The biomass and distribution of organisms in Lake George, Uganda

1973 ◽  
Vol 184 (1076) ◽  
pp. 271-298 ◽  
Keyword(s):  
Aquatic Vegetation ◽  
Open Water ◽  
Cyclopoid Copepod ◽  
Lake Basin ◽  
Total Biomass ◽  
Lake Area ◽  
Blue Green Algae ◽  
Animal Populations ◽  
Water Community ◽  
Lake George

Ninety-five per cent of the total biomass in the open water of Lake George, a shallow equatorial lake, is phytoplankton. The biomass of this and the other major groups of organisms are given and compared with some figures from other lakes. Apart from the phytoplankton, standing crop levels in Lake George are not high and may be exceeded, although only for short periods, by organisms in temperate waters. Levels in Lake George, in contrast, fluctuate little throughout the year. The specific composition of the open water community is described and shown to be dominated by blue-green algae and three herbivores which utilize them as a food source: one cyclopoid copepod and two fish. The reasons why these and other species make up the open water community in Lake George are discussed and also possible factors which may limit some of the animal populations to the levels observed. Both the phytoplankton and the zooplankton exhibit a concentric pattern of distribution across the lake. Concentrations are highest in the centre and this may be attributable to the circular movements of the water mass which result from the shape of the basin and the wind régime. It might also be correlated with grazing effects since the fish population, which also shows a concentric distribution of biomass, has its highest concentrations in the inshore regions and its lowest in the centre. The distribution and species composition of the benthos is determined primarily by the nature of the substrate. In the open water area the bottom consists of soft, unstable, de-oxygenated mud which contains few species. Inshore the substrate is firmer and more varied and carries a greater density and variety of animals. These are preyed upon by a greater variety of fish, particularly species of the cichlid genus Haplochromis , than are found in the mid-lake area. The inshore region is short, due to the regular shape of the lake basin, and narrow, but provides a variety of habitats in contrast to the homogeneity of the mid-lake area. The lake is fringed in many places by papyrus swamp, the Nile cabbage floats on the surface of the water but there is no submerged aquatic vegetation.

Feeding and grazing in Lake George, Uganda

1973 ◽  
Vol 184 (1076) ◽  
pp. 299-319 ◽  
Keyword(s):  
Food Preference ◽  
Food Selection ◽  
Trophic Levels ◽  
Food Sources ◽  
Cyclopoid Copepod ◽  
Blue Green Algae ◽  
Tilapia Nilotica ◽  
Daily Ingestion ◽  
Herbivorous Species ◽  
Lake George

The fauna of Lake George is dominated by herbivores, in particular the fish Tilapia nilotica and Haplochromis nigripinnis , and the cyclopoid copepod Thermocyclops hyalinus . Digestion, and the assimilation of carbon from algae, by these herbivores were studied in detail. It was found that, contrary to previous observations reported in the literature, both fish and zooplankton were able to digest and assimilate blue-green algae. The diurnal feeding patterns of the herbivores were examined, and methods devised for assessing, in terms of carbon, the daily ingestion of algae. Hence, using biomass data, the total amount grazed by the herbivores was calculated. Estimates of carbon requirements at other trophic levels were made, as was an assessment of the required level of net production by the algae for comparison with figures for standing crop and net algal production measured by other means. Food selection by secondary and tertiary producers is discussed, and in several species age correlated changes in selectivity were examined. Both the major herbivorous species of fish adopt phytoplankton feeding after a period of carnivorous or omnivorous feeding as fry. Thermocyclops hyalinus is herbivorous all its life, but the size of particle taken changes with age. There are more species of carnivorous than herbivorous fish and these exploit a wider variety of food sources; the few species studied also show changes in food preference with age.

Lake George, Uganda

1976 ◽  
Vol 274 (934) ◽  
pp. 375-391 ◽  
Keyword(s):  
Green Algae ◽  
Aquatic Environment ◽  
Open Water ◽  
Blue Green Algae ◽  
Plankton Biomass ◽  
Herbivorous Species ◽  
Animal Community ◽  
Lake George

This small (250 km 2 ), shallow (mean depth 2.4 m) equatorial lake has an exceptionally constant physicochemical aquatic environment. Two outstanding features are the high relative biomass of the blue-green algae (ca. 95 % of the total), and the lake’s 24 h rather than seasonal physiological cycle. In open water areas the animal community is dominated by three herbivorous species feeding on the blue-green algae. Various factors interact to produce a concentric and centripetal pattern of distribution for the plankton biomass, but a centrifugal one for fishes and benthos.

scholarly journals Effects of Climate and Land Use/Land Cover Changes on Water Yield Services in the Dongjiang Lake Basin

2021 ◽  
Vol 10 (7) ◽  
pp. 466
Author(s):  
Wenbo Mo ◽  
Yunlin Zhao ◽  
Nan Yang ◽  
Zhenggang Xu ◽  
Weiping Zhao ◽  
...  
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Water Resource Management ◽  
Water Source ◽  
Water Yield ◽  
Lake Basin ◽  
Lake Area ◽  
Land Use Land Cover ◽  
Lulc Changes ◽  
Regional Water

Spatial and quantitative assessments of water yield services in watershed ecosystems are necessary for water resource management and improved water ecological protection. In this study, we used the InVEST model to estimate regional water yield in the Dongjiang Lake Basin in China. Moreover, we designed six scenarios to explore the impacts of climate and land use/land cover (LULC) changes on regional water yield and quantitatively determined the dominant mechanisms of water yield services. The results are expected to provide an important theoretical reference for future spatial planning and improvements of ecological service functions at the water source site. We found that (1) under the time series analysis, the water yield changes of the Dongjiang Lake Basin showed an initial decrease followed by an increase. Spatially, water yield also decreased from the lake area to the surrounding region. (2) Climate change exerted a more significant impact on water yield changes, contributing more than 98.26% to the water yield variability in the basin. In contrast, LULC had a much smaller influence, contributing only 1.74 %. (3) The spatial distribution pattern of water yield services in the watershed was more vulnerable to LULC changes. In particular, the expansion of built-up land is expected to increase the depth of regional water yield and alter its distribution, but it also increases the risk of waterlogging. Therefore, future development in the basin must consider the protection of ecological spaces and maintain the stability of the regional water yield function.

scholarly journals The effect of ice phenology exerted on submerged macrophytes through physicochemical parameters and the phytoplankton abundance

2015 ◽  
Author(s):  
Wojciech Ejankowski ◽  
Tomasz Lenard
Keyword(s):  
Physicochemical Parameters ◽  
Aquatic Vegetation ◽  
Myriophyllum Spicatum ◽  
Ice Cover ◽  
Water Transparency ◽  
Ceratophyllum Demersum ◽  
Total Biomass ◽  
Eutrophic Lakes ◽  
Macrophyte Species ◽  
Tn:Tp Ratio

<p>The physicochemical parameters of water, the concentration of chlorophyll-<em>a</em> and the submerged aquatic vegetation (SAV) were studied to evaluate the effects of different winter seasons on the biomass of macrophytes in shallow eutrophic lakes. We hypothesised that a lack of ice cover or early ice-out can influence the physicochemical parameters of water and thus change the conditions for the development of phytoplankton and SAV. The studies were conducted in four lakes of the Western Polesie region in mid-eastern Poland after mild winters with early ice-out (MW, 2011 and 2014) and after cold winters with late ice-out (CW, 2010, 2012 and 2013). The concentrations of soluble and total nitrogen, chlorophyll-<em>a</em> and the TN:TP ratio in the lakes were considerably higher, whereas the concentration of soluble and total phosphorus and water transparency were significantly lower after the MW compared with after the CW. No differences were found in water temperature, reaction and electrolytic conductivity. Low water turbidity linked with low concentration of chlorophyll-<em>a</em> after the CW resulted in increased water transparency and the total biomass of the SAV. The negative effect of the MW on the macrophyte species was stronger on more sensitive species (<em>Myriophyllum spicatum</em>,<em> Stratiotes aloides</em>) compared with shade tolerant <em>Ceratophyllum demersum</em>. Our findings show that the ice cover phenology affected by climate warming can change the balance between phytoplankton and benthic vegetation in shallow eutrophic lakes, acting as a shift between clear and turbid water states. We speculate that various responses of macrophyte species to changes in the water quality after two winter seasons (CW and MW) could cause alterations in the vegetation biomass, particularly the expansion of shade tolerance and the decline of light-demanding species after a series of mild winters.</p>

scholarly journals Mapping of Major Land-Use Changes in the Kolleru Lake Freshwater Ecosystem by Using Landsat Satellite Images in Google Earth Engine

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2493 ◽  
Author(s):  
Meena Kumari Kolli ◽  
Christian Opp ◽  
Daniel Karthe ◽  
Michael Groll
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Land Use Changes ◽  
Google Earth ◽  
Nutrient Concentrations ◽  
Freshwater Ecosystem ◽  
Lake Ecosystem ◽  
Lake Basin ◽  
Lake Area ◽  
Google Earth Engine

India’s largest freshwater ecosystem of the Kolleru Lake has experienced severe threats by land-use changes, including the construction of illegal fishponds around the lake area over the past five decades. Despite efforts to protect and restore the lake and its riparian zones, environmental pressures have increased over time. The present study provides a synthesis of human activities through major land-use changes around Kolleru Lake both before and after restoration measures. For this purpose, archives of all Landsat imageries from the last three decades were used to detect land cover changes. Using the Google Earth Engine cloud platform, three different land-use scenarios were classified for the year before restoration (1999), for 2008 immediately after the restoration, and for 2018, i.e., the current situation of the lake one decade afterward. Additionally, the NDVI (Normalized Difference Vegetation Index) and NDWI (Normalized Difference Water Index) indices were used to identify land cover dynamics. The results show that the restoration was successful; consequently, after a decade, the lake was transformed into the previous state of restoration (i.e., 1999 situation). In 1999, 29.7% of the Kolleru Lake ecosystem was occupied by fishponds, and, after a decade of sustainable restoration, 27.7% of the area was fishponds, almost reaching the extent of the 1999 situation. On the one hand, aquaculture is one of the most promising sources of income, but there is also limited awareness of its negative environmental impacts among local residents. On the other hand, political commitment to protect the lake is weak, and integrated approaches considering all stakeholders are lacking. Nevertheless, alterations of land and water use, increasing nutrient concentrations, and sediment inputs from the lake basin have reached a level at which they threaten the biodiversity and functionality of India’s largest wetland ecosystem to the degree that immediate action is necessary to prevent irreversible degradation.

scholarly journals Modelling water yield with the InVEST model in a data scarce region of northwest China

2020 ◽  
Vol 20 (3) ◽  
pp. 1035-1045 ◽  
Author(s):  
Xu Yang ◽  
Ruishan Chen ◽  
Michael E. Meadows ◽  
Guangxing Ji ◽  
Jianhua Xu
Keyword(s):  
Temporal Dynamics ◽  
Northwest China ◽  
Reanalysis Data ◽  
Water Yield ◽  
Lake Basin ◽  
Lake Area ◽  
Bosten Lake ◽  
Invest Model ◽  
Unused Land ◽  
Integrated Valuation

Abstract The Bosten Lake basin is an important arid region of northwest China, and has exhibited a declining trend in both lake area and level of water during recent decades. Reliable information on water yield, an important attribute of available water resources in a region, is vital to assess the potential for socio-economic development. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model is applied here to simulate water yield in the Bosten Lake basin. The spatial and temporal dynamics of water yield, and the response of water yield to land use and precipitation change, are analysed for the period 1985 to 2015. The results show that, overall, water yield increased during 1985–2015, and that the magnitude of change was greater in the eastern part of the region. The water yield capacity, positively correlated with precipitation, is highest under grassland vegetation and lowest in cultivated and unused land. The paper demonstrates that statistical downscaling and climate reanalysis data can be used in the InVEST model to improve the accuracy of simulated water yield in data scarce regions.

The Influence of Debris Flow on Lake Depositon: An Case from Guanba River in Qionghai Lake Basin

2014 ◽  
Vol 1010-1012 ◽  
pp. 1129-1139
Author(s):  
Jian Guo Yue ◽  
Yun Long Qi ◽  
Xue Li Wei ◽  
Ning Sheng Chen
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Environmental Problem ◽  
River Estuary ◽  
Sediment Deposition ◽  
Lake Basin ◽  
Lake Area ◽  
Important Process ◽  
Mountain Slope ◽  
Control Factors

Sediment deposition caused by debris flows is an important process controlling the evolution and regression of lake, and even a pervasive environmental problem. The frequent debris flows construct a vital links between mountain slope and Qiong Lake transporting lots of sediment into lake, and further making the lake depth and lake area shallower and smaller constantly. In the paper, we select the Guanba River in the northeast of Qiong Lake as a case studying the effect of debris flows on Lake depositon and the characteristics of typical debris flow, and document the sediment deposition in the Guanba River estuary. The control factors contributing to debris flow initiation indicate that the debris flows are drove by rainfall, earthquake and human activities together, and the occurrence frequency of debris flows in the study area will continue to increase.

Ice-Push Ramparts in the George River Basin, Labrador-Ungava

ARCTIC ◽  
1965 ◽  
Vol 18 (3) ◽  
pp. 189 ◽  
Author(s):  
James A. Peterson
Keyword(s):  
River Basin ◽  
Open Water ◽  
Field Work ◽  
Baffin Island ◽  
Lake Area ◽  
Proglacial Lakes ◽  
George River

Reports field work on ice-push ramparts in the Whitegull Lake area of Quebec Province (55 30 N, 64 15 W). Modes of formation of ramparts during the partial open water season are reviewed and examples illus. Raised shorelines described by Low (No 10377) are re-interpreted as possible ice-push ramparts. Comparison of the Labrador Peninsula lakes with proglacial lakes in Baffin Island may assist interpretation of these features.

Food habits of the river otter in a boreal ecosystem

1994 ◽  
Vol 72 (7) ◽  
pp. 1306-1313 ◽  
Author(s):  
D. G. Reid ◽  
T. E. Code ◽  
A. C. H. Reid ◽  
S. M. Herrero
Keyword(s):  
Food Habits ◽  
Prey Selection ◽  
Fish Fauna ◽  
Minor Component ◽  
Open Water ◽  
Lontra Canadensis ◽  
Lake Area ◽  
River Otter ◽  
Boreal Ecosystem ◽  
A Minor

Food habits of river otter (Lontra canadensis) were quantified by analysis of 1191 scats systematically collected in the Winefred Lake area (Athabasca River drainage) of northeastern Alberta to assess seasonal prey selection, the utility of scats for fish inventory, and the prominence of beavers as otter food. Fish dominated the annual diet, being found in 91.9% of scats. Insects, molluscs, crustaceans, and waterfowl were also substantial prey. Less agile, abundant shallow-water fish, such as a catostomid and various cyprinids, were the most common prey. Coregonine fish dominated the diet during their autumn spawning, were rarely eaten in summer when in the hypolimnion, but appeared to be preferred prey. In winter, with virtually no open water, the diet was less diverse and was dominated by cyprinid and gasterosteid fish. Such a fish fauna exists in small lakes, bog ponds, and beaver impoundments. We hypothesize that in winter, otters select water bodies, and consequently available prey, on the basis of shoreline substrate and morphology and relative ease of passage from air to water. Otter scats contained 14 of 18 fish species known to be in the study area. However, the contents of scats overestimated the diversity offish species inhabiting individual lakes. Beavers were occasionally eaten by otters, but were a minor component of the diet.

scholarly journals Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado

2014 ◽  
Vol 82 (3) ◽  
pp. 477-489 ◽  
Author(s):  
Jeffrey S. Pigati ◽  
Ian M. Miller ◽  
Kirk R. Johnson ◽  
Jeffrey S. Honke ◽  
Paul E. Carrara ◽  
...  
Keyword(s):  
Alpine Meadow ◽  
Drainage System ◽  
Open Water ◽  
Lake Basin ◽  
Oxygen Isotope Stage ◽  
Left Behind ◽  
Water Conditions ◽  
Fossil Site ◽  
Geologic Setting ◽  
Over Time

AbstractThe geologic setting of the Ziegler Reservoir fossil site is somewhat unusual — the sediments containing the Pleistocene fossils were deposited in a lake on top of a ridge. The lake basin was formed near Snowmass Village, Colorado (USA) when a glacier flowing down Snowmass Creek Valley became thick enough to overtop a low point in the eastern valley wall and entered the head of Brush Creek Valley. When the glacier retreated at about 155–130 ka, near the end of Marine Oxygen Isotope Stage 6, the Brush Creek Valley lobe left behind a moraine that impounded a small alpine lake. The lake was initially ~ 10 m deep and appears to have been highly productive during most of its existence, based on the abundant and exquisitely preserved organic material present in the sediments. Over time, the basin slowly filled with (mostly) eolian sediment such that by ~ 87 ka it contained a marsh or wetland rather than a true lake. Open-water conditions returned briefly between ~ 77 and 55 ka before the impoundment was finally breached to the east, establishing ties with the Brush Creek drainage system and creating an alpine meadow that persisted until historic times.

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