year

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

number of sites sampled

105

101

105

104

90

102

106

106

101

100

all submersed vegetation

22.9

18.8

22.9

28.8

18.9

53.9

76.4

87.7

77.2

75.0

coontail

1.9

2.0

1.0

2.9

1.1

38.2

52.8

81.1

16.8

27.0

Canadian waterweed

Elodea canadensis

-

-

1.0

-

-

23.5

55.7

54.7

6.9

7.0

water stargrass

Heteranthera dubia

1.0

-

-

1.0

-

2.0

52.8

77.3

68.3

70.0

Eurasian watermilfoil

Myriophyllum spicatum

14.3

9.9

5.7

8.7

5.6

10.8

27.4

37.7

44.6

22.0

curly pondweed

Potamogeton crispus

1.0

-

1.0

1.9

-

12.7

0.9

5.7

-

1.0

leafy/small pondweed

P. foliosus/P. pusillus

-

-

-

2.9

-

14.7

7.5

17.0

5.9

3.0

longleaf pondweed

P. nodosus

1.0

-

-

1.0

1.1

2.9

0.9

2.8

1.0

5.0

sago pondweed

P. pectinatus

7.6

7.9

18.1

18.3

14.4

17.6

7.5

5.7

2.0

4.0

flatstem pondweed

P. zosteriformis

-

-

-

-

-

4.9

34.0

21.7

15.8

5.0

wild celery

Vallisneria americana

-

-

1.0

-

-

1.0

6.6

8.5

10.9

5.0

all rooted floating leaf vegetation

2.9

1.0

2.9

4.8

11.1

12.7

14.2

9.4

8.9

11.0

American lotus

Nelumbo lutea

1.9

1.0

2.9

4.8

11.1

12.7

13.2

8.5

5.9

10.0

white water-lily

Nymphaea odorata

1.9

-

1.0

1.0

-

-

1.9

0.9

2.9

1.0

Total number of species recorded

8

4

8

9

5

11

12

12

11

12