year

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

number of sites sampled

83

82

78

80

82

85

81

90

88

84

all submersed vegetation

50.6

54.9

17.9

25.0

12.2

47.1

44.4

57.8

34.0

25.0

coontail

-

-

1.3

1.3

-

3.5

22.2

31.1

10.2

1.2

Canadian waterweed

Elodea canadensis

-

2.4

-

-

4.9

9.4

12.3

18.9

5.7

1.2

water stargrass

Heteranthera dubia

3.6

-

2.6

-

-

-

13.6

17.8

13.6

7.1

Eurasian watermilfoil

Myriophyllum spicatum

42.2

46.3

12.8

1.3

-

10.6

17.3

23.3

10.2

2.4

nodding waternymph

Najas flexilis

3.6

-

7.7

6.3

-

2.4

12.3

12.2

1.1

-

curly pondweed

Potamogeton crispus

2.4

-

-

3.8

1.2

9.4

4.9

3.3

-

6.0

leafy/small pondweed

P. foliosus/P. pusillus

-

-

3.8

-

3.7

9.4

6.2

11.1

4.5

-

sago pondweed

P. pectinatus

20.5

14.6

2.6

23.8

6.1

34.1

14.8

5.6

3.4

16.7

flatstem pondweed

P. zosteriformis

-

-

-

1.3

-

-

-

-

-

-

wild celery

Vallisneria americana

-

-

-

-

-

2.4

4.9

3.3

1.1

-

horned pondweed

Zannichellia palustris

-

-

-

-

3.7

-

1.2

-

1.1

-

all rooted floating leaf vegetation

20.5

12.2

14.1

23.8

36.6

32.9

25.9

15.6

14.8

13.2

American lotus

Nelumbo lutea

18.1

8.5

12.8

21.3

32.9

31.8

17.3

8.9

6.8

6.0

white water-lily

Nymphaea odorata

4.8

4.9

2.6

2.5

7.3

1.2

8.6

7.8

11.4

9.5

Total number of species recorded

7

5

8

8

7

10

12

11

11

8