From River to Lake: Phosphorus partitioning and algal community compositional changes in Western Lake Erie Thomas B. Bridgeman a, ⁎, Justin D. Chaffin a, 1 , Douglas D. Kane b, 2 , Joseph D. Conroy c, 3 , Sarah E. Panek a, 1 , Patricia M. Armenio a a Dept. of Environmental Sciences and Lake Erie Center, University of Toledo, 6200 Bayshore Rd., Oregon, OH 43616, USA b Natural Science and Mathematics Division, Defiance College , 701 N. Clinton St., Defiance, OH 43512, USA c Aquatic Ecology Laboratory, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, 1314 Kinnear Road, Columbus, OH 43212, USA abstract article info Article history: Received 30 March 2011 Accepted 30 August 2011 Available online xxxx Communicated by Hunter Carrick Index words: Lake Erie Maumee River Phosphorus Harmful algal blooms Microcystis Lyngbya wollei The Maumee River is an important source of phosphorus (P) loading to western Lake Erie and potentially a source of Microcystis seed colonies contributing to the development of harmful algal blooms in the lake. Herein, we quan- tified P forms and size fractions, and phytoplankton community composition in the river–lake coupled ecosystem before (June), during (August), and after (September) a large Microcystis bloom in 2009. Additionally, we deter- mined the distribution and density of a newly emergent cyanobacterium, Lyngbya wollei, near Maumee Bay to es- timate potential P sequestration. In June, dissolved organic phosphorus (DOP) was the most abundant P form whereas particulate P (partP) was most abundant in August and September. Green algae dominated in June (44% and 60% of total chlorophyll in river and lake, respectively) with substantial Microcystis (17%) present only in the river. Conversely, in August, Microcystis declined in the river (3%) but dominated (32%) the lake. Lake phy- toplankton sequestered b 6% of water column P even during peak Microcystis blooms; in all lake samples b 112 μm non-algal particles dominated partP. Lyngbya density averaged 19.4 g dry wt/m 2 , with average Lyngbya P content of 15% (to 75% maximum) of water column P. The presence of Microcystis in the river before appearing in the lake indicates that the river is a potential source of Microcystis seed colonies for later lake blooms, that DOP is an impor- tant component of early summer total P, and that L. wollei blooms have the potential to increase P retention in nearshore areas. © 2011 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Introduction Summer blooms of the planktonic toxic cyanobacterium Microcystis aeruginosa have become more frequent in western Lake Erie since the mid-1990s (Conroy et al., 2005). In high-bloom years, surface scums of Microcystis may stretch for hundreds of square kilometers and pro- duce concentrations of microcystin toxin that exceed World Health Or- ganization guidelines for human consumption (Rinta-Kanto et al., 2005). Rapid growth of Microcystis in the water column begins in early summer as water temperatures increase above 15 °C (Reynolds, 1973) and blooms typically end in early fall as water temperatures decline and Microcystis colonies sink and settle on the lake floor (Thomas and Walsby, 1986). During the growing season, the development of Microcystis blooms is closely linked with available nutrient concentrations, especially nitro- gen (N) and phosphorus (P). In nutrient-poor waters, Microcystis is gen- erally out-competed for P due to the higher P uptake kinetics of green algae and diatoms (Baldia et al., 2007; Tilman et al., 1986). Cyanobac- teria have a total phosphorus (TP) threshold of 0.010 mg/L (Steinberg and Hartmann, 1988) and the probability that cyanobacteria will be- come dominant over other phytoplankton species increases with in- creasing TP to a maximum probability of about 80% when lake TP reaches or exceeds 0.100 mg/L (Downing et al., 2001). In laboratory studies, Microcystis growth increased linearly with TP and reached a plateau at 0.220 mg/L TP (Baldia et al., 2007). In addition to increasing overall Microcystis growth rates, increasing P concentration also pro- motes the growth of toxic versus non-toxic strains of Microcystis (Davis et al., 2009), thereby increasing the toxicity of the population. Toxicity may also be increased by factors such as iron deficiency and the formation of surface scums that increase the synthesis of toxin (Sevilla et al., 2008; Wood, et al., 2011). A second major harmful algal bloom (HAB) species, the filamentous benthic mat-forming cyanobacterium, Lyngbya wollei, became established Journal of Great Lakes Research xxx (2011) xxx–xxx ⁎ Corresponding author. Tel.: + 1 419 530 8373/5499 (campus). E-mail addresses: Thomas.bridgeman@utoledo.edu (T.B. Bridgeman), Justin.Chaffin@rockets.utoledo.edu (J.D. Chaffin), dkane@defiance.edu (D.D. Kane), joseph.conroy@dnr.state.oh.us (J.D. Conroy), sarah.panek@rockets.utoledo.edu (S.E. Panek), Patricia.Cope@rockets.utoledo.edu (P.M. Armenio). 1 Tel.: +1 419 530 8384. 2 Tel.: +1 419 783 2593. 3 Present address: Inland Fisheries Research Unit, Ohio Department of Natural Resources, Division of Wildlife, 10517 Canal Road, SE, Hebron, OH 43025, USA. Tel.: +1 740 928 7034x226. JGLR-00388; No. of pages: 8; 4C: 0380-1330/$ – see front matter © 2011 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jglr.2011.09.010 Contents lists available at SciVerse ScienceDirect Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr Please cite this article as: Bridgeman, T.B., et al., From River to Lake: Phosphorus partitioning and algal community compositional changes in Western Lake Erie, J Great Lakes Res (2011), doi:10.1016/j.jglr.2011.09.010