Evidence against fluvial seeding of recurrent toxic blooms of Microcystis spp. in Lake Erie’s western basin Olga A. Kutovaya a,1 , Robert Michael L. McKay a,2 , Benjamin F.N. Beall a,2 , Steven W. Wilhelm b,3 , Douglas D. Kane c,4 , Justin D. Chaffin d,5 , Thomas B. Bridgeman d,5 , George S. Bullerjahn a,2, * a Department of Biological Sciences, Bowling Green State University, Life Sciences Building, Bowling Green, OH 43403, USA b Department of Microbiology, The University of Tennessee, Knoxville, TN 37996-0845, USA c Natural Science and Mathematics Division, Defiance College, 701 North Clinton Street, Defiance, OH 43512, USA d Department of Environmental Sciences, University of Toledo, Lake Erie Center, 6200 Bayshore Road, Oregon, OH 34618, USA 1. Introduction Western Lake Erie (Laurentian Great Lakes) has been increas- ingly affected by toxic Microcystis spp. blooms in recent decades (Brittain et al., 2000; Murphy et al., 2003; Rinta-Kanto et al., 2005; Wang et al., 2009). Recognizing the Maumee River as the major source of nutrient inputs (especially phosphorus) to the western basin of Lake Erie (Baker and Richards, 2002), the influence of the river in promoting these blooms cannot be ignored. Indeed, the role of the Maumee River in providing nutrients to support Microcystis spp. growth has been widely accepted as an important factor (Wang et al., 2009; Millie et al., 2009; Rinta-Kanto et al., 2009b; Bridgeman et al., in press; Chaffin et al., 2011), along with temperature and turbidity due to sediment plumes (Brannan, 2009; Wang et al., 2009; J. Chaffin and T. Bridgeman, unpublished data). Less understood, however, are the sources of Microcystis spp. that comprise the major microcystin producers in the lake. Rinta- Kanto et al. (2005), based on qPCR analyses of Microcystis species, suggested that the river could possibly serve as a seed population for toxic blooms. Further, Conroy et al. (2008) proposed the Algal Loading Hypothesis (ALH), where nutrient-replete algae are loaded from riverine systems with high sediment concentrations into the more favorable light conditions of lacustrine systems, such as Lake Erie, and thus can grow rapidly and reach bloom conditions. In support of the ALH, surveys along the Maumee River have identified Microcystis spp. upstream in the early spring (Bridgeman et al., in press). In contrast, analysis of Lake Erie sediments demonstrated the presence of viable toxic Microcystis spp. that were genetically similar to bloom forming populations (Rinta- Kanto et al., 2009a), consistent with studies from other systems showing that Microcystis can overwinter vegetatively in the sediment (Preston et al., 1980; Takamura et al., 1984; Verspagen et al., 2004). Thus, the major reservoir of the toxic blooms in Lake Erie’s western basin remains unresolved. However, it has been Harmful Algae 15 (2012) 71–77 A R T I C L E I N F O Article history: Received 13 June 2011 Received in revised form 30 November 2011 Accepted 30 November 2011 Available online 16 December 2011 Keywords: Microcystis Planktothrix Microcystin Lake Erie Maumee River Cyanobacterial blooms A B S T R A C T For almost two decades, the western basin of Lake Erie has been plagued with recurring toxic algal blooms dominated by the colonial cyanobacterium, Microcystis spp. Since the Maumee River is a major source of nutrients and sediment inputs into the lake, and Microcystis spp. has been identified as a member of the upstream river algal assemblage, the possibility exists that the river Microcystis species serve as a seed population for the toxic blooms occurring in the lake. Genetic profiling of toxic cyanobacteria using the microcystin synthesis gene, mcyA, clearly indicates that the toxic cyanobacteria of the river are distinct from the toxic Microcystis spp. of Lake Erie. Indeed, mcyA sequences are almost exclusively from toxic Planktothrix spp., similar to what has been documented previously for Sandusky Bay. UniFrac statistical analysis of cyanobacterial community composition by comparison of 16S–23S ITS sequences also show that the Maumee River and Lake Erie communities are distinct. Overall, these data show that despite the importance of nutrient inputs and sediments from the river, the toxic cyanobacterial blooms of Lake Erie do not originate from toxic species endemic to the Maumee River and instead must originate elsewhere, most likely from the lake sediments. ß 2011 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 419 372 8527; fax: +1 419 372 2024. E-mail addresses: kolga@bgsu.edu (O.A. Kutovaya), rmmckay@bgsu.edu (R.M.L. McKay), bbeall@bgsu.edu (Benjamin F.N. Beall), Wilhelm@utk.edu (S.W. Wilhelm), dkane@defiance.edu (D.D. Kane), Justin.Chaffin@utoledo.edu (J.D. Chaffin), Thomas.Bridgeman@utoledo.edu (T.B. Bridgeman), bullerj@bgsu.edu (G.S. Bullerjahn). 1 Current address: Environment Canada, 867 Lakeshore Road, P.O. 5050, Burlington, Ontario L7R 4A6, Canada. Tel.: +1 905 836 4746. 2 Tel.: +1 419 372 8527; fax: +1 419 372 2024. 3 Tel.: +1 865 974 0665. 4 Tel.: +1 419 783 2593. 5 Tel.: +1 419 530 8373; fax: +1 419 530 8399. Contents lists available at SciVerse ScienceDirect Harmful Algae jo u rn al h om epag e: ww w.els evier.c o m/lo cat e/hal 1568-9883/$ – see front matter ß 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.hal.2011.11.007