What drives invertebrate communities in a chalk stream : from trophic relationships to allometric scaling
Abstract
Despite a slow start freshwater meiofauna research is now gathering pace. Evidence
is accumulating which indicates the importance of their inclusion in lotic metazoan studies.
Here I contribute towards this research effort by conducting an investigation of meiofauna
and macrofauna from a chalk stream.
I sampled meiofauna for a 19 month period, and macrofauna for a 12 month period
between April 2004 and October 2005 from the subsurface, macrophyte stands and gravel
beds. The chalk stream community was highly diverse with 57 taxa identified from the
subsurface and 186 from the benthos. Meiofauna outnumbered macrofauna in all habitats in
terms of density. Both meio- and macroinvertebrates preferred macrophyte stands over
gravel beds as habitat, indicated by higher densities, biomass and species richness. Speciesabundance
relationships and density-size spectra indicated the invertebrate assemblages of
the benthos to be stable over the period of the study as patterns varied little between
sampling months and habitats. Production and standing biomass were dominated by the
macroinvertebrates which suggests meiofauna had a limited role within functioning of the
stream. However, gut content data indicated meiofauna may play an important trophic role,
linking basal resources and top consumers. Combined gut content and stable isotope
analysis suggested a strong pattern of generalist feeding throughout the whole spectrum of
body size in the community, rejecting the concept of functional feeding groups.
Predominance of generalist feeding also suggested a large number of weak interactions in
food webs. While higher species richness lower in food webs indicated greater functional
redundancy of lower trophic levels.
Density-body size distributions were shallow with a biased distribution of energy
towards larger size classes. Moreover, testing of production, standing biomass and PIB
body size allometry was inconclusive with regards to theoretical predictions. The interrelationship ofbiodiversity, stability, and trophic dynamics, with body size determine
the structure and dynamics of the chalk stream community, not metabolism.
Authors
Tod, Steven PeterCollections
- Theses [4235]