On phytoplankton growth and loss rates to microzooplankton in the epilimnion and metalimnion of Lake Ontario in mid-summer

► Growth and loss rates of phytoplankton measured in Lake Ontario. ► Rates measured in epilimnetic and metalimnetic waters using a variety of methods. ► The metalimnion contained a deep chlorophyll maximum (DCM) across the lake. ► Results suggest that the DCM is as active a layer as the epilimnion during the summer. ► DCM should be included in estimates of primary and secondary production.