Influence of growth conditions on the results obtained in algal toxicity tests

Abstract

The influence of test conditions on results from algal growth inhibition tests was investigated for the toxicants atrazine, 3,4‐dichloroaniline, 3,5‐dichlorophenol, and potassium dichromate. Emphasis was put on the following four main factors: light, temperature, nitrogen source, and pH. The green alga Selenastrum capricornutum was grown in batch cultures, and the toxic response was measured as reduction in average growth rate, relative to controls. Multifactor experiments were carried out to investigate the effects of the above four factors as well as the interactions between them: light intensity (44 and 198 μE/m2/s), temperature (16 and 26°C), nitrogen source (NH +4 and NO −3), and pH of the medium (7.5 and 8.6). Within the data set generated, the highest and lowest median effective concentration estimate differed by a factor of 3.8. The sensitivity of the test system to 3,4‐dichloroaniline, potassium dichromate, and 3,5‐dichlorophenol was less under light limitation than under light saturation. Conversely, with the photosynthetic inhibitor atrazine a reduced sensitivity was found at high light intensity, which, however, was high enough to cause slight photoinhibition. The inhibitory response to the weak organic acid 3,5‐dichlorophenol was less at the high than at the low pH level, which stems from the fact that neutral species of ionizable compounds are usually more toxic than charged species. No effect of the nitrogen source on inhibitory responses could be ascertained, and temperature influenced the results only indirectly by interacting with light (the saturation intensity increases with temperature). It is concluded that the light intensity in standardized algal toxicity tests could preferably be increased to achieve light‐saturated photosynthesis as this may potentially reduce test result variability.

Toxicity evaluation of natural samples from the vicinity of rice fields using two trophic levels

“…Although ammonia is a recommended nitrogen source for algae growth (Mayer et al 1998), under certain circumstances (e.g. pH increase), there is a chance that the ion ammonium (NH + 4 ) dissociates to form un-ionised ammonia (NH 3 ), which had been demonstrated for a long time to exert negative effects on microalgae growth rate (e.g.…”

Farklı Malathion Konsantrasyonlarının Kültürel Koşullarda Alg Büyümesi Üzerine Etkileri

“…For the survival of algal species, they must maintain a high rate of photosynthesis when exposed to pesticides (Eullaffroy and Vernet, 2003). Mayer and Jensen (1995) reported examples of triazine-induced increase in algal chlorophyll content in the Selenastrum capricornutum species. This can be interpreted as a tolerance mechanism (Francois and Robinson, 1990).…”

Optimization of growth conditions for laboratory and field assessments using immobilized benthic diatoms

“…1)-for example, if at 23°C, a full light cycle seems to produce better growth than a 12 L :12 D cycle, at 15°C the opposite seems to occur. Indeed, Mayer et al (1998) observed a more conspicuous effect of temperature variations on the growth of Selenastrum capricornutum than that triggered by light intensity, nitrogen source or pH. Similarly, Lewis et al (2002) verified improved growth rates of the diatom Achnanthes longipes (free cells) as temperature increased from 10°C up to 26°C.…”