Ring test for whole-sediment toxicity assay with a benthic marine diatom

Abstract

This work presents the results of an interlaboratory proficiency exercise for whole-sedimenttoxicityassays with the benthicmarinediatomCylindrotheca closterium. An assay protocol was established and followed by all participating laboratories. Cell growth after 72 h exposure was the endpoint used. Four sediment samples of unknown toxicity were assayed. The main problem encountered during this exercise was the differences in the cell growth of algae exposed to reference sediment. Those differences may be associated with changes in the physiological status of the initial culture due to temperature changes during transport to the other laboratories. In general, the method proposed presented good replicability (precision between replicates) and reproducibility (interlaboratory precision). Around 80% (17 out of 21) of results obtained were classified as satisfactory (Z-scores < 2). The whole-sedimentassay with C. closterium presented here can be considered sufficiently successful for possible use as a standard toxicitytest. The assay is simple to perform, the proposed species is ecologically relevant as an integral component of microphytobenthos, and is widely distributed around the world. These positive factors suggest that the whole-sedimentassay with the benthicmarinediatomC. closterium can be used as a reliable tool in marinesediment quality assessment.