
%0 Journal Article
%A Walker, D. 
%T Some physical and chemical features of two upland crater lakes in tropical north-eastern Australia
%J Marine and Freshwater Research
%D 1999/02/18
%V 50
%N 2
%P 159-177
%K 
%R https://doi.org/10.1071/MF97261
%U https://www.publish.csiro.au/paper/MF97261 
%X Lakes Barrine and Eacham, ~1.0 and 0.5 km2 area, 67 and 63 m depth respectively, lie at ~740 m a.s.l., ~17&#176;S in north-eastern Australia. Seasonal changes in their volumes modelled from meteorological data correspond well with observations at Eacham. Temperature profiles through 6 years show summer stratification with a metalimnion at 20&#8211;30 m; in winter, near isothermy is usually attained. At Barrine, thermal stability varies between winter and summer (&#60;500 and &#62;4000 g-cm cm-2 respectively). Mixing is related to low ground temperatures during periods of generally low thermal stability; exceptionally it penetrates to &#62;60 m. Oxygen saturation decreases from the surface to ~20% at the base of the euphotic zone (15&#8211;21 m) but oxygen is carried lower by mixing after which anoxia commonly rises to ~40 m. At Barrine, Fe-reducing redox (&#60;200 mV) usually occurs below 50 m, but during mixing this boundary falls to within 1 m of the mud&#8211;water interface. The Barrine solution is dilute (total dissolved solids 55&#8211;58 mg L-1), and that of Eacham is more so. A concentrated monimolimnion has developed in the lowermost 2&#8211;3 m at Barrine but not at Eacham. Sedimentation at the middle of each lake results from the continuous deposition of open-water products punctuated by the redistribution of coarser detritus from the &#8216;shallows&#8217; at times of deep mixing. The resultant laminations are preserved only at Barrine, protected by the chemical stability of the monimolimnion. 
