In subarctic marine environments, nutrient stocks are replenished through physical and biogeochemical processes in winter, largely setting an upper limit on new primary production for the next growing season. In spring, marine nutrient stocks are modified by freshwater-associated additions, especially in coastal areas. Hydroelectric development of the La Grande River (LGR), in northern Québec, has shifted the timing of peak freshwater discharge from spring into winter, producing ten times the natural winter discharge. In this study, we used salinity, oxygen isotope ratio (δ18O), and nutrient (nitrate, phosphate) data collected from NEJB coastal waters in different seasons of 2016 and 2017. Here we quantify two main freshwater sources, established by freshwater tracers (LGR and sea-ice melt), and their influence on nutrient distributions along the coast. Our results show that LGR is the dominant source of freshwater to coastal waters throughout the year, especially during winter and serves as an important source of nitrate to nitrogen-limited coastal waters (winter concentrations of 4.53 μM and 3.18 μM respectively). Despite being a poor phosphate source, LGR (0.11 μM, compared to ambient seawater 0.66 μM), provides the largest portion of the phosphate stock in surface waters near the mouth of LGR. LGR regulation has changed the pattern of natural fluvial nitrate inputs, what was observed in spring (pre-development) is now observed in winter (post-development). Thus, high winter surface nitrate stocks (22.5 mmol m-2) are available to support primary production, but dispersed to offshore areas, prior to the onset of the growing season, which begins only after the return of light. In NEJB, the timing and magnitude of primary production, dependent on nutrients in the water column, is expected to have been impacted by altered freshwater input, reducing overall production in local areas and potentially increasing production further downstream with cascading effects on the marine ecosystem.

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Champ Valeur
Titre Influence of altered freshwater discharge on the seasonality of nutrient distributions near La Grande River northeastern James Bay Québec
Publication general type Journal Article
Project Name
Keyword Vocabulary Polar Data Catalogue
Keyword Vocabulary URL https://www.polardata.ca/pdcinput/public/keywordlibrary
Theme Marine
Version 1.0
Publisher Elementa Science of the Anthropocene
Date Published 2024
DOI 10.1525/elementa.2023.00133
Langue English
Champ Valeur
Authors
Authors 1
Author Name
Guzzi, Alessia
Type of Name
Personal
e-mail
alessia.guzzi@umanitoba.ca
Affiliation
Centre for Earth Observation Science - University of Manitoba
ORCID ID
0009-0003-3858-8866
Authors 2
Author Name
Ehn, Jens
Type of Name
Personal
e-mail
jens.ehn@umanitoba.ca
Affiliation
Centre for Earth Observation Science - University of Manitoba
ORCID ID
Authors 3
Author Name
Michel, Christine
Type of Name
Personal
e-mail
Affiliation
Freshwater Institute - Fisheries and Oceans Canada
ORCID ID
Authors 4
Author Name
Tremblay, Jean-Éric
Type of Name
Personal
e-mail
Affiliation
Université Laval
ORCID ID
Authors 5
Author Name
Heath, Joel
Type of Name
Personal
e-mail
Affiliation
ORCID ID
Authors 6
Author Name
Kuzyk, Zou Zou
Type of Name
Personal
e-mail
zouzou.kuzyk@umanitoba.ca
Affiliation
Centre for Earth Observation Science - University of Manitoba
ORCID ID
Champ Valeur
License Name Creative Commons Attribution 4.0 International
Licence Type Open
Licence Schema Name SPDX
Licence URL https://spdx.org/licenses
Champ Valeur
Awards
Awards 1
Funded by
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