thermocline

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thermocline

a boundary layer, found in lakes or enclosed seas, between warm upper water and cooler lower water, that is usually maintained only under calm conditions in summer.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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For most of the summer, the metalimnion acts as a barrier to walleyes.
Therefore, most of the veligers observed in the current study might come from the metalimnion and some from the epilimnion, although this needs to be confirmed in further experiments by sampling veligers at different depths.
All three daphniid treatments reduced resources to similar levels in the hypolimnion (9-10[degrees]C), but in the metalimnion (19-21[degrees]C) and epilimnion (25-26[degrees]C) the rank order of relative exploitative ability was consistently D.
A third period between 10:00 am and 10:00 pm on September 13th exhibited the same sequence of heat penetrating the upper layers and generating the stepped pattern in the thick metalimnion. From 1:00 pm on September 13th the air temperature rose from 17[degrees]C to 29.8[degrees]C (at 4:00 pm), leading to the strongest thermal stratification recorded in the period of study.
Flagellates in the fertilized lakes did not increase relative to the reference lake except for the metalimnion of Peter Lake.
and E.Bic.) were concentrated in deeper layers in daytime; at night there was a large decrease, especially in the layers near the metalimnion. Group J (Coelastrum sphaericum Nag) also contributed more during the morning, mainly between 1.0 and 3.0 m, with biomass reduction beginning at 9:00 PM (Figure 5).
The shallow enclosures were nonstratified from the surface to the sediments, whereas the deep enclosures were thermally stratified with a summer metalimnion between 3 and 5 m [ILLUSTRATION FOR FIGURE 1 OMITTED].
The region of greatest change in temperature and/or oxygen content below the epilimnion is called the metalimnion while the deepest, coldest, and relatively undisturbed region is the hypolimnion.