Effects of naturally occurring aquatic organic fractions on cadmium toxicity to Simocephalus serrulatus (daphnidae) and Gambusia affinis (poeciliidae)

Cd toxicity to Simocephalus serrulatus and Gambusia affinis in soft well water, highly organic pond water and well water containing various sized organic fractions isolated from pond water was determined and compared to Cd binding capacity of each water type and Cadmium 96 h LC 30 values cannot be predicted from Cdbinding capacities determined by selective ion electrode.

Abstract

Cadmium toxicity to Simocephalus serrulatus and Gambusia affinis in soft well water, highly organic pond water and well water containing various sized organic fractions isolated from pond water was determined and compared to Cd binding capacity of each water type. Pond organics were separated into three nomial molecular diameter fractions (> 0.0183 μm; 0.0183 0.0032 μm; 0.0032 0.0009 μm) using ultrafiltration. Cadmium binding capacity was determined using selective ion electrodes. Pond water and organic fractions bound Cd. reducing the amount of free Cd2+ as determined by Cd selective ion electrode. Whole pond water reduced Cd toxicity to S. serrulatus but had little effect on Cd toxicity to G. affinis. The three larger molecular diameter organic fractions reduced Cd toxicity to S. serrulatus, while the smallest fraction slightly increased Cd toxicity. Cadmium 96 h LC30 values cannot be predicted from Cd binding capacities determined by selective ion electrode.