• Austin Pugh

Scientist Spotlight: Diane Lavoie: Research scientist, Department of Fisheries and Oceans Canada

Updated: May 18


Dr. Diane Lavoie is a research scientist for the Department of Fisheries and Oceans Canada where her work focuses on the development of coupled 3D ice-ocean-biogeochemical (NPZD-O2-pH) models for the Gulf of St. Lawrence to study the impacts of anthropogenic forcing (e.g. hydro-electric development, eutrophication, climate change) and climate variability on primary production, aggregation of whale forage species (krill, copepods), and on the development of a hypoxic and acid zone in the estuary. Diane's broader interests include the impacts of climate change on planktonic ecosystems and on biogeochemical cycles in Arctic and Subarctic Seas and the development of coupled sea ice-ocean-ecosystem models.

Dr Lavoie sits in front of a window
Dr Diane Lavoie

Diane revealed that she followed an unconventional path into the position that she holds today. Diane’s first taste of oceanography was in a college geology class. At university she first studied Actuarial Sciences but soon discovered that this was not the field for her. After receiving her bachelor's degree, she decided to travel across the world. During this time, she met a German oceanographer, whose work inspired her to pursue oceanography as a professional. Diane stated that it was a little difficult to “get in the door” of the field of oceanography due to her background in Actuarial sciences. Her master's degree was completed a few years later at ISMER (Rimouski).


After graduating from her master's program Diane worked for the DFO (Maurice Lamontagne Institute), first in the field of hydro-acoustics (the study of sound in water) and then forecasting water levels before returning to school to pursue a PhD. Diane's PhD work focused on the impact of climate change on primary production in the Arctic using/developing a fully coupled 1D numerical model that included sea ice – ice algae –circulation - NPZD (Inorganic Nitrogen-Phytoplankton-Zooplankton) interactions. After her PhD, Diane returned to the Maurine Lamontagne Institute where she started work on the development of a 3-D biogeochemical-physical numerical model of the Gulf of St. Lawrence which includes the dissolved oxygen system and the carbonate system. The goal of the model is to inform the understanding of the functioning and variability of the system, as well as to predict future changes. Diane works with various collaborators to evaluate the impact of climate change on different marine species.


A map of the Gulf of St. Lawrence with sample sites represented as coloured dots. The colours correspond to the pH of the sample.
River pH (scale on right) taken sampled from sites along the St. Lawerence River, as well as, the Gulf of St. Lawrence and Surrounding areas.

It is Diane's goal to make a regional model that is useful to the communities, businesses, and scientists of the region and it led her and her collaborators to add many different considerations into the 3-D model of the Gulf of St. Lawrence, including both O2 levels and carbonate state. The idea of the model was to examine the freshwater/open ocean interface in contact with the two systems individually since most current models examine one system or the other independently. The model started its additions of Ocean Acidification and Hypoxia by inputting O2 conditions of the region. When adding these values to the model OA conditions caught the attention of Diane and her colleges so the pH values were collected and added as well.


A Map of the Gulf of St. Lawrence which shows pH as a heat map.
Simulated (background color) and observed (circles) bottom pH (A) and (triangles) aragonite saturation states (B) in October-November of 2014. The magenta line in panel B delimits the areas where simulated saturation states are below one. The upward-facing triangles indicate observed values above one, while the downward-facing triangle indicate that the observed values are below one. (Image From Lavoie et al. 2021)

Dr Lavoie pointed out that the pH at the head of the deep channels (about 350 m) of the Gulf of St. Lawrence can get as low as 7.5 (typical ocean pH is 8.1). pH in these regions is affected by many factors including the important freshwater runoff, primary production and circulation. Some rivers carry a high load of organic matter and have pH that vary between about 6.2 to 8.0, depending on the region. Bottom acidic conditions at the head of the Laurentian Channel in the estuary get pushed close to the surface daily under the action of tides. This upwelling and mixing of waters can result in pH changes that can be as drastic as 0.1 within a single day! The pH is quite variable in the Gulf of St. Lawrence. In some areas, the seasonal change in pH (over a year) is similar or greater than the mean change predicted for the next 50 years (given current projections).


This model can be used to project the future conditions of the region much better than global models can. Global models usually do not provide a good resolution of regional-scale changes and challenges, they specialize in predicting large trends well but give little information about particular coastal regions. However, the global models predictions have been found to be robust enough to use as boundary conditions for the Gulf of St. Lawrence regional model. The predictions for the Gulf of Maine and the Scotian Shelf, also included in the regional model domain, are however more uncertain due to a greater oceanic influence and higher variability of the global model results near the southern boundary of the regional model.


8 maps of the Gulf of St. Lawrence depict the omega calcite value at the surface and the bottom of the Guld and surrounding areas. The maps each show a different models results.
Year at which the surface and bottom calcite saturation states (Ωcal) reach a value of 1.0 (A) and a value of 1.5 (B). White areas mean that saturation states do not reach these critical values during the study period. Right panels show the inter-model change spread in the calculated year. (Image From Lavoie et al 2020 technical report)

The development of regional climate models require a lot of work and different expertise. Diane and her collaborators are constantly working to improve and add to this model to make it more precise and useful. Some ambitions that Diane has for the model include examining sediment as inputs and sinks, increasing the biological scope of the model, and adding inter-annually variable boundary conditions. This next version of the model (V3.6) will also attempt to couple with a new biogeochemical model of the north Atlantic Ocean, and include atmospheric input of Nitrogen into the system. Both processes affect the cycling and success of phytoplankton and promise to increase the scope and the quality of the model.


Now that the model is of high enough quality it has begun to be used by its intended clients. These clients work with Dr Lavoie and Colleges to predict the impact of the incorporated factors on economically important species in the region. Such as an ongoing project to determine the regional and seasonal impact of ocean acidification on American Lobster which is both economically as well as culturally important species to communities in this area.


We asked Dr Lavoie if she could pick 1 piece of OA information that all Canadians should know. Her response was that she wishes everyone would know that they can make a difference in these problems through everyday action. By being conscious of your actions every day (through activities like avoiding unnecessary idling of your cars, reducing wastes by reducing consumption, composting and recycling) anyone can reduce their carbon footprint.


 

Acknowledgments: Thanks to Diane Lavoie for her virtual “in-person” interview and written responses.

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