ý.,,: V. ý ýý . - Nottingham eTheses - University of Nottingham

undoubtedly true of Club Lake. The exceptional thermal gradients set up during the
summer combined with the rapid change in density found in Deep Lake produces a very
stable stratification. This explains why only the surface waters of the lake are ever heated
above 0°C. The stability of the thermal stratification means that heating of the water
column is exceptionally inefficient (Ferris & Burton, 1988). This is despite the retention
of 50% of solar radiation between September-December, 1977 (Ferris & Burton, 1988).
Inorganic nitrogen (NO2, NO3, NI-I1) was generally higher than in Ace Lake,
Pendant Lake or Triple Lake (Fig. 3.5,3.6 & 3.7) possibly due to low biological activity
allowing accumulation (Hand, 1980). It has been suggested (McLeod, 1964; Kerry et al.,
1977) that inorganic nitrogen is added through melt water streams, which
have been
shown to have considerably higher concentrations of these nutrients (Kerry et al., 1977).
It is not thought that decomposition of mummified remains of seals and penguins found
on the west shore of Deep Lake contributes any significant input (Kerry et al., 1977).
Ferris & Burton (1988) suggest that nitrogen is not limiting within the Deep Lake water
column - this is supported by the current data. However, they also suggest that the
inorganic nitrogen may not be available to photosynthetic organisms and absence of
detectable ammonium, as shown during September and November in the current study,
may inhibit photosynthesis, as ammonium is probably the preferred form of nitrogen for
the photosynthetic organisms (Brezonik, 1972).
Soluble reactive phosphate (SRP) concentration was generally lower in Deep
Lake and Club Lake than in Ace Lake or Pendant Lake, but higher than was
found in
Triple Lake (Fig. 3.8). SRP has an inverse relationship with bacterial abundance (r =
-0.97); thus as bacterial abundance increased, SRP concentration decreased, presumably
due to exploitation of SRP by photosynthetic bacteria. Kerry et al. (1977) suggest that in
Deep Lake the maximum production occurs when water temperatures are between 3 and
6°C. Although this is not supported by the chlorophyll a or SRP data it is supported by
the DOC data (Fig 3.9d) and by the number of bacteria cultured from water samples
during this period. DOC is generally higher in the summer when surface water
temperatures are within this range. DOC concentrations (Fig 3.9d & e) were considerably
higher in Deep and Club Lake than the other focus study lakes. Although the majority of
this large DOC pool is probably recalcitrant, a proportion of it is probably due to lo«
109