De relatie tussen het meiobenthos van een natuurlijk mangrovebos in Kenondo (Kenia) en hun specifieke omgeving: een kolonisatie-experiment = The relation between meiobenthos of a natural mangrove forest in Kenondo (Kenya) and their specific environment: a colonistation experiment
Thoonen, M. (2006). De relatie tussen het meiobenthos van een natuurlijk mangrovebos in Kenondo (Kenia) en hun specifieke omgeving: een kolonisatie-experiment = The relation between meiobenthos of a natural mangrove forest in Kenondo (Kenya) and their specific environment: a colonistation experiment. MSc Thesis. Universiteit Gent. Faculteit Wetenschappen: Gent. 84 pp.
This thesis fits in with a broader study on the rehabilitation of benthic mangrove ecosystems after degradation and reforestation. The importance of sediment type and food type for the meiobenthic community has been tested by means of a colonization experiment in a natural Rhizophora mucronata forest. For this purpose, inorganic and defaunated sediment originating from a natural and a neighboring degraded site enriched with different sources of organic matter (diatoms, sea grasses and mangrove leaves) were used. Half open experimental units with different combinations of sediment and food were planted in the natural mangrove forest and followed up during a time span of two months. This way the colonization of and changes in meiobenthic communities can be studied in relation to sediment type and food type. There was already pronounced colonization of the experimental units, by lateral interstitial migration, from day 1. The nematodes take in the available space even if there is no food present. The abundances in the experimental units with mangrove leaves are higher compared with the natural situation. This is because of the better availability of the mangrove leaves for the nematodes and elimination of competition with the epibenthic fauna for it. The diatoms and sea grasses were not nutritious enough to cause differences in densities. By means of a statistical test the effects of sediment type and food type were tested on the structure of the nematode community. There was no effect due to the food type and a weak effect due to sediment type. However there is an effect of time on the nematode assembly. The succession of nematode communities in time that colonize the experimental units with mangrove leaves is linked to the decomposition process of the mangrove leaves. When the tannin is completely disappeared (by leaching)selective deposition feeders dominate and feed presumably on bacteria associated with the mangrove detritus. After two months of colonization the nematode community in the experimental units resembles the natural situation. In the frame of the PHD for which this study has been conducted there can be concluded that the differences in nematode assembly in the natural and the degraded Rhizophora mucronata forest differ because of the absence of detritus from mangrove leaves. The diversity indexes calculated shows a higher diversity in the treatment with degraded sediment and no food in comparison with the other treatments. This particular treatment is a moderate disturbance of the environment. It is possible that the experimental unit with degraded sediment and no food is repeatedly colonized by nematodes from the neighboring environment.
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