Using chlorophyll a fluorescence to detect the onset of anthracene photoinduced toxicity in Lemna gibba, and the mitigating effects of a commercial humic acid

Article Abstract:

Possible mitigating effects of a commercial humic acid, Aldrich AHA, on development of anthracene photoinduced toxicity to the duckweed Lemna gibba has been studied using room- and low-temperature chlorophyll fluorescence assay. Exposure lasted 1-48 hours to look at changes over time in chlorophyll degradation and chlorophyll a fluorescence induction. AHA ameliorated photoinduced toxicity of anthracene and on the other hand delayed the complete inhibition of t(sub.1/2) by 1-24 hours, not permanently protecting the plants from anthracene damage to photosystem 2 (PS2). It seems that AHA may delay but not prevent the entrance of intact anthracene or its photooxidized byproducts under the given exposure conditions. Natural levels of ultraviolet (UV) light enhance the toxicity of polycyclic aromatic hydrocarbons (PAHs) to aquatic animals and plants. Little has been done to find out how much dissolved organic carbon (DOC) controls PAH toxicity or bioavailability where natural UV light levels prevail.

Canada, Usage, Ultraviolet radiation, Humic acid, Humic acids, Polycyclic aromatic compounds, Fluorimetry, Lemnaceae

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Synergism and antagonism among multiple stressors

Article Abstract:

Antagonism and synergism among multiple environmental stressors have been studied through use of simple, additive, and multiplicative comparative effects models. Model predictions were compared to results of laboratory experiments measuring interactions among toxin exposure, thermal stress and low food on reproduction and survival of two cladoceran zooplankton species. The experiments are especially applicable to episodic stresses such as those associated with short-term heat waves. In rare cases interaction among stressors cut down on effects of the worst stressor. Most multiple stress effects were antagonistic, not as severe as predicted.

United States, Evaluation, Biological models, Toxins, Thermal stresses

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