Population Dynamics Of Small Copepod

Population dynamics of four small copepods of genera Paracalanus and Acartia were studied from October 2005 to September 2006 in and around Jiaozhou Bay, China.In Jiaozhou Bay, Paracalanus parvus occurred throughout the year, with a large abundance peak in June and August and small peaks in January. This species reached the lowest abundance in April, and an obvious decrease also was found in July. Spatially, P. parvus, mostly CVs, occurred mainly in the south of the bay and the outer bay in winter, and extended to tother parts in late spring. P. parvus spawned throughout the year except in February, and the relative high egg production mainly occurred in the warming period. Egg production rate (EPR) of P. parvus peaked in May at 27.9 eggs female-1d-1. Totally, EPR positively correlated with temperature, chlorophyll a concentration and prosome length, but negative related to salinity. Spacially, EPR in the north of the bay was higher than that at the mouth of the bay and in the outer bay. The maximum EPR was found in June at 60.8 eggs.female-1d-1 in the north of the bay. EPR higher than 10 eggs.female-1d-1 persisted for 6 months (Apr.-Sept.) in the north of the bay, for 5 months (Apr.-Aug.) at the mouth of the bay and for only 3 months (May-Jul.) in the outer bay. The biomass of P. parvus peaked in June at 6.15 mg C m-3 and was lowest in April at 0.28 mg C m-3. The estival increase in copepod biomass coincided with the summer production burst, but the little biomass peak in winter overlapped the hiemal low production as the low growth rate in winter. Secondary production was highest in June of 1.77 mg C m-3 d-1 and annual copepod secondary production rate was estimated as 158.41 mg C m-3 yr-1.Paracalanus crassirostris occurred sporadically in Jiaozhou Bay from late summer to autumn. It disappeared after November 2005, and occurred again in August 2006. Spatially, this species mainly distributed in the north and south of the bay and partly in the outer bay. In September, 2006, this species only occurred in the north part of the bay but absented from other domains. Egg production rate of P. crassirostris peaked in August at 11.2 eggs female-1d-1. The maximum secondary production was also ocuured in August at 0.079 mg C m-3d-1. The annual secondary production rate of P. crassirostris was only 2.12 mg C m-3yr-1.Aartia bifilosa occurred throughout the year with burst in May and June (>8000 ind.m-3). This species mainly concentrated in the north of the bay when they reached high abundance (May-Jun.), so that it was presumed that A. bifilosa began its burst from the north of the bay. In July, this species decreased to a low abundance but concentrated in the outer bay. A. bifilosa produced eggs throughout the year except in January and February, and the highest EPR occurred in April at 16.5 eggs female-1day-1, which contributed to the high population abundance in May. Seasonal variation in biomass and production was similar, which peaked in May and June and was lowest in autumn. The annual secondary production rate of A. bifilosa was 114.61 mg C m-3yr-1.Acartia pacifica occurred seasonally in Jiaozhou Bay, increased from June and reached maximum abundance in July at 2356 ind. m-3, which is larger than the other copepod species in this month. This species decreased abruptly to a low abundance of 196 ind. m-3 in August and was absent in Jiaozhou Bay after November. This species concentrated in the north of the bay in June when they firstly occurred in Jiaozhou Bay, and then partly distributed in the south of the bay in July. Population abundance decreased from the north to the south but was not found in the outer bay. EPR of A. pacifica was successive during the period they occurred in Jiaozhou Bay and peaked in June at 37.2 eggs female-1day-1, which partly contributed to the high population abundance in July. Seasonal variation in biomass and production was similar and peaked in July. The annual secondary production rate of A. pacifica was 45.63 mg C m-3yr-1.The integrated annual copepod secondary production rate for these four species was estimated as ~320 mg C m-3 yr-1.