An investigation of biodiversity patterns and processes in nematode populations of Loch Ness

David, Rhian (1998) An investigation of biodiversity patterns and processes in nematode populations of Loch Ness. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The current literature of the subject of lake nematology is reviewed and found to be in need of quantitative ecological studies. The following thesis investigates patterns and/or processes affecting diversity, density, biomass, body size and functional groups of meiobenthic nematodes in Loch Ness. The effect of taxonomic resolution and analytical methodology on diversity patterns is investigated and discussed.

Benthic core samples were collected from the profundal (at 90-211 m) and from river mouth areas (at ~0.5 m), from surface sediment (0-1 cm) and deeper sediment layers (1-2, 2-3, 3-4 cm). Environmental parameters such as sediment particle size, organic matter content and redox potential profiles were also measured. A combination of univariate, graphical and multivariate analysis methods were used to investigate diversity patterns. The application of methods from marine meiobenthology was successful.

Sample diversity was remarkably constant throughout the loch although a change in community composition was found between river mouth and profundal samples. Higher taxon levels and analytical methodology could both increase or decrease pattern information of the diversity study. A high degree of spatial aggregation was apparent in most species, the majority of species were independently aggregated within sites. Loch Ness was found to have high gamma-diversity of nematodes (94 species) in comparison with other European lakes although samples were dominated in abundance by Eumonhystera species (78%). The low diversity of ancient lakes in comparison to Loch Ness contradicts the stability-time hypothesis. Juveniles accounted for 60-70% of abundance and, of the adult specimens, females dominated at 90% of abundance. Functional group (feeding-type and tail-shape) composition was not significantly different between sites, largely due to the dominance of one functional group. The dominant species in Loch Ness had characteristics of coloniser spices in low-disturbance environments. Evidence is provided that oligotrophic lakes are impoverished in diversity when compared to marine and tropical soil habitats.

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