Michael Hickman

Effects of the discharge of thermal effluent from a power station on Lake Wabamun, Alberta, Canada — The epipelic and epipsamic algal communities

Abstract1.The epipelic algal standing crops were increased by the discharge of thermal effluent into Lake Wabamun, particularly in the discharge canal at station (03–04) and 05.2.The increase in the standing crop size of the epipelon was due to Oscillatoria amoena and O. borneti in the heated area, while the discharge canal provided the inoculum of the algae for the heated area of the lake.3.At station (03–04) the increased standing crop size was also a function of increased light penetration to the sediment due to the heated effluent keeping an area of the lake free of ice during the winter.4.The species composition of the diatoms was similar at all stations except in the discharge canal where there was a reduction in the number of diatom species.5Navicula cuspidate developed best in the discharge canal in the summer where water temperatures of 31°C were recorded.6.Amphora ovalis var. pediculus was the dominant diatom species during the winter under ice-cover.7.The heated effluent had no effect upon the standing crop or species composition of the epipsammon.8.Results obtained from the sediment core study showed that the shallow littoral zone of the lake is very disturbed due to wind-induced wave action.

Late glacial — early holocene palaeosalinity in Alberta, Canada — climate implications

Palaeolimnological and palynological records from climatically variable central Alberta, Canada, document periods of hypersaline lake conditions indicative of late glacial and early Holocene drought. The sensitivity of palaeolimnological indicators for inferring palaeoclimates is examined by comparing records from two sites at opposite ends of the regional precipitation gradient. Palaeosalinity is identified by the presence of Ruppia pollen, a hypersaline aquatic plant not presently growing in either lake, and diatom assemblages comprising both saline epipelic and planktonic species. Goldeye Lake (52° 27′ N; 116° 12′ W), in the relatively moist Rocky Mountain Foothills remained saline from its inception before ca 14500 years BP until ca 10400 years BP by which time pioneering forests had replaced tundra vegetation; however, freshwater planktonic diatoms dominated ca 12500 to 11500 years BP. However, dating problems endemic to the Foothills region make this chronology only tentative. Moore Lake (54° 30′ N; 110° 30′ N), in dry, east-central Alberta contained Ruppia only between ca 9000 and 6000 years BP. Freshwater diatoms dominated until ca 10000 years BP when they were succeeded by taxa characteristic of saline water. The lake remained saline until ca 6000 years BP. The late glacial period of palaeosalinity at Goldeye Lake occurred because the lake was surrounded by Cordilleran and Laurentide glacial ice, and therefore, cut off from moisture sources until the early Holocene by which time significant ice recession had occurred. Factors causing the second period of salinity remain unknown at this time. In contrast, by the early Holocene, Moore Lake was influenced by drought caused by high summer insolation induced by orbital fluctuations. Freshwater conditions were maintained through the Holocene in the Foothills region of west-central Alberta, but occurred consistently only over the last 4000 years in central and east-central Alberta. The warmer, drier climate during the early Holocene did affect lake levels in at least one headwater Foothills lake (Fairfax Lake — 52° 58′ N; 116° 34′ W). The severity of the drought increased in an easterly direction across the province.

The Late Quaternary palaeoenvironmental history of a presently deep freshwater lake in east-central Alberta, Canada and palaeoclimate implications

Abstract The palaeoenvironmental history of Moore Lake, Alberta, Canada (54°30′N; 110°30′W) has been investigated through analysis of pollen, diatoms, total chrysophyte stomatocysts, and sedimentary pigments, including the blue-green algal xanthophylls, oscillaxanthin and myxoxanthophyll. The initial lake was shallow. Vegetation of the region was treeless and no doubt reflected the unique late-glacial pioneering environment. Planktonic diatoms characteristic of a deep, eutrophic lake were dominant by ca. 11400 yr B.P., when a birch-spruce-dominated Boreal Forest developed. However, in response to early Holocene warmth and aridity the lake had become saline by ca. 10,000 yr B.P. when Chaetoceros spp. and Cyclotella caspia became dominant, while an open parkland/grassland vegetation had developed, subject to increased fire frequency. Freshwater taxa reappeared between ca. 9100 and ca. 8400 yr B.P. providing evidence of a wetter period. However, after ca. 8400 yr. B.P. planktonic saline taxa returned as dominants. By ca. 6200 yr B.P. birch-spruce forests were once again developed in the area in response to more effective precipitation. Between ca. 5800 and 4000 yr B.P. oscillations between fresh and saline diatom taxa occurred suggesting some aridity reversals. During the last ca. 4000 years planktonic eutrophic diatom taxa dominated. Diatom numbers were initially low but increased ca. 11,400 yr B.P. and remained high until ca. 10,000 yr B.P. They were minimal during the saline interval. Afterwards as the lake freshened numbers of diatoms increased and several large peaks occurred, perhaps in response to internal nutrient loading coupled with increased runoff and erosion. Oscillaxanthin concentrations were initially high, but during the saline interval they became undetectable, except during the freshwater interlude, and then, as the lake became fresh large maxima occurred. In contrast, myxoxanthophyll concentrations were high during this saline interval. Large myxoxanthophyll peaks occurred simultaneously with those of oscillaxanthin as the lake freshened. Overall lake palaeoproduction levels during the Holocene appear to have altered little. The Moore Lake record demonstrates short-lived palaeoclimatic changes of unknown cause superimposed upon the broad trends, and the value of the palaeolimnological record which can be much more sensitive than fossil pollen vegetation reconstruction in demonstrating climate history. Results are compared with others for western Canada and the Great Plains.

A palaeoenvironmental study of Fairfax Lake, a small lake situated in the rocky mountain foothills of west-central Alberta

Fairfax Lake is a small, oligotrophic to mesotrophic headwater lake situated in the Foothills of the Rocky Mountains of west-central Alberta (Latitude 52° 58′ N; Longitude 116° 34′ W). Through acquisition of a sediment core, and analyses of the diatoms, chrysophyte stomatocysts, pollen and sedimentary pigments, including myxoxanthophyll and oscillaxanthin, a palaeoenvironmental history of the lake has been determined. The sedimentary record spans ca. 13 200 years. An open tree-less vegetation existed in the region ca. 13 200–ca. 11 600 years BP. Maximum oscillaxanthin and myxoxanthophyll concentrations, hence the largest blue-green algal populations, occurred during the same interval. With increasing temperature pioneering parkland vegetation appeared ca. 11 600 years BP but was replaced ca. 10 100 years BP by spruce forest. Pine appeared ca. 7800 years BP and this marked the development of the present day montane boreal forest. Diatoms were not found until ca. 11 255 years BP. Benthic taxa dominated but by ca. 10 100 years BP planktonic taxa had become more prominent. Lake levels are interpreted as having risen, and the lake water was probably more transparent. Maximum chlorophyll and total carotenoid concentrations occur ca. 11 255 to ca. 7000 years BP corresponding to the warm early to mid-Holocene period. Lake nutrient levels appear to have been higher prior to ca. 7000 years BP, and the lake has changed from being eutrophic during the early Holocene to its present status as an oligotrophic to mesotrophic lake. Subtle hydrological changes have also occurred in the catchment as water levels do not appear to have remained constant.

Baptiste Lake, Alberta — A late Holocene history of changes in a lake and its catchment in the southern Boreal forest

Palaeoenvioonmental investigations based upon sediment cores retrieved from Baptiste Lake, Alberta (longitude 114° 34′ W; latitude 54° 45′ N) show that the sedimentary record spans approximately 4600 years. The pollen record reflects the dynamic nature of the southern boreal forest. These dynamic changes are reflected in the lake record itself. Climate and vegetation do not appear to have changed significantly; however, the lake does appear to have responded to climate change, particularly during the last 1000 to 700 years when temperatures decreased to modern values. It is at this time that there is a marked change from laminated to unlaminated sediments suggesting a change from meromixis to one where complete circulation takes place. As a result monolimnetic nutrients are released into the epilimnion. Catchment perturbations have occurred with fire appearing most important. Sedimentation rates are high on average and irregular, due in part to the many inflowing streams, catchment topography and fire. Lake production has always been high. Carbonate bands occur in the core at irregular intervals and appear to originate biogenically. Peaks in the number of pyrite spherules suggest that deoxygenation of the water column occurs irregularly, and the intensity of anaerobic conditions again varies. The diatom record indicates a eutrophic lake with Stephanodiscus hantzschii the dominant species. The lake appears to have steadily become more eutrophic with time and a succession of species has occurred with Asterionella formosa being succeeded in turn by Stephanodiscus niagare, Cyclotella comta and finally, Melosira granulata. The appearance of Melosira granulata corresponds to the change from laminated to unlaminated sediments, and to then both autochthonous and allochthonous nutrient input.

Effects of the discharge of thermal effluent from a power station on Lake Wabamun, Alberta, Canada — Limnological features

The physical and chemical aspects of Lake Wabamum have been described. Modifications to the thermal and dissolved oxygen regimes through the discharge of thermal effluent into the eastern region of the lake are discussed. This discharge has, therefore, changed the environmental conditions under which the biota exists in the eastern portion of the lake. It was also shown that this discharge of heated water had no effect upon the water chemistry while the power station itself contributed silica, in the form of fly ash, to the system. Tables of the phytoplankton, zooplankton, aquatic macrophytes, and fish are provided. From a biological and limnological stand point the lake can be classified as a moderately eutrophic lake, especially in the eastern portion.

The effect of the discharge of thermal effluent from a power station on the primary productivity of an epiphytic algal community

The discharge of thermal effluent from a power station has been shown to cause an increase in the standing crop size of the epiphyton associated with Scirpus validus. As a result the mean primary productivity, as measured by the 14C method, increased, primarily because of the large spring and summer maxima caused by Oedogonium and Spirogyra, Epithemia turgida, Mougeotia, Amphipleura pellucida, Nitzschia fonticola and Rhopalodia gibba were apparently detrimentally affected by the thermal effluent. The algal populations in the non-heated areas did not appear to be photosynthesising at optimum temperatures, while the continuous flow of heated water appeared to cause a decrease in photosynthetic efficiency of the algae in the heated area.

Late Quaternary diatom response to vegetation and climate change in a subalpine lake in Banff National Park, Alberta

The late Quaternary diatom record from subalpine Crowfoot Lake, Banff National Park, Alberta (lat. 51° 61′N; long. 116° 31′W) has been analyzed. Results are related to independently inferred vegetation and climate changes. No diatoms were found in the basal diamict that predates 11330 14C yr BP. Very few occur until ca. 10 10014 C yr BP probably due to the short time between de-glaciation and an advance of the Crowfoot Glacier during the ‘Younger Dryas Chron’. Initial pioneering species were characteristic of alkaline water and calcareous organic sediments. They appeared as sediments became organic and laminated suggesting increasing water clarity, and as the Pinus-dominated forest expanded and the climate warmed. After ca. 9060 14C yr BP diatom numbers increased rapidly, reaching a maximum prior to the Mazama tephra; they remained high until ca. 3500 14C yr BP. The period between ca. 9060 and 3500 14C yr saw timberline elevation increase and the dominance of xerophytic taxa. These are consistent with early to mid-Holocene warmth and aridity. Diatom productivity reflects the warm climate and presumably longer ice-free season, a stable catchment and transparent water. Decreases in diatom productivity coincide with a vegetation change with reduction of xerophytic taxa and the appearance of a closed Picea-Abies forest, hence a cooler, wetter climate at ca. 4100 to 3500 14C yr BP. The diatom numbers during the Neoglacial were of the same magnitude as prior to ca. 9060 14C yr BP. Small species of Fragilaria (overwhelmingly Fragilaria construens v. venter) became extremely dominant during the period of high diatom productivity, and remained so thereafter. Recovery of the lake appears to have been rapid after deposition of the Mazama tephra. Maximum occurrence of Cyclotella radiosa occurred ca. 8000 14C yr BP during the warm early Holocene and may reflect this warmer climate, a longer ice-free season than presently, perhaps less turbid water, or it may reflect a subtly higher nutrient status of the lake water. The diatom record of Crowfoot Lake has responded with sensitivity, particularly in terms of productivity, to the Holocene vegetation and climate changes.

A COMPARISON OF PERIPHYTIC ALGAL BIOMASS AND COMMUNITY STRUCTURE ON SCIRPUS VALIDUS AND ON A MORPHOLOGICALLY SIMILAR ARTIFICIAL SUBSTRATUM1

Chemically inert, cylindrical rods positioned in the littoral of two eutrophic Alberta lakes supported higher periphytic algal biomass (measured as total chlorophyll a) than nearby morphologically similar culms of Scirpus validus Vahl. during most of the summer. Upon initiation of macrophyte senescence, biomass on the two substrata became more similar. Experiments were conducted to investigate the basis for these observations. Whole extracts of intact vegetative Scirpus culms had no effect on periphyton photosynthesis, suggesting that the natural substrata do not produce water‐soluble allelochemicals. Various modifications of the rod surfaces (roughening, wax coating, wax color) were used to test whether surficial properties of Scirpus culms influenced periphyton accumulation. Roughened rods supported levels of biomass similar to those of smooth rods, and both substrata developed structurally complex periphyton communities. Rods covered with paraffin wax had periphyton communities that were lower in biomass and structurally more simple than those on un‐coated rods or on Scirpus culms. Coloring of the wax coating had no consistent effect on periphyton accumulation. We hypothesize that the hydrophobic cuticle on actively growing Scirpus culms retards the development of precursors for attachment by periphytic algae. Upon senescence of the culm and loss of epidermal integrity, colonization of culm surfaces by periphytic algae may occur in a manner similar to that on artificial substrata.

THE RELATIONSHIP BETWEEN PLANKTONIC ALGAE AND BACTERIA IN A SMALL LAKE

The seasonal changes and vertical distribution of the aerobic and anaerobic bacteria in a small edaphically eutrophic lake which exhibited thermal and chemical stratification are described. There was some correspondence between the phytoplankton and particularly the aerobic bacteria but this was not consistent. Increases in the numbers of anaerobic bacteria coincided with the low dissolved oxygen concentrations in the hypolimnion when algal populations were first senescent and then increasing actively in size.