Sea-level rise in northern Australia’s Kakadu National Park: a survey of floodplain eukaryotes
Sarah A. Stephenson A E , Tiffanie M. Nelson B , Claire Streten B , Karen S. Gibb C , David Williams B , Paul Greenfield A D and Anthony A. Chariton A DA CSIRO Oceans and Atmosphere, Locked Bag 2007, Kirrawee, NSW 2232, Australia.
B Australian Institute of Marine Science, Sustainable Coastal Ecosystems and Industries in Tropical Australia, Arafura Timor Research Facility, 23 Ellengowan Drive, Casuarina, NT 0810, Australia.
C Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT 0810, Australia.
D Environmental Genomics, Ecology and Ecotoxicology Lab (EGEEL), Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
E Corresponding author. Email: sarah.stephenson@csiro.au
Marine and Freshwater Research 69(7) 1134-1145 https://doi.org/10.1071/MF18067
Submitted: 26 February 2018 Accepted: 29 April 2018 Published: 12 June 2018
Abstract
Forecasted climate-change models predict that much of northern Australia’s coastal habitats will be in retreat because of saltwater intrusion (SWI) from sea-level rise. A region of primary concern is the nutrient-rich and biodiverse floodplains of world heritage-listed Kakadu National Park (KNP). To understand the implications of SWI, we need fundamental baseline information for floodplain biota from the South Alligator River, KNP, northern Australia, and informative data on how increased and prolonged exposure to salt is likely to shape the eukaryotic community. To assist in addressing these key knowledge gaps, we used amplicon sequencing to examine the composition of eukaryotic soil communities from the South Alligator River floodplain, an ecologically important area at the ‘coalface’ of sea-level rise. Samples were obtained from three river zones and three floodplain morphologies, capturing a wide range of habitats and episodic exposures to both saltwater and freshwater. We found that both the floodplain morphology and positioning along the river significantly influenced eukaryotic composition. However, the influence of these variables varied greatly among the floodplain morphologies, with correlative evidence suggesting that both salinity and pH played a dominant role in shaping communities within lower parts of the floodplain, with this being particularly evident in those regions subjected to major tidal influence (estuarine funnel and sinuous, and cuspate).
Additional keywords: climate change, flood morphology, metabarcoding, river zone, saltwater.
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