Alkyl Polyglucoside Compound Influences Freshwater Plankton Community Structure in Floating Mesocosms

Synthetic surfactants in detergents and cleaners commonly contaminate freshwater systems, therefore developing low-toxicity alternatives derived from natural products such as alkyl polyglucosides (APGs), is important. Although APGs degrade rapidly and reduce chemical exposure time, they can still have toxic effects on aquatic organisms, and microbial oxygen consumption increases during the process of biodegradation. Despite being 2-12 times less toxic than synthetic surfactants such as alcohol ethoxylate, it is still toxic to aquatic organisms, including primary producers (such as microalgae) and zooplankton. Zooplankton are also affected by APG, and species may demonstrate different sensitivities to APGs direct toxicity. Species not affected by direct toxicity may be affected by trophic interaction such as removal of a food source or changes in predator densities, potentially resulting in changes in zooplankton community structure. Determining the effects of APG toxicity on multiple trophic levels of the plankton community under environmental conditions requires an in situ mesocosm approach to provide ecologically relevant information for how a pollutant affects aquatic systems. I hypothesized that APG-containing products adversely affect plankton communities via direct toxicity to algae and zooplankton, as well as indirectly through reduced food availability to zooplankton and water quality. Floating mesocosms (440 L) were deployed in a blackwater pond in southeast Georgia, USA and dosed with 0, 0.01, 2.5, 5, or 10 mg L-1 APG. Zooplankton community composition, phytoplankton abundance (as chlorophyll-a), and dissolved oxygen (DO) were determined weekly for one month. Both plankton abundance and community composition were altered following exposure to APG concentrations of 2.5 mg L-1 or greater. Despite reductions in DO (4.4-16.7%), DO never dropped below 5.70 mg L-1, but the observed reductions \u3e10% in treatments of 2.5 mg L-1 APG and greater could reach stressful levels in periods of higher temperatures. Chlorophyll-a also declined (24.6-81.1%) with increasing APG concentration resulting in decreased autochthonous carbon production. Changes in the zooplankton community likely resulted from differential sensitivity among zooplankton to APG. The decrease in zooplankton abundance was primarily due to loss of copepods and a subsequent shift toward domination by small-bodied cladocerans (Bosmina sp.). Thus APG-induced decreases in DO availability, losses of autochthonous carbon production, and shifts from invertebrate predator (copepod) dominated communities to cladocerans has important implications for food availability and quality to higher trophic levels such as planktivorous fishes