Colony formation in three species of the family Scenedesmaceae (Desmodesmus subspicatus, Scenedesmus acutus, Tetradesmus dimorphus) exposed to sodium dodecyl sulfate and its interference with grazing of Daphnia galeata

By mimicking the info-chemicals emitted by grazers, the common anionic surfactant sodium dodecyl sulfate (SDS) can induce colony formation in the green algal genus Scenedesmus at environmentally relevant concentrations. The morphogenetic effects can hinder the feeding efficiency of grazers, reducing energy flow along the pelagic food chain from Scenedesmus to consumers. Despite this potential ecological risk, few studies exist on whether the SDS-triggered induction of colonies is common in other species of the family Scenedesmaceae. Here, we investigated the effects of SDS on the growth and morphology of three species of Scenedesmaceae (Desmodesmus subspicatus, Scenedesmus acutus, and Tetradesmus dimorphus) and on the clearance rates of Daphnia galeata grazing on the SDS-induced colonies. SDS triggered colony formation in all algal species at concentrations nonlethal to them; however, the induction levels of colony formation were generally lower than for those in the Daphnia culture medium. We also found that the SDS-induced colonial algae reduced D. galeata clearance rates. Our results highlight the potential effect of SDS on the Daphnia–Scenedesmaceae system by evoking the morphological response of Scenedesmaceae at concentrations below those that exert toxicity. Such disruptive effects of pollutants on predator–prey interactions should be considered within the framework of ecological risk assessments.

Determination of the Ecotoxicity of Herbicides Roundup® Classic Pro and Garlon New in Aquatic and Terrestrial Environments

Herbicides help increase agricultural yields significantly, but they may negatively impact the life of non-target organisms. Modifying the life cycle of primary producers can affect other organisms in the food chain, and consequently in the whole ecosystem. We investigated the effect of common herbicides Roundup® Classic Pro (active substance glyphosate) and Garlon New (triclopyr and fluroxypyr) on aquatic organisms duckweed Lemna minor and green algae Desmodesmus subspicatus, and on the enzymatic activity of soil. We also compared the effects of Roundup® Classic Pro to that of a metabolite of its active substance, aminomethylphosphonic acid (AMPA). The results of an algal growth test showed that AMPA has a 1.5× weaker inhibitory effect on the growth of D. subspicatus than the Roundup formula, and the strongest growth inhibition was caused by Garlon New (IC50Roundup = 267.3 µg/L, IC50Garlon = 21.0 µg/L, IC50AMPA = 117.8 mg/L). The results of the duckweed growth inhibition test revealed that Roundup and Garlon New caused 100% growth inhibition of L. minor even at significantly lower concentrations than the ready-to-use concentration. The total chlorophyll content in the fronds was lowest when Garlon New was used. The highest dehydrogenase activity was observed in soil treated with Garlon New, and the lowest in soil treated with Roundup® Classic Pro. The results of this study showed that all three tested substances were ecotoxic to the tested organisms.