Ladoga
Baltic Fund for Nature

Plankton

Composition of the Lake Ladoga zooplankton includes 378 species: Protozoa - 90 species, Rotatoria - 200, Cladocera - 61, Copepoda - 27. (Dengina, Sokolova, 1968).

The size structure of the community in the shallow areas of Lake Ladoga has changed towards an increase of small crustaceans and rotifers, and the contribution of small-sized zooplankton in general has increased (Ogorodnikova, 1995).

Quantitative development and structure of zooplankton.

As seen from Table - 3.1., the biomass of zooplankton has remained rather low in the open regions of Lake Ladoga and no major changes have been observed during the four decades.

At the same time, in the shallow areas of Lake Ladoga the process of eutrophication is more evident than in the deeper pelagic zones. In southern Lake Ladoga the community structure and species proportions have changed considerably (Ogorodnikova, 1995). The size structure of the community has changed towards relative and absolute increase of the small crustaceans and rotifers and, as a whole, the contribution of small-sized zooplankton has increased. This structural change of zooplankton community is due to eutrophication and enrichment of the water by nutrients and allochthonous organic matter.

Table A-3.1. Number (N), biomass (B) and percentage of main taxonomic groups of summer zooplankton according to long-term investigations in the pelagic zone of Lake Ladoga, (mean and range for the early observations, X SE for the later decadal values) (Andronikova, 1996).

Characteristics

 

1948 - 1963

1970-

1980-

1990-

N, ind x 103 m-3

 

11.1 (10.3-12.0)

12.6  3.6

16.4  3.1

13.3  2.2

B, mg m-3

 

214 (132-348)

291  58

224  36

268  88

Rotatoria

N

43

16

36

38

 

B

23

6

11

10

Cladocera

N

7

25

12

13

 

B

22

29

16

16

Copepoda

N

50

59

52

49

 

B

73

65

73

74

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