Статті в журналах: "Eutrophication Victoria"

1

Hecky, R. E. "The eutrophication of Lake Victoria." SIL Proceedings, 1922-2010 25, no. 1 (September 1993): 39–48. http://dx.doi.org/10.1080/03680770.1992.11900057.

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2

Marshall, Brian E. "Guilty as charged: Nile perch was the cause of the haplochromine decline in Lake Victoria." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 9 (September 2018): 1542–59. http://dx.doi.org/10.1139/cjfas-2017-0056.

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Debate on the contribution of Nile perch (Lates niloticus) to the demise of Lake Victoria’s 500+ endemic haplochromine cichlids centers around the “top-down” and “bottom-up” hypotheses. The former suggests Nile perch destroyed the haplochromines, causing the disruption of food chains and nutrient cycling and so initiating the accelerated eutrophication of the lake. The latter proposes that haplochromines suppressed Nile perch by preying on its eggs and fry or competing with juveniles for food. A recent paper argued that accelerated eutrophication caused by a climatic event led to their collapse, allowing Nile perch to explode. However, the Nile perch population grew before haplochromines decreased, and they only collapsed once Nile perch biomass exceeded theirs. The chronology indicates that accelerated eutrophication of the lake followed rather than preceded the haplochromine collapse, suggesting that eutrophication was not its cause. A size-selective predation model developed to support the bottom-up hypothesis is discussed in light of existing data, but does not support the bottom-up hypothesis. It was concluded that the top-down model better fits the data and conforms to the law of parsimony.

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3

Ngupula, Godfrey William. "How Does Increased Eutrophication and Pollution in the Lake Victoria Waters Impacts Zooplankton?" Journal of Environment and Ecology 4, no. 2 (January 21, 2014): 151. http://dx.doi.org/10.5296/jee.v4i2.4397.

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4

Simiyu, Benard Mucholwa, and Rainer Kurmayer. "Response of planktonic diatoms to eutrophication in Nyanza Gulf of Lake Victoria, Kenya." Limnologica 93 (March 2022): 125958. http://dx.doi.org/10.1016/j.limno.2022.125958.

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5

Luyiga, Suzan, Sigrid Haande, Ronald P. Semyalo, Yusuf S. Kizito, Anne Miyingo-Kezimbira, Pål Brettum, Anne Lyche Solheim, et al. "How water exchange and seasonality affect the eutrophication of Murchison Bay, Lake Victoria." Limnologica 53 (July 2015): 60–73. http://dx.doi.org/10.1016/j.limno.2015.06.001.

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6

Kabenge, Martin, Hongtao Wang, and Fengting Li. "Urban eutrophication and its spurring conditions in the Murchison Bay of Lake Victoria." Environmental Science and Pollution Research 23, no. 1 (November 4, 2015): 234–41. http://dx.doi.org/10.1007/s11356-015-5675-0.

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7

Stager, J. Curt, Robert E. Hecky, Dustin Grzesik, Brian F. Cumming, and Hedy Kling. "Diatom evidence for the timing and causes of eutrophication in Lake Victoria, East Africa." Hydrobiologia 636, no. 1 (November 9, 2009): 463–78. http://dx.doi.org/10.1007/s10750-009-9974-7.

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8

GAVRILESCU, Elena, and Gilda Diana BUZATU. "Water Quality of Some Lakes in Dolj County." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 70, no. 2 (November 25, 2013): 370–76. http://dx.doi.org/10.15835/buasvmcn-agr:9679.

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In Dolj County there are a number of lakes that are particularly important, because they have a large quantity of water, some of them originating from hydrotechnical accumulations, and other from natural waters. In the present study, it was performed the monitoring of the water quality of the lakes in Dolj County, in the year of 2012, namely: Victoria - Geormane, BistreÅ£ and Caraula. The ecological conditions of the natural and artificial lakes was established based on the state of acidification, of the oxygen regime (dissolved oxygen, biochemical oxygen demand and chemical oxygen demand), the degree of eutrophication (biogenic substances, phytoplankton biomass and chlorophyll â€œaâ€) and also based on transparency. The water samples were taken from three points: tail, middle and upstream of the lake and were analyzed using high performance equipment, namely: pH-meter, spectrophotometer DR 2010, Sechi disc, BOD5 system. In terms of the degree of eutrophication, the water from the studied lakes belongs to the third category of water quality. Geormane is a natural lake which has a very good ecological status, except regarding the eutrophication, which is considerably visible. Bistret lake has a good environmental status and is visible eutrophic. Caraula lakeâ€™s water belongs to the third category of water quality, being heavily eutrophic.

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9

Andama, M., J. B. Lejju, and C. U. Tolo. "Late holocene trends of phytoplankton productivity and anoxia as inferred from diatom and geochemical proxies in Lake Victoria, Eastern Africa." Biogeosciences Discussions 10, no. 11 (November 12, 2013): 17663–82. http://dx.doi.org/10.5194/bgd-10-17663-2013.

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Abstract. Lake Victoria ecosystem has undergone major ecological changes in the recent decades. Sedimentary diatom analysis and Fe / Mn determined by Energy Dispersive X-ray Fluorescence (EDXRF) have provided phytoplankton (diatom) productivity and the resultant anoxia (Fe / Mn) in Lake Victoria at Napoleon Gulf during the late Holocene (1778 cal yr BP (calibrated years before present) to 2008 AD) with radiocarbon dates determined using Accelerator Mass Spectrometry standard method. The results showed that increased total diatom counts in Napoleon Gulf during the late Holocene correspond with increased Fe / Mn ratio (anoxia) in some of the profiles and not in others and in most cases those that correspond correlate very well with increased eutrophication from nitrate input (Total Nitrogen, TN). Therefore slightly increased anoxia not related to increased diatom productivity was recorded in Lake Victoria at Napoleon Gulf from the period 1778 to 1135 cal yr BP. There was slightly increased diatom productivity at Napoleon Gulf from the period 857 to 758 cal yr BP but it did not increase anoxia in the lake. The period 415 cal yr BP to 2008 AD recorded increased anoxia at Napoleon Gulf related to high diatom productivity especially from 415 to 390 cal yr BP and 191 cal yr BP to 2008 AD.

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10

van Rijssel, Jacco C., Robert E. Hecky, Mary A. Kishe-Machumu, Saskia E. Meijer, Johan Pols, Kaj M. van Tienderen, Jan D. Ververs, Jan H. Wanink, and Frans Witte. "Climatic variability in combination with eutrophication drives adaptive responses in the gills of Lake Victoria cichlids." Oecologia 182, no. 4 (September 14, 2016): 1187–201. http://dx.doi.org/10.1007/s00442-016-3721-3.

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11

Nyawacha, S. O., V. Meta, and A. Osio. "SPATIAL TEMPORAL MAPPING OF SPREAD OF WATER HYACINTH IN WINUM GULF, LAKE VICTORIA." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2021 (June 28, 2021): 341–46. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2021-341-2021.

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Abstract. Water hyacinth (Eichhornia crassipes) is an invasive hydro plant that invaded the waters of Lake Victoria and has since been spreading rapidly affecting the socio-economic livelihood of the community around the Lake. The weed's rapid spread is due to various anthropogenic activities in the surrounding environment among them being the eutrophication of the lake waters.This study aims at using remote sensing applications and presenting the results of the analysis of the water hyacinth Normalized Difference Vegetation Index (NDVI), water extent, and analysis of correlation with the water quality over time from Sentinel 2 satellite imagery in January 2017 to January of 2021. The analysis aims at understanding the vegetation growth coverage in the five years and sets the basis of monthly predictive modelling of the behavior of water hyacinth. Predictive modelling applies historical statistical data while trying to use trend analysis in predicting the future behavior of a phenomenon. This study also seeks to answer the research question of the role of suspended sediments and dissolved minerals in abating the spread of and growth of water hyacinth.

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12

Ogutu-Ohwayo, Richard, and R. E. Hecky. "Fish Introductions in Africa and Some of Their implications." Canadian Journal of Fisheries and Aquatic Sciences 48, S1 (December 19, 1991): 8–12. http://dx.doi.org/10.1139/f91-299.

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Fish introductions in Africa have been made at various spatial scales from small fish ponds to the largest lakes, primarily to sustain or increase production, though some were to develop sport fisheries and to control unwanted organisms. Some introductions have fulfilled their objective in the short term, but several "successful" introductions have created uncertainties about their long-term sustainability. Lates niloticus, Oreochromis niloticus, O. leucostictus, Tilapia melanopleura and T. zilli were introduced into Lakes Victoria and Kyoga in 1950's and early 1960's; by the 1980's L. niloticus and O. niloticus dominated the fisheries, having virtually eliminated a number of endemic species. In Lake Victoria, the loss of genetic diversity has been accompanied by a loss of trophic diversity; the transformation of the fish community coincided with profound eutrophication (algal blooms, fish kills, hypolimnetic anoxia) which might be related to alterations of the lake's food-web structure. By contrast, the introduction of a planktivore, Limnothrissa miodon into Lake Kivu and the Kariba reservoir has established highly successful fisheries with little effect on the pre-existing fish community or trophic ecology. The endemic species-rich African Great Lakes may be particularly sensitive to introductions. Species extinctions, introgressive hybridization and ecosystem alterations may occur following introductions.

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13

Shayo, Salome, and Samwel M. Limbu. "Nutrient release from sediments and biological nitrogen fixation: Advancing our understanding of eutrophication sources in Lake Victoria, Tanzania." Lakes & Reservoirs: Research & Management 23, no. 4 (November 5, 2018): 312–23. http://dx.doi.org/10.1111/lre.12242.

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14

Paterson, John. "Water Management and Recreational Values; Some Cases in Victoria, Australia." Water Science and Technology 21, no. 2 (February 1, 1989): 1–12. http://dx.doi.org/10.2166/wst.1989.0021.

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The growing recognition of recreational and amenity demands on water systems introduces a multitude of issues, many of them complex, to the established tasks of water quality management and water management generally. Victorian case studies are presented. They (1) illustrate the range and diversity of situations that can arise in managing competition and enhancing compatibility between traditional water supply objectives and recreational demands. (2) Fluctuation of storage levels, essential to storage operations, detract from recreational value. Recreational and tourism demands upon Lake Hume have grown to threaten traditional operating flexibility. (3) Mokoan is another such instance, but with its supply function in a state of flux, Lake Mokoan provides more scope for a shift in the balance. (4) Salinity management has become an issue in the management of lakes and wetlands when water supply interests and environmental/recreation interests respectively have different perspectives on salt disposal. (5) Recreational use of town supply sources has long been a vexed issue, although marked shifts in the attitudues of many supply authorities have occurred in recent years. (6) Eutrophication of lakes and estuaries raises difficult issues of responsibility and scientific uncertainty, and the water management connection may be tenuous but will attract public attention. (7) The water body attributes valued by specialised recreational interests require definition in terms that water managers can deal with using routine techniques of systems analysis and evaluation. (8) The demands of the fish population and anglers introduce a new perspective in river management and perceptions of instream values are changing markedly. (9) Direct costs of recreational services supplied by water authorities are not fully accounted: allocation choices and fiscal incidence will emerge as issues of significance. (10) These case studies raise only a fraction of the total range of matters that will, in the years to come, tax the technology and political skills of governments and management.

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15

Agwanda, Paul Omondi, and Muhammad Mazhar Iqbal. "Engineering Control of Eutrophication: Potential Impact Assessment of Wastewater Treatment Plants Around Winam Gulf of Lake Victoria in Kenya." Journal of Coastal Research 91, sp1 (August 28, 2019): 221. http://dx.doi.org/10.2112/si91-045.1.

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16

Kipkemboi, J., F. Kansiime, and P. Denny. "The response ofCyperus papyrus(L.) andMiscanthidium violaceum(K. Schum.) Robyns to eutrophication in natural wetlands of Lake Victoria, Uganda." African Journal of Aquatic Science 27, no. 1 (January 2002): 11–20. http://dx.doi.org/10.2989/16085914.2002.9626570.

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17

Zouiten, Hala, César Álvarez Díaz, Andrés García Gómez, José Antonio Revilla Cortezón, and Javier García Alba. "An advanced tool for eutrophication modeling in coastal lagoons: Application to the Victoria lagoon in the north of Spain." Ecological Modelling 265 (September 2013): 99–113. http://dx.doi.org/10.1016/j.ecolmodel.2013.06.009.

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18

Onyango, Dancan O., Christopher O. Ikporukpo, John O. Taiwo, and Stephen B. Opiyo. "Monitoring the extent and impacts of watershed urban development in the Lake Victoria Basin, Kenya, using a combination of population dynamics, remote sensing and GIS techniques." Environmental & Socio-economic Studies 9, no. 2 (June 1, 2021): 11–25. http://dx.doi.org/10.2478/environ-2021-0007.

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Abstract Several urban centres of different sizes have developed over time, and continue to grow, within the basin of Lake Victoria. Uncontrolled urban development, especially along the lake shore, puts environmental pressure on Lake Victoria and its local ecosystem. This study sought to monitor the extent and impacts of urban development (as measured by population growth and built-up land use/land cover) in the Lake Victoria basin, Kenya, between 1978 and 2018. Remote sensing and GIS-based land use/land cover classification was conducted to extract change in built-up areas from Landsat 3, 4, 5 and 8 satellite imagery obtained for the month of January at intervals of ten years. Change in population distribution and density was analysed based on decadal census data from the Kenya National Bureau of Statistics between 1979 and 2019. A statistical regression model was then estimated to relate population growth to built-up area expansion. Results indicate that the basin’s built-up area has expanded by 97% between 1978 and 2018 while the population increased by 140% between 1979 and 2019. Urban development was attributed to the rapidly increasing population in the area as seen in a positive statistical correlation (R2=0.5744) between increase in built-up area and population growth. The resulting environmental pressure on the local ecosystem has been documented mainly in terms of degradation of lake water quality, eutrophication and aquatic biodiversity loss. The study recommends the enactment and implementation of appropriate eco-sensitive local legislation and policies for sustainable urban and rural land use planning in the area. This should aim to control and regulate urban expansion especially in the immediate shoreline areas of the lake and associated riparian zones.

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19

van Zwieten, Paul A. M., Jeppe Kolding, Michael J. Plank, Robert E. Hecky, Thomas B. Bridgeman, Sally MacIntyre, Ole Seehausen, and Greg M. Silsbe. "The Nile perch invasion in Lake Victoria: cause or consequence of the haplochromine decline?" Canadian Journal of Fisheries and Aquatic Sciences 73, no. 4 (April 2016): 622–43. http://dx.doi.org/10.1139/cjfas-2015-0130.

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We review alternative hypotheses and associated mechanisms to explain Lake Victoria’s Nile perch (Lates niloticus) takeover and concurrent reduction in haplochromines through a (re)analysis of long-term climate, limnological, and stock observations in comparison with size-spectrum model predictions of co-existence, extinction, and demographic change. The empirical observations are in agreement with the outcomes of the model containing two interacting species with life histories matching Nile perch and a generalized haplochromine. The dynamic interactions may have depended on size-related differences in early juvenile mortality: mouth-brooding haplochromines escape predation mortality in early life stages, unlike Nile perch, which have miniscule planktonic eggs and larvae. In our model, predation on the latter by planktivorous haplochromine fry acts as a stabilizing factor for co-existence, but external mortality on the haplochromines would disrupt this balance in favor of Nile perch. To explain the observed switch, mortality on haplochromines would need to be much higher than the fishing mortality that can be realistically reconstructed from observations. Abrupt concomitant changes in algal and zooplankton composition, decreased water column transparency, and widespread hypoxia from increased eutrophication most likely caused haplochromine biomass decline. We hypothesize that the shift to Nile perch was a consequence of an externally caused, climate-triggered decrease in haplochromine biomass and associated recruitment failure rather than a direct cause of the introduction.

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20

Wanink, Jan, Frans Witte, and Mary Kishe-Machumu. "Dietary shift in benthivorous cichlids after the ecological changes in Lake Victoria." Animal Biology 58, no. 4 (2008): 401–17. http://dx.doi.org/10.1163/157075608x383700.

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AbstractCichlid fishes of Lake Victoria are well known for their trophic specializations. In our study area, the sub-littoral waters of the Mwanza Gulf (Tanzania), at least 12 trophic groups coexisted in the 1970s. After the Nile perch upsurge and eutrophication in the 1980s, most cichlids disappeared from the area. During the 1990s, heavy exploitation of Nile perch reduced the abundance of this predator. Subsequently, some cichlid species, mainly zooplanktivores and small benthivores, recovered. To establish their ecological role in the changed environment, among other factors we studied their diet. Stomach contents of fish caught before and after the ecological changes were compared. The small benthivores shifted from a diet dominated by detritus and phytoplankton, supplemented with small quantities of midge larvae and zooplankton, to a diet of invertebrate preys of larger sizes. Currently, the diet includes zooplankton, midge larvae, shrimps and molluscs, and a very small amount of detritus and phytoplankton. Apparently, the recovering benthivores have a more carnivorous than a herbivorous diet. Concomitantly, the ratio of intestine length to standard length of the benthivores decreased with 30% and the average stomach fullness decreased as well. The observed dietary shifts may be due to (1) the changed availability of food types and a decline of the nutritious quality of detritus and phytoplankton due to the strong increase of cyanobacteria in the lake, (2) the decline of the former trophic specialists, and (3) the reduced water clarity. The diet of the former detritivores is currently very similar to that of the zooplanktivores. Consequently, if diet plays a role in the relatively slow recovery of the small benthivores compared to the zooplanktivores, this would only hold if they are relatively poorly adapted to their new diet.

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21

Mchau, Geofrey J., Edna Makule, Revocatus Machunda, Yun Yun Gong, and Martin Kimanya. "Harmful algal bloom and associated health risks among users of Lake Victoria freshwater: Ukerewe Island, Tanzania." Journal of Water and Health 17, no. 5 (July 24, 2019): 826–36. http://dx.doi.org/10.2166/wh.2019.083.

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Abstract There is a global concern regarding the occurrences of harmful algal blooms (HABs) and their effects on human health. Lake Victoria (LV) has been reported to face eutrophication challenges, resulting in an increase of bloom-forming cyanobacteria. This study is aimed at understanding the association of HABs and health risks at Ukerewe Island. A cross-sectional study conducted on 432 study subjects and water samples for cyanobacteria species identification were collected at LV shores. The results reveal that concentrations of cyanobacteria cells are beyond (WHO) acceptable limits; species of Microcystis aeruginosa range from 90,361.63 to 3,032.031.65 cells/mL and Anabaena spp. range from 13,310.00 to 4,814,702 cells/mL. Water usage indicates that 31% use lake water, 53% well water and 16% treated supplied pipe water. Vomiting and throat irritation was highly reported by lake water users as compared to wells and pipe water (P < 0.001). Gastrointestinal illness (GI) was significantly elevated among lake water users as compared to pipe and well water users (P < 0.001). Visible blooms in lake water were associated with GI, skin irritation and vomiting as compared to water without visible blooms (P < 0.001). The concentration of cyanobacteria blooms poses greater risks when water is used without treatment.

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22

Simiyu, Benard, Steve Oduor, Thomas Rohrlack, Lewis Sitoki, and Rainer Kurmayer. "Microcystin Content in Phytoplankton and in Small Fish from Eutrophic Nyanza Gulf, Lake Victoria, Kenya." Toxins 10, no. 7 (July 3, 2018): 275. http://dx.doi.org/10.3390/toxins10070275.

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The human health risks posed by exposure to cyanobacterial toxins such as microcystin (MC) through water and fish consumption remain poorly described. During the last two decades, coastal regions of Lake Victoria such as Nyanza Gulf (Kisumu Bay) have shown severe signs of eutrophication with blooms formed by Microcystis producing MC. In this study, the spatial variability in MC concentration in Kisumu Bay was investigated which was mostly caused by Microcystis buoyancy and wind drifting. Small fish (<6 cm) mainly composed of Rastrineobola argentea were examined for MC content by means of biological methods such as ELISA and protein phosphatase inhibition assay (PPIA) and partly by chemical-analytical methods such as LC-MS/MS. Overall, the MC content in small fish was related to the MC content observed in the seston. When comparing the MC content in the seston in relation to dry weight with the MC content in small fish the latter was found three orders of magnitude decreased. On average, the ELISA-determined MC contents exceeded the PPIA-determined MC contents by a factor of 8.2 ± 0.5 (SE) while the MC contents as determined by LC-MS/MS were close to the detection limit. Using PPIA, the MC content varied from 25–109 (mean 62 ± 7) ng/g fish dry weight in Kisumu Bay vs. 14 ± 0.8 ng MC/g in the more open water of L. Victoria at Rusinga channel. Drying the fish under the sun showed little effect on MC content, although increased humidity might indirectly favor photocatalyzed MC degradation.

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23

Kanda, Edwin K., Emmanuel C. Kipkorir, and Job R. Kosgei. "Modelling of nitrates in River Nzoia using MIKE 11." Water Practice and Technology 12, no. 1 (March 1, 2017): 217–23. http://dx.doi.org/10.2166/wpt.2017.026.

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Eutrophication is a serious problem in Lake Victoria as a result of enrichment by nutrients transported by the rivers draining into it. River Nzoia is one of the main rivers draining into the lake. The main aim of this study was to simulate the level of nitrates using MIKE 11 and to establish relationship between nitrogen and phosphorus. The model was calibrated using water quality data for 2009 and validated with March 2013 data and then it was used to simulate nitrate concentration for the wet month of April 2013. The model performance was good with R2 values of between 0.87 and 0.98 and EF values of between 0.73 and 0.96. From the simulations, the effluent discharge from municipal and industrial wastewater ponds elevated the concentration of the nitrates in the river. Analysis of the concentrations of nitrates for wet and dry periods showed significant variations indicating significant contributions from the catchment through run-off. The relationship between total nitrogen and total phosphorus was analysed and found to have a strong positive correlation (r = 0.714, p < 0.05) indicating that both originate from similar sources or are influenced by the same factors such as agriculture.

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24

I. Z., Mukasa-Tebandeke, Karume I., Wasajja H. Z., and Nankinga R. "Improving Quality of Water from Murchison bay Using Clay from Chelel, Kapchorwa District, Uganda." Academic Journal of Chemistry, no. 411 (November 10, 2019): 102–17. http://dx.doi.org/10.32861/ajc.411.102.117.

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Pollution resulting from increased human activities is threatening Lake Victoria, its effects are characterized by eutrophication, high turbidity, pH, iron(II) concentration and chemical oxygen demand (COD). In this study we have investigated the effect of Fe-montmorillonite clay from Chelel on turbidity, pH, concentration of iron, total suspended soils, total nutrients and COD of water sampled from Murchison bay watershed of Nakivubo channel south of Kampala. Varying amounts of clay powder was vigorously stirred with water samples for 5 minutes, filtered using Whatman paper at ambient temperatures. The optimum concentration of clay of 0.4 gL-1 was found to produce 73.5+2% fall in COD indicating elimination of microbes and organic waste. The pH of water became 6.3+ 0.2 showing that impurities had been bound to clay. The TSS and nutrients in MB water also decreased greatly when clay was stirred with water at ambient temperatures. The available data can be relied on to recommend use of this clay in treatment of waste water and/or sewage from Kampala. Further studies on combined use of clays with alums, zeolites and/or lime need to be carried out.

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25

O'Brien, Allyson L., Liz Morris, and Michael J. Keough. "Multiple sources of nutrients add to the complexities of predicting marine benthic community responses to enrichment." Marine and Freshwater Research 61, no. 12 (2010): 1388. http://dx.doi.org/10.1071/mf10085.

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Understanding biological responses to nutrient enrichment under different environmental conditions is integral for the effective management of eutrophication in coastal environments. However, current conceptual models of nutrient enrichment are limited as they are based on studies that only consider a single source of nutrients, when in reality it is more likely that enrichment is a result of multiple sources. Here, we test the hypothesis that biological responses to nutrient enrichment in intertidal mudflat assemblages depend on the source by comparing enrichment from a controlled release fertilizer with that from decomposing macroalgae. Sediment at two sites in Port Phillip Bay, Victoria, were dosed with the different nutrient sources and monitored through time. After six weeks, the macroalgae-enriched plots had significantly higher abundances and biomass of some taxa of deposit-feeding polychaetes. In the fertilizer-enriched plots, the porewater nutrients increased but there was no detectable change in abundances or biomass of infauna, suggesting that the nutrients did not assimilate into the foodweb. The rate of assimilation of anthropogenic nutrients potentially occurs over longer time scales compared with the rapid assimilation and biological responses to decomposing macroalgae. Responses to the different nutrient sources provide new insights into the complexity of nutrient enrichment models that are applied to the management of aquatic ecosystems worldwide.

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26

Yin, Kedong, and Paul J. Harrison. "Influence of the Pearl River estuary and vertical mixing in Victoria Harbor on water quality in relation to eutrophication impacts in Hong Kong waters." Marine Pollution Bulletin 54, no. 6 (June 2007): 646–56. http://dx.doi.org/10.1016/j.marpolbul.2007.03.001.

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27

Beeton, Alfred M. "Large freshwater lakes: present state, trends, and future." Environmental Conservation 29, no. 1 (March 2002): 21–38. http://dx.doi.org/10.1017/s0376892902000036.

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The large freshwater lakes of the world are an extremely valuable resource, not only because 68% of the global liquid surface fresh water is contained in them, but because of their importance to the economies, social structure, and viability of the riparian countries. This review provides decision makers with the knowledge of large lakes (≥ 500 km2) essential to establishing policies and implementing strategies compatible with sustainable development. This is achieved by considering the present state of the lakes, the extent of changes and factors causing them, long-term consequences of these changes, major threats and possible states of the lakes into the year 2025. Case studies of lakes are presented, namely the St Lawrence Great Lakes of North America as representatives of glacial scour lakes of North America, northern Europe and Asia, and the African Great Lakes as representatives of tropical tectonic lakes. Lake Baikal is also included because it is unique for its species, great age, and largest single volume of liquid surface fresh water. The Aral Sea is further included because of the ecological disaster following diversion of water away from its basin. The major impacts on large lakes are diversions, eutrophication, invasive species, land-use change, overexploitation of resources, and pollution. These impacts can or do affect all the representative lakes, but to varying degree. The St Lawrence Great Lakes have been severely impacted by eutrophication, land-use change, overfishing, invasive species and pollution. Eutrophication has been reversed for these lakes and constraints are now in place on land use change, such as shoreline alteration and destruction of wetlands. With the demise of most commercial fishing, overfishing is no longer as important. Invasive species have become a major problem as increasingly non-indigenous species gain access to the lakes. Pollution continues as a major impact. These problems are likely to continue and seriously impact use of the resources as well as bring about changes in the biota. Among the African Great Lakes, invasive species are a major problem in Lake Victoria, and eutrophication associated with land-use change and overexploitation of resources is a growing problem. Many endemic species have been lost and many are threatened, so that species associations will have changed by 2025. The Aral Sea continues to disappear and in the future, the remaining largest part of it will continue to become increasingly saline and eventually disappear. A small body of water will remain as a freshwater lake with a productive, although small, fishery. Lake Baikal shows evidence of pollution in the southern basin and is likely to be impacted by land-use changes, primarily logging. Some non-indigenous species are present, but so far, they are not a major problem. Overexploitation of resources in the watershed could lead to adverse impacts on inshore waters. Overfishing has been recognized and appears under control. The major threat to Baikal is continued and growing pollution. Climate change and pollution are global problems that will affect all lakes, large and small. At present, while some warming has occurred, climate change appears not to have impacted large lakes. Present studies on the Laurentian Great Lakes predict possible major impacts. Pollution, especially from persistent toxic substances such as PCBs, is a global problem. Diversion of water out or away from large lakes will become more of a threat as global human population growth continues and water supplies from rivers and ground water become depleted.

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Kotut, Kiplagat, Andreas Ballot, and Lothar Krienitz. "Toxic cyanobacteria and their toxins in standing waters of Kenya: implications for water resource use." Journal of Water and Health 4, no. 2 (June 1, 2006): 233–45. http://dx.doi.org/10.2166/wh.2006.0020.

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Phytoplankton biodiversity studies in Kenya's standing waters were carried out between 2001 and 2003. Toxin producing cyanobacteria were recorded in twelve water bodies. Microcystis and Anabaena were the most common species in freshwaters while Anabaena and Anabaenopsis were common in alkaline saline lakes. Seven lakes with cyanobacteria blooms and a hot spring had detectable levels of microcystins and anatoxin-a. Cell bound microcystins (LR equivalents) concentration ranged from 1.6–19800 μg g−1 Dry Weight (DW) while anatoxin-a varied from below the limit of detection to 1260 μg g−1 DW. In alkaline-saline lakes, microcystins and anatoxin-a were also present in stomach contents and liver samples of dead flamingos. Monoculture strains of A. fusiformis from Lakes Sonachi and Bogoria had detectable levels of microcystins while anatoxin-a was present in strains isolated from Lakes Sonachi, Bogoria and Nakuru. Two freshwater sites, Nyanza Gulf (L. Victoria) and Lake Baringo recorded cyanotoxin concentration exceeding WHO's upper limit of 1.0 μg l−1 for drinking water. The results confirm that cyanotoxins could have played a role in the mortality of flamingos in Lakes Bogoria and Nakuru. The implications of these findings on water resource use, measures to be taken to reduce the risk of exposure and eutrophication control steps to reduce cyanobacteria bloom formation are considered in this paper.

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Masso, Cargele, Fredrick Baijukya, Peter Ebanyat, Sifi Bouaziz, John Wendt, Mateete Bekunda, and Bernard Vanlauwe. "Dilemma of nitrogen management for future food security in sub-Saharan Africa – a review." Soil Research 55, no. 6 (2017): 425. http://dx.doi.org/10.1071/sr16332.

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Food security entails having sufficient, safe, and nutritious food to meet dietary needs. The need to optimise nitrogen (N) use for nutrition security while minimising environmental risks in sub-Saharan Africa (SSA) is overdue. Challenges related to managing N use in SSA can be associated with both insufficient use and excessive loss, and thus the continent must address the ‘too little’ and ‘too much’ paradox. Too little N is used in food production (80% of countries have N deficiencies), which has led to chronic food insecurity and malnutrition. Conversely, too much N load in water bodies due mainly to soil erosion, leaching, limited N recovery from wastewater, and atmospheric deposition contributes to eutrophication (152 Gg N year–1 in Lake Victoria, East Africa). Limited research has been conducted to improve N use for food production and adoption remains low, mainly because farming is generally practiced by resource-poor smallholder farmers. In addition, little has been done to effectively address the ‘too much’ issues, as a consequence of limited research capacity. This research gap must be addressed, and supportive policies operationalised, to maximise N benefits, while also minimising pollution. Innovation platforms involving key stakeholders are required to address N use efficiency along the food supply chain in SSA, as well as other world regions with similar challenges.

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Monbet, Phil, Ian D. McKelvie, and Paul J. Worsfold. "Phosphorus speciation, burial and regeneration in coastal lagoon sediments of the Gippsland Lakes (Victoria, Australia)." Environmental Chemistry 4, no. 5 (2007): 334. http://dx.doi.org/10.1071/en07049.

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Environmental context. Eutrophication can lead to the production of harmful algal blooms and is one of the world’s most serious water quality issues. Phosphorus is potentially the limiting macro-nutrient in fresh, estuarine and some marine waters. Consequently, it plays a crucial role in determining the ecological status of many aquatic ecosystems. Considerable effort has been invested in monitoring dissolved reactive phosphorus and total phosphorus in the water column, but less is known about the speciation of phosphorus, particularly in the sediment. This compartment is an important and dynamic reservoir of phosphorus and a potential long-term source of phosphorus release to the water column by the sediment–water interface. This paper investigates the solid-phase speciation and reorganisation of phosphorus within the sediments of a shallow lake system in south-east Australia (the Gippsland Lakes) which suffers from recurring harmful algae blooms. Various strategies are proposed to determine the minimum realistic timescale required to deplete the sediment of labile and reactive phosphorus species. Abstract. Solid-phase phosphorus pools in the sediments of two shallow lakes (Wellington and Victoria) in the Gippsland Lakes coastal lagoon system of south-east Australia are discussed. Cores (20-cm depth) were taken in summer and winter in both lakes and a sequential extraction scheme (SEDEX) was used to profile the exchangeable P (Pex), iron oxide/hydroxide bound P (PFe), authigenic P (Pauth), detrital P (Pdet) and organic P (Porg). Pore-water (Ppw) dissolved reactive phosphorus concentration profiles were also measured. The dominant forms of P were PFe (up to 53%) and Porg (35–55%), with the PFe fraction playing a key role in the short-term retention of P in the sediment. Benthic phosphorus fluxes at the sediment–water interface (μmol m–2 d–1) were determined from the sequential extraction data. The results were compared with flux measurements from the complementary approaches of benthic chamber experiments and Fickian diffusion calculations, to allow an insight into the nature and seasonal variations of the fluxes. The burial flux of phosphorus was also estimated from excess 210Pb profiles in the sediment of the lakes. All of these data were used to produce a phosphorus budget for the Gippsland Lakes which suggested that the sediment represents a substantial source of phosphorus within the lakes and thus clearly highlights the importance of the sedimentary compartment in shallow eutrophic ecosystems. Minimum realistic timescales for complete labile phosphorus depletion from the sediment (assuming no resupply from the sediment–water interface) were calculated and ranged from 8 to 22 years.

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I. Z, Mukasa-Tebandeke, Karume I, Wasajja H. Z, and Nankinga R. "Improving Quality of Water from Murchison Bay using Clay from Chelel, Kapchorwa District, Ugandao." JOURNAL OF ADVANCES IN CHEMISTRY 17 (January 4, 2020): 1–29. http://dx.doi.org/10.24297/jac.v17i.8537.

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Pollution resulting from increased human activities is threatening Lake Victoria, its effects are characterized by eutrophication, high turbidity, pH, iron(II) concentration and chemical oxygen demand (COD). In this study we have investigated the effect of Fe-montmorillonite clay from Chelel on turbidity, pH, concentration of iron, total suspended soils, total nutrients and COD of water sampled from Murchison bay watershed of Nakivubo channel south of Kampala. Varying amounts of clay powder was vigorously stirred with water samples for 5 minutes, filtered using Whitman paper at ambient temperatures. The optimum concentration of clay of 0.4gl-1 was found to produce 73.5+ 2% fall in COD indicating elimination of microbes and organic waste. The pH of water became 6.3+ 0.2 showing that impurities had been bound to clay. The turbidity of filtrate dropped to 15.7+ 0.3NTUshowing that clarity of water was improved by adsorption of suspended solids to clay minerals. The concentration of iron(II) fell from 3.7 + 0.3 to 2.5+ 0.2mgl-1 indicating fairly high extent of heavy metal removal from Murchison bay (MB) waters. The TSS and nutrients in MB water also decreased greatly when clay was stirred with water at ambient temperatures. The available data can be relied on to recommend use of this clay in treatment of waste water and/or sewage from Kampala. Further studies on combined use of clays with alums, zeolites and/or lime need to be carried out.

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Mchau, Geofrey J., Edna Makule, Revocatus Machunda, Yun Yun Gong, and Martin Kimanya. "Phycocyanin as a proxy for algal blooms in surface waters: case study of Ukerewe Island, Tanzania." Water Practice and Technology 14, no. 1 (January 8, 2019): 229–39. http://dx.doi.org/10.2166/wpt.2019.005.

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Abstract Knowledge of the parameters that contribute to water body eutrophication is essential for proper monitoring and management of water quality for human consumption. This study assessed water quality parameters in relation to phycocyanin (PC) as a proxy indicator for harmful algal blooms (HABs). Samples were collected from 23 water sources – lakes, wells, springs and boreholes – in selected villages, for six months. Parameters measured included temperature, pH, redox potential, dissolved oxygen, electrical conductivity, total dissolved solids, nitrate nitrogen, nitrite nitrogen, phosphorus, reactive phosphate and total chlorophyll, which were related to (PC) occurrence. The PC concentration detected in Lake Victoria ranged from 5 to 58.4 μg/l above the WHO alert level and exceeded that in other water sources by almost 30 μg/l (P < 0.001). Univariate relationship between water quality parameters and PC indicates association with temperature, redox potential, total chlorophyll, nitrate nitrogen, nitrite nitrogen, phosphate and reactive phosphorus (P < 0.001). The multivariate model indicates that redox potential, nitrate nitrogen and phosphorus are significant statistically (P < 0.05). A predictive model indicates that nitrate nitrogen and reactive phosphorus contribute significantly to PC occurrence whereby unit (1 mg/l) increases in these parameters increase PC by 9.55 and 4.38 μg/l (P < 0.05) respectively. This study demonstrates that water quality parameters can be used to predict increases in PC and hence as a proxy for HABs. It remains important to be able to classify algal blooms, to understand which species are present and their potential cyanotoxin production.

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Mathers, Nicole J., and David M. Nash. "Effects of tillage practices on soil and water phosphorus and nitrogen fractions in a Chromosol at Rutherglen in Victoria, Australia." Soil Research 47, no. 1 (2009): 46. http://dx.doi.org/10.1071/sr08106.

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Phosphorus (P) and nitrogen (N) exports from cropping areas can be greater than those from uncropped areas. Conservation farming methods, involving minimal tillage and full stubble retention, offer significant benefits to grain cropping, but may increase nutrient concentrations in surface (i.e. 0–20 mm) soils, resulting in increased risks of nutrient mobilisation and loss. The effects of tillage and stubble management on soil nutrients that are potentially mobilised into runoff from a long-term trial site at Rutherglen (established in 1981) were investigated. On 2 different sampling dates (February and August 2006) soils from the 0–20, 20–50, and 50–150 mm depths were collected from 3 treatments: conventional cultivation with stubble burning (CCb); direct drill with stubble burning (DDb); and direct drill with stubble retained (DDr). In 2004, the trial was sown with wheat (Triticum aestivum cv. Dollarbird), followed by faba beans in 2005 (Vicia faba L.) and wheat again in 2006. In August 2006, a rainfall simulation experiment was also conducted on these sites. All nutrient concentrations decreased with depth to 150 mm in all treatments, when both sampling dates were analysed together. This indicated that soil nutrient stratification was occurring in all 3 treatments. The CCb treatment only displayed differences between the 0–20 and 20–50 mm depths for soil organic C and ammonium-N. DDr significantly increased some nutrient concentrations in the 0–20 mm soil depth compared with the CCb treatment, including CaCl2-extractable P (0.76 and 0.50 mg/kg, for DDr and CCb, respectively), total N (1.23 and 1.00 g/kg, for DDr and CCb, respectively), and nitrate-N (12.6 and 8.63 mg/kg, for DDr and CCb, respectively), while the ammonium-N concentration was greater under CCb (9.71 mg/kg) than DDr (6.46 mg/kg). Being water-soluble, CaCl2-extractable P and nitrate-N are more likely be mobilised into streams from the 0–20 mm depth, where they are highly bioavailable and may contribute to increased eutrophication. Direct drilling with stubble retention contributed a greater proportion of particulate P and N to TP (Total P) and TN (Total N) in surface runoff than either of the burnt systems. Particulate P accounted for 75%, 67%, and 83% of TP in surface runoff from the CCb, DDb, and DDr treatments, respectively. However, the highly bioavailable dissolved reactive P (DRP) was the dominant form of dissolved P, with concentrations exceeding the recommended guidelines of 0.05 mg P/L in the lowlands of south-east Australia. Total N (0.44, 0.68, and 0.73 mg N/L for DDr, DDb, and CCb, respectively) in surface runoff was dominated by nitrate-N and also exceeded current Australian guidelines of 0.5 mg N/L, except for TN from the DDr treatment. These results would indicate that P, particularly the non-dominant but highly bioavailable form of DRP, exported from these systems is more likely to adversely affect catchment water quality than N exports. The increase in surface runoff volumes and nutrient loads from the CCb treatment observed in this study indicate that DDr systems have increased soil infiltration properties and retained nutrients within the soil–plant system. Therefore, direct drilling with stubble retention in the high rainfall zone cropping areas of north-east Victoria is more likely to retain nutrients on-site and improve soil fertility than burning stubble and cultivating the soil.

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Nyamweya, C. S., H. M. Nyaboke, C. M. Aura, K. N. Momanyi, E. Mlaponi, C. O. Odoli, and J. M. Njiru. "Lake Victoria’s bounty: A case for riparian countries’ blue economic investment." Frontiers in Environmental Science 10 (September 8, 2022). http://dx.doi.org/10.3389/fenvs.2022.952654.

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People residing in Lake Victoria’s basin and riparian countries benefit from ecosystem services provided by the lake. However, the lake’s resources, particularly fish, are under threat from pressures caused by humans such as overfishing, alien species invasion, rising eutrophication, and climate change. In this assessment, we look at how to maximize the lake’s benefits through product diversification, value addition, and sustainable use of its fisheries. We show that minimizing post-harvest losses of the silver cyprinid (Rastrineobola argentea), locally known as Dagaa, will provide more high-quality fish for human consumption, while significantly increasing fishing earnings. Furthermore, by utilizing biowaste (frames, skin, and fish mouth), revenues from Nile perch could be increased up to thrice. Furthermore, if fishing could target maximum sustainable yield (MSY), landings of Nile perch and Dagaa could increase significantly in the long run. These, combined with investments in other areas such as lacustrine tourism and recreation, as well as fish cage culture, can help the Lake Victoria region’s blue economy expand.

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Marshall, Brian, Charles Ezekiel, John Gichuki, Oliva Mkumbo, Lewis Sitoki, and Fred Wanda. "Global warming is reducing thermal stability and mitigating the effects of eutrophication in Lake Victoria (East Africa)." Nature Precedings, September 8, 2009. http://dx.doi.org/10.1038/npre.2009.3726.1.

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Odhiambo, Moses, Dennis Njagi, Joyanto Routh, Gayatri Basapuram, Chen Luo, Daniel Olago, J. Val Klump, and Curt Stager. "A Century of Human-Induced Environmental Changes and the Combined Roles of Nutrients and Land-Use in Lake Victoria Catchment on Eutrophication." SSRN Electronic Journal, 2022. http://dx.doi.org/10.2139/ssrn.3998981.

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Lu, Zhongming, Liuqian Yu, and Jianping Gan. "External and Internal Forcings for Hypoxia Formation in an Urban Harbour in Hong Kong." Frontiers in Marine Science 9 (April 19, 2022). http://dx.doi.org/10.3389/fmars.2022.858715.

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Eutrophication-driven hypoxia is one of the reasons for the deterioration of coastal waters, especially those adjacent to densely inhabited urban cities. Thus, effective hypoxia management is urgently needed, and quantitative knowledge of factors controlling hypoxia is required. A case in point is the coastal water around Hong Kong, a megacity that has over 7.5 million residents and is located downstream of the large and nutrient-rich Pearl River. The Victoria Harbour (VH) is the core area of Hong Kong water and has been suffering from marine environment deterioration for years because of external biogeochemical influxes from adjacent waters and internal physical and biogeochemical responses. Three channels orienting from south to north (C1), southeast to northwest (C2), and west to east (C3) connect the VH to adjacent waters and serve as the primary exchange pathways for water mass and biogeochemical substances. Using observational data and a coupled physical–biogeochemical model, we showed that the northward transport of low dissolved oxygen (DO) water from the coastal transition zone by the shoreward bottom current mainly through C1 directly contributes to the hypoxia formation in VH. The external influx of anthropogenic nutrients and organic matter through C2 further enhances the bottom water hypoxia in VH by stimulating phytoplankton bloom and microbial consumption of oxygen in water columns and sediments. Although the horizontal oxygen influx to VH is weak, the comparatively strong vertical mixing in C3 facilitates the replenishment of bottom water in the VH, mitigating bottom hypoxia. Locally in the VH, sediment oxygen demand is the dominant biogeochemical contributor (~93%) to hypoxia formation, while the contribution of water column remineralization is relatively minor (~6-7%). In general, vertical diffusion serves as the largest source (~57%) of DO in the VH because of the strong vertical DO gradient, whereas vertical motion ranks the second largest source of DO (~24%) and serves as a critical physical factor regulating the oxygen budget of the entire VH. In the spatial constriction area where the vertical DO gradient is weak, the magnitude of vertical motion exceeds vertical diffusion to become the largest source of DO (~48%).

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