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The study in the spatial distribution of meiobenthos in the Voordelta (the Southern Bight of the North Sea)
Jian, L. (1989). The study in the spatial distribution of meiobenthos in the Voordelta (the Southern Bight of the North Sea). MSc Thesis. VUB: Yerseke. 77 pp.
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| Beschikbaar in | Auteur |
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Abstract |
The sampling design (i.e. the scale of horizontal distance between sampling sites), for ecological monitoring using structural parameters of meiofaunal communities, is examined in this study. Six stations from two areas (Grevelingen and Oosterschelde area) in the Voordelta (Southern Bight of the North Sea), are examined. At each station, three boxes corer ( 14. 7cm diam.) were taken and out of each box corer, three replicate cores (2.4 cm diam.) were randomly taken (total of 54 core samples to be analysed). The six stations have similar sediments (very well, sorted, fine sand with small amounts of silt (0.8-4,4 %). From each sample, meiofauna composition (densities of the 16 higher taxa encountered) and nematode genera (up to 65 in this study) have been determined. By means of several mathematical calculations (e.g. 3-level nested ANOVA) the differences between areas, among stations, among boxes and within boxes are analysed. Significant differences among stations for total meiofauna, Nematoda, Harpacticoida and Turbellaria densities are present; similar significant differences are present comparing the two areas (except for Turbellaria densities). No differences were found for the data among the boxes (exception Nematoda densities). From the Taylor's power law, it is shown that the same degree of aggregation of the individual distribution is found for all dominant taxa at the four groups of data: cores, boxes, stations and areas. Results of sample ordination (DCA) at high taxon level showed that only two stations (3 boxes x 3 cores-samples for each station) were separated from the other samples; the other samples were randomly mixed not only among cores and boxes but also among stations and area. Results of the sample ordination (DCA) of the Nematoda genera show that only samples from the same station were separated from the others; within the six 'clouds' on the DCA-plot, all other samples were randomly distributed. From the rarefactian method, it is shown that the expected nematode genus number on standard sample size of 100, 150, 180 and 200 individuals show always a distinct increase from station to area level. The nematode diversity values on genus level increase between the level of stations and the area; this indicates that the largest differences in nematode genus composition is supported at the station level (km-level). According to these results, we conclude that, for ecological monitoring in open sea, sampling with km-scale is sufficient to examine the variation of the meiofauna within the area. When replicate samples are needed, replicate sampling from m-scale is the same as from cm-scale. |
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