Zooplankton occurrences (present/absent) and community structure in three habitat types in northern Lake Victoria, Uganda

Study Extent

Sampling was conducted from October 2009 to January 2010. Sampling was done in the three habitats in northern Lake Victoria, including sewage lagoons at the lake shores, Napoleon Gulf (NG) and the interface between the lake and the Nile River (also known as Source of the Nile River). A total of 18 sites were sampled per trip (two transects per habitat, with three sites per transect), resulting in a total of 72 samples collected during the study period.

Sampling

Zooplankton samples were collected with a conical plankton net (Nansen type; mesh size 60 µm; mouth diameter 0.25 m), towed vertically through the water column, as described by Mwebaza-Ndawula (1994). Each sample was washed with tap water in the laboratory over a 53 µm sieve to remove the preservative and then diluted to a suitable volume, depending on the concentration of organisms in each sample. Sub-samples of 2, 2, 5 and 10 mL were taken with a wide bore automatic pipette from a well agitated sample. The sub-sample series were performed to consider the more abundant organisms in 2, 2 mL series, and the rarer organisms in 2, 2, 5, 10 mL series. Each sub-sample was put into a counting chamber and examined under inverted microscope (Hund, Wetzlar, Germany) at X100 magnification for taxonomic determination, and X40 for counting and organism body measurements.

Quality Control

Some zooplankton were able to be identified to species level using published taxonomic keys (Sars 1895; Pennak 1953; Brooks 1957; Rutner-Kolisko 1974; Koste 1978; Boxshall & Braide 1991; Korinek 1999). Taxonomic names were cross-checked using the World Register of Marine Species (WoRMS). Volume densities of organisms were calculated from the counts data, with reference to the sample net mouth diameter and water column depth at each sampling site (Mwebaza-Ndawula L., 1998).

Method steps

1. Collection of the zooplankton In the field, a conical plankton net (Nansen type; mesh size 60 µm; mouth diameter 0.25 m), towed vertically through the water column to have an integrated sample was used to collected the zooplankton. Three hauls were taken per site and were combined to make a composite sample. Preserving the samples The composite sample was preserved with sugar-formalin, in a ratio of 1-part formalin to 10 parts sample volume, the sugar was to stop the ballooning of cladocerans for easy identification. Identification of zooplankton taxa In the laboratory, samples were washed using a sieve of 53 µm to remove the fixatives. Some organisms were identified to species level using published keys (Sars, 1895, Pennak, 1953, Brooks, 1957, Rutner-Kolisko, 1974, Koste, 1978, Boxshall and Braide, 1991, Korinek, 1999). Density of organisms were calculated from the counts data, with reference to the sample net mouth diameter and water column depth at each sampling site (Mwebaza-Ndawula, 1998, unpubl. PhD Thesis)

This dataset covers freshwater zooplankton.

1. Afrocyclops
   rank: genus
2. Ascomorpha
   rank: genus
3. Asplanchna
   rank: genus
4. Bosmina longirostris
   rank: species
5. Brachionus
   rank: genus
6. Brachionus angularis
   rank: species
7. Brachionus bidentata
   rank: species
8. Brachionus budapestinensis
   rank: species
9. Brachionus calyciflorus
   rank: species
10. Brachionus caudatus
    rank: species
11. Brachionus dimidiatus
    rank: species
12. Brachionus falcatus
    rank: species
13. Brachionus forficula
    rank: species
14. Brachionus patulus
    rank: species
15. Brachionus plicatilis
    rank: species
16. Brachionus quadridentatus
    rank: species
17. Brachionus urceolaris
    rank: species
18. Calanoidae
    rank: family
19. Ceriodaphnia cornuta
    rank: species
20. Chydorus
    rank: genus
21. Cyclopoidae
    rank: family
22. Daphnia longispina
    rank: species
23. Daphnia lumholtzi
    rank: species
24. Diaphanosoma excisum
    rank: species
25. Euclanis
    rank: genus
26. Eucyclops
    rank: genus
27. Filinia longiseta
    rank: species
28. Filinia opoliensis
    rank: species
29. Harpacticoida
    rank: order
30. Hexathra
    rank: genus
31. Keratella cochlearis
    rank: species
32. Keratella tropica
    rank: species
33. Lecane bulla
    rank: species
34. Lecane luna
    rank: species
35. Macrothrix
    rank: genus
36. Mesocyclops
    rank: genus
37. Moina micrura
    rank: species
38. Copepoda
    rank: subclass
39. Platyias
    rank: genus
40. Platyias quadricornis
    rank: species
41. Polyarthra
    rank: genus
42. Polyarthra vulgaris
    rank: species
43. Synchaeta
    rank: genus
44. Synchaeta pectinata
    rank: species
45. Thermocyclops decipiens
    rank: species
46. Thermocyclops emini
    rank: species
47. Thermocyclops incisus
    rank: species
48. Thermocyclops neglectus
    rank: species
49. Thermocyclops oblongatus
    rank: species
50. Thermodiaptomus galeboides
    rank: species
51. Trichocerca
    rank: genus
52. Trichocerca cylindrica
    rank: species
53. Tropocyclops confinnis
    rank: species
54. Tropocyclops tenellus
    rank: species
55. Tropodiaptomus stuhlmanni
    rank: species

The study was undertaken in the Napoleon Gulf, Lake Victoria and nearby stabilizing waste water ponds.