Phytoplankton Ecology of Lake Ontario 2013: Structure of Epilimnion and Metalimnion Layers

Session: State of Lake Ontario: 2003-2018 CSMI Overview (1)

Mohiuddin Munawar, Fisheries & Oceans Canada, [email protected]
Lars Rudstam, Cornell University Bio Field Station, Dept. of Natural Resources, [email protected]
James Watkins, Cornell University, [email protected]
Heather Niblock, GLLFAS, DFO, [email protected]
Mark Fitzpatrick, Fisheries & Oceans Canada, [email protected]

Abstract

Our knowledge of phytoplankton structure at various strata within Lake Ontario is limited although higher chlorophyll a values are expected in deeper layers. Integrated epilimnetic (?0-10 m) samples were compared to metalimnetic and deep chlorophyll layers (?15-30m) collected during April, May, July and August 2013. During May, the epilimnion included 0.3 g m^-3 of biomass and contained a mixture of Diatomeae (41%) and phytoflagellates including Cryptophyceae (30%) and Dinophyceae (21%). In contrast the metalimnion had both a higher biomass (0.8 g m^-3) and a higher proportion of diatoms (66%) with fewer Cryptophyceae (15%). During July, biomass was similar in both the epilimnion and deep chlorophyll layer (0.5 g m^-3). The epilimnion contained diatoms (58% )and phytoflagellates (32%), but the DCL was overwhelmingly Diatoms (80%). Species composition, however, was similar with both strata containing a mixture of Fragilaria, Cyclotella, Synedra, Cryptomonas, Rhodomonas and Ceratium despite more flagellates in the epilimnion compared to the DCL. A holistic picture of phytoplankton composition in different water column strata will be attempted.