Hydrological change in the Coorong Estuary, Australia, past and present : Evidence from fossil invertebrate and algal assemblages
- Authors: Reeves, Jessica , Haynes, Deborah , Garcia, Adriana , Gell, Peter
- Date: 2015
- Type: Text , Journal article
- Relation: Estuaries and Coasts Vol. 38, no. 6 (2015), p. 2101-2116
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- Description: Estuaries are defined by change; both on a diurnal basis, balancing tidal inflow with riverine outflow, and over hundreds or thousands of years through geomorphic evolution and sea level variability. However, contemporary management and protection underpinned by international agreements, such as the Ramsar Convention, presume that wetlands change within only limited ranges based on their contemporary conditions. Adaptive management strategies for cyclic or even directional change are more robust if underpinned by evidence from longer-term records, such as those obtained from palaeoecological records preserved in sediment cores. Such is the case for the Coorong lagoon in southern Australia; here analysis of assemblage changes of key invertebrates and algae preserved in the sediments reveals the variability of natural conditions well before the instrumental record. During the mid-Holocene to late Holocene and up until the mid-twentieth century, assemblage changes in microfauna and flora indicate variable salinity and water clarity associated with both fresh continental and marine water inputs. By contrast, in the south lagoon, the proxies indicate periodically enhanced salinity. The most significant changes in ecology and sedimentation are apparent after the 1950s; hydrological modifications have changed the influence of both continental and tidal water, producing conditions that are unusual in the long-term history of the site. © 2014, Coastal and Estuarine Research Federation.
A history of aquatic plants in the Coorong, a Ramsar-listed coastal wetland, South Australia
- Authors: Dick, J. , Haynes, Deborah , Tibby, John , Garcia, Adriana , Gell, Peter
- Date: 2011
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. 46, no. 4 (2011), p. 623-635
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- Description: The Coorong in South Australia is an internationally recognised ecologically significant coastal lagoon that extends 140 km south-east from the mouth of the River Murray. The Coorong has increasingly been impacted by a variety of human activities. Declining migratory bird abundance has been linked to the loss of Ruppia tuberosa, an aquatic plant that is the main feedstock for a wide variety of water birds. Analysis of Ruppia remains from a radiometrically dated core in the southern lagoon of The Coorong shows that the salt-tolerant annual Ruppia tuberosa has only been present at this site in recent times. By contrast, the perennial Ruppia megacarpa, which has limited tolerance to elevated salinity, appears to have been present at the site for several millennia, although it had never been observed in ecological surveys of this part of The Coorong. Diatom analysis from the same core reveals a shift from estuarine/marine assemblages to an assemblage reflective of elevated salinity levels. Charophyte, ostracod and foraminifera remains also indicate that the change in the aquatic plant community is associated with increased salinity at the study site since European settlement. Elevated salinity is the result of catchment modifications which have reduced freshwater inflows at the northern and southern extremities of The Coorong, and marine input via the Murray Mouth. This study demonstrates the utility of multiproxy palaeoecological data in addressing complex management questions. In the absence of such information, managers must ultimately rely on data sourced only from the historical record which, more often than not, is already skewed by the impact of European settlement. © 2011 Springer Science+Business Media B.V.