Respiration rates of copepod larvae and a ciliate from Bowling Green Bay, North Queensland

Full description

Laboratory experiments were carried out on copepod larvae and a ciliate (Placus sp.), collected from inshore waters in Bowling Green Bay. Surface seawater was collected at the same time and filtered for later use in experiments. Five series of experiments were conducted on the copepod larvae, which were separated from phytoplankton and other material in the plankton samples, using the phototactic response of the zooplankton. Two series of experiments were carried out on the ciliate, Placus sp., which was collected in an almost pure sample from the study site.A series of experiments consisted of between 5 and 12 measurements on animals from a plankton sample. A new sub-sample of animals, consisting of between 200 and 1300 individuals was used for each measurement. Each series was completed within 2-7 hours of collection, except for one of the copepod samples, when measurements commenced one day after collection.Respiration rates were measured using an oxygen electrode method. At the end of each measurement, the animals were preserved and later counted under a dissecting microscope. For each experimental series, animals were pooled and the size distribution measured with a Coulter Counter TAII.Average biovolume was calculated, based on the diameters of animals in each experimental series. This value was then used to calculate average body wet weight (µg).
This research was initiated to:1. measure respiration rates of microzooplankton (2. compare the results with published respiration rates of other similar sized animals and net-zooplankton (>200-300 µm body size)3. estimate the relative importance of microzooplankton respiration to total zooplankton respiration in tropical marine ecosystems.

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Maintenance and Update Frequency: notPlanned

Statement: Statement: Sampling method:Microzooplankton were sampled using a 51 cm diameter, 142 cm long, conical net with 20 µm mesh. The net was fitted with a 500 ml, removable plastic container at the cod end. A 130 µm or 60 µm mesh screen was mounted at the mouth of the net to prevent contamination with larger sized zooplankton. The net was gently towed through subsurface water (1-2 m depth) for 3-5 minutes.Copepod larvae sample composition: The major constituents of the copepod larvae used in experiment series 1,2 and 3 were nauplius stages (71-87 % of the total number) and the remaining 12-28 % of the larvae were copepodite stages, most of which appeared to belong to the genera Oithona, Macrosetella, Paracanus and Acrocalanus. In the series 4 experiment, 95.5 % of the total number were nauplius stages. The samples also contained a small percentage of ciliates, radiolarians and the larvae of polychaetes and molluscs. Since the body size of these animals were similar or smaller than the copepod larvae, the effect on the experimental results should have been insignificant.Oxygen electrode:Respiration rate was measured with a Clark type oxygen electrode (YSI Model 53 oxygen monitor). The Winkler titration method (Strickland and Parsons, 1972) was used to calibrate the oxygen electrode.Strickland JDH, Parsons TR (1972) A practical handbook of seawater analysis. Bull. Fish. Res. Bd. Can., 167. 1-310.Incubation cells:The design of the cell to incubate the animals was similar to that of Teal and Halcrow (1962), but it differed in the following point; a mesh screen to separate a magnetic stirrer bar from the animals was not used and the stirrer bar (3 mm X 10 mm) was placed directly on the bottom of the cell. The cell volume was adjusted to 3.5 ml in this study.Teal JM, Halcrow K (1962) A technique for measurement of respiration of single copepods at sea. J. Cons. perm. int. Explor Mer., 27, 125-128.

Notes

Credit
Ikeda, Tsutomu, Dr (Principal Investigator)