Attached Algae on Artificial and Natural Substrates in Lake Winnipeg, Manitoba

1972 ◽  
Vol 29 (1) ◽  
pp. 31-44 ◽  
Author(s):  
D. Evans ◽  
John G. Stockner
Keyword(s):  
Artificial Substrates ◽  
Limiting Factor ◽  
The South ◽  
Lake Winnipeg ◽  
South Basin ◽  
Attached Algae ◽  
The North ◽  
Specific Composition ◽  
Natural Rock ◽  
Algal Assemblages

The attached algal assemblage on navigational buoys and natural rock substrate in Lake Winnipeg in 1969–70 was examined, in the fall after 145 days growth, as part of an overall limnological survey of this important Canadian Great Lake. Only three phyla were represented: Cyanophyta, Chlorophyta, and Chrysophyta (Bacillariophyceae). Green and blue-green algae were more abundant in the south basin, and diatoms were more common in the more oligotrophic north basin. Ulothrix zonata occurred only on substrates in the north basin, and Cladophora cf. callicoma was found only in the south basin. On both natural and artificial substrates a distinct zonation pattern related to water transparency or available light was prevalent. Preliminary results indicated that light was the most important physical factor affecting growth and specific composition of attached algae on substrates in Lake Winnipeg. Biomass values from all stations (dry weight) ranged from 1.7 to 29.1 mg/cm2; with the greatest values consistently occurring between 10 and 25 cm deep on buoys in the south basin. Diatom density and diatom volume were estimated from buoy samples and varied respectively, within the range 2.00 × 105–6.65 × 106 diatoms/cm2 and 0.32–10.00 mm3/cm2. Though direct evidence is lacking, it appears that nutrients may limit growth of attached algae in the north basin, whereas in the south basin, light is the major limiting factor. The specific composition of the algal assemblages on particular buoys was more related to the physical–chemical features of a major river plume in close proximity to the buoy than to a homogeneous Lake Winnipeg water mass. This factor, together with greater turbidity in the shallower south basin, is largely responsible for the observed heterogeneity among the attached algal assemblages in Lake Winnipeg.

Growth rate and condition of walleye (Sander vitreus), sauger (Sander canadensis), and dwarf walleye in a large Canadian lake

2018 ◽  
Vol 96 (7) ◽  
pp. 739-747 ◽  
Author(s):  
K.T. Sheppard ◽  
B.J. Hann ◽  
G.K. Davoren
Keyword(s):  
Dreissena Polymorpha ◽  
Sander Vitreus ◽  
Osmerus Mordax ◽  
Bythotrephes Longimanus ◽  
The South ◽  
Rainbow Smelt ◽  
Lake Winnipeg ◽  
South Basin ◽  
The North ◽  
North And South

The second largest inland walleye (Sander vitreus (Mitchill, 1818)) and sauger (Sander canadensis (Griffith and Smith, 1834)) fishery in Canada is found in Lake Winnipeg, Manitoba. To manage the fishery for a sustainable future, the growth and condition of these fish must be understood. Objectives were to (1) examine baseline growth and condition of walleye and sauger in Lake Winnipeg, (2) evaluate variation between the North and South basins, and (3) contribute observational findings on the distribution of dwarf walleye. Gill nets were set to catch walleye, sauger, and dwarf walleye throughout both basins at various locations and in all seasons during 2010 and 2011. North Basin walleye and sauger had higher growth rates and condition relative to the South Basin. This may be due to differential exploitation rates or diets such as the consumption of invasive rainbow smelt (Osmerus mordax (Mitchell, 1814)) in the North Basin and not in the South Basin. Dwarf walleye were observed more frequently in the South Basin than in the North Basin. Overall, this study provides important baseline data on the growth and condition of walleye and sauger populations prior to invasion of the spiny waterflea (Bythotrephes longimanus Leydig, 1860) and zebra mussels (Dreissena polymorpha (Pallas, 1771)).

Phytoplankton Succession and Primary Production in Babine Lake, British Columbia

1975 ◽  
Vol 32 (12) ◽  
pp. 2413-2427 ◽  
Author(s):  
John G. Stockner ◽  
K. R. S. Shortreed
Keyword(s):  
Primary Production ◽  
Sockeye Salmon ◽  
Mixed Layer Depth ◽  
Carbon Assimilation ◽  
Annual Production ◽  
Phosphate Limitation ◽  
The South ◽  
South Basin ◽  
The North ◽  
Principal Factors

Ten stations located in six zones (subbasins) were sampled biweekly from May to October 1973 to detect possible regional differences in production in this large, 155 km long, dystrophic lake. The spring bloom occurred in all zones while a fall bloom occurred only in Zones 5 and 6. Carbon assimilation showed two peaks in south basin zones, but only one (spring) at zones north of Topley Landing. Seasonal variation in phytoplankton numbers and volume, seston, and chlorophyll a followed a pattern similar to that noted for primary production. Mean production was 100 mg C∙m−2∙day−1 in Zones 1–4, but was 145 in Zones 5 and 6. Annual production was estimated at 25 g C∙m−2 in the north basin and 40 in the south basin. Reasons for the regional disparities are discussed, with greatest significance given to regional variations in mixed layer depth, surface inflows (loading), and basin mean depth. The development and sustainment of the autumnal bloom of Tabellaria fenestrata is thought to be one of the principal factors responsible for greater production in the south basin.An estimated 0.05 g TP∙m−2 enters the lake yearly. This can vary depending on the return of adult sockeye salmon (Oncorhynchus nerka), whose carcasses contribute up to 20% of the total. An estimated 30% is lost via the Babine River, and it is speculated that of the remaining 70%, most is lost to the sediments. Phosphate limitation is implied as a chief factor limiting primary production in the north basin stations, but not in the south basin. On the basis of total phosphorus load the lake is classed as oligotrophic, but in terms of annual production and its humic stained waters it is more correctly considered mixotrophic.

The ecological impact of the sea urchin Paracentrotus lividus (Lamarck) in Lough Ine, Ireland

1983 ◽  
Vol 300 (1101) ◽  
pp. 513-552 ◽  
Keyword(s):  
Sea Urchin ◽  
Animal Species ◽  
Paracentrotus Lividus ◽  
Coralline Algae ◽  
Diurnal Fluctuation ◽  
Tide Pool ◽  
Crustose Coralline Algae ◽  
The South ◽  
South Basin ◽  
The North

An ecological account is given of the rocky shallow sublittoral of Lough Ine, County Cork, Republic of Ireland, from low water level to about 1 m below this level. With increasing distance from the Rapids mouth a forest of laminarian algae gives way to low algal bush, and still further into the lough the sea urchin Paracentrotus lividus destroys all soft upstanding algae. Much of the grazed area becomes overgrown by crustose coralline algae. Patches of the green algae Codium fragile ssp. tomentosoides and Enteromorpha clathrata fringe the Paracentrotus graze patches. An account is given of the effects of Paracentrotus on the shallow sublittoral community. Algae in the ungrazed areas accommodate large numbers of individuals and many species of invertebrates, especially amphipods, small gastropods and small polychaetes. In grazing, Paracentrotus destroys this population and its habitat. However, the removal of these algae, and of the sediment that they trap, provides a new habitat, suitable for plant and animal species that can resist Paracentrotus . Crustose coralline algae cover much of the rock, and are burrowed into or enclose the tubes of a characteristic and entirely different polychaete fauna. On the surface of the rocks are found saddle oysters ( Anomia ephippium ), limpets ( Patella aspera ) and other hard- shelled animal species. The relations between Codium and Paracentrotus have been investigated by transfer experiments in the ‘field’ and by observations with an aquarium tank. Paracentrotus readily eats Codium , especially when the urchins are at a high population density; but Codium benefits from the clearance of other algae, and is a quick recolonist, so that on balance it benefits from the presence of the urchin. Paracentrotus feeds mainly by day, and on a steep shore some wander up into the littoral region as the tide rises and destroy Fucus serratus . This accounts for the almost complete absence of F. serratus from the North Basin. Paracentrotus does not move upwards by night. The hard-shelled animal species Anomia, Patella, Chlamys varia , adult Gibbula cineraria and Pomatoceros , found plentifully on graze patches in the North Basin, diminish in abundance southwards even within grazed areas, while the numbers of the starfish Marthasterias glacialis under the rocks increase. Experiments show that Marthasterias readily eats Anomia . These Marthasterias are quite small. As they grow bigger they move away onto muddy areas and extend their diet to include large buried lamellibranchs. Small Paracentrotus are usually found in larger numbers underneath boulders than above, while larger ones tend to come up by day onto the tops, where they form graze patches. From a study of growth lines in the interambulacral plates and from growth in cages we conclude that a horizontal diameter of 30-40 mm (with considerable variation) is reached in 3-4 years from settlement. The peak in numbers of Paracentrotus visible in the South Basin in 1979 might perhaps be ascribed to a good settlement in the warm summers of 1975 and 1976. Temperature of the shallow marginal water of the lough is subject to diurnal fluctuation, as in a tide pool, and can reach high levels in summer. This might favour Paracentrotus . However, numbers of Paracentrotus are probably severely reduced by predators in the South Basin. Crabs have already been implicated. It is possible that the small or half grown Marthasterias under shallow sublittoral rocks might destroy newly settled Paracentrotus , although this still has to be demonstrated.

scholarly journals Water column stability as an important factor controlling nitrite-dependent anaerobic methane oxidation in stratified lake basins

2021 ◽  
Author(s):  
Guangyi Su ◽  
Moritz Lehmann ◽  
Jana Tischer ◽  
Yuki Weber ◽  
Jean-Claude Walser ◽  
...  
Keyword(s):  
Water Column ◽  
Electron Acceptor ◽  
Nitrite Reduction ◽  
Redox Conditions ◽  
Series Data ◽  
Anaerobic Oxidation Of Methane ◽  
The South ◽  
South Basin ◽  
Water Column Stability ◽  
The North

Anaerobic oxidation of methane (AOM) with nitrate/nitrite as the terminal electron acceptor may play an important role in mitigating methane emissions from lacustrine environments to the atmosphere. We investigated AOM in the water column of two connected but hydrodynamically contrasting basins of a south-alpine lake in Switzerland (Lake Lugano). The North Basin is permanently stratified with year-round anoxic conditions below 120 m water depth, while the South Basin undergoes seasonal stratification with the development of bottom water anoxia during summer. We show that below the redoxcline of the North Basin a substantial fraction of methane was oxidized coupled to nitrite reduction by Candidatus Methylomirabilis. Incubation experiments with 14CH4 and concentrated biomass from showed at least 43-52%-enhanced AOM rates with added nitrate/nitrite as electron acceptor. Multiannual time series data on the population dynamics of Candidatus Methylomirabilis in the North Basin following an exceptional mixing event in 2005/2006 revealed their requirement for lasting stable low redox-conditions to establish. In the South Basin, on the other hand, we did not find molecular evidence for nitrite-dependent methane oxidizing bacteria. Our data suggest that here the dynamic mixing regime with fluctuating redox conditions is not conducive to the development of a stable population of relatively slow-growing Candidatus Methylomirabilis, despite a hydrochemical framework that seems more favorable for nitrite-dependent AOM than in the North Basin. We predict that the importance of N-dependent AOM in freshwater lakes will likely increase in future because of longer thermal stratification periods and reduced mixing caused by global warming.

High resolution sediment microfabric and geochemical analysis reveals seasonal scale redox mineralisation, anthropogenic environmental change and pollution in England's largest natural lake - Windermere

2020 ◽  
Author(s):  
James Fielding ◽  
Alan Kemp ◽  
Ian Croudace ◽  
Peter Langdon ◽  
Richard Pearce ◽  
...  
Keyword(s):  
Toxic Elements ◽  
Slope Failure ◽  
Sediment Quality ◽  
Quality Standards ◽  
Potentially Toxic Elements ◽  
The South ◽  
South Basin ◽  
The North ◽  
Natural Lake ◽  
Sediment Anoxia

<p>Many lakes in industrialised areas have undergone anthropogenically driven eutrophication and increases in pollution leading to decreased water and sediment quality. In some cases, these effects are enhanced by seasonally changing lake redox conditions that may act to concentrate potentially toxic elements sufficiently to exceed internationally recognised Sediment Quality Standards, impacting key species and jeopardizing water supply.  A combined, geochemical and sediment microfabric analysis is applied to reconstruct the history of cultural eutrophication and pollution in the North and South Basins of Windermere, England’s largest natural lake. We also document a record of seismicity and link increased sedimentation rates and sediment instability. The onset and development of eutrophication in Windermere occurred from the mid-19th to the early 20th centuries.  Raised lake productivity is indicated by an increase in sedimentary δ<sup>13</sup>C, and increased pollution by elevated sedimentary trace metals (Pb, Zn, Cu, Hg, and As), likely enhanced by incorporation and adsorption to settling diatom aggregates, preserved as sedimentary laminae. In the South Basin of the lake, contemporaneous increasing sediment δ<sup>15</sup>N values also occur in step with increasing Zn, Hg, Cu from this time, linking metal enrichment to the input of isotopically heavy nitrate (N) from anthropogenic sources including sewage. From around 1930, a decrease in Mn and Fe-rich laminae indicate reduced deep water ventilation, and increased incidence of sediment anoxia, being most intense in the deeper North Basin where benthic activity intermittently ceased. Strongly reducing conditions in the sediment promoted Fe and Mn reduction and the formation of unusual Pb-bearing barite, hitherto only described from toxic mine wastes and contaminated soils. In the North Basin cores a clay rich laminae dated 1979-1980 is shown to be a mass transport deposit linked to large scale slope failure likely caused by the 4.7 ML 1979 Carlisle earthquake. Slope failure was exacerbated by preconditioning principally by increased sedimentation as a result of anthropogenic activities. From 1980 there was a partial recovery in oxygenation with Mn and Fe rich laminae returning in some parts. But in the South Basin, the continued impacts of sewage discharge is indicated by elevated δ<sup>15</sup>N of organic matter. Imaging and X-ray microanalysis using scanning electron microscopy has enabled the identification of seasonal-scale redox mineralisation of Mn, Fe and Ba related to intermittent sediment anoxia. Elevated concentrations of Mn, Fe, Ba, and As also occur in the surficial sediment and provide evidence for dynamic redox mobilisation of potentially toxic elements that may be released to the lake waters. Concentrations of As, in particular, exceed international Sediment Quality Standards. These surface enrichments in As and other toxic elements may become more prevalent in the future with climate change driving lengthened summer stratification in the lake.</p>

phytoplankton Communities of Lakes Experimentally Acidified with Sulfuric and Nitric Acids

1990 ◽  
Vol 47 (7) ◽  
pp. 1378-1386 ◽  
Author(s):  
D. L. Findlay ◽  
S. E. M. Kasian
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Species Diversity ◽  
Species Composition ◽  
Phytoplankton Species ◽  
The South ◽  
South Basin ◽  
The North ◽  
Late Fall ◽  
Phytoplankton Communities

Additions of sulfuric acid to the South Basin and nitric acid to the North Basin of Lake 302 caused major changes in the phytoplankton communities. The basins were separated by a nylon-reinforced vinyl sea curtain. In the South Basin, below pH 5.6, species composition shifted from chrysophycean dominance to one of Dinophyceae. Diatoms and cyanophytes were eliminated below pH 5.3. Phytoplankton species diversity decreased as pH decreased. Total epilimnetic biomass was unchanged, except in late fall, when entrainment of dense layers of hypolimnetic species caused increases. The assemblage in the North Basin changed immediately upon additions of HNO3 to resemble systems experimentally fertilized with nitrogen. Chrysophycean dominance gave way to chlorophytes and dinoflagellates. Once pH decreased below 6.0, diatoms and cyanophytes were eliminated from the assemblage, as in the South Basin. Phytoplankton species diversity decreased, but total epilimnetic biomass remained unaffected.

A Late Minoan III ‘kitchen’ at Makritikhos (Knossos) (Knossos Survey 90)

1959 ◽  
Vol 53 ◽  
pp. 182-193 ◽  
Author(s):  
Sinclair Hood ◽  
Piet de Jong
Keyword(s):  
Ground Level ◽  
Western Boundary ◽  
The South ◽  
Deep Trench ◽  
The North ◽  
Natural Rock ◽  
High Bank ◽  
Small Room ◽  
North End

In the summer of 1951 N. Dadoudis, while digging a deep trench to bury stones from a plot of land belonging to him on the east edge of Makritikhos village, about 250 metres north of the Palace of Minos, found a complete Minoan amphora (Plan, Fig. 5, no. 3). He reported this discovery to the Ephor of Antiquities for Crete, Dr. N. Platon, who invited Piet de Jong, then the School's Curator at Knossos, to examine the area. Excavation revealed a small room, against the east wall of which the amphora had evidently once stood. The room was cleared by Piet de Jong assisted later by Sinclair Hood. To judge from the character of the vases found in it, the room might have been used as a kitchen.The ground on the edge of Makritikhos village here slopes steeply down through a series of terraces to the bed of the Kairatos stream about 40 metres to the east. The ‘Kitchen’ lay just below a high bank, forming the western boundary of the plot of ground, with the natural rock exposed at the north end and Minoan house walls showing in it to the south. There seems to have been a marked slope down towards the north as well as to the east here in Minoan times. The wall a–a (Fig. 2) at the north end of the original trench dug by Dadoudis, of squared limestone blocks measuring up to about half a metre in length and 0–35 thick, lay at a lower level than the Kitchen, although it appeared to be of the same period with it. A roughly constructed wall b–b south of a–a may have supported a terrace marking this change in ground level. The corner d–d of another, presumably contemporary, house built of squared limestone blocks was exposed in the south part of the original trench.

Limnology and macrophytic vegetation of Loch Obisary, a deep brackish lake in the Outer Hebrides

1979 ◽  
Vol 78 (1-2) ◽  
pp. 123-138
Author(s):  
D. H. N. Spence ◽  
A. M. Barclay ◽  
P. C. Bodkin
Keyword(s):  
Water Chemistry ◽  
Sea Water ◽  
Red Light ◽  
Potamogeton Pectinatus ◽  
The South ◽  
Brackish Lake ◽  
Attenuation Coefficients ◽  
South Basin ◽  
The North ◽  
Outer Hebrides

SynopsisLoch Obisary has a narrow sea inlet to a north basin which is 45 m deep, stratified in summer and winter and joined by shallow channels to an unstratifled south basin.Mean conductivity (25°C) and sodium measurements indicate that in summer and winter the north basin epilimnion and the south basin comprises about 50%, and the north basin hypolimnion about 80%, sea water. It is calculated that 56% of high tides enter the loch.Vertical diffuse attenuation coefficients for blue, green and red light are the same in epilimnion and south basin, the blue coefficient being slightly higher than the red in July and much higher in January. In July the blue coefficient in the hypolimnion is lower that the red, as in clear coastal water.Six out of 24 macrophytes, and eight epiphytes, are confined within 200 m of the sea inlet. Distribution and depth limits of those and other species are discussed in relation to substrate, water chemistry and light. The presence of a halocline in the north basin and its absence from the south basin allow a comparison to be drawn between depth limits set by water chemistry (north basin), and those predicted on the basis of light (south basin) for Potamogeton pectinatus and Nitella opaca.

scholarly journals Trends in the numbers of red kangaroos and emus on either side of the South Australian dingo fence: evidence for predator regulation?

2000 ◽  
Vol 27 (3) ◽  
pp. 269 ◽  
Author(s):  
A. R. Pople ◽  
G. C. Grigg ◽  
S. C. Cairns ◽  
L. A. Beard ◽  
P. Alexander
Keyword(s):  
Canis Lupus ◽  
Predation Rate ◽  
Aerial Survey ◽  
Limiting Factor ◽  
The South ◽  
North East ◽  
The North ◽  
Red Kangaroo ◽  
Dromaius Novaehollandiae ◽  
Over Time

Most of Australia’s sheep rangelands are enclosed by a dingo-proof fence. Within these rangelands, where dingoes (Canis lupus dingo) are rare, red kangaroos (Macropus rufus) are considered to be food limited because their numbers respond to fluctuations in pasture biomass that are driven by highly variable rainfall. Outside this region, where dingoes are common, kangaroo densities are generally substantially lower, suggesting that dingoes are an important limiting factor. However, it is unclear whether dingoes can regulate kangaroo populations. In this study, red kangaroo and emu (Dromaius novaehollandiae) numbers were monitored for varying periods during 1978–92 by aerial survey on both sides of the dingo fence in three areas in the north of the South Australian pastoral zone. Densities of red kangaroos and emus were lower outside the fence, although the disparity varied between areas and over time. The similarity in the environments on both sides of the fence and the marked step in kangaroo density at the fence are consistent with dingoes strongly limiting these prey populations. In the north-east of the pastoral zone, where kangaroo and emu densities are greatest, the contrast in density across the fence was most pronounced. Furthermore, the trends in density over time differed across the fence. Outside the fence, red kangaroos and emus remained at low densities following drought as dingo numbers increased. Inside the fence, red kangaroo and emu populations showed a ‘typical’ post-drought recovery. The data therefore suggest that, in some situations, dingoes may not simply limit red kangaroo and emu populations, but also regulate them. For this to occur, predation rate would need to be density dependent at low prey densities. The availability of alternative prey, and the reduction in the numbers of all prey during drought may provide the mechanism.

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