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Journal article
Empirical evidence of alternative stable states in an estuary
The Science of the total environment, Vol.954, 176356
2024
Abstract
Due to human activity, ecosystems are exceeding their ecological thresholds and shifting into undesired alternative stable states with new ecological configurations. Despite their purported ubiquity, it is uncertain whether estuaries can exist in multiple stable states. We use data from a 3.5-year study of invertebrate communities in an Australian estuary that is usually closed to the ocean to test for their existence. Sampling spanned a 1.5-year period of hypersalinity (>40 ppt) during a prolonged estuary closure, where salinity reached 122 ppt, and for 2 years during and after the estuary opened to the ocean when salinities were mesohaline (5–19 ppt). Two distinct community states occurred before and after the sandbar breached, with an intermediary period of invertebrate community impoverishment due to sediment scouring. During the closure, the community was simple (average of 1 taxa) and dominated by larvae of terrestrial insects, most notably the halotolerant, non-biting midge Tanytarsus barbitarsis. After opening, the richness and abundance of invertebrates increased (average of 4 taxa and 84 individuals 100 cm−2) as polychaetes, molluscs and crustaceans colonised the estuary, although recovery was incomplete according to previous species records. Duration of closure and salinity were the strongest drivers of composition. This study, together with evidence from the literature, suggests a salinity threshold of 60–65 ppt between states. These empirical data meet key criteria of alternative states, i.e. a clear transition between two distinct self-sustaining communities, indicating a regime shift triggered by an exogenous event. Our findings suggest that temporarily open and closed estuaries can exist in alternative stable states, with prolonged closures, hypersalinity, and sandbar breaching being key determinants of the switch between states. This situation may apply to other low-inflow estuarine systems, particularly in arid, semi-arid, or seasonally arid climates, and may become more frequent due to human-induced climate change.
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Details
- Title
- Empirical evidence of alternative stable states in an estuary
- Authors/Creators
- S. Cronin-O'Reilly - Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, Murdoch, Western Australia 6150, AustraliaK.N. Krispyn - Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, Murdoch, Western Australia 6150, AustraliaC. Maus - Murdoch UniversityR.J. Standish - Murdoch University, School of Environmental and Conservation SciencesN.R. Loneragan - Murdoch University, Centre for Sustainable Aquatic EcosystemsJ.R. Tweedley - Murdoch University, Centre for Sustainable Aquatic Ecosystems
- Publication Details
- The Science of the total environment, Vol.954, 176356
- Publisher
- Elsevier B.V
- Identifiers
- 991005703763507891
- Copyright
- © 2024 The Authors.
- Murdoch Affiliation
- Centre for Sustainable Aquatic Ecosystems; Centre for Terrestrial Ecosystem Science and Sustainability; School of Environmental and Conservation Sciences
- Language
- English
- Resource Type
- Journal article
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