The influence of ionic concentration on population parameters, development time, activity, and respiration rate of Arctodiaptomus spinosus (Daday) (Calanoida, Copepoda).

For A. spinosus, significant correlations were found between population parameters and the ecological parameters of alkalinity and temperature. For the birth rate, 43.33% of variance is explained by alkalinity and 56.33% by alkalinity and temperature. Alkalinity, and alkalinity and temperature combined account for 48.22% and 70.23% respectively of the observed variances in nauplii hatching. It was demonstrated that, provided sufficient time for adaptation is allowed, the activity of individuals is not affected by differences in the alkalinity of the medium within the normal range of concentration. Embryonic development does not appear to be influenced by the ionic concentration, but significant increases in time of development of the nauplii (at alkalinity 100 meq/l: 8.8 days/20°C) and of the copepodites (at alkalinity 100 meq/l: 12.6 days/20°C) were recorded at both low and high ionic concentrations. The lowest respiration rates (3.7 nl O2·h-1·μg dw-1/20°C) occurred at an alkalinity of 100 meq/l. Rates increased at lower (10 meq/l: 5.7 nl) and at higher (400 meq/l: 11.9 nl) alkalinities.