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suggested that input of bacteria and PNAN may occur from melt water streams in which
PNAN are especially abundant (Kerry et al., 1977; Hand, 1980). but the 1999/2000
summer was abnormally cold and overcast (Laybourn-Parry et al., 2002) and most lakes
did not melt out during this season. It is therefore possible that there was a severe
reduction in melt water input into Deep Lake which would have meant a severe reduction
in biotic input during favourable growth conditions. This would have left the lake
impoverished and could account for the overall low bacterial population and absence of
PNAN.
3.3.3 -
Oval Lake
Oval Lake was not studied during the focus study but has subsequently been
shown to support one AFP+ bacterial isolate within its culturable biota (Chapter 4).
Therefore it was considered prudent to compare this lake to Ace Lake, Pendant Lake and
Triple Lake (Table 3.2 - subsequent AFP analysis has shown that only these four lakes
have AFP active bacteria in their populations, refer to chapter 4), to note any similarities
between them.
Oval Lake is meromictic (permanently stratified) (Burke and Burton, 1988;
Gibson, 1999), therefore its salinities and temperatures in the mixolimnion were expected
to increase with depth as is seen in Ace Lake (Laybourn-Parry et al., 2000).
Inorganic nitrogen (NO2, NO3, NH4) (Table 3.2) showed a similar concentration
at Om during the summer as in Pendant Lake, Ace Lake and Triple Lake (Fig 3.5-3.7).
There was no detectable nitrate, and ammonium was significantly lower than Pendant
Lake or Triple Lake. This is indicative of Oval Lake's meromictic status. Nitrite
concentrations were very similar to those of Ace Lake, Pendant Lake and Triple Lake.
Oval Lake had an identical concentration of SRP to Ace Lake, strengthening the
similarity between these two meromictic lakes. Higher levels of DOC in Oval Lake
compared with Ace Lake could be due to inefficient degradation of DOC due to the high
salinity inhibition of activity as seen in Triple Lake.
Chlorophyll a concentration was similar to Ace Lake, although slightly higher,
possibly due to increased nutrient levels as seen in higher salinity lakes, e. g. Triple Lake
(Table 3.2) (Laybourn-Parry et al., 2002). There are no records for bacterial, PNAN or
HNAN abundance as these were not recorded for the summer lake samples. Further study