Browsing by Author "De Troch, Marleen"

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    Community Structure and Microhabitat Preferences of Harpacticoid Copepods in a Tropical Reef Lagoon (Zanzibar Island, Tanzania)
    (2008) Gheerardyn, Hendrik; De Troch, Marleen; Ndaro, Simon G. M.; Raes, Maarten; Vincx, Magda; Vanreusel, Ann
    Three microhabitat types (dead coral fragments, coral gravel and coral sand) were distinguished and sampled at two locations (Matemwe and Makunduchi) in a tropical lagoon (Zanzibar Island, Tanzania), and the community structure, habitat preferences and biodiversity of the associated harpacticoid copepod fauna was investigated. The harpacticoid fauna is affected by sediment granulometry and by the structural differences between coral and both gravel and sediment. The coral fragments contained a specific assemblage composed of typical ‘phytal’ taxa (Tisbe, Paradactylopodia and Dactylopusia) along with other eurytopic and sediment-dwelling forms (Ameira, Ectinosoma and Amphiascus), which may be attracted by the sediment retained between the coral branches. The assemblages of coral gravel and upper sediment layer did not differ signifi- cantly from each other and had mostly the same dominant genera. The sediment from Matemwe was dominated by the interstitial Paramesochridae and the sediment from Makunduchi by Tetragonicipitidae. The coral fragments from Makunduchi sustained a more diverse assemblage than gravel and the different sediment layers. It was assumed that coral form and complexity, with implications for habitable space, nutritional resources and level of predation, are important in structuring diversity of the associated assemblage.
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    Effect of nutrient enrichment on seagrass associated meiofauna in Tanzania
    (Elsevier Ltd, 2012) Daudi, Lilian Nduku; Lugomela, Charles Venance; Uku, Jacqueline Nduku; De Troch, Marleen
    Abundance, diversity and community structure of meiofauna, with special emphasis on epiphytic harpacticoid copepods, occurring in Tanzanian seagrass beds under various nutrient inputs was determined. All measured parameters for epiphytic meiofauna and diatoms (fucoxanthin) were negatively affected by nutrient input and this was detected even at the higher taxonomic levels of meiofauna, supporting the validity of higher taxon surrogacy in environmental impact studies. However, benthic meiofauna and other biofilm characteristics (chlorophyll a) did not show any difference between sites suggesting that nutrient enrichment had less impact on these variables. This indicates a differential impact of pollution on epiphytic vs. benthic communities. Consequently, different trophic levels will be impacted in various ways and hence the effects of pollution on the overall ecosystem functioning of seagrass beds are complex and not straightforward. Although the seagrass plants themselves don’t show any major changes under different nutrient input, associated organisms that guarantee energy flow at basal levels of the food web in this ecosystem can be largely impacted.
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    Harpacticoid copepod colonization of coral fragments in a tropical reef lagoon (Zanzibar, Tanzania)
    (2012) Callens, Martijn; Gheerardyn, Hendrik; Ndaro, Simon G. M.; De Troch, Marleen; Vanreusel, Ann
    Colonization experiments were conducted in a tropical lagoon (Zanzibar Island, off the coast of Tanzania) to investigate thetemporal dynamics and mode of colonization of the harpacticoid copepods community on dead coral fragments. There wasfast colonization of the coral fragments attaining a substantial diversity after only two days. The ability to colonize dead coralfragments is thought to be related to the morphology and life style of different harpacticoid species. Phytal taxa (e.g. Tisbidae)were fast colonizers, reaching high abundances during the initial colonization phase. Sediment-associated and eurytopic taxa(e.g. Ameiridae, Miraciidae and Ectinosomatidae) showed lower colonization rates and became the dominant group duringthe later colonization phase. Most species are able to colonize the coral fragments through the water column. However,colonization along the substrate surface is also considered to be an important colonization mode, especially forsediment-associated taxa, which showed lower colonization rates when migration through the sediment was hindered.
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    The Structuring Role of Microhabitat Type in Coral Degradation Zones: A Case Study with Marine Nematodes from Kenya and Zanzibar
    (Springer Link, 2007) Raes, Maarten; De Troch, Marleen; Ndaro, Simon G. M.; Muthumbi, Agnes; Guilini, Katja; Vanreusel, Ann
    Nematode genus assemblages were identified from four locations in coral degradation zones (CDZs) along the African east coast: Watamu and Tiwi Beach (Kenya) and Matemwe and Makunduchi (Zanzibar). Three microhabitat types were distinguished: coralline sediment, coral gravel and coral fragments. Nematode community composition was comparable to that of other studies dealing with the same habitat. The presence of a common genus pool in CDZs was reflected in the considerable similarities between samples. The addition of coral fragments as a habitat for nematodes resulted in an increased importance of taxa typical for coarse sediments and large substrata. Local and regional turnover were of the same order of magnitude. The structuring effect of microhabitat type clearly overrode the effect on a local and regional scale. Differences in sediment characteristics were more important in structuring the nematode assemblages than differences between the coralline sediment and coral fragments. No effect related to the three-dimensional structure of coral fragments was found. Differences between nematode assemblages in the coralline sediment and on coral fragments were attributed to the exposed nature of the latter habitat, its large surface area and its microbial or algal cover. Differences in available food sources were reflected in nematode trophic composition.