The Effects of 2, 4-Dichlorophenoxyacetic Acid, Pentachlorophenol and Mixtures of These on an Aero-aquatic Fungus

ABSTRACT

The biocides pentachlorophenol (PCP) and 2, 4-dichlorophenoxyacetic acid (2, 4-D) are applied in oil or oil-based carrier formulations. In lentic systems these accumulate in the surface microlayer, the top 60–150 um of the water. We have designed a unique bioassay system involving the germination of buoyant propagules of an aero-aquatic fungus, Pseudoaegerita matsushimae, which can assess the toxicity of contaminants present in this zone.

PCP dissolved in the oil emulsion carrier and oil carrier alone inhibited propagule germination. Mixtures of 1, 2 and 3 parts 2, 4-D to 1 part PCP stimulated germination at low concentrations but inhibited germination at higher concentrations. Mixtures of 2 and 3 parts PCP to 1 part 2, 4-D inhibited germination at all concentrations tested. Pesticide mixtures differed from their components with respect to net toxicity.