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Articles

Spatio-temporal variation of benthic metabolism in a large, regulated river

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Pages 144-157 | Received 04 Jul 2019, Accepted 28 Jan 2020, Published online: 07 Feb 2020
 

Abstract

Large rivers provide important ecosystem services to society, yet little is known about patterns and controls of key ecological functions, such as benthic metabolism, in these ecosystems. This study describes patterns of temporal and spatial variation of benthic metabolism (gross primary production (GPP) and community respiration (CR)) in the Saint John River, New Brunswick, Canada; a large, regulated river. Temporal variation and drivers of metabolism were assessed throughout the summer using measurements of dissolved oxygen from benthic chambers in the river’s wadeable margins. Differences in metabolism between channel locations (main and side channel) and patches of cobble and sand substrates were also determined. Rates of GPP and CR varied in accordance with a quadratic function throughout the summer months with peak rates attained in mid-July. Variability in metabolism was associated with light and water temperature. Spatial heterogeneity in metabolism was not observed between channel locations. Differences in metabolism between substrates were dependent upon time of year, as differences were only observed in early summer. Findings of this study suggest benthic metabolism in the margins of the Saint John River is controlled by variations temperature and light availability that vary with climatic patterns in the summer months. Consequently, these findings have implications for management of river health given projected scenarios of climate change.

ABSTRAIT

Les grandes rivières fournissent d’importants services écosystémiques à la société, mais très peu est connu sur les fonctions écologiques clés de ces écosystèmes, comme par exemple le métabolisme benthique. Notre étude décrit les patrons de variation temporelle et spatiale du métabolisme benthique (production primaire brute (PPB) et de la respiration communautaire (RC)) dans la rivière Saint-Jean, Nouveau-Brunswick, Canada; une grande rivière régulée. Nous avons évalué la variation temporelle et les facteurs affectant le métabolisme tout au long de l’été en mesurant l’oxygène dissous dans des chambres benthiques déployées en marges de la rivière. Nous avons également comparé le métabolisme benthique entre différents emplacements (canal principal et canal latéral) et entre des parcelles de substrats de galets et de sable. Les taux de PPB et de RC ont varié selon une fonction quadratique tout au long des mois d’été, avec des taux maximaux atteints à la mi-juillet. La variabilité du métabolisme était associée à la lumière et à la température de l’eau. Aucune hétérogénéité spatiale dans le métabolisme n’a été observée entre les emplacements des canaux. Les différences de métabolisme entre les substrats dépendaient de la période de l’année; les différences n’étant observées qu’au début de l’été. Nos résultats suggèrent que le métabolisme benthique en marges de la rivière Saint-Jean est contrôlé par les variations de température et la disponibilité de la lumière qui varient pendant les mois d’été. Par conséquent, nos résultats ont des implications pour la gestion de la santé des rivières compte tenu des scénarios projetés de changement climatique.

Acknowledgement

Authors thank J. Howland, J. Sirois, D. Hryn and E. Luiker for assistance with field sampling.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding was provided by Environment and Climate Change Canada, Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Grants to A.G. Yates and J.M. Culp, as well as a NSERC Collaborative Research and Development grant (Mactaquac Aquatic Ecosystem Study). C.E. Irwin was funded by a NSERC Collaborative Research and Training Experience WATER scholarship.

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