hypolimnionn.

1910 E. A. Birge in Trans. Wisconsin Acad. Sci., Arts & Lett. 16 ii. 1005 I employ two new words in this paper... These terms are epilimnion, for the upper warm layer of water..and hypolimnion, for the lower colder water.

1936 Nature 5 Dec. 971/1 The result of this warming is that, in summer, a warm upper layer of less dense water, the epilimnion, comes to lie over a cold deeper water mass, the hypolimnion.

1957 G. E. Hutchinson Treat. Limnol. I. v. 341 The hypolimnia of all lakes.

1960 New Scientist 31 Mar. 773/3 The hypolimnion..has become deoxygenated as the vegetation decomposes and provides ideal living conditions for sulphate-reducing bacteria.

1971 Nature 26 Feb. 596/1 In summer months..the upper layers warm up more quickly than the lower regions and a sharp division in temperature—a thermocline—is formed... The reservoir or lake becomes divided into a lower, anaerobic cool layer or hypolimnion and an upper, warm aerobic epilimnion.

1928 Proc. Linn. Soc. CXL. 101 On account of the depth the hypolimnetic body of water is great compared with the epilimnetic.

1964 Oceanogr. & Marine Biol. 2 126 Alsterberg (1927) suggests that hypolimnetic (upper) water movements are confined to thin horizontal laminae, with currents in alternate directions.

1940 Nature 24 Aug. 255/1 The epilimnial current..opposes the hypolimnial current, causing turbulence at the thermocline.