the Finnish Environment Institute. The studied non-impacted lakes covered eight of ten lake types described in the prelimi- nary Finnish typology B, which includes the fol- lowing obligatory factors: altitude or latitude for differentiating lakes (e.g. northernmost Lapland), geology (nutrient richness, calcium, organic soil) and lake basin area. The preliminary Finnish lake types proposed by Pilke et al. (2002) are: 1. high mountain lakes, 2. naturally eutrophic lakes, 3. calcareous lakes, 4. small–moderately large (< 40 km2), oligo- humic (< 30 mg l–1 Pt) lakes, 5. large (> 40 km2), oligo-humic (< 30 mg l–1 Pt) lakes, 6. small (< 5 km2), moderately humic (30−90 –1 Fig. 1. The observation sites in July 2002. For further mg l Pt ) lakes, information about the lakes, see Tables 1 and 2. Ref- 7. moderately large (5−40 km2), moderately erence lakes are indicated as squares and impacted humic (30−90 mg l–1 Pt) lakes, lakes as dots. 8. large (> 40 km2), moderately humic (30−90 mg l–1 Pt) lakes, species composition and biomass (Niinioja et al. 9. small (< 5 km2), highly humic (> 90 mg l–1 Pt) 2000, Lepistö et al. 2004). lakes, The aim of this study was to evaluate the 10. moderately large and large, highly humic applicability of total phytoplankton biomass and (> 90 mg l–1 Pt) lakes. the number of phytoplankton taxa in ecological classification, and to test the preliminary Finnish An ordination of non-impacted lakes (Table lake typology using phytoplankton assemblages. 1) by detrended correspondence analysis (ter Furthermore, we considered how the phytoplank- Braak 1987, 1990) was used to separate the ton total biomass and the number of taxa indicate lakes on the basis of the biomass of phyto- the ecological status of impacted lakes. plankton species. The medians of total biomass and number of taxa were estimated for each non-impacted lake group, and used as reference Material and methods values. Taxa, which were observed only in a specific reference lake type, were nominated as Phytoplankton data sampled from a depth of 0–2 type-specific taxa for the lake groups (Lepistö et meters during one week in mid July 2002 from al. 2004). BOREAL ENV.RES. Table 1. Some characteristics of the studied non-impacted lakes. No. = the number of the observation site in Fig.1. Lake types: the preliminary Finnish B typology and lake groups clustered in the DCA ordination analysis (shown in Fig. 2). The general water quality classification is according to Vuoristo (1998). nd = not determined. Lake and No. Lake types Lake groups* Lake Mean Ptot Ntot Water pH Phytopl. Taxa General water municipality (Finnish B (DCA ordination) basin depth (µg l–1) (µg l–1) colour (bm. mg l–1) number quality 2 –1 typology) (km ) (m) (mg l Pt) classification Änätti Kuhmo 1 7 I 23.7 9.9 8 280 50 6.9 0.95 56 good Vol. Karjalan Pyhäjärvi/Kitee 2 5 I 206.8 8.0 6 240 10 7.6 0.25 70 excellent Inarijärvi Inari 3 5 I 1040.3 14.3 4 150 10 7.2 0.15 61 excellent 11 Iso-Haukivesi Rantasalmi 4 5 I 562.3 11.5 8 490 35 7.2 0.40 61 excellent • Kukkia Luopioinen 5 5 I 43.4 6.6 9 360 20 7.3 0.62 82 excellent Kuolimo Suomenniemi 6 5 I 79.1 8.5 4 320 20 7.2 0.44 61 excellent Phytoplankton asacriterionintheecologicalclassifi Pielinen Lieksa 7 8 I 900.0 12.9 8 370 40 7.3 0.21 63 good Punelia Loppi 8 7 I 8.2 6.0 8 350 40 7.2 0.59 70 good Saimaa, Ilkons. Taipalsaari 9 5 I 382.0 11.2 6 380 25 7.1 0.37 61 good Saimaa, Riutan.Taipalsaari 10 5 I 45.8 12.0 15 380 20 7.3 0.98 78 good Sääksjärvi Nurmijärvi 11 4 I 2.6 3.1 8 360 8 6.9 0.89 51 excellent Vuohijärvi Jaala 12 5 I 86.2 11.3 5 380 15 7.2 0.27 58 excellent Mallasvesi Pälkäne 13 5 I 55.7 7.4 11 390 15 7.4 0.66 74 excellent Yli-Kitka Kuusamo 14 8 I 237.3 4.6 11 250 10 7.4 0.25 60 excellent Päijänne Asikkala 15 5 I 76.7 16.9 6 550 25 7.4 0.51 53 excellent Hormajärvi Lohja 16 4 II 5.0 6.9 12 300 10 7.3 0.24 42 good Iso-Hietajärvi Lieksa 17 4 II 0.8 3.6 5 210 20 6.8 0.12 43 nd Iso-Löytäne Längelmäki 18 4 II 8.8 7.2 5 370 15 7.3 0.51 69 excellent Iso-Arajärvi Vesilahti 19 6 II 2.3 5.5 13 370 40 7.0 0.48 56 excellent Iso-Helvetinjärvi Ruovesi 20 6 II 0.5 0.5 7 340 60 6.1 0.35 34 nd Kattilajärvi Espoo 21 4 II 0.3 3.3 5 230 15 6.5 0.58 38 nd Puujärvi Karjalohja 22 4 II 6.4 8.5 9 390 15 7.4 0.52 68 excellent Siikajärvi Orivesi 23 4 II 0.9 5.9 7 490 25 6.1 0.68 40 nd Vehkajärvi Kuhmalahti 24 4 II 25.9 5.4 8 370 15 7.0 0.33 61 excellent cation oflakes Näsijärvi Ylöjärvi 25 8 II 210.2 13.3 13 500 45 7.1 0.51 55 good Haukkajärvi Ruovesi 26 6 III 2.6 4.2 10 480 100 5.8 0.67 53 excellent Pihlajavesi Keuruu 27 10 III 20.7 5.0 23 570 120 6.2 0.95 47 good Unarinjärvi Sodankylä 28 10 III 28.8 6.1 24 380 110 6.8 1.17 81 good Lika-Pyöree Sonkajärvi 29 2 IV 1.9 0.8 37 510 160 5.8 0.73 39 nd Kalliojärvi Juupajoki 30 9 IV 0.2 13.0 28 540 160 6.2 6.86 55 nd Valkea-Kotinen Lammi 31 nd V 0.04 2.6 14 440 100 5.5 0.30 12 nd Iso-Hanhijärvi Orivesi 32 9 V 0.3 12.0 16 380 160 5.3 0.88 30 nd 37 * I = Oligo-humic large lakes, II = Oligo-humic moderately large lakes, III = Humic moderately large lakes, IV = Highly humic lakes, IV = Acidic, highly humic lakes.