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

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.