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Guibourd de Luzinais, Vianney

University of British Columbia

Intensifying climate change is increasingly affecting marine life in the world's oceans. Associated with climate change, extreme events such as marine heatwaves (MHWs) are expected to increase in duration, intensity and frequency, exerting additional impacts on marine ecosystems to slow on-set climate change over the 21st century. In this dissertation, I investigated the effects of climate change and MHWs on biomass flows in marine food webs and their consequences on ecosystem structure and functioning. First, I developed a dynamic version of the EcoTroph model named EcoTroph-Dyn, which represents the functioning of marine ecosystems as a single flow of biomass surging up the food web from primary producers to top predators. To examine the effects of MHWs on marine ecosystems using EcoTroph-Dyn, I estimated the mortality associated with MHWs, causing biomass loss through marine food webs, using the thermal preference of various taxa from 1982 to 2021. Through a virtual approach, using the EcoTroph-Dyn modelling framework and estimates of MHWs-induced mortality, I highlighted that MHWs may have impacted biomass flow through the perturbation of the kinetic of biomass flow through the food web, the transfer efficiency, and MHWs’ induced biomass loss by instantaneous mortality. Then, using the same modelling framework, I hindcasted the consumer biomass in marine food webs associated with past MHWs from 1998 to 2021. Using changes in temperature and primary production, marine animal biomass has been estimated at each trophic level on a 1° x 1° grid of the global ocean. Results showed that MHWs have induced significant additional biomass loss, with more pronounced impacts at higher trophic levels. Finally, marine animal biomass is estimated from 1950 to 2100 under the “very high greenhouse gas emissions” climate scenario. The projections showed that the projected alteration of biomass flows from MHWs could lead to an additional global decline in consumer biomass scaling with ocean warming, with more pronounced impacts than background climate change. Overall, this dissertation showed that climate change and associated MHWs would alter conjointly biomass flows in marine ecosystems, causing a decrease in the future ocean animal biomass and direct repercussions on fisheries.

Text

2024-12-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89942

Oceans and Fisheries

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/