Physiological responses of estuarine phytoplankton to ultraviolet light-induced fluoranthene toxicity

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are common pollutants associated with urbanization and suburbanization in estuarine systems, but little is known about their effects on the physiological properties of microalgae. We examined the effects of ultraviolet (UV)-activated fluoranthene toxicity on (a) the growth, chlorophyll a content cell −1, and pigment composition of axenic Ankistrodesmus sp. (an estuarine benthic green microalga) and (b) the phytoplankton population growth and pigment composition of natural communities from an urbanized (Murrells Inlet) vs. forested (North Inlet) salt marsh estuary. The zeaxanthin/violaxanthin ratio increased in Ankistrodesmus sp. cultures exposed to UV light in the presence of fluoranthene, supporting the hypothesis that xanthophyll cycling is an energy dissipative response to photoinduced PAH toxicity in this species. Exposure of natural communities to the combination of UV light and fluoranthene resulted in decreased chlorophyll production and increased zeaxanthin violaxanthin −1 in samples from the urbanized estuary (Murrells Inlet), but not North Inlet, suggesting that phytoplankton in the former “fluoranthene-impacted” estuary were more susceptible to fluoranthene toxicity. Consideration of xanthophyll cycling as a microalgal response to UV-activated PAH toxicity has implications to understanding the influence of these contaminants on microbial food web structure and ecosystem production.