Research papers Effects of a surfacing effluent plume on a coastal phytoplankton community Kristen M. Reifel a,n , Alina A. Corcoran b,1 , Curtis Cash c , Rebecca Shipe d , Burton H. Jones a,e a Marine Environmental Biology, Department of Biological Sciences, University of Southern California, 3616 Trousdale Parkway, Los Angeles, CA 90089, United States b Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA 90095, United States c City of Los Angeles Environmental Monitoring Division, 12000 Vista del Mar, Playa del Rey, CA 90293, United States d Institute of the Environment and Sustainability, University of California Los Angeles, La Kretz Hall, Suite 300, Los Angeles, CA 90095, United States e Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia article info Article history: Received 29 September 2012 Received in revised form 24 March 2013 Accepted 3 April 2013 Available online 15 April 2013 Keywords: Akashiwo sanguinea Cochlodinium sp. Lingulodinium polyedrum Coastal water quality Wastewater Pacific Ocean abstract Urban runoff and effluent discharge from heavily populated coastal areas can negatively impact water quality, beneficial uses, and coastal ecosystems. The planned release of treated wastewater (i.e. effluent) from the City of Los Angeles Hyperion Wastewater Treatment Plant, located in Playa del Rey, California, provided an opportunity to study the effects of an effluent discharge plume from its initial release until it could no longer be detected in the coastal ocean. Non-metric multi-dimensional scaling analysis of phytoplankton community structure revealed distinct community groups based on salinity, temperature, and CDOM concentration. Three dinoflagellates (Lingulodinium polyedrum, Cochlodinium sp., Akashiwo sanguinea) were dominant (together 450% abundance) prior to the diversion. Cochlodinium sp. became dominant (65–90% abundance) within newly surfaced wastewater, and A. sanguinea became dominant or co-dominant as the effluent plume aged and mixed with ambient coastal water. Localized blooms of Cochlodinium sp. and A. sanguinea (chlorophyll a up to 100 mg m -3 and densities between 100 and 2000 cells mL -1 ) occurred 4–7 days after the diversion within the effluent plume. Although both Cochlodinium sp. and A. sanguinea have been occasionally reported from California waters, blooms of these species have only recently been observed along the California coast. Our work supports the hypothesis that effluent and urban runoff discharge can stimulate certain dinoflagellate blooms. All three dinoflagellates have similar ecophysiological characteristics; however, small differences in morphology, nutrient preferences, and environmental requirements may explain the shift in dinoflagellate composition. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction The effects of point and non-point pollution sources (e.g. stormwater runoff, other forms of urban runoff, sewage discharge, effluent discharge) on coastal water quality are well known (Ahn et al., 2005; Jickells, 1998; Lotze et al., 2006; Stein and Cadien, 2009). Coastal waters provide numerous beneficial uses including recreation, commercial and sport fisheries, marine habitat, com- merce and transportation, and esthetic enjoyment. With high concentrations of sediment or settleable solids, nutrients, and even human pathogens, runoff and effluent discharge from heavily developed areas often negatively impact these uses (Anderson et al., 2008; Clarke et al., 2006; Davies-Colley and Smith, 2001; Geesey, 1993; Lyon and Sutula, 2011). Nutrient loading into the coastal ocean from urban runoff and from submarine wastewater or effluent outfalls can stimulate phytoplankton growth and production, sometimes resulting in nuisance or harmful algal blooms (Dagg and Breed, 2003; Glibert et al., 2005; Hu et al., 2004; Riegman, 1995). In particular, reduced and organic nutrient forms typically prevalent in anthropogenic sources have been linked to harmful algal blooms (Glibert et al., 2006; Heisler et al., 2008). The Hyperion Wastewater Treatment Plant (WWTP), located in Playa del Rey, California, is one of the largest wastewater treat- ment plants on the west coast of the United States and is one of the four municipal wastewater treatment facilities that discharge Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/csr Continental Shelf Research 0278-4343/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.csr.2013.04.012 n Corresponding author. Current address: Department of Plant Pathology, Oregon State University, Corvallis, OR 97331, United States. Tel.: +1 541 737 1355; fax: +1 541 737 3573. E-mail addresses: kmreifel@gmail.com, reifelk@science.oregonstate.edu (K.M. Reifel). 1 Current address: Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, 100 Eighth Avenue SE, St. Petersburg, FL 33710, United States. Continental Shelf Research 60 (2013) 38–50