Control of Suitability of the Culture Daphnia magna Straus for Bioassays of Aquatic Environments, Taking into Account Demographic Indicators of Model Populations

Anna Olkova

doi:10.3390/w13010047

Abstract

The purpose of this work was to experimentally determine conditional reference demographic indicators of laboratory populations of Daphnia magna Straus (1820). These indicators can be used when determining suitability of the aquaculture for bioassays of aquatic environments. The experiments were carried out with parthenogenetic clones of D. magna, the temperature of the environment was 20 °C, the light period was 12 h. It was found that the maximum lifetime of crustaceans is observed in groups with a density of 25 individuals/dm3. In these groups, other demographic characteristics of D. magna such as the day of the first offspring (10 ± 2 days), average lifetime (79.7 ± 1.0 days), specific fertility (74.3 ± 2.4 days) and other related parameters of well-being were established. Then, it was showed that the culture of D. magna, having the necessary sensitivity to the model toxicant K2Cr2O7, can significantly differ in demographic characteristics from the conventional reference groups. Audit of the conditions of keeping this aquaculture revealed a complex reason for the unsatisfactory state of D. magna: the lack of daily aquaculture care and increased concentration of nitrate ions in the cultivation water. Therefore, regular monitoring of D.magna demographic characteristics can complement procedures of standardization of test-cultures. This will contribute to improving the accuracy of bioassay results.

Highlights

At present, the pollution of environmental components is characterized by the appearance of new toxicants, multicomponent emissions and discharges, the transformation of pollutants in the air, water and soil, and other complex processes
Bioassays allow one to determine the integral toxicity of the studied environment and extrapolate the data obtained to real ecosystems
The objectivity of bioassay results largely depends on the level of “reliability” of the test cultures used

Summary

Introduction

The pollution of environmental components is characterized by the appearance of new toxicants (nanomaterials, new polymers, medical substances), multicomponent emissions and discharges, the transformation of pollutants in the air, water and soil, and other complex processes. The need to combine chemical methods and bioassays is a generally recognized trend in planning environmental studies [1,2,3]. Bioassays allow one to determine the integral toxicity of the studied environment and extrapolate the data obtained to real ecosystems. It is necessary to take into account the sensitivity of various biological species to toxicants, the adaptive capabilities of organisms in the environment, as well as the action of a complex of abiotic and biotic factors. The objectivity of bioassay results largely depends on the level of “reliability” of the test cultures used. Scientists at Moscow State University (Moscow, Russia) propose to solve the problem of providing bioassay laboratories with standardized test cultures by forming a single national bank of test cultures, which would guarantee that the test culture meets the specified criteria [4]

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