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Extreme changes in salinity drive population dynamics of Catostylus mosaicus medusae in a modified estuary

Extreme changes in salinity drive population dynamics of Catostylus mosaicus medusae in a modified estuary
Extreme changes in salinity drive population dynamics of Catostylus mosaicus medusae in a modified estuary
Modifications to estuaries through the construction of barrages alter the natural dynamics of inhabitant species by controlling freshwater inputs into those systems. To understand the effects of modified freshwater flows on a native scyphozoan jellyfish, Catostylus mosaicus, and to identify the environmental drivers of medusa occurrence, we analysed a 20-year observational dataset composed of 11 environmental variables and medusa presence/absence from 15 sampling stations located below the Fitzroy Barrage, in the Fitzroy River, Queensland. Major decreases in salinity (minimum salinity 0) occurred approximately 16 times during the 20-year period and medusae disappeared from the estuary following every major freshwater flow event. Salinity was identified as the most influential variable contributing to variation in the number of upper estuary sites reporting jellyfish. We then ran two laboratory experiments to test the following hypotheses: (i) prolonged decreases in salinity impair survival, pulsation, and respiration rates of C. mosaicus medusae; and (ii) transient decreases temporarily impair pulsation and respiration but medusae recover when salinity returns to normal levels. Medusae were unable to survive extended periods at extreme low salinities, such that they would experience when a barrage opens fully, but had significantly higher survival and recovery rates following smaller, transient changes to salinity that might occur following a moderate rainfall event. This demonstrates for the first time that modification of freshwater flow by a barrage regulates the population dynamics of an estuarine jellyfish, and highlights the need for robust, long term datasets, and to firmly embed experimental approaches in realistic ecological contexts.
Barrages, Declarations, Estuaries, Jellyfish, Medusa, Population dynamics, Salinity
0141-1136
Loveridge, Alexandra
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Pitt, Kylie A.
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Lucas, Cathy H.
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Warnken, Jan
8cc57344-ec3a-4ac2-a6fe-2c80d1e30d37
Loveridge, Alexandra
7c2ba4b2-905f-4ec5-8daa-3ad3202d62fa
Pitt, Kylie A.
5aa1bb5c-3ee9-4b32-b27f-1f3373989148
Lucas, Cathy H.
bdb636c6-c2b8-43d6-9d9c-d8d571d67533
Warnken, Jan
8cc57344-ec3a-4ac2-a6fe-2c80d1e30d37

Loveridge, Alexandra, Pitt, Kylie A., Lucas, Cathy H. and Warnken, Jan (2021) Extreme changes in salinity drive population dynamics of Catostylus mosaicus medusae in a modified estuary. Marine Environmental Research, 168, [105306]. (doi:10.1016/j.marenvres.2021.105306).

Record type: Article

Abstract

Modifications to estuaries through the construction of barrages alter the natural dynamics of inhabitant species by controlling freshwater inputs into those systems. To understand the effects of modified freshwater flows on a native scyphozoan jellyfish, Catostylus mosaicus, and to identify the environmental drivers of medusa occurrence, we analysed a 20-year observational dataset composed of 11 environmental variables and medusa presence/absence from 15 sampling stations located below the Fitzroy Barrage, in the Fitzroy River, Queensland. Major decreases in salinity (minimum salinity 0) occurred approximately 16 times during the 20-year period and medusae disappeared from the estuary following every major freshwater flow event. Salinity was identified as the most influential variable contributing to variation in the number of upper estuary sites reporting jellyfish. We then ran two laboratory experiments to test the following hypotheses: (i) prolonged decreases in salinity impair survival, pulsation, and respiration rates of C. mosaicus medusae; and (ii) transient decreases temporarily impair pulsation and respiration but medusae recover when salinity returns to normal levels. Medusae were unable to survive extended periods at extreme low salinities, such that they would experience when a barrage opens fully, but had significantly higher survival and recovery rates following smaller, transient changes to salinity that might occur following a moderate rainfall event. This demonstrates for the first time that modification of freshwater flow by a barrage regulates the population dynamics of an estuarine jellyfish, and highlights the need for robust, long term datasets, and to firmly embed experimental approaches in realistic ecological contexts.

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Extreme changes in salinity - Accepted Manuscript
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Accepted/In Press date: 11 March 2021
e-pub ahead of print date: 25 March 2021
Published date: 1 June 2021
Additional Information: Funding Information: This research was supported by the University of Southampton and Griffith University, through the NERC-funded SPITFIRE Doctoral Training Partnership International Placement Scheme. We want to thank Ashley Johnston for her invaluable assistance throughout the experiment, Jonathan Lawley and Carolina Jacobson for technical assistance, and staff at Sea Jellies Illuminated, Sea World, for their help throughout the study. This paper contains data provided by the State of Queensland (Department of Environment and Science, 2019). Funding Information: This work was supported by the Natural Environmental Research Council [grant number NE/L002531/1 ]. Publisher Copyright: © 2021 Elsevier Ltd Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
Keywords: Barrages, Declarations, Estuaries, Jellyfish, Medusa, Population dynamics, Salinity

Identifiers

Local EPrints ID: 449272
URI: http://eprints.soton.ac.uk/id/eprint/449272
ISSN: 0141-1136
PURE UUID: 573b52e8-a1c8-414d-b99c-298bed9f93ef

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Date deposited: 21 May 2021 16:30
Last modified: 25 Nov 2021 17:47

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Contributors

Author: Kylie A. Pitt
Author: Cathy H. Lucas
Author: Jan Warnken

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