| dc.description.abstract | In October, 1968, 5.0 Kilograms of wild rice (Zizania aquatica
L.) seed were planted at 11 selected sites in Grassy Lake, in an attempt
to introduce a self-sustaining crop. Some success was obtained at all
sites, subject to the various effects of wind and wildfowl. As a sound
understanding of the aquatic environment was necessary before further
research could be carried out in connection with the wild rice, the temperature
relations, of primary importance in all limnological investigations,
were chosen as the subject of this study.
Temperatures in air, water, and soils were measured by a series
of 55 thermocouple units, mounted on 4 standards established in line
across the shore zone. Sixteen sets of weekly and diurnal readings
illustrate a pattern of uniform temperature in the vertical water column,
and the lack of any evidence of seasonal thermal stratification in the
water mass. Turbidity in varying degrees was present at all times, and
with increased adsorption of solar radiation in the upper layers of the
lake, mean water temperatures remained higher than mean air temperatures.
The distribution of heat in the surface layers of the water
was found to be relatively uniform, and temperature checks made throughout
the depth of the lake supported the findings at the thermocouple
station.
Heat energy was found to be readily transferred to the bottom
sediments, and mean temperatures for the first 20 centimetres of the substrate
remained within a few centigrade degrees of the temperature of
the vertical water column. Grassy Lake, situated near the southern tip of Sibley Peninsula,
on the north shore of Lake Superior, is exposed to the force of
the wind, and comparative anemometer readings give strong support to
this fact. The wind is believed to be instrumental in the constant
turnover and mixing of the lake waters, and to a considerable extent in
governing the distribution of the aquatic macrophytes in the region of
the shore. | |
