Diatoms as indicators of wetland salinity in the Upper South East of South Australia

Abstract

Wetland degradation in the Upper South East of South Australia is an urgent management concern. Scant recent environmental data is available for the region and long-term monitoring data is lacking. Usually a palaeoecological analysis is able to reveal environmental change in the medium-to long-term past. However, the region is not conducive to palaeoecological investigation due to a fluctuating upper groundwater aquifer and alkaline soils whiclh have destroyed most microfossils. It was found that the diatom assemblage was preserved in the wetlands of the region for the period of European settlement. Analysis of the diatom assemblage enabled production of an inferred salinity curve. In combination with a small amount of historical information that was available, the salinity trend for the wetlands, for the period of European agricultural activities, was identified. It was found that, while groundwater salinity has been increasing, the wetland areas have experienced a freshening of surface water. This is due to an increase of throughflow of surface water, a result of constructed drainage systems flushing salts from the wetlands. Despite the freshening of wetlands they continue to degrade due to the changed hydrology, an impact of the drainage structures.

Recent human‐induced salinity changes in Ramsar‐listed Orielton Lagoon, south‐east Tasmania, Australia: a new approach for coastal lagoon conservation and management

“…In particular, many have been affected by hydrological modifications through the construction of causeways and artificial openings. An applied palaeoecological approach provides a method of determining and interpreting environmental trends and changes in ecosystem assemblages and dynamics that have occurred as a result of human activities (Taffs, 2001;Denys, 2003).…”

The Role of Surface Water Drainage in Environmental Change: a Case Example of the Upper South East of South Australia; an Historical Review

“…These changes and the alteration of the direction of surface water flow have been described in the preceding section. Additional hydrological changes are a change of wetland water depth with a tendency for wetlands to become shallower as surface water is encouraged northward via drains (Taffs, 2001), and a change in the period of inundation as the drains encourage through-flow of surface water (Taffs, 2001). Likely ecological impacts resulting from hydrological change are changes in the distribution and health of the aquatic and riparian vegetation communities by favouring salt tolerant vegetation adapted to infrequent periods of water logging (Jensen, 1993).…”

“…The main concern with this scheme, and hence its likely impact, is whether the quantity and quality of surface water required to maintain the water quality of wetlands will be available. Prior to drainage construction the wetlands received large volumes of surface water which continually flushed salts from the wetlands (Taffs, 2001). The endemic flora and fauna are adapted to such an environment and if it can not be recreated may experience difficulty adapting to a changed hydrological environment.…”

Holocene Diatoms From Gulf of Suez Sediments, Egypt

“…Fossil diatoms have been widely used to reconstruct past changes in pH, salinity, nutrients and climatic changes (Fritz, 1990;Fritz et al, 1991 andBrooks et al, 2001 andTaffs, 2001). Their indicator value is based on their welldefined ecological tolerances (Laušević and Cvijan, 1994).…”