hypolimnion
(haɪpəʊˈlɪmnɪən)
Pl. hypolimnia.
[f. hypo- 2 + Gr. λιµνίον, dim. of λίµνη lake.]
The lower, cooler layer of water below the thermocline in a stratified lake.
| 1910, 1936 [see epilimnion]. 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. |
Hence hypolimˈnetic [cf. Gr. λιµνήτης living in marshes], hypoˈlimnial adjs., of or within the hypolimnion.
| 1928 Proc. Linn. Soc. CXL. 101 On account of the depth the hypolimnetic body of water is great compared with the epilimnetic. 1940 Hypolimnial [see epilimnion]. 1964 Oceanogr. & Marine Biol. II. 126 Alsterberg (1927) suggests that hypolimnetic (upper) water movements are confined to thin horizontal laminae, with currents in alternate directions. |