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hydro-biologist
hydro-biologist n.
Brit. 
/ˌhʌɪdrə(ʊ)bʌɪˈɒlədʒɪst/
, /ˌhʌɪdrə(ʊ)bʌɪˈɒlədʒɪst/U.S. /ˌhaɪdroʊˌbaɪˈɑlədʒəst/
one engaged in the study of hydrobiology./ˌhaɪdroʊˌbaɪˈɑlədʒəst/ΘΚΠ
the world > life > biology > study > person who studies > [noun] > ecology
migrationist1845
marine biologist1885
synecologist1913
ecologist1930
hydro-biologist1932
cryobiologist1962
saprobiologist1965
1932 Ecology 13 110 The fresh water hydrobiologists, especially the limnologists, have developed a third type of nomenclature based more upon the habitat than on the biotic communities.
1938 Times 19 Feb. 13/2 With Papanin..on Franz Josef Land..were P. P. Shirshoff, a hydrologist and hydrobiologist, E. K. Federoff, [etc.].
1964 Oceanogr. & Marine Biol. 2 379 The three large brackish water lagoons on the continental coast of the Baltic..have long attracted the interest of hydrobiologists.
1972 Nature 28 July 194/1 It is hoped that the committee will be able to produce a register of hydrobiologists working in Britain.
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