marazzi flood pulse symposium 2010

Phytoplankton biomass and biodiversity in the Okavango Delta

Luca Marazzi1

Anson W. Mackay1, Lars Ramberg2

1. Department of Geography, University College London

2. Harry Oppenheimer Okavango Research Centre

Maun - 1 February 2010

Algae

Fish

1. Introduction and aims

Homo sapiens

Algae are food for fish

Fish are food for people

Phytoplankton = basis of food webs

Ecosystem Service: food provision

Energy & Matter

E & M

Zooplankton

E & M

E & M

Nutrients (N, P...)

Sunlight

from inflow water, dust, soil

CO2

Birds

E & ME & M

The Okavango Delta: a unique inland freshwater ecosystem

1. Introduction and aims

Hydoperiod is a critical factor inshaping this ecosystem: flood pulsevaries highly the inundated area

Cronberg (1996) found 50 commonalgal species in the Boro region;several hundreds of species in theDelta (Ramberg et al., 2006)

Ph.D. for a specific study to generate new knowledge

Aims of the research

• Monitoring phytoplankton in seven floodplainsevery two months (about 100 samples in 2009-2010)

• Investigating the distribution of algae across habitatsand relationships with hydroperiod and otherenvironmental variables

• Generating new baseline data on phytoplankton coveringvast areas of the Delta (95 samples from 2006-2007

campaigns)

41. Introduction and aims

5

Summary of sites

Sample Date Time Flooding

Pool C (G) 6.05.09 9.05 Frequently (F)Pool C (S) 9.45 F

Pool C (OW) 10.30 F

Water lilly pool (G1) 11.45 Intermediate (I)Water lilly pool (G2) 12.20 I

Hippo pool (OW) 13.00 Frequently (F)Hippo pool (S) 13.20 FHippo pool (G) 15.00 F

Wildebeest pool (G) 7.05.09 9.00 Intermediate (I)Wildebeest pool (S) 9.40 I

Aldrovanda pool (OW) 10.30 Frequently (F)Aldrovanda pool (S) 10.55 F

Daunara (OW) 13.00 Rarely (R)Daunara (G) 13.15 R

Buffalo fence (G) 8.05.09 12.00 Rarely (R)Buffalo fence (OW) 12.15 R

1. Introduction and aims

Map of floodplain sites

6

1. Introduction and aims

Darwin initiative project sites: P.Wolski – www.orc.ub.bw

Sampling campaign in floodplains 2-3 habitats: Open Water, Sedges and Grassland

2. Methods

Grassland

Sedges

Open Water

Sampling of water column Concentration

2. Methods

Preservation in Lugol’s

Phytoplankton identification & counting

2. Methods

Utermohl technique: inverted microscope (add picture)Sedimentation chambers: Volume: 5 ml, 10 ml or 15 ml

Counting 200-500 algal units(cells, colonies or filaments) inrandom fields of view at 100xand 400x magnification

http://www.hydrobios.de/

N algal units - phyla

16 samples from 7 floodplain sites (April/May 2009)

10

0

100

200

300

400

500

600

700

N a

lga

l u

nit

s

Phyla

Aldrovanda Hippo pool Pool C Wildebeest Waterlilly Buffalo fence Daunara

3. Results

Principal Component Analysis

Environmental data in 7 sites:depth, conductivity, TDS, Turbidity, pH, DO, %O2 sat. (measured in the field)

3. Results

12

0

10

20

30

40

50

60

70

80

90

Physical data: turbidity (NTU) 3. Results

Hippo pool: frequently flooded site

13

0

50

100

150

200

250

300

350

N a

lga

l u

nit

s

Phyla

Open Water Sedges Grassland

Mougeotia sp.

3. Results

Coniugation

0

10

20

30

40

50

60

70

80

90

N a

lga

l u

nit

s

Open Water Sedges Grassland

14

Pool C: most abundant taxa 3. Results

Pennate Diatoms, Cryptomonas sp. in deeper water

Desmids in flooded grasslands

3. Results

RedundancyAnalysis

16

Wildebeest pool: intermediate flooding frequency

0

50

100

150

200

250

300

350

N a

lga

l u

nit

s

Phyla

Sedges Grassland

Daunara pool: rarely flooded site

17

0

20

40

60

80

100

120

140

N a

lga

l u

nit

s

Phyla

Open Water Grassland

Cryptomonas sp.

Euglena sp.

3. Results

Phacus longicauda Euglenales

Closterium dianae Zygnematales (Closteriineae)

Goniochhloris smithiiXanthophyta (Mischococcales)

Xanthidium sp.Zignematales (Desmidiinae)

Stauroneis sp. Bacillariophyta (Pennate Diatom)

Identification of species and genera

Zignema sp. (Zygnemataceae)

3. Results

100 µm

200 µm

10 µm

60 µm

60 µm

100 µm

Identification of species

6 species & 2 varieties of Micrasterias in Pool C Grassland:

30 cells counted in the whole chamber (identified at 400x)

M. pinnatifida M. rotata M. mahabuleshwarensis M. americana

M. truncata M. tropica (var. elongata)M. tropica (var. elegans)

100 µm

3. Results

Estimate of biovolume / algal biomass

Algal units in 10 ml subsample from a 0,275 L sampleconcentrated into a 50 ml sterelin: concentration factor = 5.5

Formula used:

Biomass of algae (mg/L) = (Biovolumesubsample * 5 [um^3])/

(0.275 [L]* 1,000,000 [um^3/mm^3=mg])

Biovolume = Biomass in wet weight: mg=mm^3

50 µm

6,35

6,40

6,45

6,50

6,55

6,60

6,65

6,70

6,75

6,80

6,85

0

1

2

3

4

5

6

7

8

9

10

Open Water Sedges Grassland

pH

Bio

vo

lum

e (

mg

/l)

21

Algal biomass and pH...

N=5

N=4

N=7

3. Results

Conclusions

Geographical and habitat diversity results in highphytoplankton biodiversity in floodplains: 122 species and86 genera in 16 samples

Mougeotia, Cryptomonas, Cosmarium, Staurastrumand Staurodesmus are the most abundant genera

Algal biomass is higher in the flooded grasslands andDesmids are the major algal group there

Cyanophyta seem to be more abundant in the sites withintermediate flooding regime

22

Research development

• Chemistry analyses to understand relationships betweenN, P, micronutrients and algal biomass & biodiversity

• Improve temporal, spatial and taxonomic resolution ofthe study on phytoplankton

• Data exchange and integration with Nqobizitha Siziba’sPh.D. on zooplankton to investigate the food webs in ajoint project HOORC-UCL

23

References

• Whitton et al. “Freshwater algae of the British Isles”

• Cronberg et al. (1996). “Major ion chemistry, plankton andbacterial assemblages of the Jao/Boro river, Okavango Delta,Botswana: the swamps and the floodplains”. Archiv furHydrobiologie, vol. 107/3 335-407.

• Ramberg et al. (2006) “Species diversity of the Okavango Delta,Botswana”. Aquat. Sci. 68 (2006) 310–337.

• “Water quality – Guidance standard for the routine analysis ofphytoplankton abundance and composition using inverted

microscopy (Utermöhl technique)”. prEN 15204:2005European Committee for standardization.

24

Acknowledgements

Sophie des Clers (co-supervisor), Thomas Davidsonand Gina Clarke (UCL)

Nqobizitha Siziba, Ponde Kauheva, Ineelo Mosie,Richard Mazebedi, Thebe Kemosedile, MonicaMorrisson (HOORC)

Royal Geographical Society (www.rgs.org)

UCL Geography Department & Graduate School

UK DEFRA Darwin Initiative

Responding To Climate Change

Thank you for your interest!

l.marazzi@ucl.ac.uk