The Lake Ontario ecosystem: An overview of current status and future directions

Lake Ontario is the most eastern of the Laurentian Great Lakes, receiving significant inputs from Lake Erie and the other Great Lakes, and draining to the St. Lawrence River. While Lake Ontario is a well-studied lake, lakewide assessments of all lower trophic levels have only been periodic over the past 40 years. The first lakewide plankton surveys were initiated in the 1970s (Vollenweider et al., 1974); more comprehensive surveys including various trophic levels were carried out in the 1990s (Munawar, 2003). These intensive monitoring surveys of the Lake Ontario foodweb by Fisheries and Oceans Canada (DFO) ended in the mid1990s, just about the time that Zebra Mussels (Dreissena polymorpha) started to establish in the lake. However, zooplankton monitoring by the United States Geological Survey (USGS) and Cornell University continued and was expanded to sites along the US shore in 1995 through cooperation with New York State Department of Environmental Conservation (NYSDEC), the United States Fish and Wildlife Service (USFWS; Hall et al., 2003) and by the Environmental Protection Agency (EPA) Great Lakes National Program Office (Barbiero et al., 2014). In addition, both the EPA and the Environment Canada Surveillance Program measured nutrients and chlorophyll levels in the lake on an annual basis (Dove, 2009; Barbiero et al., 2014). Realizing the need for new information about all trophic levels of the lake, a group of government and academic researchers initiated a collaborative program, the Lake Ontario Lower-trophic Assessment (LOLA) in 2003. This approach was applied by research and management groups on the other Great Lakes, and became formalized as the Cooperative Science and Monitoring Initiative (CSMI; Richardson et al., 2012). The CSMI is a rotating 5-year lake-intensive monitoring activity intended to coordinate the activities of the research community around a Great Lake each year to assess the current state of the lake and address outstanding research priorities. In 2012, this activity was formally incorporated into the Great Lakes Water Quality Agreement (GLWQA). The results of the 2003 LOLA program were previously reported in Aquatic Ecosystem Health and Management (Munawar and Mills, 2008). The 2008 intensive year for Lake Ontario attempted to examine both the offshore and nearshore zones of the lake. The nearshore work was published in the Journal of Great Lakes Research (Makarewicz and Howell, 2012). The current special issue includes the results of the offshore sampling, covering topics from water quality through phytoplankton, primary production, zooplankton, benthic invertebrates, and fishes. Lake Ontario has been exposed to many stressors: the most influential have been identified (Mills et al., 2003) as reduced phosphorus loading, invasion by Dreissenid Mussels,