INTEGRATED MODELLING OF CLADOPHORA, DREISSENIDS, PHOSPHORUS, AND PHYTOPLANKTON IN THE NEARSHORE OF LAKE ONTARIO

Cladophora glomerata has re-emerged as a dominant benthic macrophyte in the nearshores of the lower Great Lakes, leading to extensive fouling of local beaches with decaying organic material. These blooms are influenced by several factors, including nutrient loading, light availability, and the presence of dreissenid mussels, thus requiring a more granular approach to modelling its growth and impacts. We present a novel process-based model that couples dissolved and particulate phosphorus with three interacting biotic compartments – phytoplankton, dreissenid mussels, and Cladophora. While these submodels have been studied individually, the evaluation of the range of dynamics they can collectively produce has been limited. Our analysis presents the findings from a comprehensive sensitivity analysis that identifies key drivers and ecological thresholds that control macrophyte biomass, nutrient retention, and the balance between benthic and pelagic production. Our study clearly identifies and addresses several knowledge gaps and outstanding questions to improve our understanding of the nearshore system. We discuss how these results can guide monitoring design and data collection, and identify management levers for reducing nuisance blooms, ultimately contributing to the effective management of macrophyte proliferation in the nearshores of Lake Ontario.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Yasasi Fernando, University of Toronto (yasasi.fernando@mail.utoronto.ca)

Authors:

Lisa Yu, University of Toronto  (liisa.yu@mail.utoronto.ca)

Alexey Neumann, University of Toronto  (alex.gudimov@utoronto.ca)

David Depew, Environment and Climate Change Canada  (David.Depew@ec.gc.ca)

Reza Valipour, Environment and Climate Change Canada  (Reza.Valipour@ec.gc.ca)

George Arhonditsis, University of Toronto  (george.arhonditsis@utoronto.ca)