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Effects of salinization on tropical freshwater wetland primary producers and aquatic invertebrates.

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Title: Effects of salinization on tropical freshwater wetland primary producers and aquatic invertebrates.
Authors: Dedman, Tegan L.1 (AUTHOR) teganlouise.dedman@cdu.edu.au, Garcia, Erica A.1 (AUTHOR), Davis, Jenny1 (AUTHOR), Kopf, R. Keller1 (AUTHOR)
Source: Oikos. Nov2025, p1. 14p. 11 Illustrations.
Subject Terms: *SALINIZATION, *AQUATIC invertebrates, *FRESHWATER ecology, *WETLANDS, *BIODIVERSITY, *AUTOTROPHS, *SALTWATER encroachment, *ABSOLUTE sea level change
Geographic Terms: KAKADU National Park (N.T.), DARWIN (N.T.), AUSTRALIA
Abstract: Sea level rise is expected to transform coastal aquatic ecosystems world‐wide. The freshwater wetlands of tropical northern Australia are among the most biodiverse and productive ecosystems on the continent, but owing to high regional rates of sea level rise coupled with low‐lying land and large tides they are increasingly affected by saltwater intrusion. The propagule bank, including seeds of aquatic primary producers and eggs of aquatic invertebrates, stored in wetland sediments is vital for the establishment of ecological communities, and ultimately to primary and secondary production. This experimental study examined the impact of increasing salinity on emergence of primary producers and invertebrates from sediment cores collected from tropical freshwater wetlands between Darwin and Kakadu National Park in northern Australia. Sediment cores (n = 216) were placed in microcosms and inundated with one of four salinity treatments: 0 ppt (freshwater/control); 7 ppt; 16 ppt and 35 ppt (sea water) and decanted on approximately days 10, 20 and 90. In comparison to freshwater controls, median chlorophyll a of phytoplankton and benthic algae declined sharply with increasing salinity, and in the highest salinity treatment were reduced by 93% and 60% respectively. Macrophyte biomass, aquatic invertebrate density and richness were reduced to near zero in all salinity treatments. Increasing salinity decreases the abundance of primary producers and aquatic invertebrates that emerge from sediment cores in seasonally inundated tropical freshwater wetlands. Macrophyte emergence exhibits no tolerance to salinities above freshwater (0 ppt) and aquatic invertebrate emergence declines rapidly in both abundance and diversity as salinity increases. Our results suggest that freshwater aquatic primary producers and aquatic invertebrates will be severely impacted by sea level rise and saltwater intrusion. Reduced freshwater aquatic primary production and aquatic invertebrates may have important implications for food webs, and other social and biodiversity values of tropical freshwater wetlands. [ABSTRACT FROM AUTHOR]
Database: Academic Search Index
Description
Abstract:Sea level rise is expected to transform coastal aquatic ecosystems world‐wide. The freshwater wetlands of tropical northern Australia are among the most biodiverse and productive ecosystems on the continent, but owing to high regional rates of sea level rise coupled with low‐lying land and large tides they are increasingly affected by saltwater intrusion. The propagule bank, including seeds of aquatic primary producers and eggs of aquatic invertebrates, stored in wetland sediments is vital for the establishment of ecological communities, and ultimately to primary and secondary production. This experimental study examined the impact of increasing salinity on emergence of primary producers and invertebrates from sediment cores collected from tropical freshwater wetlands between Darwin and Kakadu National Park in northern Australia. Sediment cores (n = 216) were placed in microcosms and inundated with one of four salinity treatments: 0 ppt (freshwater/control); 7 ppt; 16 ppt and 35 ppt (sea water) and decanted on approximately days 10, 20 and 90. In comparison to freshwater controls, median chlorophyll <italic>a</italic> of phytoplankton and benthic algae declined sharply with increasing salinity, and in the highest salinity treatment were reduced by 93% and 60% respectively. Macrophyte biomass, aquatic invertebrate density and richness were reduced to near zero in all salinity treatments. Increasing salinity decreases the abundance of primary producers and aquatic invertebrates that emerge from sediment cores in seasonally inundated tropical freshwater wetlands. Macrophyte emergence exhibits no tolerance to salinities above freshwater (0 ppt) and aquatic invertebrate emergence declines rapidly in both abundance and diversity as salinity increases. Our results suggest that freshwater aquatic primary producers and aquatic invertebrates will be severely impacted by sea level rise and saltwater intrusion. Reduced freshwater aquatic primary production and aquatic invertebrates may have important implications for food webs, and other social and biodiversity values of tropical freshwater wetlands. [ABSTRACT FROM AUTHOR]
ISSN:00301299
DOI:10.1002/oik.11130