Lake Albert, near Meningie
2011 Aquatic Ecosystem Condition Report
- Recent flooding freshened the lake but it continues to be saline, turbid and nutrient enriched.
- Low diversity and abundance of macroinvertebrates and absence of rare or sensitive species.
- Macroinvertebrate community includes saline tolerant species and a few freshwater species usually found in newly flooded freshwater wetlands.
- Very low diversity of aquatic plants with only one sedge growing around the edge of the lake but large blooms of algae recorded.
- Biological condition remains poor and it is unlikely it will improve due to the high salinity of the lake.
About the location
Lake Albert is connected to the southeast of Lake Alexandrina via the Narrung Narrows. It is a shallow lake with a catchment area of about 280 km2, which includes the major town of Meningie on its southeastern shore, about 150 km southeast of Adelaide.
The site selected for monitoring was located in the southern part of the lake, off Warrengie Drive on the western outskirts of Meningie.
The site was given a Poor rating because the ecosystem showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystem functions.
Prolonged drought and changes in water levels associated with limited River Murray flows in the mid to late 2000s had degraded the biological community of the site when it was assessed in February 2011. Until the recent prolonged drought, freshwater conditions had prevailed in the lake since the Goolwa Barrages were installed in the 1940s; salinity levels rarely exceeded 1,000 mg/L at a site monitored regularly near Meningie during the 1990s. During 2010, salinities over 16,000 mg/L were recorded from this section of the lake and would have contributed to the very poor biological communities present in the lake. In 2011, some improvement in community structure has occurred but many groups are still missing, and those species that were collected were present in very low numbers.
The recent refilling of the lake had extended the waterline back towards its historical shoreline, when it was sampled in February 2011. A sparse community of about 13 macroinvertebrate species was collected and included worms, eusirid amphipods, freshwater shrimps, soldierflies, at least four chironomids, a waterbug, three odonates and a type of caddisfly. Only the amphipods were abundant, with the other species occurring in very low numbers.
Most were generalists and tolerant invertebrates, capable of surviving in moderately saline to brackish waters. The presence of both freshwater species commonly found in floodwaters (freshwater shrimp Paratya and chironomid Cladotanytarsus) and saline specialists (chironomids Tanytarsus and Dicrotendipes) indicates that the site was in a state of change when it was sampled. No rare or sensitive species were collected.
The water was saline (salinity of 4,230 mg/L), well oxygenated (80% saturation), alkaline (pH 8.5) and very turbid or opaque. It contained very high concentrations of nutrients such as nitrogen (4.2 mg/L) and phosphorus (0.11 mg/L).
The sediments were mostly detritus, algae, sand and silt; they were anaerobic and sulfidic below the surface, which meant that they lacked oxygen and provided harsh conditions for most burrowing species to be able to tolerate.
Only one emergent plant, a club-rush (Bolboschoenus), occurred at the site. A large growth of a type of green filamentous alga (Cladophora) covered more than 35% of the edges of the shoreline and a large amount of small, free-floating algae called phytoplankton was also present, and probably contributed to the turbid appearance of the lake.
Patches of Common Reed (Phragmites australis), rushes (Juncus), Lignum (Muehlenbeckia cunninghamii) and introduced grasses grew in the riparian zone. Housing and private gardens associated with the rural township of Meningie covered most of the surrounding area.
Special environmental features
The site sampled lies within the Coorong and Lakes Alexandrina and Albert Wetland which is listed as a Ramsar Wetland of international importance due to the wide range of wetland habitats present, its importance for waders and waterfowl, and the presence of many nationally threatened species. No special features were noted at the site when it was sampled in February 2011.
Pressures and management responses
|The extended drought conditions prior to 2010 caused severe salinity related impacts. The salinity has decreased but it has not returned to its normal level, despite freshwater inflows (reducing ecological integrity).||The SA government is negotiating through the Basin Planning process to secure water to achieve water quality and ecosystem health objectives for the region. South Australia has determined the environmental water requirements for the CLLMM site, this report can be obtained from the Goyder Institute. For further information follow the link to the DENR website on environmental water requirements.|
|Livestock have direct access to many creeks in the catchment, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).|
|Limited riparian vegetation throughout the catchment, which means there is minimal buffer protection from agricultural runoff carrying sediments and nutrients (causing habitat disturbance and algal growth).|