Title: Chronic herbicide exposures affect the sensitivity and community structure of tropical benthic microalgae
Abstract: The effects of prolonged exposure to low concentrations of herbicides on tropical periphyton (biofilm) communities are largely unknown. Tropical estuarine biofilms established in microcosms were therefore exposed to diuron (photosystem-II-inhibitor) at 2–16 μg L−1 for 4 weeks. The biofilms, consisting of diatoms, filamentous brown algae and cyanobacteria, developed a tolerance to diuron during this period as measured by Phyto-PAM fluorometry. Microscopy and pigment analysis revealed that this decrease in sensitivity was accompanied by a shift in species composition towards communities dominated by diatoms. The combination of techniques enabled the first identification of pollution-induced community tolerance (PICT) in tropical estuarine periphyton in response to chronic herbicide exposures. Community composition changed compared to controls at environmentally relevant concentrations of 1.6 μg L−1, while development of PICT was evident at 6.5 μg L−1 diuron, with no recovery (over 2 weeks) in uncontaminated water, indicating chronic pollution induced shifts in community structure. [Marie Magnusson, Kirsten Heimann, Michael Ridd &Andrew P. Negri (2011). Chronic herbicide exposures affect the sensitivity and community structure of tropical benthic microalgae.Marine Pollution Bulletin, online 22 October, dx.doi.org/10.1016/j.marpolbul.2011.09.029]