Factors related to mixing depth in meromictic lakes

Although the factors that influence the mixing depth of holomictic lakes have been well investigated, meromictic lakes, which never mix completely, have received little attention in this regard. The purpose of the present study was to determine if the geographic variation in mixing depth of the mixolimnion is related to the same factors as is the epilimnion depth. Data on the lake morphometry, elevation, latitude, salinity in the mixo- and monimolimnia, and the depths of the epi- and mixolimnia were obtained for 56 meromictic lakes worldwide. The depth of the mixolimnion was most closely related to the maximum depth of the lake (r2 = 0.69); no other variables were significant after accounting for depth. In the same data set, epilimnetic depth was also most closely related to maximum depth, rather than fetch, as earlier studies had found. Our results suggest that wind-induced turbulence has much less effect on the depth to which both the epilimnion and the mixolimnion circulate in meromictic lakes than does morphometry.