Interaction Among Copper Toxicity, Temperature and Salinity on the Population Dynamics of Brachionus Rotundiformis (Rotifera)

Abstract

Heavy metals may interact with ecological factors such as temperature, food level and salinity, causing both mortality and reduced reproduction in organisms. Among different heavy metals, copper compounds are commonly used for eliminating algal blooms in aquaculture tanks. At certain concentrations, copper is toxic to rotifers. In the present work, we evaluated the combined effects of salt concentrations (2.5 and 5.0 g l )1 NaCl), copper levels (0, 0.03125, 0.0625, 0.125 and 0.25 mg l )1 as CuCl 2 ) and two temperatures (20 and 25°C) on the population growth of B. rotundiformis using Chlorella as the algal food (at 0.5 · 10 6 cells ml )1 for every 24 h). Regardless of salinity and temperature, copper at concentrations as low as 0.03 mg l )1 had an adverse effect on the population growth of rotifers and above 0.125 mg l )1 , the populations did not grow. The effect of the toxicant on B. rotundiformis was more severe at 25°t han at 20°C at lower salinity. In general, we observed peak densities of rotifers around day 12 at 20°C but 6-8 days earlier at 25°C. Peak population densities of B. rotundiformis in the controls at the salinity of 2.5 g l )1 ranged from 90 to 180 ind. ml )1 , depending on temperature; at a salinity of 5.0 g l )1 , these were lower. The population growth rates, r, in our study varied from +0.31 to -0.12 depending on the test conditions. There was a significant impact of temperature, salinity and toxicity level on the population growth rate of B. rotundiformis. Our results suggested that even narrow changes in salinity could negatively influence the toxicity of heavy metal on the population growth rates of B. rotundiformis.

Population growth of Brachionus macracanthus (Rotifera) in relation to cadmium toxicity: Influence of algal (Chlorella vulgaris) density

“…In addition, it is also more sensitive than other species of Brachionus (B. calyciflorus: 1.3 mg L −1 ; B. plicatilis: 39 mg L −1 . [21] Population growth curves of B. macracanthus in general are similar to many other brachionids (B. calyciflorus [18] ; B. rotundiformis: [22] ), where rotifers reach peak population abundances in about 10-15 days before declining, similar to the one observed here. A decrease in population growth with increase in Cd levels has been documented in other zooplankton species.…”

Effect of Cadmium Level and Exposure Time on the Competition between Zooplankton Species Moina macrocopa (Cladocera) and Brachionus calyciflorus (Rotifera)

“…[1] Peak population density and the rate of population increase are two population level variables sensitive to stress from competition and pollution. [18,22] It is known that both these variables generally decrease with increasing toxicant levels. [23] Peak population density is also related to the body size of zooplankton species.…”

Temperature-dependent toxicities of four common chemical pollutants to the marine medaka fish, copepod and rotifer

“…With elevated temperatures, copepods also showed less tolerance to other pollutants, such as oil water accommodated fractions (8.5-31.2°C;Jiang et al 2012) and potassium dichromate (13-25°C; Larrain et al 1998). Cu toxicity to the rotifer Brachionus rotundiformis has been reported to increase with increasing temperature (20-25°C; Gama-Flores et al 2005). Studies from Snell and Persoone (1989) and Cairns et al (1978) also demonstrated that toxicities of potassium dichromate to the rotifer Brachionus plicatilis as well as chromate and arsenate to the rotifer Philodina roseola increased when temperature was increased over a range from 10 to 31°C and from 5 to 35°C, respectively.…”