PHYTOPLANKTON DYNAMICS IN LAKE CHALLA AS DERIVED

FROM SEDIMENT TRAP ANALYSES

Christine Cocquyt

National Botanic Garden of BelgiumLimnology Unit, Ghent University

National Botanic Garden of Belgium

2

Quantitative phytoplankton analyses

Uthermöhl method:- “sedimentation chamber” of 10 ml- inverted microscope - counts of organisms and colonies (known surface area)

Calculation- number of cells/ml- conversion to biovolumes

30/1

2/20

06

10/0

2/20

07

28/0

2/20

07

31/0

3/20

07

30/0

4/20

07

4/06

/200

7

30/0

6/20

07

31/0

7/20

07

24/0

8/20

07

28/0

9/20

07

30/1

0/20

07

30/1

1/20

07

31/1

2/20

07

30/0

1/20

08

29/0

2/20

08

31/0

3/20

08

30/0

4/20

08

31/0

5/20

08

30/0

6/20

08

31/0

7/20

08

31/0

8/20

08

28/0

2/20

10

31/0

3/20

10

28/0

4/20

10

31/0

5/20

10

28/0

6/20

10

30/0

7/20

10

31/0

8/20

10

30/1

1/20

10

31/1

2/20

10

31/0

1/20

11

28/0

2/20

11

31/0

3/20

11

30/0

4/20

11

31/0

5/20

11

30/0

6/20

11

31/0

7/20

11

30/0

8/20

11

0%

20%

40%

60%

80%

100%

Phytoplankton composition %

diatoms Chlorophyta Cyanobacteria Dinophyta Chrysophyta/Cryptophyta Euglenophyta

2007 201120102008

Major algal groups - percentages derived from biovolumes

Lake Challa

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100Gomphocymbella

Synedra/Ulnaria

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

Nitzschia “long”

2007 201120102008percentages derived from biovolumes

Encyonema/Cymbella spp.

Staurosira/ Staurosirella spp.

Rhopalodia spp.

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

2007 201120102008percentages derived from biovolumes

Cosmarium spp.

Closteriopsis acicularis

Oocystis sp.

2007 201120102008

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

01

-12

-06

01

-02

-07

01

-04

-07

01

-06

-07

01

-08

-07

01

-10

-07

01

-12

-07

01

-02

-08

01

-04

-08

01

-06

-08

01

-08

-08

01

-10

-08

01

-12

-08

01

-02

-09

01

-04

-09

01

-06

-09

01

-08

-09

01

-10

-09

01

-12

-09

01

-02

-10

01

-04

-10

01

-06

-10

01

-08

-10

01

-10

-10

01

-12

-10

01

-02

-11

01

-04

-11

01

-06

-11

01

-08

-11

0

20

40

60

80

100

percentages derived from biovolumes

Filtered versus water sample

Challa phytoplankton productivity

flux

(ce

ll vo

lum

e/d

ay

cm2

)

01

/12

/06

01

/01

/07

01

/02

/07

01

/03

/07

01

/04

/07

01

/05

/07

01

/06

/07

01

/07

/07

01

/08

/07

01

/09

/07

01

/10

/07

01

/11

/07

01

/12

/07

01

/01

/08

01

/02

/08

01

/03

/08

01

/04

/08

01

/05

/08

01

/06

/08

01

/07

/08

01

/08

/08

01

/09

/08

01

/10

/08

01

/11

/08

01

/12

/08

01

/01

/09

01

/02

/09

01

/03

/09

01

/04

/09

01

/05

/09

01

/06

/09

01

/07

/09

01

/08

/09

01

/09

/09

01

/10

/09

01

/11

/09

01

/12

/09

01

/01

/10

01

/02

/10

01

/03

/10

01

/04

/10

01

/05

/10

01

/06

/10

01

/07

/10

01

/08

/10

01

/09

/10

01

/10

/10

01

/11

/10

01

/12

/10

01

/01

/11

01

/02

/11

01

/03

/11

01

/04

/11

01

/05

/11

01

/06

/11

01

/07

/11

01

/08

/11

0

20

40

60

80

100

120

140

160

Cyanobacteria Chlorophyta Euglenophyta

Dinophyta Chrysophyta/Cryptophyta Bacillariophyta

2007 201120102008

filtered sample water sample

30

/12

/20

06

10

/02

/20

07

28

/02

/20

07

31

/03

/20

07

30

/04

/20

07

4/0

6/2

00

7

30

/06

/20

07

31

/07

/20

07

24

/08

/20

07

28

/09

/20

07

30

/10

/20

07

30

/11

/20

07

31

/12

/20

07

30

/01

/20

08

29

/02

/20

08

31

/03

/20

08

30

/04

/20

08

31

/05

/20

08

30

/06

/20

08

31

/07

/20

08

31

/08

/20

08

28

/02

/20

10

31

/03

/20

10

28

/04

/20

10

31

/05

/20

10

28

/06

/20

10

30

/07

/20

10

31

/08

/20

10

0%

20%

40%

60%

80%

100%

biovolumes - %

28

/02

/20

10

31

/03

/20

10

28

/04

/20

10

31

/05

/20

10

28

/06

/20

10

30

/07

/20

10

31

/08

/20

10

30

/11

/20

10

31

/12

/20

10

31

/01

/20

11

28

/02

/20

11

31

/03

/20

11

30

/04

/20

11

31

/05

/20

11

30

/06

/20

11

31

/07

/20

11

30

/08

/20

11

0%

20%

40%

60%

80%

100%

diatoms Chlorophyta Cyanobacteria Dinophyta Chrysophyta/Cryptophyta

Euglenophyta

filtered samples

water samples

Lake Challa – July 2010 – filtered sample

Lake Challa – January 2011 – water sample

12

Species diversity

Species diversity

Diatoms 44Chlorophyta 40Cyanobacteria 15Euglenophyta 2Dinophyta 2Chrysophyta 3

Total 106

Achnanthidum exiguumAchnanthidum sp.Amphora copulataAmphora pediculusCymatopleura clavataCymbella sp.Diploneis sp.Encyonema meulleriEncyonema minutumGomphocymbella sp.Gomphonema affineGomphonema parvulumGomphonema sp.Hantzschia amphioxysNavicula sp. 1Navicula sp. 2Navicula sp. 3Navicula sp. 4Nitzschia bacataNitzschoa epiphyticoidesNitzschia fonticolaNitzschia lancettula

Nitzschia paleaNitzschia palea var. tropicaNitzschia vanoyeiNitzschia sp. 1Nitzschia sp. 2Nitzschia sp. 3Nitzschia sp. 4Placoneis gastrumRhopalodia gibbaRhopalodia gibberulaRhopalodia gracilisRhopalodia hirudiniformisSellaphora nyassensisSellaphora pupulaStauroneis sp.Staurosira construensStaurosirella pinnataSurirella sp.Ulnaria acusUlnaria danicaUlnaria ulnaUrosolenia sp.

Bacillariophyta

Chlorophyta

Ankistrodesmus sp.Chlorococcus sp.Chlorella sp.Closteriopsis acicularisClosteriopsis acicularis var. africanaCrucigeniella quadrataCrucigeniella sp.Dictyosphaerium pulchellumDictyosphaerium tetrachotomumDidymosphenia sp.Eremosphaeria sp.Kirchneriella arcuataKirchneriella contorta var. elongataKirchneriella microscopicaKirchneriella obesacf. Kirchneriella sp.Lagerheimia chodatiiLagerheimia ciliataLagerheimia citriformisLagerheimia subsalsa

Lobocystis planctonicaMonoraphidium arcuatumMonoraphidium irregulareMonoraphidium mirabileMonoraphidium minutumOocystis sp.Oonephris sp.cf. Oonephris sp.Podohedra falcataSchroederia planctonicaTetraedron triangulareTetraedron minimumTreubaria setigeraTetrastrum komareckiisp. 1sp. 2sp. 3Cosmarium sp. 1Cosmarium sp. 2Staurastrum

Cyanobacteria

Chroococcus limneticusChroococcus dispersusChroococcus sp.Chroococalles sp.cf. Aphanocapsa microscopicacf. Gloeotrichia sp.Gomphosphaeria cf. natansSynechococcus elongatusPlanktolyngbya sp.Microcrocis sp.Microcystis sp.Snowella sp.sp. 1sp. 2sp. 3

Euglenophyta

Trachelomonas volvocinaTrachelomonas volvocinopsis

Dinophyta

Peridinium sp.Gymnodinium sp.

Chryso/Cryptophyta

Chrysomonas sp.cf. Chrysomonas sp.sp.

Bacillariophyta - Diatoms

Staurosira construens

Gomphocymbella

Rhopalodia gibba

Encyonema minutum

Sellaphora nyassensis

Nitzschia “small”

Nitzschia “long”

GomphonemaDiploneis

Chlorophyta – green algae

Oocystis

Tetraedron minimum

Cosmarium

Closteriopsis acicularis

Treubaria setigera Staurodesmus

Tetrastrum

cf. Eremosphaera

Kirchneriella

sp.Lagerheimia

Chlorophyta – green algae

Oocystis

Tetraedron minimum

Cosmarium

Closteriopsis acicularis

Treubaria setigera Staurodesmus

Tetrastrum

cf. Eremosphaera

Kirchneriella

sp.Lagerheimia

Trachelomonas

Euglenophyta

Peridinium cf. africanum

Dinophyta

Conclusions

National Botanic Garden of Belgium

- phytoplankton dominated by a Diatom-Chlorophytes community

- seasonal and interannual variability in major algal groups

- interannual variability in diatom composition, e.g. Synedra/Ulnaria spp. and “long” Nitzschia spp.

- “small” Nitzschia not important in the actual phytoplankton, probably benthic species

- water samples more reliable than filtered samples

- non-diatoms probably underestimated – disintegration during sedimentation

- need of actual phytoplankton samples (taken during the monthly sampling of the sediment trap)

Acknowledgement

National Botanic Garden of Belgium

Dirk Verschurenall persons involved in the sampling of the sediment trap and in the proceeding of the samples

Thank you for your attention

National Botanic Garden of Belgium