Combined effects of sediment and lead (PbCl) on the demography of Brachionus patulus (Rotifera: Brachionidae)
Garcca-Garcca, G.; Picazo-Paez, E.A.; Nandini, S.; Sarma, S.S.S.
Hydrobiologia 593(1): 209-218
ISSN/ISBN: 0018-8158 Accession: 015305302
We studied the response of Brachionus patulus to different concentrations of the heavy metal Pb in the presence and absence of sediments. We conducted acute (LC) and chronic (life table demography and population growth) toxicity tests using sediment levels of 0, 30 and 280 mg l-p# (=0, 17 and 170 NTU) and Pb at 0, 0.06 and 0.6 mg l-p#. Experiments were conducted at 20 pl 1pC on a horizontal shaker and algal food (Chlorella vulgaris) was added at a density of 1.0 x 10e cells ml-p#. The median lethal concentration (LC pl 95% Confidence intervals) of PbCl for B. patulus was 6.15 pl 1.08 mg l-p#. Age-specific survivorship and fecundity curves showed increase in turbidity level resulted in decreased survival and offspring production of the rotifers. Increase in Pb concentration too had a negative effect on the survival and reproductive output of B. patulus. Statistically, average lifespan, life expectancy at birth, gross and net reproductive rates and the rate of population increase were all significantly influenced by the concentration of Pb, turbidity level as well as the interaction of Pb concentration x turbidity level. Rotifers exposed to 170 NTU did not grow regardless of the heavy metal concentration in the medium. Similarly, B. patulus exposed to 0.6 mg l-p# Pb did not survive beyond 10 days regardless of the turbidity level in the medium. The rate of population increase of B. patulus derived from the growth experiments was negative in all treatments containing Pb as low as 0.06 mg l-p# or turbidity level as low as 17 NTU. In treatments containing Pb or sediments, there existed no relation between the egg ratio and the population density.