Lakes and Watercourses

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Chlorophyll-a concentrations refer to seasonal means (May – October) over three years, based on monthly readings taken in the epilimnion or, if only one sample is taken, surface water (0.5 m). Alternatively, August readings taken over three years can be used, although account must then be taken of the relatively high variation from one year to another, particularly in eutrophic environments (class 4 and 5). The chlorophyll concentrations represent the intervals on the phytoplankton scale and the corresponding interval on the total phosphorus scale. The chlorophyll concentration has been assumed to constitute 0.5 per cent of plankton volume. Discrepancies in relation to the concentration of total phosphorus depend on lake depth, among other things. TABLE 27. CURRENT CONDITIONS: spring-developing diatoms (mm 3 /l) Class Description Biomass 1 Very small biomass ≤ 0.05 2 Small biomass 0.05 – 0.5 3 Moderate biomass 0.5 – 2.0 4 Large biomass 2.0 – 4.0 5 Very large biomass > 4.0 TABLE 28. CURRENT CONDITIONS: water-blooming cyanobacteria (mm 3 /l) Class Description Biomass 1 Very small biomass ≤ 0.5 2 Small biomass 0.5 – 1.0 3 Moderate biomass 1.0 – 2.5 4 Large biomass 2.5 – 5.0 5 Very large biomass > 5.0 The class boundaries have been set on the basis of the greatest biomass of diatoms occurring in corresponding classes for total volume of algae. 53
TABLE 29. CURRENT CONDITIONS: potentially toxin-producing cyanobacteria Class Description Number of genera, August 1 None or few ≤ 2 3 A moderate number 3 – 4 5 A large to very large number > 4 The boundary between class 1 and 2 represents a level below which nuisance caused by water-blooming cyanobacteria does not usually occur (biomass 0.5 mm 3 /l). Other class boundaries represent approximately the 25th, 50th and 75th percentiles in that part of the background material comprising lakes having a biomass exceeding 0.5 mm 3 /l. The number of genera of potentially toxin-producing cyanobacteria indicates whether there is a short or a long-term problem in a lake used for bathing, a reservoir or a lake where fish or shellfish are farmed. The more genera found on a single sampling occasion, the greater the risk of persistent problems, since conditions for development vary from one species to another. Toxin-producing cyanobacteria are not unique to highly eutrophic lakes. They may also be found in true oligotrophic waters. As a rule, only one toxic genus is found in mountain lakes: Anabaena, which develops during a limited period of the summer season, but in other nutrient-poor lakes another genus may appear, eg, Aphanizomenon. The boundary for class 1 has therefore been set at 2 genera. The following genera and species of planktonic cyanobacteria may produce toxins in Sweden (Willén & Mattsson, 1997). Anabaena: A. circinalis, A. farciminiformis, A. flos-aquae, A. lemmermannii, A. solitaria Aphanizomenon: A. flos-aquae, A. gracile, A. klebahnii, A. yezoense Microcystis: M. aeruginosa, M. botrys, M. flos-aquae, M. viridis, M. wesenbergii Planktothrix: P. agardhii (alt. Oscillatoria agardhii) Woronichinia: W. naegeliana (alt. Gomphosphaeria naegeliana) Gloeotrichia: G. echinulata Toxic forms of Woronichinia and Gloeotrichia have not yet been discovered in Sweden, which is probably due to a lack of analysis, since their ability to produce toxins has been verified in many other countries. These two genera are more frequently found mass-developing in moder- 54
Page 1 and 2:
Environmental Quality Criteria - La
Page 3 and 4: TO ORDER Swedish Environmental Prot
Page 5 and 6: Reference Group Mats Bengtsson, Swe
Page 7 and 8: Summary This report on lakes and wa
Page 11 and 12: included. In addition to a large nu
Page 13 and 14: ased estimates are used. Given that
Page 15 and 16: TABLE 1. SUMMARY of parameters incl
Page 17 and 18: 16 The current conditions scale in
Page 19 and 20: (in Swedish with English summary).
Page 21 and 22: conditions for watercourse flora an
Page 23 and 24: show the availability of nitrogen i
Page 25 and 26: Mean concentration of total phospho
Page 27 and 28: TABLE 9. DEVIATION from reference v
Page 29 and 30: Comments Classifications must be ba
Page 31 and 32: winter/spring, i.e. ice-covered per
Page 33 and 34: Light conditions Introduction Light
Page 35 and 36: TABLE 13. CURRENT CONDITIONS: turbi
Page 37 and 38: Acidity / acidification Introductio
Page 39 and 40: industrial pH). The change in acidi
Page 41 and 42: The pre-industrial concentration of
Page 43 and 44: very high degree of reliability and
Page 45 and 46: TABLE 19. CURRENT CONDITIONS: metal
Page 47 and 48: TABLE 22. DEVIATION from reference
Page 49 and 50: TABLE 24. (continued) Cu Zn Cd Pb C
Page 51 and 52: Swedish EPA (1993): Metals and the
Page 53: Assessment of current conditions TA
Page 59 and 60: References Cronberg, G., Lindmark,
Page 61 and 62: (see Appendix 1). If submerged and
Page 63 and 64: References Andersson, B. (1998): Va
Page 65 and 66: The genera in question and their tr
Page 67 and 68: Benthic fauna Introduction Benthic
Page 69 and 70: TABLE 41. CURRENT CONDITIONS: botto
Page 71 and 72: Comments The assessment must be bas
Page 73 and 74: has yielded better results than did
Page 75 and 76: TABLE 45. CURRENT CONDITIONS: fish,
Page 81 and 82: TABLE 48. (Contd.) Proportion of al
Page 84 and 85: Presentation of data When using the
Page 86 and 87: APPENDIX 1 Ceratophyllum demersum 1
Page 88 and 89: APPENDIX 2 Calculation of index and
Page 90 and 91: APPENDIX 2 Table 1b. Indicator gene
Page 92 and 93: Genus Indicator value -------------
Page 94 and 95: APPENDIX 2 45 Planorbis sp. 46 Anis
Page 96 and 97: APPENDIX 2 214 Leuctra hippopus 215
Page 98 and 99: APPENDIX 2 384 Tinodes waeneri 385
Page 100 and 101: APPENDIX 2 (6) O/C index (Wiederhol
Page 102 and 103: APPENDIX 3 Dace Stäm Leuciscus leu
Page 106:
REPORT 5050 Environmental Quality C
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