Introduction
    Drainage Basin Characteristics
    Lake Basin Characteristics
    Water Quality
    Biological Characteristics (Introduction)
    Biological Characteristics (Plants)
    Biological Characteristics (Invertebrates)
    Biological Characteristics (Fish)
    Biological Characteristics (Wildlife)
    References

Biological Characteristics (Plants)

Plants

Plants are primary producers on land and in water. On land the primary producers are plants like grasses, mosses, flowers and trees; in water they are tiny plants like algae (which can float freely in a buoyant world as phytoplankton, or grow attached to the lake bottom and other surfaces such as other plants, rocks or even sand grains) or large conspicuous aquatic macrophytes which are sometimes called "weeds" but also include cattails and bulrushes that grow along many natural lakeshores.

Phytoplankton

Algae are the most primitive plants, having no roots, no vascular system and no flowers. In lakes they may grow attached to other plants, to rocks or upon the submerged sediments, but usually the most conspicuous algae in Alberta lakes are the phytoplankton. The word "plankton" comes from the Greek word planktos which means "wandering" and so the phytoplankton is an assemblage of tiny aquatic plants which are freely suspended in water. Bacteria and fungi are also a component of the plankton, but they are not conspicuous.

Most people become aware of planktonic algae when the population becomes so abundant that the water turns bright green, or a bluish-green scum forms on the surface of the lake and drifts onto shore to die and release distinctly unpleasant odours. Phytoplankton may not be appealing en masse, but taken individually and viewed with a microscope, algae are spectacularly beautiful, as lovely as Christmas tree ornaments and as delicate as snowflakes.

TYPES OF PHYTOPLANKTON  The incredible beauty and diversity of the algal form has awed lake scientists since it was first discovered that a single drop of lake water could contain more than a hundred algal species. Morphological characteristics such as cell shape, cell walls and the presence or absence of flagella, and biochemical characteristics such as pigment composition as well as physiological traits such as the mode of nutrition, are some of the features used to classify algae into a number of major taxonomic groups. The important ones found in Alberta lakes include the blue-green algae (Cyanophyta or Cyanobacteria), green algae (Chlorophyta), golden-brown algae (Chrysophyta), diatoms (Bacillariophyta), cryptophytes (Cryptophyta), dinoflagellates (Pyrrhophyta or Dinophyta) and euglenoid flagellates (Euglenophyta).

The blue-green algae (Cyanophyta) are the most primitive group of algae, in fact, there is ongoing debate among scientists as to whether this group is more closely allied to bacteria than to plants. Like bacteria, the blue-green algae are single-celled organisms which lack a true nucleus; instead, the chromosomal material is dispersed throughout the cell. However, unlike bacteria, they contain the photosynthetic pigment chlorophyll a. In most plant cells the pigments are localized in discrete chloroplasts, but in blue-green algae they are dispersed throughout the cell. There are two groups of blue-green algae (Fig. 30). In one group, cells are solitary or cluster into colonies, for example Microcystis and Synechococcus. Species in the other group form filaments resembling beaded necklaces with occasional specialized cells including heterocysts, which are capable of fixing nitrogen gas, and akinetes, which appear to be specialized to withstand adverse conditions. Examples of filament-forming blue-greens common in Alberta include species of Anabaena, Aphanizomenon, Lyngbya and Oscillatoria.

The green algae (Chlorophyta) have a true nucleus and the pigments are localized in one or more discrete chloroplasts in each cell. Pigments are predominantly chlorophylls and food is stored as starch. Some species have two, four, or up to eight flagella and are either solitary (single celled) or colonial (Volvox spp.). Some species are nonflagellate and solitary as in the genus Ankistrodesmus or colonial as in the genus Scenedesmus (Fig. 31). In one group of green algae, the desmids, each cell is constricted into two semi-cells, making each individual look as though it is floating attached to its own mirror image, as in the genus Staurastrum. Chlorophytes also grow as long filaments attached to rocks and aquatic plants and form long, hairlike masses, for example, species of Cladophora and Oedogonium. There is also a species of Cladophora that forms matted balls up to the size of tennis balls which roll around in shallow water.

The golden-brown algae (Chrysophyta) have a true nucleus and chloroplasts in which the dominant pigments are brown or golden brown (carotenes and xanthophylls) as well as green chlorophylls. Food storage is in the form of oils. Species are unicellular or colonial and some have flagella. Examples are species of Dinobryon and Synura (Fig. 32).

The diatoms (Bacillariophyta) are among the most exquisitely beautiful of the algae. They have a true nucleus and their photosynthetic pigments (carotenes, xanthophylls and chlorophylls) are contained in chloroplasts. Food storage is in the form of oils. Species are unicellular or colonial; they have no flagella. Diatoms usually have thick, ornate cell walls of silica although some planktonic genera have only very lightly silicified cell walls (eg. Rhizoselenia). The walls form two distinct halves, like the top and bottom of a box, and they are marked with grooves and holes which form definite, intricate species-specific patterns (Fig. 33). Diatoms are usually of two basic shapes: elongate, as in cigar-shaped Navicula, Pinnularia and Nitzschia, or round, as in species of Stephanodiscus and Cyclotella. Colonial diatoms include the star-shaped Asterionella and ribbonlike Fragilaria. The cell walls of the diatoms and the golden-brown algae resist decay and remain in the lake sediment for thousands of years. Therefore, when a core of lake sediments is taken and the age of various strata identified, the kinds of diatoms present thousands of years ago can indicate the predominating conditions of pH, water level, salinity and trophic conditions. Paleolimnological studies of diatoms and pollen grains have been conducted by researchers at the University of Alberta on 18 Alberta lakes, including Baptiste, Buffalo, Cooking, Hastings, Moore, Spring and Wabamun.

The cryptophytes (Cryptophyta) are single, biflagellate cells with pigments concentrated into two chloroplasts. Food is stored as starch. Examples are species of Cryptomonas and Rhodomonas (Fig. 34).

The dinoflagellates (Pyrrhophyta) are single biflagellate cells with flagella of different lengths. One flagellum is located in a transverse furrow which encircles the entire cell, and the other is in a longitudinal furrow running backwards along one half of the cell. Of all the algae, the dinoflagellates are the fastest moving. Each cell contains numerous chloroplasts; food is stored as starch or oil. Some species of this group can be consumers as well as producers; their main food is other algae. The most common dinoflagellate in Alberta, Ceratium hirundinella, looks like a three-legged, scaly Eiffel tower (Fig. 35).

The euglenoid flagellates (Euglenophyta) are unicellular flagellate algae. Pigmented and nonpigmented genera occur; the pigmented ones usually have conspicuous green chloroplasts. The common genera include Euglena, Trachelomonas and Phacus. They occur in most Alberta lakes in all habitats and can become particularly abundant in organically polluted water.

MEASUREMENTS OF ALGAL POPULATIONS  The size of planktonic algae is extremely variable, ranging over seven orders of magnitude. If one of the tiniest forms (for example, a blue-green, Chroococcus spp.) were the size of a golf ball, then a large colony of Microcystisaeruginosa would be as big as a house. Nevertheless, even this "large colony" would actually be smaller than the head of a pin! With individual cells and colonies so small, scientists need efficient ways to assess the crop of algae in a lake. The simplest way to estimate the amount of phytoplankton in a lake is to measure the chlorophyll a concentration in a representative sample of water as described in the Water Quality section. Chlorophyll a, which is a major photosynthetic pigment and universally distributed among algae, accounts for approximately 0.5% to 2% of the dry weight of algae, depending on the species. Chlorophyll a concentrations are not only fairly simple to measure but results are very reproducible. As a rough guideline, lakes with average summer concentrations of chlorophyll a less than 5 µg/L are clear and appear algae-free, lakes with average concentrations over 25 µg/L are soupy and not attractive for swimming. A chlorophyll a concentration over 30 µg/L at any time is considered to be an "algal bloom".

Although an estimate of the concentration of chlorophyll a in a lake is very useful, it tells nothing of the species of algae present which can be indicative of various conditions. Therefore, biologists sometimes undertake a more painstaking way to assess the amount of algae in a lake. The relative abundance of each species of algae present in a representative sample of water is determined, then the biomass of each species is estimated. The sample of water is usually taken from the euphotic zone with a tube that is lowered from the surface to the depth of the bottom of the euphotic zone. The water is trapped in the tube, the sample is brought to the surface, placed in a jar and a preservative is added so the algae cannot reproduce or be eaten before the sample can be analyzed in the laboratory. To measure the weight (biomass) of each algal group and determine its proportion of the total biomass, algae are allowed to settle to the bottom of the water sample in a special cylinder; individual cells, colonies or filaments are then identified and counted under a microscope. The number of individuals for each species is then converted to a volume based on measurements made on representative cells of that species in the sample. The size of cells of different species covers a wide range, for example, one cell of blue-green Anabaena flos-aquae has an approximate volume of 50 µm³; one cell of dinoflagellate Ceratium hirundinella has an approximate volume of 65,200 µm³. Since phytoplankton cells are neutrally buoyant, a volume of phytoplankton weighs the same as a similar volume of water, 1 cubic centimetre weighs 1 gram. Once the weight of each species is determined, the weights are then totalled to give an estimate of the total phytoplankton biomass (wet weight) per unit volume of water. Estimates of algal crop based on chlorophyll a measurements and biomass calculation usually follow the same pattern over a season, if samples are taken from the same lake at the same time.

SEASONAL VARIATION  Seasonal variation in phytoplankton biomass and species composition occurs because algae are affected by physical factors such as temperature, currents, lake mixing, light intensity and day length; chemical factors such as dissolved oxygen, nutrient concentrations and salinity; and biological factors such as disease and the density and community composition of their consumers. The abundance of a particular species of algae depends on the balance between factors that cause the population to increase (reproduction, recruitment from lake sediments and immigration via inflowing water) and factors that cause the population to decrease (sinking, death, including grazing by zooplankton or other algae, and loss from the lake through outflowing streams).

In Alberta lakes, as in other north-temperate lakes, phytoplankton biomass is generally lowest from December through February because the cold and darkness under ice and snow result in minimal algal growth. If the ice on a lake is clear and free of snow, under-ice algal blooms may occur occasionally, as in Driedmeat Lake in the winter of 1985/86 when chlorophyll a concentrations reached an amazing 459 µg/L. Algal biomass often peaks in the spring when temperature, light levels and nutrient concentrations increase, the latter as a result of lake mixing or a high concentration of nutrients in runoff. A decline in late spring usually occurs as the lake water becomes thermally stratified and nutrient levels in the upper layers of water decrease and algal production slows. At the same time, the abundance of phytoplankton consumers, such as zooplankton, increases. In shallow nutrient-rich lakes such as Nakamun, Baptiste, Tucker, Little Fish, Amisk and Figure Eight lakes, algal blooms occur regularly all summer. In lakes with lower concentrations of nutrients, such as Narrow, Twin and Ethel lakes, algal biomass may remain low until fall. Another peak may occur as the lake water mixes in the fall because nutrients are again recycled into the surface water. In reservoirs with low nutrients and rapid flushing rates, like Spray Lakes, Ghost, Travers and Little Bow Lake reservoirs, algal biomass is low all year.

In spring and fall, the phytoplankton community is dominated by a mixed community of small-celled species from the diatom, green algae, golden-brown algae and cryptophyte groups that have adapted to grow rapidly at low temperatures, relatively low light levels and short day-lengths. These small-celled species are generally very susceptible to grazing by zooplankton. In summer, larger-celled species such as Ceratium hirundinella, large diatoms or colonial blue-greens such as Anabaena flos-aquae are often dominant. These species grow less rapidly, but are generally resistant to zooplankton grazing. This seasonal succession is clearly seen in freshwater lakes such as North Buck, Buck, Baptiste and Isle, and slightly saline lakes such as Gull. In more saline lakes such as Miquelon, Oliva and Peninsula, this typical seasonal succession is altered and fewer algal species are present because fewer species can thrive in saline water.

Blue-green algal blooms in summer are a concern in many Alberta lakes because these algae tend to accumulate in very thin layers near the lake surface. Wind and wave action concentrate these unattractive scums into bays or along the shore. When the algae in the scum eventually decompose, blue pigments in the cells are released and it looks as if blue paint has been spilled in the water or along the shore (Fig. 36). Strong sewagelike odours are produced. In general, the development of summer blue-green algal blooms in Alberta is triggered by high water temperatures and the onset of low dissolved oxygen concentrations over bottom sediments, which often results in high total phosphorus concentrations.

The most troublesome blooms in Alberta are caused by three species of blue-green algae (Anabaena flos-aquae, Microcystis aeruginosa and Aphanizomenon flos-aquae) although other species can also cause blooms. Blooms of the first two species can make the lake water look like pea soup. Aphanizomenon flos-aquae occurs in flakes that look like tiny grass clippings. Some species of blue-green algae produce toxins which can be fatal to animals. The distribution of these toxins is not well documented in Alberta, although certain lakes such as Hastings, Baptiste and Little Fish have had known occurrences of toxic blooms, and the death of wildlife by algae has been documented in a number of lakes including Steele Lake. In general, avoid drinking water from a bloom-infested lake, and provide alternative water sources for pets and livestock.

J.M. Crosby and A.M. Trimbee

Aquatic Macrophytes

Aquatic macrophytes are also primary producers in fresh water, but unlike individual members of the phytoplankton, they are large and usually conspicuous. Macrophytes are the flowers, bushes and trees of the underwater world. They provide cover and spawning ground for fish, habitat for both the invertebrate community and epiphytic algae, and food and habitat for ducks, moose, muskrats and other animals. In addition, macrophytes release oxygen which can be used by freshwater animals. Aquatic macrophytes are vital components of all fresh water and must be preserved in moderate abundance for a healthy, productive lake.

GROWTH HABITS OF AQUATIC MACROPHYTES  Aquatic macrophytes can be classified into four categories based on their growth habits: emergent, floating-leaved, free-floating and submergent. Emergent macrophytes, such as cattails (Typha latifolia), bulrushes (Scirpus spp.) and sedges (Carex spp.), are rooted in water-saturated or submerged soils but the shoots emerge above the water surface (Fig. 37). They occur over a depth range from about 0.5 m above the water's edge to a depth of 1.5 m into the water. Emergent plants can take advantage of constituents of both the terrestrial habitat (for example, light and atmospheric carbon dioxide) and aquatic habitat (unlimited water supply), and are one of the most productive plant communities in the world. The floating-leaved macrophytes, such as water lily (Nuphar variegatum) and some pondweed species (Potamogeton natans), are generally rooted in the lake sediments at water depths from about 0.5 to 3 m. These plants are usually restricted to calm waters where their leaves are protected from tearing by strong waves or currents (Fig. 38). Free-floating macrophytes are not rooted in the lake bottom, but instead float freely on the water surface or in the water column. They range in form from minute (less than 1 cm in diameter) surface-floating plants with few or no roots, such as duckweed (Lemna minor), to large branched forms suspended in the water column, such as bladderwort (Utricularia vulgaris) and coontail (Ceratophyllum demersum) (Fig. 39). Submergent macrophytes such as northern watermilfoil (Myriophyllum ex-albescens) and many pondweeds (Potamogeton spp.), are rooted in the lake bottom and, with the exception of the flowers, do not emerge above the water surface (Fig. 40). They may occur at water depths that receive sufficient light for photosynthesis down to depths as great as 10 m.

CONDITIONS FOR MACROPHYTE GROWTH  In any lake, the extent to which macrophytes colonize an area is determined by the physical factors of sediment texture, wave action, water depth, and light (Fig. 41). Water depth restricts emergent vegetation to a maximum depth of about 1.5 m. In addition, wave action abrades emergent, free-floating and floating-leaved foliage, disturbs the bottom sediments and pulls up rooted vegetation; it also increases turbidity and reduces light availability to submerged plants. The scouring of near-shore areas by drifting ice during spring break-up can create a zone relatively free of aquatic plants down to a depth of about 1 m. As a result, aquatic macrophytes grow at shallower depths along protected shorelines than in wave-exposed areas. Good examples of this distribution can be seen in Wabamun, Moose and Muriel lakes.

The maximum depth to which aquatic plants can grow in any lake is largely determined by light. As light passes through water it is rapidly reduced in intensity as a result of both scattering and absorption by the water and the particles suspended in it. Aquatic macrophytes generally colonize to depths receiving 1% to 4% of the surface light intensity. The depth to which 1% of the surface light penetrates is determined by the density of planktonic algae, turbidity (concentration of suspended sediment), and water colour (which can range from clear to brown). In eutrophic, turbid or brown-water lakes, aquatic macrophytes are restricted to shallow depths due to the low light penetration, for example, Cooking, Hastings, Isle and Sturgeon lakes. In contrast, plants have been found as deep as 6 to 7 m in Alberta lakes with relatively clear water such as Muriel and Narrow lakes.

Information on the maximum depth of macrophyte colonization is not yet available for many of the lakes discussed in the Atlas. However, scientists at the University of Alberta developed a simple formula to predict this depth based on Secchi disc depth and information derived from 23 Alberta lakes. For example, the formula (given in Section 1 of the Appendix) indicates that in a lake with a mean summer Secchi depth of 1.3 m, macrophytes might be expected down to a depth of 3.3 m.

Within the area where plants can live, the variety and abundance of macrophytes is determined by a complex interaction of physical and chemical factors, such as light, depth, sediment texture and nutrient availability. In general, aquatic macrophytes are in low abundance in oligotrophic lakes such as Rock and Crowsnest and Chain Lakes Reservoir, presumably due to low nutrient availability. In mesotrophic and eutrophic lakes such as Wabamun, Elkwater, Island, Crimson and Skeleton, macrophytes grow abundantly, probably because of the higher concentrations of nutrients in these lakes. In hyper-eutrophic lakes, such as Cooking Lake, macrophytes are restricted to a fringe along the shoreline because light levels under water are low as a result of high planktonic algal concentrations. In addition to changes in aquatic macrophyte abundance, the forms of plants dominating the community also change with lake trophic status. Thus, nutrient-poor lakes like Narrow, Hubbles and Hasse tend to be dominated by short, slow-growing, often evergreen, species such as stoneworts, whereas nutrient-rich lakes like Pine, Ste. Anne and Pigeon support tall, highly branched species such as northern watermilfoil (Myriophyllum exalbescens), coontail (Ceratophyllum demersum) and large-sheath pondweed (Potamogeton vaginatus).

The growth of macrophytes may be limited by chemical factors. Some of Alberta's lakes are moderately saline, such as Miquelon and Buffalo. Here, the only macrophytes to thrive are Ruppia occidentalis and Potamogeton pectinatus. Other pondweeds, northern watermilfoil, coontails and other macrophytes cannot survive. In extremely saline lakes, such as Oliva Lake, the only macrophyte present is salt-tolerant Ruppia occidentalis.

CLASSIFICATION OF AQUATIC MACROPHYTES  Aquatic macrophytes encompass the larger aquatic plants as distinct from the microscopic planktonic and benthic algae, and include representatives from most of the major divisions of the Plant Kingdom, specifically macroscopic algae (stoneworts), mosses, horsetails and flowering plants.

Stoneworts and mosses are the most ancient groups of aquatic macrophytes. Stoneworts, also called muskgrasses because of their strong musky odour, are a large form of algae. Like all algae, the stoneworts have no roots; instead they are attached to the lake bottom by rhizoids (rootlike filaments without vascular tissue). These plants consist of an upright jointed stem from which arises a whorl of cylindrical branches. Species of the genus Chara are by far the most conspicuous members of the stoneworts found in Alberta. They grow attached to the sediment and reach a height of up to 1 m and occur most abundantly in mesotrophic to mildly eutrophic lakes such as Pigeon, Hasse, Seibert, Wabamun, Spring and Narrow lakes. Aquatic mosses are commonly found in northern soft-water or acidic lakes, although some species can be found in a lake such as Wabamun. They closely resemble terrestrial mosses.

Aquatic horsetails and flowering plants are more developmentally advanced than the algae. They possess a system for transporting nutrients and carbohydrates between the leaves and roots. Aquatic horsetails include members of the genus Equisetum, the horsetail or scouring rush, which is found near the lake edge both in and out of the water as, for example, in Gregoire, Crimson and Musreau lakes.

Flowering plants are by far the most common and most widely distributed aquatic macrophytes. Freshwater flowering plants appear to be descended from terrestrial forms that adapted to life in fresh water. Although aquatic flowering plants still possess relics of their terrestrial heritage, including a waxy outer layer and pores (stomata) on the leaf surface to regulate water loss, they have also undergone major modifications to adapt to an underwater habitat. For example, leaves have become thinner, larger and more finely dissected so as to capture more light. The amount of chlorophyll (photosynthetic pigment) on the leaf surface has also increased to enable the plants to use light more efficiently. As well, support tissue, which is no longer necessary in water, has been lost and replaced by air spaces used for storing carbon dioxide to provide buoyancy. Certain species have also gained the ability to use bicarbonate ions as a source of carbon for photosynthesis rather than carbon dioxide. While carbon dioxide is plentiful in air, it is relatively scarce in the hard-water lakes of Alberta. Therefore, plants that can take advantage of the higher levels of bicarbonate in water have an advantage over those that cannot. In addition, freshwater flowering plants have developed a wide variety of ways to reproduce asexually and thus overcome the problem of having to reach the water surface to flower. Many species of submergent macrophytes can reproduce vegetatively-a small cutting can rapidly grow into a new plant.

The largest and most widely distributed group of freshwater flowering plants in Alberta is the genus Potamogeton, the pondweeds. They are present in nearly all of the lakes for which plant surveys have been conducted. The pondweeds show great variability in shape: some possess ribbonlike leaves (P. zosteriformis) or thread-like leaves (P. pectinatus), whereas others have broad, smooth-edged leaves (P. richardsonii), and still others have both floating leaves that are broad and submerged leaves that are threadlike (P. natans). The pondweeds are a source of food for waterfowl, muskrats, beaver and moose. They also provide cover for fish and for many invertebrates that are a food source for fish.

Other species of flowering plants common in Alberta lakes include coontail (Ceratophyllum demersum), northern watermilfoil (Myriophyllum exalbescens), common cattail (Typha latifolia), common great bulrush (Scirpus validus) and sedges (Carex spp.). Coontail and northern watermilfoil are found in many Alberta lakes down to a maximum depth of about 6 m. They are eaten by muskrats and waterfowl, shelter young fish and harbour fish food organisms. Cattails, bulrushes and sedges are common in marshy waters and along lakeshores. They are important because they provide food and cover for birds and small animals, and prevent erosion by binding the soil together and by protecting the shoreline from wave action.

STUDIES OF AQUATIC MACROPHYTES IN ALBERTA LAKES  The naturally abundant growth of macrophytes in many Alberta lakes can impair recreational activities, lead to summer and winter fish kills, and impede boat traffic. The conflict between plants and recreation prompted many of the studies of aquatic vegetation in Alberta lakes. In particular, Baptiste, Nakamun, Garner, Skeleton, Pine, Crimson, Muriel, Moore, St. Cyr, Ethel, Driedmeat, Coal, Pigeon and Buffalo lakes have been sites of extensive investigation by or for Alberta Environment. Aquatic macrophyte surveys have also been conducted by scientists from the University of Alberta at Figure Eight, Narrow and Long (near Athabasca) lakes. The longest and most intensive macrophyte study in Alberta was started in 1974 at Wabamun Lake by consultants for TransAlta Utilities Corporation in response to abundant growth of Canada waterweed (Elodea canadensis), a plant that is rare in the rest of Alberta. Twice-yearly mapping continued for five years and mapping every third year was still ongoing in 1989.

In most of these surveys, transect lines perpendicular to shore were established at 15 to over 100 locations, depending on the size of the lake. Either a large rake was used to obtain samples of plants from sites along the transect line, or plants from within quadrat frames were collected by SCUBA divers. Species were identified and relative abundance was assessed. In addition, the entire shoreline was surveyed to the maximum depth that plants could be seen, to assess plant growth in areas between transect lines. The University of Alberta surveys also determined the fresh and dry weight of plants per unit area of lake bottom. Results of these studies are usually presented as maps of distribution patterns of the dominant species. Most of these maps show plant beds and species composition only for the year surveyed. Emergent beds tend to occur in similar locations year after year, but the long-term Wabamun study showed that submergent beds may vary in abundance, location and composition from year to year.

Alberta Environment has published several manuals on aquatic plants, including a key for identifying the common aquatic macrophytes of Alberta and a guideline for controlling aquatic weed growth in ponds and dugouts. However, it should be noted that aquatic plant control in Alberta lakes requires approval from Alberta Environment and Alberta Forestry, Lands and Wildlife.

P.A. Chambers