T. G. NORTHCOTE A N D ?'. C;. F ~ . I L S R Y

P i s k ~ r i c ~ X F S C O I C ~ nnd T e c h ~ ~ i r a k S P ~ V ~ C ~ S S c r l i o ? ~ B r i t k s l ~ C o k ~ r m hia Fish and U7ildlgc j e r ~ v z r I ~ , 04Ed

I ~ t s t i t t ~ f e of Fisheries , T h e U~aiversi ty nf Brilisl~ L'olrrrnbia Vancotcocr 8 , R.C.

XOR.~I~CO.FE, T. G., A N D T. 6. HALSEY. 1969. Seasonal changes in the lirnnology of some meromictic lakes in southern British Columbia. 9. Fish. Res. Bd. Canada 26: 1763-1 '787.

Sasonal changes in physical, chemical, and biological features are descr ikd in four small lakes which show diflerent types and degrees of rnerornixis. There is a wide range in total dissolved solid content between lakes as well as within lakes (surface to near-bottom): Yellow, 282 (surface) to 337 (bottom); White, 6229-7918; hlahoney,

basin rather than a strong chernocline; in the other lakes cotnplete mixing is inhibited rn

and between lakes are discussed. Other physical-chemical characteristics are given i r ~ less detail.

Purple sulphur bacteria occur in three of the lakes (White, ?+lahoney, Lyons) and in the latter two form discrete "plates" detectable by high frequency echo sounding (con- firmed by sampling). Seasonal changes in depth of the bacterial plates are considered in relation to some physical and chemical parameters. Ph>.toplankton, zooplankton. and benthos communities are discussed in relation to the degree of rnerornixis showrl by the lakes. I Received lanuarv 10. $969 I , ,

INTRODUCTION

I N A REGION such a s British Columbia which exhibits considerable lirr~nological diversity (Northcote and Idarkin, %963), it is surprising tha t inland meromictic lakes have not been described previously, although several coastal meromictic lakes are known (Williams e t a]., 1961; Northcote e t al., 1964; Northcote and Johnson, 1964).

circulation periocls (Hutch i~ l son , 1957) does not preclude t h e possibility tha t mixing m a y be inhibited by means other than chemical density gradients, bu t this is usually implied, especially since the bour-~clar-y betiyeen the mixo- limnion and t h e rnonimolirnnion is designated as a "chernocline." However,