Cyanobacteria are widespread in freshwater benthic environments, which include wetlands, lake littoral zones, streams and rivers. This chapter outlines the major constraints on cyanobacteria in these environments. Environmental and ecological factors that determine the diversity and biomass of cyanobacteria in the freshwater benthos include physical disturbance in the form of turbulent energy and wetting/drying cycles, temperature, light, nutrients and grazing. Nutrients are particularly important, because their concentrations can control cyanobacteria within and among benthic habitats, and cyanobacteria can reciprocally influence nutrient availability via nitrogen fixation and phosphorus co-precipitation by calcareous species. Top-down control via grazing may also help to explain diverse patterns of cyanobacterial abundance, because of the interactions which occur between the cyanobacteria and their predators. Anthropogenic activities sometimes have a pronounced effect on the environmental conditions that control cyanobacterial diversity and abundance in these habitats and the resulting functional changes in the communities can result in a loss of important ecosystem services provided by these organisms.

Cyanobacteria in Freshwater Benthic Environments

Results from paleoenvironmental investigations of Lake Wabamun, Alta. (longitudes 114°26′ and 114°44′ W; latitudes 50°30′ and 53°35′ N), show that the sedimentary record spans the Holocene period i...

Lake Wabamun, Alta.: a paleoenvironmental study

The planktonic microflora of lakes.

Conservation efforts to sustain water resources and aquatic biodiversity in boreal watersheds will require reliable information on the recent status of various indicator species and an improved understanding of the risks to aquatic biodiversity posed by resource development activities. We reviewed the recent state of knowledge on the responses of aquatic biodiversity to forest management, pulp and paper mill effluents, hydroelectric impoundments, mining of minerals and metals, oil sands extractions, and peat mining and offer a prognosis for aquatic biodiversity under each of these environmental stressors. Despite the prevalence of natural resource development in Canada's largest forest ecosystem, there was a limited amount of published literature on the effects of many of the disturbance types on various indicators of aquatic biodiversity, making it difficult to produce a current and reliable status assessment. Across most of the boreal zone, there is a lack of coordinated, consistent data collection for many of the bioindicators and disturbance types discussed in this review. Forecasting the future state of aquatic biodiversity across the boreal zone is challenged by increasing natural resource development and its interactions with other stressors, especially climate change. The cumulative effects of multiple stressors coupled with resource development activities in boreal watersheds remain largely unknown. More importantly, the ecological thresholds for these cumulative effects (that is, the point at which aquatic ecosystems and their biodiversity cannot recover to a desired state within a reasonable time frame) are also unknown and remain gaps in our knowledge. The recent literature identifies a number of risks to aquatic biodiversity at local (tens of square kilometres) to regional (hundreds of square kilometres) scales associated with natural resource develop- ment. There are indications that many of these risks can be minimized by "greener" technologies for resource development and reclamation, practical conservation planning and regulation, and increased stewardship in watershed management, although the effectiveness of many of these measures cannot yet be assessed from the published literature.

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Impacts and prognosis of natural resource development on aquatic biodiversity in Canada's boreal zone 1

Effects of thermal effluents on the dynamics of larval helminth parasites and on populations of Chaetogaster limnaei limnaei and Chaetogaster limnaei vaghini (Annelida: Oligochaeta) harbored by Physa gyrina (Mollusca: Pulmonata) were studied at Lake Wabamun, Alberta. Thermal effluents provided the necessary conditions to maintain digenean parasite transmission throughout the year between definitive and intermediate hosts, and increased the prevalence of certain parasites, especially the metacercarial stages.At temperatures above 24 °C prevalences of C. l. limnaei and C. l. vaghini decreased in the lake, and at these temperatures in the laboratory C. l. limnaei abondoned the snails and perished. Under experimental conditions the number of Echinoparyphium recurvatum larvae penetrated Physa gyrina was inversely related to the number of C. l. limnaei present. It was also observed that these oligochaetes actively ingested digenean larvae. Elimination of C. l. limnaei caused by thermal effluents has augmented t...

Effects of thermal effluents on parasites and commensals of Physa gyrina Say (Mollusca: Gastropoda) and their interactions at Lake Wabamun, Alberta

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.

Donald N. Gallup

Papers

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