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salinity decreased from July to September, but the difference in salinity between Om and
8m increased dramatically from 4ppt to 15ppt. This could be due to settling out of denser
saline waters, although overall salinity decreased from July to September despite an
increase in ice thickness (Fig 3.1 c). Salinity showed a further decrease during November.
as warmer ambient temperatures started to melt the ice cover and thickness halved from
40cm to 20cm. This input of freshwater in to the lake decreased the overall salinity of the
whole water column (Fig. 3.4c).
Inorganic nitrogen (NO2, NO3 and NH4), e. g. nitrate, was much lower (35µg U')
for Triple Lake than previously recorded nitrate concentrations of >I OOpg U1 (Perriss et
al., 1995) (Fig 3.5c). However, it is not known which of the three basins that comprise
Triple Lake was sampled by Perriss et al. (1995). It is thought to of been one of the other
basins, as the maximum depth sampled during their study was 1 Om, when maximum
depth during this study was 8m. As none of the other basins were measured in the current
study and each basin is a virtually isolated system during the winter, it is possible that
inorganic nitrogen concentrations could be significantly higher in them. Nitrite levels
were uniform with time and depth, indicating a well mixed system. These concentrations
were similar to those seen in Ace and Pendant Lakes during September (Fig 3.6c).
Ammonium concentrations showed significant fluctuation throughout the year (Fig 3.7c).
Concentrations were higher in January than those seen in Ace Lake and Pendant Lake
during the first summer (Fig 3.7a and b). During July the concentrations increased more
than 4x to an average of 26µg L-1. These fluctuated with depth, but similar concentrations
were seen at Om and 8m while there was a small decrease between these depths. It is
presumed that low biological activity during the winter enabled the ammonium to re-
accumulate (Hand, 1980).
Soluble reactive phosphate (SRP) concentration (Fig 3.8c) showed significant
fluctuation during the year. Concentrations during January were initially high for Triple
Lake (-12µg L-1), but low compared with Ace (-52µg L-1) and Pendant Lakes (-17µg U
1), which may have been caused by high photosynthetic activity as seen by high
chlorophyll a levels ('-1.6µg U) in the surface water during January (Fig 3.1Oc)
compared with Ace Lake (-0.7µg U) or Pendant Lake (-0.2µg L-1). This may be a
consequence of the warm temperatures seen in Triple Lake during January (Fig 3.2c).
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