Staff View: Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania

Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania

Microbial respiration of organic matter (OM) is a key driver of deoxygenation and hypoxia. In fjord-like estuaries with established aquaculture industries understanding drivers of oxygen demand, and the relative importance of different drivers, is crucial for improving fish farming management in tho...

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Main Authors:	Maxey, Johnathan D., Hartstein, Neil D., Then, Amy Yee Hui, Barrenger, Matt
Format:	Article
Published:	Elsevier 2020
Subjects:	Q Science (General) QH301 Biology
Online Access:	http://eprints.um.edu.my/36266/
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spelling	my.um.eprints.362662023-11-29T11:35:22Z http://eprints.um.edu.my/36266/ Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania Maxey, Johnathan D. Hartstein, Neil D. Then, Amy Yee Hui Barrenger, Matt Q Science (General) QH301 Biology Microbial respiration of organic matter (OM) is a key driver of deoxygenation and hypoxia. In fjord-like estuaries with established aquaculture industries understanding drivers of oxygen demand, and the relative importance of different drivers, is crucial for improving fish farming management in those systems. We designed a study to examine patterns of pelagic oxygen demand (POD) in a fjord-like estuary on the west coast of Tasmania, Mac-quarie Harbour, and relate those observations to physical forcings and major OM sources. Monthly water column sampling and bottle incubation experiments were conducted from June to November 2017. Water was collected throughout the harbour including river and oceanic endmembers as well as transects leading away from fish farms. Water was incubated from 4 different depths spanning the surface water to the seabed. Regression modelling was used to examine the relationship between POD, riverine OM loading, proximity to fish farms and the major system endmembers, depth, harbour region, concentration of dissolved oxygen, and month. POD reached rates as high as 0.108 mg L-1 hour 1 with the greatest POD observed above the halocline and during high river flow/OM loading months. Regression modelling showed that important drivers of POD are spatially specific along vertical and longitudinal gradients. The importance of riverine OM loading waned with depth primarily due to mixing dynamics of dissolved organic carbon across the halocline. Proximity to fish farms was an important but localized explanatory variable for POD in the halocline and basin waters, but not a significant driver of POD compared to the Gordon River. Based on the POD rates observed in this study, hypoxia can be established in less than 9 days in the basin waters and is primarily driven by pelagic oxygen sinks (95%-98%), not sediment sinks. It is crucial that aquaculture management accounts for natural, and/or preexisting, variation in endmember OM loading and its effect on DO dynamics, in these systems. Elsevier 2020-11 Article PeerReviewed Maxey, Johnathan D. and Hartstein, Neil D. and Then, Amy Yee Hui and Barrenger, Matt (2020) Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania. Estuarine, Coastal and Shelf Science, 246. ISSN 02727714, DOI https://doi.org/10.1016/j.ecss.2020.107016 <https://doi.org/10.1016/j.ecss.2020.107016>. 10.1016/j.ecss.2020.107016
institution	Universiti Malaya
building	UM Library
collection	Institutional Repository
continent	Asia
country	Malaysia
content_provider	Universiti Malaya
content_source	UM Research Repository
url_provider	http://eprints.um.edu.my/
topic	Q Science (General) QH301 Biology
spellingShingle	Q Science (General) QH301 Biology Maxey, Johnathan D. Hartstein, Neil D. Then, Amy Yee Hui Barrenger, Matt Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
description	Microbial respiration of organic matter (OM) is a key driver of deoxygenation and hypoxia. In fjord-like estuaries with established aquaculture industries understanding drivers of oxygen demand, and the relative importance of different drivers, is crucial for improving fish farming management in those systems. We designed a study to examine patterns of pelagic oxygen demand (POD) in a fjord-like estuary on the west coast of Tasmania, Mac-quarie Harbour, and relate those observations to physical forcings and major OM sources. Monthly water column sampling and bottle incubation experiments were conducted from June to November 2017. Water was collected throughout the harbour including river and oceanic endmembers as well as transects leading away from fish farms. Water was incubated from 4 different depths spanning the surface water to the seabed. Regression modelling was used to examine the relationship between POD, riverine OM loading, proximity to fish farms and the major system endmembers, depth, harbour region, concentration of dissolved oxygen, and month. POD reached rates as high as 0.108 mg L-1 hour 1 with the greatest POD observed above the halocline and during high river flow/OM loading months. Regression modelling showed that important drivers of POD are spatially specific along vertical and longitudinal gradients. The importance of riverine OM loading waned with depth primarily due to mixing dynamics of dissolved organic carbon across the halocline. Proximity to fish farms was an important but localized explanatory variable for POD in the halocline and basin waters, but not a significant driver of POD compared to the Gordon River. Based on the POD rates observed in this study, hypoxia can be established in less than 9 days in the basin waters and is primarily driven by pelagic oxygen sinks (95%-98%), not sediment sinks. It is crucial that aquaculture management accounts for natural, and/or preexisting, variation in endmember OM loading and its effect on DO dynamics, in these systems.
format	Article
author	Maxey, Johnathan D. Hartstein, Neil D. Then, Amy Yee Hui Barrenger, Matt
author_facet	Maxey, Johnathan D. Hartstein, Neil D. Then, Amy Yee Hui Barrenger, Matt
author_sort	Maxey, Johnathan D.
title	Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
title_short	Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
title_full	Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
title_fullStr	Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
title_full_unstemmed	Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania
title_sort	dissolved oxygen consumption in a fjord-like estuary, macquarie harbour, tasmania
publisher	Elsevier
publishDate	2020
url	http://eprints.um.edu.my/36266/
_version_	1783945851261943808
score	13.211869

Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania

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