Comparative toxicity of nine metals to two Malaysian aquatic dipterian larvae with reference to sediment composition

Abstract

A study was conducted on the effects of sediment type in modifying the toxicity of heavy metals to chironomus and culicoides larvae. Three types of sediment were obtained from three locations within the University Malaysia Terengganu compound and analyzed for sediment type. Based on the analysis, the sediment samples were classified as silt loam, silty–clay loam, and loam. Sediment toxicity tests were conducted following the standard methods of ASTM (2005). Toxicity studies using the three sediment samples were conducted to determine if sediment type affected the toxicity of heavy metals to the two dipterian larvae. The LC₅₀ of the different heavy metals was observed to vary between the three sediment types. In the case of zinc, the LC₅₀ value was observed to be 38.53 mg L⁻¹ for silt loam, 42.22 mg L⁻¹ for silty-clay loam and 70.99 mg L⁻¹ for loam, in the case of Chironomus plumosus. This trend was observed for all nine heavy metals tested, as well as for both dipterian larvae. The data indicate that sediment type plays a role in the manner in which these organisms react to pollutants entering their habitat.

Keywords:

• sediment
• toxicity
• heavy metals
• Chironomids
• Culicoids