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PHYTOPLANKTON DYNAMICS IN LAKE CHALLA AS DERIVED FROM SEDIMENT TRAP ANALYSES

PHYTOPLANKTON DYNAMICS IN LAKE CHALLA AS DERIVED FROM SEDIMENT TRAP ANALYSES. Christine Cocquyt National Botanic Garden of Belgium Limnology Unit, Ghent University. National Botanic Garden of Belgium. Quantitative phytoplankton analyses Uthermöhl method:

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PHYTOPLANKTON DYNAMICS IN LAKE CHALLA AS DERIVED FROM SEDIMENT TRAP ANALYSES

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  1. PHYTOPLANKTON DYNAMICS IN LAKE CHALLA AS DERIVED FROM SEDIMENT TRAP ANALYSES Christine Cocquyt National Botanic Garden of Belgium Limnology 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

  3. Lake Challa 2007 2008 2010 2011 Major algal groups - percentages derived from biovolumes

  4. Gomphocymbella Synedra/Ulnaria Nitzschia “long” percentages derived from biovolumes 2007 2008 2010 2011

  5. Encyonema/ Cymbella spp. Staurosira/ Staurosirella spp. Rhopalodia spp. percentages derived from biovolumes 2007 2008 2010 2011

  6. Cosmarium spp. Closteriopsis acicularis Oocystis sp. percentages derived from biovolumes 2007 2008 2010 2011

  7. Filtered versus water sample

  8. Challa phytoplankton productivity filtered sample water sample flux (cell volume/day cm2) 2008 2010 2007 2011

  9. filtered samples water samples

  10. Lake Challa – July 2010 – filtered sample

  11. Lake Challa – January 2011 – water sample

  12. Species diversity

  13. Species diversity Diatoms 44 Chlorophyta 40 Cyanobacteria 15 Euglenophyta 2 Dinophyta 2 Chrysophyta 3 Total 106

  14. Bacillariophyta Achnanthidum exiguum Achnanthidum sp. Amphora copulata Amphora pediculus Cymatopleura clavata Cymbella sp. Diploneis sp. Encyonema meulleri Encyonema minutum Gomphocymbella sp.Gomphonema affine Gomphonema parvulum Gomphonema sp. Hantzschia amphioxys Navicula sp. 1 Navicula sp. 2 Navicula sp. 3 Navicula sp. 4 Nitzschia bacata Nitzschoa epiphyticoides Nitzschia fonticola Nitzschia lancettula Nitzschia palea Nitzschia palea var. tropica Nitzschia vanoyei Nitzschia sp. 1 Nitzschia sp. 2 Nitzschia sp. 3 Nitzschia sp. 4 Placoneis gastrum Rhopalodia gibba Rhopalodia gibberula Rhopalodia gracilis Rhopalodia hirudiniformis Sellaphora nyassensis Sellaphora pupula Stauroneis sp. Staurosira construens Staurosirella pinnata Surirella sp. Ulnaria acus Ulnaria danica Ulnaria ulna Urosolenia sp.

  15. Chlorophyta Ankistrodesmus sp. Chlorococcus sp. Chlorella sp. Closteriopsis acicularis Closteriopsis acicularis var. africana Crucigeniella quadrata Crucigeniella sp. Dictyosphaerium pulchellum Dictyosphaerium tetrachotomum Didymosphenia sp. Eremosphaeria sp. Kirchneriella arcuata Kirchneriella contorta var. elongata Kirchneriella microscopica Kirchneriella obesa cf. Kirchneriella sp. Lagerheimia chodatii Lagerheimia ciliata Lagerheimia citriformis Lagerheimia subsalsa Lobocystis planctonica Monoraphidium arcuatum Monoraphidium irregulare Monoraphidium mirabile Monoraphidium minutum Oocystis sp. Oonephris sp. cf. Oonephris sp. Podohedra falcata Schroederia planctonica Tetraedron triangulare Tetraedron minimum Treubaria setigera Tetrastrum komareckii sp. 1 sp. 2 sp. 3 Cosmarium sp. 1 Cosmarium sp. 2 Staurastrum

  16. Cyanobacteria Chroococcus limneticus Chroococcus dispersus Chroococcus sp. Chroococalles sp. cf. Aphanocapsa microscopica cf. Gloeotrichia sp. Gomphosphaeria cf. natans Synechococcus elongatus Planktolyngbya sp. Microcrocis sp. Microcystis sp. Snowella sp. sp. 1 sp. 2 sp. 3

  17. Euglenophyta Trachelomonas volvocina Trachelomonas volvocinopsis Dinophyta Peridinium sp. Gymnodinium sp. Chryso/Cryptophyta Chrysomonas sp. cf. Chrysomonas sp. sp.

  18. Bacillariophyta - Diatoms Gomphonema Diploneis Encyonema minutum Staurosira construens Gomphocymbella Nitzschia “small” Nitzschia “long” Rhopalodia gibba Sellaphora nyassensis

  19. Chlorophyta – green algae Tetraedron minimum Oocystis cf. Eremosphaera Closteriopsis acicularis Cosmarium Tetrastrum sp. Lagerheimia Treubaria setigera Kirchneriella Staurodesmus

  20. Chlorophyta – green algae Tetraedron minimum Oocystis cf. Eremosphaera Closteriopsis acicularis Cosmarium Tetrastrum sp. Lagerheimia Treubaria setigera Kirchneriella Staurodesmus

  21. Euglenophyta Dinophyta Trachelomonas Peridinium cf. africanum

  22. Conclusions • - 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) National Botanic Garden of Belgium

  23. Acknowledgement Dirk Verschuren all persons involved in the sampling of the sediment trap and in the proceeding of the samples National Botanic Garden of Belgium

  24. Thank you for your attention National Botanic Garden of Belgium

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