The study of spatial and temporal nutrient limitation in Meiliang Bay, Lake Taihu

Longyuan Yang1, Feizhou Chen1, Yunling Zhang1,

Shixin Wang2

(1 Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences;

2 Institute of Remote Sensing Applications,Chinese Academy of Sciences )

Purpose• To measure nitrogen and phosphorus concent

rations in Meiliang Bay, Lake Taihu, and analyze spatial and temporal variation of water quality parameters;

• To analyze the relationship between nutrient concentrations and dominant algae species.

• To study nutrient limitation status in Meiliang Bay, Lake Taihu.

Redfield Ratio• If N:P ratio > 16, there is P

limitation in the aquatic ecosystem;

• If N:P ratio < 16, there is N limitation in the aquatic

ecosystem.

Background about limitation factor research in Lake Taihu

• Phosphorus is the limitation factor in Lake Taihu (traditional opinion);

• There is nitrogen limitation sites in some seasons and in some aquatic area (Martin Dokulil et al. 2000);

• There is a limitation factor change phenomenon that from Liangxi river discharge area to the main body of Lake Taihu (McCarthy et al. 2007)

Sampling sitesRegular site: 25 (per 3 months)

Add specific site: 20 (2 times in 2004)

Total sites: 45

Distribution of sampling areaName Sites NL Range S Number

River discharge

L0 K5

B3 B4 B6 B7 B8

31.31-31.33 7

Inner bay L1 L2

K2 K3 K4 K6

B5 B9 B10 B11 B12

31.28-31.31 11

Outer bay L3 L4 K1 K7 K8

B1 B2 B13 B14 B15

31.24-31.28 10

Open area L5 L6 K9 K10 K11

K12 K19 K20

31.18-31.24 8

Central area L7 L8 L9 K13 K14

K15 K16 K17 K18

31.13-31.18 9

Function of Distribution

Name Function Distance

River Discharge

Pollution area by point source from Liangxi and Lvjing River

0 km

Inner B Near pollution source area of Bay

8 km

Outer B Fare pollution source and near open area of Bay

16 km

Open A Open area that connect with the Outer Bay

24 km

Central A Main body of Lake Taihu 36 km

Results

(Oct-2003 to Aug-2005)

For whole research area

Spatial and temporal variation calculate of nutrients

• Spatial variation in research area were calculated by average of all sites in one distribution area;

• Annual variation were calculated by all sites in same distribution area and separated seasons.

Interval to Average Index (IA Index)

I %=(Ci-Cm)*100/Cm

Where: I mean the IA index coefficient ;

Ci concentration of individual parameter;

Cm mean concentration of whole area

TN I ndex

-80. 0

-60. 0

-40. 0

-20. 0

0. 0

20. 0

40. 0

60. 0

80. 0

Wi n Spr Sum Fal l

Season

%

B1 B2 B3 B4 B5

TP I ndex

-60

-40

-20

0

20

40

60

Wi n Spr Sum Fal l

Season

%

B1 B2 B3 B4 B5

TN MB1

0

2

4

6

8

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

TN MB2

0

2

4

6

8

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

TN MB3

0123456

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

TN MB4

0

1

2

3

4

5

Wi nter Spri ng Summer Fal l

C mg

/L

200320042005Mean

TN MB5

0

12

34

5

Wi nter Spri ng Summer Fal l

C mg

/L200320042005Mean

MB1 TP

0. 00

0. 10

0. 20

0. 30

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

MB2 TP

0. 00

0. 10

0. 20

0. 30

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

MB3 TP

0. 00

0. 10

0. 20

0. 30

Wi nter Spr i ng Summer Fal l

200320042005Mean

MB4 TP

0. 00

0. 10

0. 20

0. 30

Wi nter Spr i ng Summer Fal l

C mg

/L

200320042005Mean

MB5 TP

0. 00

0. 10

0. 20

0. 30

Wi nter Spr i ng Summer Fal l

C mg

/L200320042005Mean

R (TN: TP)

0306090

120

MB1 MB2 MB3 MB4 MB5

R

Wi n Spr Sum Fal l

TP

0. 000. 050. 100. 150. 200. 25

Wi n Spr Sum Fal l

C mg

/L

MB1

MB2

MB3

MB4

MB5

TN

0. 02. 04. 06. 08. 0

Wi n Spr Sum Fal l

C mg

/L

MB1MB2MB3MB4MB5

The ratio of nitrogen over phosphorus

TN:TP Win Spr Sum Fall

MB1 78.5 79.4 29.8 41.5

MB2 98.7 81.7 24.0 35.4

MB3 92.3 81.2 25.1 30.2

MB4 74.9 85.0 27.4 20.8

MB5 53.4 76.0 27.9 15.9

Annual variation characters summary

• In winter and spring seasons the mole ratio of TN:TP are more higher than Readfield ratio (16) ; but in summer and fall seasons the mole ratio of TN:TP are almost equal to Readfield ratio.

• So there is dominant P limitation in Winter and Spring seasons (Colder season, water temperature < 20 oC ) and there is dominant N limitation in some areas in Summer and Fall seasons (Warmer season, water temperature > 20 oC ) except the P limitation in shore area of Lake Taihu.

• In open and central areas(B4 and B5) the mole ratio of TN:TP reduced serious than in river discharge area(B1) in whole year; so the open and central areas is the hot point for nitrogen limitation or nitrogen and phosphorus co-limitation mainly occur areas.

Dominant algae species in different areas (Oct. 27, 2003)

Area Name %

B1

Microcystis 29.19

Merismopedia 12.20

Scenesdesmus 36.22

Cyclotella 22.39

B2

Microcystis 67.51

Chlamydomonas 12.36

Euglena 8.08

Cyclotella 5.24

Cryptomonas 6.82

B3

Microcystis 93.27

Merismopedia 1.81

Chlamydomonas 2.80

Scenesdesmus 2.12

B4 Merismopedia 100.00

B5Merismopedia 81.53

Scenesdesmus 18.47

Conclusion• There is a phenomenon that phosphorus limitation ch

ange to nitrogen limitation from Liangxi river discharge area to the main body (open area) of Lake Taihu;

• Summer and Fall seasons is the nitrogen Limitation occur season; especially in the area that far away from pollution river discharge area such as in central area of Lake Taihu

• The phenomenon that limitation factor changes may occur in all large shallow eutrophication lakes and estuaries in east part of China and other north temperate zones

谢谢莅临指导 !

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Welcome to Taihu Field Station !

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