Ecology of humic and non-humic dune lakes, Fraser Island, with emphasis on the effects of sand infilling in Lake Wabby

Abstract

Aspects of physicochemical limnology and the zooplankton, littoral invertebrates and fish of dune lakes on Fraser Island are described and compared. The comparisons highlight differences between perched, humic lakes and the non-humic Lake Wabby, a water-table window with some morphometric and biological features typical of dune barrage lakes. Lake Wabby has been partially infilled by a mobile sand dune moving mainly in a north-westerly direction across the northern end of the lake. The maximum rate of dune advance estimated from aerial photos was 5.03 m year-1, between 1948 and 1958. Sand infilling between 1975 and 1984 altered the morphometry and substrate characteristics of the lake's eastern region and reduced maximum depth from 13.0 to 11.5 m and volume by 43%. The number of benthic invertebrates was reduced from 14 taxa in 1975 to six taxa in 1984; there was also a significant decrease in abundance of benthic Chironomini during this period (ANOVA, P < 0.05). In both years, an undescribed species of Conochironomus was the most abundant benthic invertebrate in Lake Wabby (250-700 individuals m-2). A new genus of Chironomini (near Paralauter borniella) was discovered. Lake Wabby supported 11 species of fish in 1975 and 1984, but the perched lakes had only one or two species. The five most abundant species in Lake Wabby in 1975 showed evidence of partitioning of food resources, of which the main components were benthic invertebrates and filamentous algae. Allochthonous food resources were not important in fish diets. The possible long-term effects of sand infilling on food resources, fish diets and the composition of the zooplankton in Lake Wabby are discussed.

Limnology of naturally acidic, oligotrophic dune lakes in subtropical Australia, including chlorophyll — phosphorus relationships

“…They are acidic, well-oxygenated, polymictic water bodies of low conductivity with dominant ions derived from a marine source. In these features, they resemble other 'water-table window' lakes such as Blue Lake on North Stradbroke Island (Bensink & Burton, 1975) and Lake Wabby on Fraser Island (Arthington et al, 1986). However, transparency is much lower in Lake Freshwater and Blue Lagoon, where Secchi disc depths were l-4.6 m compared to > 7 m in Blue Lake and Lake Wabby.…”

“…Lake Freshwater and Blue Lagoon have many physico-chemical features characteristic of other sand dune lakes in eastern Australia (cf. Bayly, 1964;Bayly et al, 1975;Arthington et al, 1986;Timms, 1986). They are acidic, well-oxygenated, polymictic water bodies of low conductivity with dominant ions derived from a marine source.…”

“…sand masses of eastern Australia are among the 'Water-table window' lakes (surface extrusions of world's naturally most acidic and oligotrophic ground water) are usually very transparent, with water bodies. Typically, total phosphorus in these Secchi disc depths > 7 m (Bensink & Burton, systems is < 10 pg * l-l, inorganic nitrogen 1975 ; Arthington et al, 1986). Conversely, the <50pg*l-',andpH<5.5,reaching<5.0inthe 'perched' type (in dune depressions elevated above local aquifers) usually have low transparency due to high concentrations of dissolved humic acids derived from basin humus layers and swamp leachates.…”

“…Dune lakes are unusual in two important aspects. First, whereas most Australian lakes are monomictic (Bayly &Williams, 1973), dune lakes are typically polymictic but may temporarily exhibit stratification and hypolimnetic anoxia (Arthington et&., 1986;Longmore, 1986). Secondly, despite depauperate phytoplankton and vascular plant communities, these systems support an unusual aquatic fauna, with at least 12 endemic macroinvertebrate species; also, several fishes and amphibians are abundant only there (Bensink & Burton, 1975;Neboiss, 1978;Arthington & Watson, 1982;Arthington, 1984;Arthington et al, 1986).…”

“…First, whereas most Australian lakes are monomictic (Bayly &Williams, 1973), dune lakes are typically polymictic but may temporarily exhibit stratification and hypolimnetic anoxia (Arthington et&., 1986;Longmore, 1986). Secondly, despite depauperate phytoplankton and vascular plant communities, these systems support an unusual aquatic fauna, with at least 12 endemic macroinvertebrate species; also, several fishes and amphibians are abundant only there (Bensink & Burton, 1975;Neboiss, 1978;Arthington & Watson, 1982;Arthington, 1984;Arthington et al, 1986). Thus, the basic limnology of Australian dune lakes is reasonably well understood; however, seasonal and spatial variations in chemical and biological parameters are largely unknown, apart from a general description in Longmore (1986) of seasonal trends in Hidden Lake, Fraser Island.…”