Extreme dissolved oxygen variability in urbanised tropical wetlands: the need for detailed monitoring to protect nursery ground values

Dubuc, Alexia, Waltham, Nathan, Malerba, Martino, and Sheaves, Marcus (2017) Extreme dissolved oxygen variability in urbanised tropical wetlands: the need for detailed monitoring to protect nursery ground values. Estuarine, Coastal and Shelf Science, 198 (Part A). pp. 163-171.

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Little is known about levels of dissolved oxygen fish are exposed to daily in typical urbanised tropical wetlands found along the Great Barrier Reef coastline. This study investigates diel dissolved oxygen (DO) dynamics in one of these typical urbanised wetlands, in tropical North Queensland, Australia. High frequency data loggers (DO, temperature, depth) were deployed for several days over the summer months in different tidal pools and channels that fish use as temporal or permanent refuges. DO was extremely variable over a 24 h cycle, and across the small-scale wetland. The high spatial and temporal DO variability measured was affected by time of day and tidal factors, namely water depth, tidal range and tidal direction (flood vs ebb). For the duration of the logging time, DO was mainly above the adopted threshold for hypoxia (50% saturation), however, for around 11% of the time, and on almost every logging day, DO values fell below the threshold, including a severe hypoxic event (<5% saturation) that continued for several hours. Fish still use this wetland intensively, so must be able to cope with low DO periods. Despite the ability of fish to tolerate extreme conditions, continuing urban expansion is likely to lead to further water quality degradation and so potential loss of nursery ground value. There is a substantial discontinuity between the recommended DO values in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality and the values observed in this wetland, highlighting the limited value of these guidelines for management purposes. Local and regional high frequency data monitoring programs, in conjunction with local exposure risk studies are needed to underpin the development of the management that will ensure the sustainability of coastal wetlands.

Item ID: 50809
Item Type: Article (Research - C1)
ISSN: 1096-0015
Keywords: dissolved oxygen, hypoxia, fish adaptation, coastal management, coastal wetland, urbanisation
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A version of this publication was included as Chapter 2 of the following PhD thesis: Dubuc, Alexia Ida Anne (2019) Dissolved oxygen as a constraint for the structure of mangrove fish assemblages and their patterns of mangrove utilisation: a comparison between natural and disturbed mangrove ecosystems through the Australian and Caledonian coastlines. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Date Deposited: 03 Oct 2017 04:17
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4105 Pollution and contamination > 410599 Pollution and contamination not elsewhere classified @ 50%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960511 Ecosystem Assessment and Management of Urban and Industrial Environments @ 50%
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