Preface

Lake Ontario was formed as a result of glacial shifting and melting at the end of the most recent ice age. Its name was derived from the First Nations word for “lake of shining waters” or “beautiful Great Lake.” The first documented European to reach the lake was Etienne Brule in 1615. As per tradition, the French named the lake in 1632 first as Lac St. Louis and in 1656 as Lac de St. Louis, probably after Louis XIV. Historian Francis Creuxius called it Lacus Ontarius in 1660. In 1712 Jean-Baptiste de Couagne identified the lake as “Lac Frontenac.”Permanent non-military European settlement began during the American Revolution. As the nearest lake to the Atlantic seaboard of Canada and the US, its population centres are the oldest in the Great Lakes basin such as Kingston, Ontario. The lake became a hub of commercial activity following the war of 1812, with canal building on both sides of the border and heavy travel by lake steamers. Steamer activity peaked in the mid-19th century before competition from railway lines.Lake Ontario is the smallest of the Great Lakes and located at the downstream end. It has a maximum length of 311 km, width of 85 km, an area of 18,960 km2 and an extensive shoreline length of 1168 km (Schertzer, 2003). Its mean and maximum depths are 86 and 244 m, respectively. Its flushing time is about 7.5 years. Every spring the lake is affected by the characteristic lake wide development of the thermal bar which in practice separates the offshore zone (cold, deep, nutrient poor) from the nearshore zone (warmer, shallow, nutrient rich). Total phosphorus levels have been declining and currently are lower than 10 μg l−1. During 2008, the mean phytoplankton biomass and chlorophyll a concentrations were lower in the spring but higher in early summer, reflecting a potential change in the trophic status of the lake.The ecological integrity of Lake Ontario has been a concern for a long time. The lake has experienced significant changes during the past four decades associated with eutrophication, phosphorus reduction programs, toxic chemicals, invasion of exotics with large impacts (Dreissena spp., Round Goby, predatory water fleas), increased water transparency, declines in Alewife, Diporeia, Lake Whitefish and implementation of management practices such as stocking of exotic salmonids, and the control of Sea Lamprey and Double-Crested Cormorants (Mills et al., 2003). However, lake wide biological surveys including multi-trophic and integrated foodweb studies have been limited. Published literature includes the following studies: the International Field Year for the Great Lakes (IFYGL, 1972); lake wide planktonic/primary production surveys of 1970s (Vollenweider et al., 1974); Lake Ontario Nutrient Assessment Study-LONAS (Lean, 1987); and the Lake Ontario Trophic Transfer Study-LOTT (Sprules et al., 1994; Mills et al., 2003; Munawar, 2003). More recent surveys of Lake Ontario were conducted during 2003/2008 and have continued as part of the five-year rotating focus of the binational Coordinated Science and Monitoring Initiative (CSMI) program which has resulted in extensive collaborations among U.S. and Canadian federal, provincial and state agencies around the lake, as well as universities. These surveys were comprehensive, multidisciplinary, multi-trophic and conducted on a lake wide basis. The 2008 program included a nearshore component, published by Makarewicz and Howell (2012).The Lake Ontario portion of this issue focuses on the results of the offshore component of the 2008 study (spring, summer and fall cruises) and results from additional surveys by Ontario Ministry of Natural Resources (OMNR) and the New York State Department of Environmental Conservation (NYSDEC). Most of the articles are based on the 2008 lake wide surveys with the R/V Lake Guardian (U.S. Environmental Protection Agency) and CCGS Limnos (Fisheries and Oceans Canada). Hypotheses and data analyses were discussed at two binational workshops in April 2011 at the Cornell Biological Field Station, and during November 2011 at Fisheries and Oceans, Canada. As a result of these workshops, collaborations were developed resulting in papers co-authored by both U.S. and Canadian scientists with affiliations that span federal, state, and provincial agencies, as well as academia. Plans were also made to organize a special session at the 2012 conference of the International Association for Great Lakes Research (IAGLR). Much of the data are available to download from the Knowledge Network for Biocomplexity (Rudstam et al., 2012a, b). Comparisons are made primarily with the similarly structured 2003/2008 surveys, but also with long-term data available through various agencies and in the literature.Comprehensive publications about Lake Ontario during the past decade include the monograph “State of Lake Ontario” (Munawar, 2003), the review of changes in Lake Ontario from 1975 to 2000 (Mills et al., 2003), and the special issue “Checking the Pulse of Lake Ontario” (AEHMS, 2008, 2009, 2010). This present issue is the most recent addition to the series of articles on the ecology of Lake Ontario and constitutes a substantial addition to our understanding of the lake. It contains eight articles which originated from a Lake Ontario symposium organized during the 2012 IAGLR Conference held in Cornwall, Ontario. The articles focus on a variety of topics, namely: Changes in water qualitySpatial extent and dissipation of deep chlorophyll layerPhytoplankton community: Structure, biodiversity and long term changesZooplankton community: Community changes and vertical redistributionAbundance and distribution of MysisLong term trends in benthic macro invertebrate communityFish species composition, distribution and abundance trendsLake Ontario ecosystem: Current status and future directionsThis compendium of articles provides interesting and unique coverage of the current ecological state of Lake Ontario, as well as a great opportunity to look into future prospects and management strategies. The research conducted under the CSMI banner is an excellent example of binational planning and cooperation which is essential for the organization and implementation of large scale and multi-disciplinary initiatives in the Great Lakes. We hope this issue will provide insights into the structure and function of Lake Ontario's ecosystem to fill in existing knowledge gaps and to support the sustainable management of this precious resource in the future.We sincerely thank the AEHMS and IAGLR for jointly sponsoring the Lake Ontario symposium at the Cornwall conference. The financial support of Fisheries and Oceans Canada, Environment Canada and the U.S. EPA is gratefully acknowledged for the publication of this special issue. Thanks are also due to Fred Luckey of the U.S. EPA for his continued interest in the project, as well as for procurement of partial funding for the publication of this issue. Finally, we thank I. F. Munawar, Managing Editor, and the editorial staff of AEHMS, namely, Susan Blunt, Jennifer Lorimer, Lisa Elder and Robin Rozon for their hard work in the production and publication of this issue.

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