Free-living nematodes in the carbonate sands of Davies Reef, Great Barrier Reef (MECOR Workshop)

Full description

The population structure and trophic composition of free-living nematodes from carbonate sands within different reef zones (reef crest, reef flat and lagoon) at Davies Reef in the Great Barrier Reef were examined.Seven benthic stations (C-I) were sampled across the southeastern side of the reef in the following reef zones: within an open basin at the fore-reef crest (C); in bare sandy hollows on the reef flat (D, E, F); in an unprotected shallow lagoon area (G); in a protected shallow lagoon area (H) and in a deeper lagoon area among sediment mounds constructed by ghost shrimps (Callianassa spp.) (I). Sediments at all stations were carbonate sands consisting of coral, mollusc and crustacean shell, coralline algae and Halimeda debris as well as foraminiferan and radiolarian tests. At each station, 6 cores (2.5 cm diameter and 5 cm length) were collected by hand by SCUBA divers. At (I), 6 cores each were taken from the top, side and the area between the Callianassa mounds. Each core was placed into a plastic jar while under water and later preserved in a 1:500 mixture of Rose Bengal-buffered seawater:5% formalin. The depth at which cores were collected was also recorded. Sediments were passed through 500 µm and 45 µm sieves. Nematodes retained in the 45 µm sieve were identified to species level when possible and counted. Each species was also classified according to a feeding-type scheme: selective deposit feeder (1A); non-selective deposit feeder (1B); epistrate feeder (2A); predator/omnivore (2B). Separate sediment cores were taken at each station for grain size analysis. Median grain size, sorting coefficient and percentage sand, silt and clay (by weight) were determined. Total organic matter (% by weight) was measured.
To determine any variations of the population structure and trophic composition of free-living nematodes from carbonate sands within different reef zones (reef crest, reef flat and lagoon).
This research was undertaken as a component of the workshop "Microbial Ecology on a Coral Reef" (MECOR), organised by the Australian Institute of Marine Science. This workshop brought together 35 scientists from a range of disciplines to examine the role of microorganisms in coral reef ecosystems. Davies Reef was chosen as the study site and research was undertaken during the winter season (July-August 1984).

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Maintenance and Update Frequency: notPlanned

Statement: Statement: The feeding type scheme used to classify nematodes is described in:Weiser W (1953) Die beziehung swischen mundhohlengestalt, ernahrungswiese und vorkommen bei freilebenden marinen nematoden. Ark. Zool. 4: 181-194.Grain size analysis followed the methods described in: Folk RL (1974) Petrology of sedimentary rocks. Hemphill's, Austin, Texas.Silt and clay concentrations were estimated by sieve and pipette analysis. The sand fraction was analysed using a sonic sifter and each interval weighed to determine particle size distribution.Total organic matter was determined by the method described in:Buchanan JB (1984) Sediment analysis. In: Eds. Holme NA and McIntyre AD, Methods for the study of marine benthos. pp.41-65. Blackwell Scientific Publications, Oxford.

Notes

Credit
Alongi, Daniel M, Dr (Principal Investigator)