The effects of riverine nutrients and phytoplankton transport in an oligotrophic embayment

Session: Physical Ecology in Large Lakes and Their Watersheds

Chris Farrow, University of Guelph, [email protected]
Josef Ackerman, University of Guelph, [email protected]
Ralph Smith, Biology Dept., Univ. of Waterloo, [email protected]
David Snider, Bruce Power, [email protected]

Abstract

We investigated the effects of riverine transport of algal taxa and nutrients on the nearshore phytoplankton composition of an oligotrophic embayment. Imaging flow cytometry was used to identify and enumerate phytoplankton. Multivariate analysis (perMANOVA and RDA) and a dilution model were used to examine how nutrients and the transport of algal taxa affected community composition. In general, phytoplankton cells transported from the river were smaller (< 30 mm) than those in the bay. Phytoplankton communities differed significantly among sampling stations with different percentages of river water. Most of the 51 taxa identified in the river in 2016 had abundances that corresponded to the dilution of river water, whereas the abundances of 11 taxa did not. Of the taxa found at higher than predicted abundance (3 cyanobacteria, a diatom, chrysophyte, and dinoflagellate), four had moderate to weak associations with nutrients in RDA. Two of five taxa found at lower abundance in the bay (2 diatoms, 2 chlorophytes, and a cryptophyte) were also < 30 mm. These results indicate relatively rapid changes spatially in the phytoplankton community of Nottawasaga Bay due to the transport of algal taxa and nutrients from the Nottawasaga River as well as potential trophic interactions in the bay.