An assessment of the meiobenthos from nine mountain lakes in Western Canada

The numbers and biomass of meiobenthic invertebrates of nine representative mountain lakes were assessed relative to the macrobenthic invertebrates retained on 0.425 mm mesh. The meiobenthos accounted for an average of % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSGaaeaaca% aIXaaabaGaaG4maaaaaaa!3777!\[{\raise0.7ex\hbox{$1$} \!\mathord{\left/{\vphantom {1 3}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$3$}}\]of the total biomass and 97% of total numbers retained on 0.045 mm mesh. In general surveys in these lakes, the use of 0.250 mm mesh instead of 0.425 mm mesh would be unlikely to improve estimates of total numbers and biomass enough to justify the additional effort needed. Accepting the meiobenthic turnover rate to be three to five times that of the macrobenthos, meiobenthic production is probably close to or much higher than the macrobenthic production in these lakes.     

Balance between primary and bacterial production in North Patagonian shallow lakes

The shallow Andean North Patagonian lakes are suitable environments for the evaluation of autotrophic and heterotrophic production under a scenario of high radiation in high dissolved organic matter (DOM) systems. We aimed to study the balance between primary and bacterial production in three shallow Andean lakes, in a summer sampling (high irradiance condition). Our hypothesis is that two factors would interact: high light and high DOM, affecting bacteria and algae. We carried out experiments of bacterial production (BP) by measuring [¹⁴C]-l-leucine incorporation and PP by ¹⁴C uptake in two fractions: picophytoplankton and phytoplankton >2 μm. Cell abundance, chlorophyll a, nutrients, DOM, light, and temperature were also measured. The contribution of picophytoplankton to total primary production (PP) was, in general, very high exceeding 50%. Picophytoplankton was photosynthetically more efficient than the larger autotrophs in all lakes. We observed a decrease in PP at surface levels due the high solar irradiances, while BP was not affected. Changes in the PP:BP ratios were observed in relation to DOM content and light effect. Our data indicate that the amount of available DOM drives the balance between PP and BP. However, solar radiation should be included as an important factor since PP:BP ratio may decrease because of PP photoinhibition.     

Production and population dynamics of Leptodiaptomus sicilis in a mountain lake in Alberta, Canada

Leptodiaptomus sicilis (S. A. Forbes 1882) in Pyramid Lake, Alberta, Canada, has only one main generation per year. A small summer generation probably does not survive. Adults may persist for 7 to 12 months, and individual copepods may live for up to 17 months. Retardation of the development of copepodid C4 and C 5 seems to be food linked. The high percentage of survivors (up to 97%) from the first egg pulse of the main generation, and the low percentage of survivors (as low as 3%) from the second egg pulse, is likely due to the absence of cyclopoid adults and copepodids in spring, and to both cyclopoid predation and a poor food regime in summer. Production estimates by several methods gave closely comparable results. Mean daily production by L. sicilis is 0.29 mg dry weight m^-3, and the annual P/B ratio is 2.63.     

Circulation of parasites among fishes from lakes in the Caribou Mountains,Alberta, Canada

Circulation of 24 macroparasite species among 12 species of fish was evaluated within samples of hosts collected from 9 lakes on an isolated plateau in northern Alberta, Canada. Twenty-seven parasite taxa (24 species plus the larval stages of Triaenophorus crassus, T. stizostedionis, and Raphidascaris acus) had the potential to be circulated among hosts. Sixteen parasite taxa were recovered from a single host species within a lake. Of the 11 remaining nonspecialist taxa, 4 were larval stages that matured in fish or birds and 7 were adults. Eight of the 11 cases of circulation among hosts involved lake whitefish, and this host was involved in the transmission of 5 species to piscivorous fishes. Despite evidence for the circulation of 7 taxa among the 4 species of sympatric Salmonidae, 60-99% of all worms were recovered from just 1 species of host. These results indicated that approximately 60% of the parasite taxa that infected fish in these lakes were absolute host specialists. The remaining 40% of parasite taxa had restricted host ranges, with most examples of parasite circulation limited to the 2 species of sympatric coregonid.     

Empirical relationships between profundal macroinvertebrate biomass and environmental variables in boreal lakes of Alberta, Canada

1. We empirically modelled profundal macroinvertebrate biomass (PMB) from collections of macroinvertebrates and a suite of trophic, water chemistry and morphometric variables from 26 lakes located within the Boreal Mixedwood and Boreal Subarctic ecoregions of Alberta, Canada.
2. Hypolimnetic dissolved oxygen (DO) concentrations (mg L⁻¹) explained 37% of the variance in PMB ((g m⁻²)^0.1) as a quadratic function, whereas water temperature (°C) explained 23% of variance in a linear relationship.
3. In contrast with other studies based on oligotrophic systems, indirect indicators of food availability (i.e. chlorophyll a and total phosphorus concentrations and Secchi depth) were not significant predictors of PMB in this study.
4. The predictive power of our models may be improved by obtaining more frequent (seasonal) estimates of PMB and hypolimnetic DO concentration and by quantifying biotic factors such as competition, predation, life history phenologies and recruitment success.     

The relationship between fish yield and primary production in large European freshwater lakes

The data published on fish yield (Yf) and primary production (PP) in three large European freshwater lakes (Ladoga, Ilmen and Pskovsko-Chudskoe) were analyzed on a long-term basis. The ratios between Yf and PP were found to vary from 0.02% to 0.46%. It was shown that there was an optimal level of PP, above which the efficiency of energy transfer in the pelagic food chain began to decrease. An individual optimum of PP was characteristic of each of the lakes studied. This level was primarily determined by the original trophic status of a given lake as well as by its morphometry and hydrochemistry. The results warn practical ecologists against erroneously predicting commercial harvests from PP.     

Paleolimnological investigation of three manipulated lakes from Sudbury,Canada

Stratigraphic changes in diatoms and chrysophytes from three manipulated Sudbury lakes were explored in an attempt to examine the influence of fertilization and/or neutralization on algal microfossil assemblages. Both diatom- and chrysophyte-inferred pH profiles indicate that the pH of Labelle Lake has remained fairly stable in the past. The study of Labelle and Middle lakes indicates that the addition of nutrients to acidic and non-acidic oligotrophic lakes did not directly influence diatom and chrysophyte species composition, perhaps because pH remained stable. The diatom and chrysophyte assemblages of Middle Lake only changed when the pH was raised. In Mountaintop Lake the recent shift in chrysophyte species composition and the resulting inferred pH decline is most likely related to a decline in mid-summer epilimnetic pH. Reliable paleolimnological inferences are difficult in lakes such as these because it is difficult to track limnological conditions in the absence of modern analogues.     

Walleye, Stizostedion vitreum, and northern pike, Esox lucius, populations in three Alberta lakes

Results are presented from a survey of walleye and northern pike in Ethel, Marie and Wolf Lakes, Alberta conducted May-September, 1983. Three types of experimental gill net were fished, mainly inshore. Northern pike were abundant in all three lakes but white sucker and yellow perch also were common. Walleye were caught in largest numbers in Wolf Lake. Age and growth of both walleye and northern pike were determined from examination of the opercular bones. The walleye in the three lakes were represented by a few strong year classes but there was no synchronism between the lakes. The strong 1975 year class in Ethel and Wolf Lakes may have been correlated with high spring precipitation and heavy run-off. Although there were dominant year classes in the northern pike populations (especially the 1979 year class) the variability was not so marked as in the walleye. There were no significant differences between length-at-age for year classes of walleye in Ethel and Marie or northern pike in all three lakes. In Wolf Lake the 1978 and 1979 year classes grew faster than in previous years. Walleye and northern pike growth was well described by the von Bertalanffy growth model. Females of both species grew to a greater ultimate length and had a longer lifespan than the males. Fecundity data are presented for walleye from Wolf Lake (log₁₀ absolute fecundity = 0.856 + 2.441 log₁₀ length) and northern pike from Marie Lake (log₁₀ absolute fecundity =?2.671+4.052 log₁₀ length). The stomach contents of both species were examined during May and June. The majority of walleye had empty stomachs. Walleye and northern pike in Ethel and Wolf Lakes fed on a variety of fish and invertebrate species but both fed mainly on fish (in particular whitefish) in Marie Lake. The similarity of diet suggests competition for prey species. A walleye yield to commercial fishermen of c. 0.69 kg ha^?1 year^?1 in Wolf Lake has made up 8% of the total catch. Since 1970/71 when mesh size of nets was increased, the yield has been reduced to c. 0.30 kg ha^?1 year^?1. Anglers remove an additional c. 0.48 kg ha^?1 year^?1 walleye from Wolf Lake. Northern pike yields to commercial fishermen have been c. 2.00 kg ha^?1 year^?1 in Wolf Lake. Ethel and Marie Lakes have yielded only poor catches of walleye and northern pike. A yield model was used to illustrate that faster-growing northern pike have higher potential yields than walleye. Walleye produce higher yields in Wolf Lake than in Marie Lake, the reverse being true for northern pike. It is suggested that northern pike could be cropped at a higher rate in Marie and Wolf Lakes with a possible improvement in walleye stocks.     

Phytoplankton of shallow lakes: Seasonal succession, standing crop and the chief determinants of primary productivity, 1. Cooking Lake, Alberta, Canada

Cooking Lake (113°02′W, 53°26′N), a well-mixed, shallow (mean depth (1.59 m), eutrophic lake in Alberta, Canada, is characterized by eutrophic chlorococcalean and cyanophycean phytoplankton associations, and little change in standing crop with increasing depth. Standing crop and primary productivity are low during the winter but pronounced spring and summer maxima occur. Mean yearly areal standing crop (ΔB) and primary productivity (ΔA) were 212.4 mg m^?2 chlorophyll a and 301.8 mg C h^?1 m^?2 respectively. Annual productivity was estimated at 1322 g C m^?2. The mean increase in the extinction coefficient (?) per unit increase in standing crop (B) was 0.03 In units m^?1. High non-algal light attenuation (?_q) occurred avenging 41 which prevented the ratio B/? from attaining more than 65% of the theoretical maximum except once when algal self-shading occurred. Close correlations existed between B (mg m^?3 chlorophyll a) and A _max (mg h_?1 m_?3) ΔA and ΔB, ΔA and B, A_max, and A_max/?, and ΔA and I_o′, (W m^?2). The depth of the euphotic zone (Z_eu) varied between 0.5 and 1 25 m; the average relationship between z_eu and E was Z_eu= 3.74/?, and the mean standing Crop found in the euphotic zone represented 55.2% of the theoretical maximum, The high ?_q, values made the model of Tailing (1957) inapplicable to Cooking Lake. The Q₁₀ value for the lake was 2.2. The maximum rate of photosynthesis per unit of population per h. Ø^max, (mg C sag chlorophyll a_?1 h_?1) was more closely related to temperature than irradiance and ma depressed by pH values greater than 9.1. Growth of the phytoplankton was not nutrient limited: instead irradiance and temperature were more important. Indirect evidence that free CO₂ limited photosynthetic rates, is provided by the Ø_max: pH relationship.     

Asynchronous onset of eutrophication among shallow prairie lakes of the Northern Great Plains,Alberta, Canada

Coherent timing of agricultural expansion, fertilizer application, atmospheric nutrient deposition, and accelerated global warming is expected to promote synchronous fertilization of regional surface waters and coherent development of algal blooms and lake eutrophication. While broad‐scale cyanobacterial expansion is evident in global meta‐analyses, little is known of whether lakes in discrete catchments within a common lake district also exhibit coherent water quality degradation through anthropogenic forcing. Consequently, the primary goal of this study was to determine whether agricultural development since ca. 1900, accelerated use of fertilizer since 1960, atmospheric deposition of reactive N, or regional climate warming has resulted in coherent patterns of eutrophication of surface waters in southern Alberta, Canada. Unexpectedly, analysis of sedimentary pigments as an index of changes in total algal abundance since ca. 1850 revealed that while total algal abundance (as β‐carotene, pheophytin a) increased in nine of 10 lakes over 150 years, the onset of eutrophication varied by a century and was asynchronous across basins. Similarly, analysis of temporal sequences with least‐squares regression revealed that the relative abundance of cyanobacteria (echinenone) either decreased or did not change significantly in eight of the lakes since ca. 1850, whereas purple sulfur bacteria (as okenone) increased significantly in seven study sites. These patterns are consistent with the catchment filter hypothesis, which posits that lakes exhibit unique responses to common forcing associated with the influx of mass as water, nutrients, or particles.     

Differing influences of natural and artificial disturbances on riparian cottonwoods from prairie to mountain ecoregions in Alberta, Canada

Aim Ecoregions represent biophysical zones where environmental factors enable the development of particular plant communities. Ecoregions are generally large but abrupt transitions occur in areas with rapid physical change. A particularly abrupt transitional sequence occurs in the Rocky Mountain region of south‐western Alberta where fescue prairie, aspen parkland and mountain ecoregions occur within 15 km. To investigate plant adaptation across ecoregions, our study investigated the influences of a natural disturbance (flooding) and an artificial disturbance (cattle grazing) on reproductive and population processes of black cottonwood (Populus balsamifera subsp. trichocarpa, Torr. & Gray), the dominant riparian tree. Location We studied cottonwoods throughout their elevational range along two free‐flowing, first‐order streams, Yarrow and Drywood creeks. Cottonwood was the only prominent tree in the prairie ecoregion, the dominant riparian tree in the parkland and extended upward through the montane ecoregion where it was a pioneer species for the mixed coniferous–deciduous woodland. Cottonwoods did not occur in the higher elevation sub‐alpine ecoregion. Methods Thirty‐six cross‐sectional sampling transects were located across the three ecoregions with cottonwoods, and in ungrazed and grazed areas of each ecoregion. Rectangular 100 m² tree and 2 m² seedling quadrats were positioned along the transects, and substrate and vegetation were assessed. Historic hydrological data were analysed relative to flood recurrences and seasonal flow patterns. Results Overall, the cottonwoods displayed a sawtooth shaped ‘punctuated progressive age structure’ with many young trees, progressively fewer older trees, and about four pulses of increased recruitment over the past century. This was considered to provide a healthy cottonwood population and recruitment pulses were apparently associated with flood events with appropriate peak timing and magnitude and a gradual post‐flood stage recession. However, analyses of tree, sapling and seedling data indicated that flood‐associated seedling recruitment was less important and clonal processes were more important for cottonwood recruitment in the montane ecoregion, the highest ecoregion with cottonwoods. The correlation between flood events and cottonwood recruitment was strongest in the mid‐elevation parkland ecoregion suggesting greater reliance on flood‐associated seedling recruitment. There was little correlation with flooding and limited recruitment in the fescue prairie ecoregion in recent decades and the disturbed age structure probably results from cattle impacts that have prevented recruitment and produced a decrepit cottonwood forest population. Main conclusions These analyses suggested that a healthy cottonwood population displayed a sawtooth shaped ‘punctuated progressive age structure’ and that cottonwood reproduction processes varied across ecoregions with increased clonality in the highest montane ecoregion. Cattle grazing impacts on reproduction were most severe in the lowest prairie ecoregion that is treeless except for the riparian zone. We conclude that appropriate strategies of instream flow regulation, land‐use policies and practices, and conservation and restoration efforts should be refined according to ecoregion to recognize the differences in cottonwood reproductive and population ecology.     

Aboveground plant production and nutrient content of the vegetation in six peatlands in Alberta,Canada

We examined the effects of water level, surface water chemistry, and climatic parameters on aboveground primary plant production, and the tissue nutrient concentrations in the dominant herb species in a bog, three fens, and two marshes. In the fens, total NPP correlated best with NO ₃ ^- and total phosphorus surface water concentrations in 1993 and 1994. Total NPP in the marshes correlated best with alkalinity in 1993, and with soluble reactive phosphorus in 1994. Climatic parameters, such as mean annual growing season temperature, growing degree days, and precipitation, had the most notable effect on moss growth, whereas shrub and herb production correlated significantly with the water level relative to the moss surface. Herb production correlated positively and shrub production correlated negatively with the water level relative to the moss surface. Tissue nutrient concentrations of carbon (C), nitrogen (N), and total phosphorus (TP), and the C:N quotient in Carex lasiocarpa exhibited similar trends in the fens and the marshes. Carbon tissue concentrations in C. lasiocarpa remained unchanged, whereas N and TP tissue levels decreased throughout the growing season. In the site with the highest NPP and presumably the highest stand density, C. lasiocarpa exhibited the highest tissue N and TP levels. Furthermore, TP tissue concentrations in C. lasiocarpa were substantially higher in the marshes than in the fens. Tissue nutrient concentrations in Eriophorum vaginatum in the bog showed variable response patterns. N tissue levels increased, whereas tissue TP concentrations decreased from late June to late August. In the bog, E. vaginatum exhibited similar tissue TP levels to C. lasiocarpa in the fens; however, they were both substantially lower than those found in C. lasiocarpa from the marshes.     

Primary production in three lakes of differing salinity in Victoria,Australia

Lakes Purrembete, Bullenmerri and Gnotuk are relatively deep lakes with salinities of 0.4, 8 and 58 respectively. From Carbon-14 experiments conducted monthly over a year annual primary production was 96.2, 182.1 and 90.1 gCm^-2. These values correlate well with chlorophyll-a in Purrumbete and Bullenmerri, but not in Gnotuk. There is considerable dark fixation in both the saline lakes.     

Adiaspiromycosis in striped skunks in Alberta, Canada

Pulmonary adiaspiromycosis was diagnosed in seven of 25 striped skunks (Mephitis mephitis) in east-central Alberta. The infection varied from mild, where only microscopic lesions were seen, to severe, where gross lesions of grayish-white nodules were observed in the lung parenchyma. Mild lesions were restricted to the lung, while severe lesions extended to the tracheobronchial and mediastinal lymph nodes. Histologically, the lesions were characterized by a centrally located fungal spherule, surrounded by granulomatous inflammation. The morphology of the fungal spherules was consistent with that of Emmonsia crescens. By electron microscopy, the fungal cells had an outer thick fibrillar wall and an inner cytoplasm filled with large lipid vacuoles with relatively few mitochondria, ribosomes or glycogen inclusions. The absence of endosporulation and budding suggested that each fungal cell in the lung represented a separate inhaled spore. Infection was by inhalation, nevertheless adiaspores may disseminate to the regional lymph nodes.     

Physical and chemical limnology of northern boreal lakes, Wood Buffalo National Park, northern Alberta and the Northwest Territories, Canada

Physical and chemical variables were measured in 35 lakes from Wood Buffalo National Park, northern Alberta and the Northwest Territories, Canada. Of these lakes, 22 were sinkholes, situated on limestone and gypsum, five were situated on the Canadian Shield and eight were shallow 'muskeg' lakes located on calcareous shales. All of the lakes were small to moderate in size. For each of the 35 lakes, 37 environmental variables were measured. Principal component analysis (PCA) revealed that underlying geology strongly influenced limnic properties. Shield lakes were characterized by higher concentrations of A1 and Fe, and lower pH values, specific conductivities and concentrations of ions such as, Ca, SO4, Li, Mg and Na, than either the sinkhole or the muskeg lakes. The muskeg lakes were differentiated from the sinkhole lakes by decreased Secchi depth owing to higher concentrations of dissolved organic carbon (DOC) and greater productivity, as evidenced by high concentrations of particulate organic carbon (POC) and chlorophyll a. Nitrogen (NH3 and NO2) was also notably higher at these sites. The 22 sinkhole lakes were further classified by the type of surrounding vegetation. Six vegetation groups were recognized: (1) spruce; (2) pine; (3) mixed; (4) shrubs/poplar; (5) recently burned and (6) rocky. These vegetation groups largely reflect fire history, but also differences in soils and drainage. Unlike geology, surrounding vegetation, and therefore recent fire history, generally had little influence on limnic properties. PCA showed that of the six vegetation groups, only the spruce lake group, which was characterized by high levels of DIC, was distinct. This revised version was published online in July 2006 with corrections to the Cover Date.     

Flowering plant phenology and weather in Alberta,Canada

Plant phenology can be used for biomonitoring climate change. The flowering of certain temperate zone plant species occurs in response to accumulated heat. Networks of observers presently provide data on the timing of the growth of native and crop plants to Agro-meteorological Departments in Europe and the United States. In Alberta, a phenological survey which began in 1987 records flowering times for 15 native plants, with about 200 volunteers contributing observations annually. Six years of data have been summarized and correlated with temperature measurements. The Alberta phenological data can provide a key to sound decision-making in two ways: by providing proxy data on key variables to which vegetation responds, and by providing a model for transforming simple weather data into biologically meaningful zones.     

Carbon dioxide supersaturation promotes primary production in lakes

A majority of the world's lakes are supersaturated with respect to carbon dioxide (CO(2) ). By experimental manipulation of the CO(2) concentration in supersaturated boreal lakes, we demonstrate that phytoplankton primary production was up to 10 times higher in supersaturated lake water in comparison with water with CO(2) at equilibrium concentrations and that CO(2) , together with nutrients, explained most of the variation in pelagic primary production and phytoplankton biomass over a wide variety of unproductive lakes. These results suggest that phytoplankton can be co-limited by CO(2) and nutrients in unproductive lakes. As import of terrestrial organic carbon and its subsequent microbial mineralisation in lakes is a driving force of CO(2) -supersaturation our results suggest that lake productivity and carbon cycling may respond to variations in terrestrial organic carbon export, (e.g. caused by land use or climate change) in ways not described before.     

Composition of the rumen ciliate population in experimental herds of cattle and sheep in Lethbridge, Alberta, Western Canada

Rumen ciliate populations were surveyed in 11 Holstein cattle and 6 sheep in Lethbridge (Alta., Canada) to determine species distribution in this Western Canadian environment. A total of 28 ciliate species were identified in cattle and 17 in sheep. The average total number of ciliates per millilitre of rumen content was 6.9 X 10(4) in cattle and 1.9 X 10(5) in sheep. The average number of species per host was 20.5 in cattle and 13.8 in sheep. Of the ciliate species detected, species of Entodinium appeared most frequently both in cattle and in sheep. Diplodinium polygonale, Eodinium lobatum, Eo. monolobum, Eremoplastron rostratum, Ostracodinium clipeolum, Os. mammosum, and Ophryoscolex purkynjei were not detected in sheep. In contrast, Ophryoscolex caudatus was not found in cattle. These data indicate that the ciliate faunas of cattle and sheep in this Western Canadian environment are similar to those found in Japan.