Intertidale benthische diatomeeën van Gazi Bay (Kenya). Intertidal benthic diatoms of Gazi Bay (Kenya)
Van Zele, M. (1992). Intertidale benthische diatomeeën van Gazi Bay (Kenya). Intertidal benthic diatoms of Gazi Bay (Kenya). MSc Thesis. Rijksuniversiteit Gent. Faculteit Wetenschappen: Gent. VOL. 1 (114 P.); VOL. 2 (PL., fig.); vol. 3 (photoalbum pp.
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| Keywords |
Algae > Diatoms
Aquatic communities > Benthos
Environments > Aquatic environment > Marine environment > Intertidal environment
ISW, Kenya, Gazi Bay [Marine Regions]
Marine/Coastal |
| Abstract |
The intertidal diatom flora of East-Africa is poorly known. The main goal of our study was to make an inventory of the intertidal diatom flora of the bay. Secondly, we studied the relationship between the composition and the distribution of the diatom assemblages, and abiotic characteristics. Samples were taken on 7-11 and 23 September 1991. A wide variety of habitats in the intertidal zone were sampled, including mangroves and seagrass meadows. From each station 2 samples were taken from the upper 1 centimeter. One was used for the identification and counting of the diatoms, and the second was used for sediment analysis. Temperature and conductivity were measured on the spot. On some places salinity was determined by refractometry. Identification was done on material which was cleaned with H2O2 by light and electron microscopy. The relative abundance of the different taxa in each sample was determined. The resulting dataset was then processed with the computer programs TWINSPAN, a classification technique and DCA, an ordination technique. A total of 279 taxa was found, 66 of them could only be identified on genus level. The identification of these taxa requires a further microscopic investigation, literature studies and examination of type material. The majority (about 89%) of the taxa belonged to the Pennatae. From the 279 taxa the most abundant genera were: Mastogloia (about 13%), Navicula (about 11.5%), Nitzschia (about 10%), Amphora (about 9%) and Achnanthes (about 6.5%). Among the Centricae (about 11%) the most abundant were: Coscinodiscus ( about 1.8% of the 279 taxa), Auliscus (about 1.4%), Biddulphia (about 1.4%) and Triceratium (about 1.4%). The multivariate analysis revealed 2 main groups, corresponding with the 2 rivers, the Kidogoweni and the Mkurumu. We also saw that there was a relation with the salinity and the texture of the sediment. Main group 0 comprises 22 samples, all from the Kidogoweni River. The dynamic regions, mostly higher than in main group 1. In the second division of main group 0, the creek and the rest of the bay were separated from each other. Main group 1 consists of 8 samples, all of which, except sample 9, were taken in the Mkurumu River. The sediment had an important fraction of coarse sand because of the strong tides, and the diatom flora is able to cope with strong changes in salinity (this is necessary because of the great quantities of sea water coming in and fresh water going out at the respective tides). Summarizing we can say that Gazi Bay has a rich and diversified intertidal diatom flora. Further studies on the taxonomy of benthic diatoms are required. It would be most interesting to study in more detail the relationship between the composition, production and the dynamics of the different habitats on the mangrove systems. |
| Dataset |
- Inventory of intertidal benthic diatoms of Gazi Bay (Kenya) sampled in September 1991, more
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