Showing papers in "Lakes and Reservoirs: Research and Management in 2001"
TL;DR: The Lake Victoria Fisheries Organization (LVFO) as discussed by the authors is a regional international institution for the management of Lake Victoria fisheries, which was established by the governments of Tanzania, Uganda and Kenya.
Abstract: Lake Victoria is the largest lake in Africa (68 800 km2) and is the eighth largest lake in the world by volume. The three East African countries of Tanzania, Uganda and Kenya share Lake Victoria and its resources. The total annual catch of fish from the lake ranges between 400 × 106 kg and 500 × 106 kg, bringing these riparian countries a combined annual income of approximately US$250 000–500 000 from exports alone. Approximately 30 million people live in the riparian region and the catchment, with about 2 million of these depending directly or indirectly on fishing activities. Tragically, Lake Victoria’s extremely diverse fauna was decimated in only 30 years following the introduction of non-native Nile perch in the early 1960s. An estimated 200 endemic cichlid species became extinct. Dramatic increases in overfishing, pollution from various sources, effects of noxious water weeds and other associated problems threaten the sustainability of the lake’s resources and the economies of the riparian governments and peoples. Regulations governing Lake Victoria’s resources are different in each country. The laws concerning treatment of effluents from point sources in the three countries are not harmonized, neither are implementation or enforcement provisions. The governments of Kenya, Uganda and Tanzania have begun to put in place regional mechanisms to address the lake’s many problems including the creation of a permanent regional international institution through the establishment of the Lake Victoria Fisheries Organization (LVFO). A strategic vision document and action plans have been developed. Efforts are being made at local, national and regional levels to control the water hyacinth, including manual pulling, mechanical harvesting and introduction of weevils that weaken hyacinth root systems. To address the problem of overfishing, fishermen committees at landing beaches have been put in place. Each country has committed to take all necessary measures including legislation to implement the decisions of the LVFO governing bodies. All three countries have agreed to adopt and enforce legislation and regulations prohibiting the introduction of non-indigenous species to the lake and to enforce existing regulations regarding fisheries. A Global Environment Facility project which provides funding to the Lake Victoria Fisheries Organization addresses land use management, catchment forestation, fisheries research and management, water hyacinth control, industrial effluent treatment and municipal waste treatment.
127 citations
TL;DR: In this paper, a field survey and interviews were used to study wetland use and their impact on Lake Victoria, and general recommendations for planning and management issues, as well as suggestions of specific research needs that should form the basis of action and investment initiatives are given.
Abstract: This article reports on a study of wetland use and impact on Lake Victoria conducted in March and April 1995. A field survey and interviews were used to study wetland use and their impact on Lake Victoria. This article identifies management issues and establishes a broad vision for the future. It also addresses the need to balance the competing demands for wetland use and development with the need to conserve a healthy and functional Lake Victoria. Investment proposals are made that would minimize destruction of the wetlands and negative impacts on the lake. General recommendations for planning and management issues, as well as suggestions of specific research needs that should form the basis of action and investment initiatives, are given.
61 citations
TL;DR: During the last 20 years recovery measures have reduced the external P load from about 250 to 70–80 tonnes year–1 and the goal to be reached is 40 tonnes year-1, notwithstanding an increase in the thickness of the trophogenic layer.
Abstract: Lake Lugano is located at the border between Italy and Switzerland and is divided into three basins by two narrowings. The geomorphologic characteristics of these basins are very different. The catchment area is characterized by calcareous rock, gneiss and porphyry; the population amounts to approximately 290 000 equivalent inhabitants. The external nutrient load derives from anthropogenic (85%), industrial (10%) and agricultural (5%) sources. The limnological studies carried out by Baldi et al. (1949) and EAWAG (1964) revealed early signs of eutrophication, with a phosphorous concentration of about 30–40 mg m–3 and an oxygen concentration of less than 4 g m–3 in the deepest hypolimnion. Subsequently Vollenweider et al. (1964) confirmed these data and was the first to point out the presence of a meromictic layer in the hypolimnion of the northern basin. From the 1960s, as a result of an increase in the population and internal migration, the lake became strongly eutrophic with the P concentration reaching 140 mg m–3 and the oxygen in the hypolimnion reduced to zero. Fifty-five per cent of the P was from metabolic sources and 45% from detergents and cleaning products. In 1976, a partial diversion of waste water from the northern to the southern basin was begun, and gradually eight waste water treatment plants came into operation using mechanical, chemical and biological treatments. In 1986, Italy and Switzerland began to eliminate the P in detergents and cleaning products. Since 1995, the main sewage treatment plants have improved their efficiency by introducing P post-precipitation, denitrification and filtration treatments. The recovery of the lake is due to be completed by the year 2005. Altogether, during the last 20 years recovery measures have reduced the external P load from about 250 to 70–80 tonnes year–1; the goal to be reached is 40 tonnes year–1. In-lake phosphorous concentrations have decreased from 140 to 50–60 mg m–3, with the target at 30 mg m–3. Dissolved oxygen concentration is satisfactory only between the depths of 0 and 50 m, falling rapidly to zero in the deepest layers. Below a depth of 90 m, high CH4, HS–, NH4+, Fe2+ and Mn2+ concentrations exist. Primary production has decreased from 420 to 310 g Cass m–2 year–1, notwithstanding an increase in the thickness of the trophogenic layer. Structure and dynamic biomass show marked changes: phytoplankton dry weight has decreased from 16 to 7 g m–2, while zooplankton dry weight has increased from 3 to 4.5 g m–2. Chlorophyll concentration has fallen from 14 to 9 mg m–3 and Secchi disk transparency has increased from 3.5 to 5.5 m. The current sources of the external load are uncollected small urban conglomerations, storm-water overflows from outfall sewers, and the residual load from sewage treatment plants, particularly those without P post-precipitation.
53 citations
TL;DR: Harmonizing Albanian and Macedonian laws and regulations may be the Lake Ohrid Conservation Project’s greatest challenge, particularly on fisheries and wastewater treatment issues.
Abstract: Lake Ohrid is the oldest lake in Europe and one of the oldest lakes in the world, formed 4–10 million years ago Lake Ohrid serves as a refuge for numerous freshwater organisms from the tertiary period, whose close relatives can be found only as fossils A breeding programme that artificially hatches the native and endemic trout supports the natural recruitment of lake Ohrid trout and since 1935 the lake has been stocked with more than 600 million young trout The critical transboundary issue for Lake Ohrid water quality is phosphorus pollution The current phosphorus load of the lake is estimated at 150 ton per year and needs to be reduced to 50 ton per year to keep the mean concentration of phosphorus below 7 mg m–3 in the lake water In 1996, a Memorandum of Understanding between the Macedonian and Albanian governments was signed and a binational Lake Ohrid Management Board was established, with substantial funding by the Global Environmental Facility Both governments agreed to undertake appropriate legal, institutional, investment and technical measures to protect Lake Ohrid The Lake Ohrid Conservation Project has four main goals: (i) to develop the institutional legal and regulatory framework for environmental management in the Lake Ohrid watershed; (ii) to establish a comprehensive binational monitoring programme, (iii) to mobilize and secure commitments from all the stakeholders in the watershed who will need to take measures to prevent degradation of the lake; and (iv) to increase public awareness and participation Harmonizing Albanian and Macedonian laws and regulations may be the Lake Ohrid Conservation Project’s greatest challenge, particularly on fisheries and wastewater treatment issues
36 citations
TL;DR: The conceptual framework for lake management has evolved at an accelerating rate in recent years to include the basic principles of a watershed approach: (i) citizen and stakeholder involvement is important throughout the planning and management process; (ii) the geographic focus for management activities includes the lake and its entire watershed; and (iii) mechanisms need to be in place to promote cooperation among different government jurisdictions and organizations in the watershed.
Abstract: The conceptual framework for lake management has evolved at an accelerating rate in recent years to include the basic principles of a watershed approach: (i) citizen and stakeholder involvement is important throughout the planning and management process; (ii) the geographic focus for management activities includes the lake and its entire watershed; and (iii) mechanisms need to be in place to promote cooperation among different government jurisdictions and organizations in the watershed. Creating effective institutional arrangements for implementing this watershed approach in lake regions is perhaps the most challenging and important issue facing the world’s lakes. LakeNet organized a workshop at the 8th International Conference on the Conservation and Management of Lakes in May 1999. This article is a synthesis of the results of the workshop and the eight case reports prepared by the workshop participants published in this special issue. Seven major threats to lakes were identified: (i) accelerated eutrophication; (ii) invasive species; (iii) toxic contamination; (iv) overfishing; (v) water diversion, (vi) acidification; and (vii) climate change. Institutions and institutional arrangements for addressing these issues and for implementing a watershed approach are just beginning to emerge on lakes around the world. All of the institutions described in the case reports were established or formalized during the 1980s and 1990s. The legal mechanisms creating these institutions range from cooperative agreements among jurisdictions for purposes of policy and planning to national laws and international treaties with full regulatory powers. The knowledge base, political will and financial resources for these activities were very small in comparison with the complexity of the task at hand.
32 citations
TL;DR: In this article, the authors used a variogram to estimate the mean chlorophyll concentration of two British lakes and found that the sampling regime must be calibrated to the spatial dynamics of the lake under investigation, and suggests that remote sensing is the ideal means by which to determine such dynamics.
Abstract: In planning a sampling regime, it is desirable that the sampling procedure should involve minimum estimation error for a given sample size or minimum sampling effort for a given accuracy. Two approaches for matching sampling effort to accuracy may be used: a classical approach, which ignores spatial dependence between observations, and uses a random scheme; and a geostatistical approach, which exploits spatial dependence, and uses a systematic scheme. Four Airborne Thematic Mapper images of two British lakes were processed to provide a chlorophyll index, reflecting variations in chlorophyll-a concentration. Spatial structure was characterized using the variogram, and the modelled variogram was used in Kriging to plan sampling regimes for estimating the mean chlorophyll. For a given sample size, the systematic scheme incurred less error than the random scheme; and for a given error, the systematic scheme required smaller sample sizes than the random scheme. The relative advantage of the systematic approach over the random sampling approach increased with an increase in sample size and an increase in the proportion of variance in the data that was spatially dependent. This paper demonstrates that the sampling regime must be calibrated to the spatial dynamics of the lake under investigation, and suggests that remote sensing is the ideal means by which to determine such dynamics.
30 citations
TL;DR: In this paper, an investigation was performed in a pond (San Miguel) directly associated with the Salado River (Pampean grasslands) in order to determine the effects of changes in hydrological conditions.
Abstract: An investigation was performed in a pond (San Miguel) directly associated with the Salado River (Pampean grasslands). The aim of the study was to analyze river interactions. Physical and chemical conditions and the plankton community were studied in order to determine the effects of changes in hydrological conditions. The main factors that influenced the physical–chemical characteristics of the pond have been identified by means of cluster analysis. Conductivity was the main factor that determined groups in sampling periods. Changes in conductivity were clearly associated with the water-level of the pond and depended on the flow of the Salado River and fluctuations of its conductivity, which is itself a function of evaporation and the inflow of underground water of high conductivity. Other factors that affected the physical–chemical conditions included concentrations of phosphorus and polyphenols, the main allocthonous sources. The concentration of these compounds was decreased in low water conditions. Principal Components Analysis suggested that there were four major regulatory factors in the pond, as follows. First, a dry season, with a prolonged isolation phase and a considerable increase in conductivity, turbidity and suspended solids, during which the abundance of plankton was greatly reduced, as were incorporated benthic species. A high and sudden increase of river flow determines the second regulatory factor, the flood season, when dissolved allocthonous material enters, conductivity decreases and there is a conspicuous dominance of cyanophytes, protozoans and crustaceans. The different degrees of hydrological connection with the Salado River produce changes in dissolved phosphorus forms and the composition of the plankton. The third regulatory factor is an increase in particulate material. This is associated with the highest total phosphorus values as a consequence of the phosphorus– particle relationship. The opposite situation, the fourth regulatory factor (a decrease in particulate material), produces clear water conditions with a dominance of chlorophytes, planktonic diatoms and rotifers.
30 citations
TL;DR: The potential chemical effects of motorized recreational activities (power boating, water skiing, jet skiing) on Brown Lake, an Australian perched, acid dune lake, were investigated.
Abstract: The potential chemical effects of motorized recreational activities (power boating, water skiing, jet skiing) on Brown Lake, an Australian perched, acid dune lake, were investigated. The objective of this study was to identify and quantify polycyclic aromatic hydrocarbon compounds (PAHs) that may have accumulated in the water and/or the organic bottom sediments of the test lake as a result of the operation of powered recreational watercraft, and to evaluate any risk to aquatic biota. To achieve this, a detailed sampling and analysis programme of the lake water and sediments was implemented. Basic water quality, ionic and nutrient data gave no indication of any deterioration in the water quality of the lake, which was attributable to human usage in general or motorized recreational activities in particular. However, analysis of samples taken from the organic bottom sediments of the lake revealed the presence of 10 PAH, including benzo(a)pyrene, chrysene, fluoranthene, phenanthrene and pyrene, which are known to be indicative of fossil fuel combustion processes. Three PAH compounds were found at all survey sites: benzo(a)pyrene (in 46% of samples), fluoranthene (in 53% of samples) and pyrene (in 44% of samples). Results of the analyses were compared with values from published guidelines for residues in freshwaters and sediments, as well as with previous studies dealing with the effects of fossil fuel combustion products on lakes. The highest PAH concentrations in sediments were recorded for benzo(a)pyrene, with three values (830, 955 and 1070 μg kg–1 dryweight) exceeding the upper threshold recommended in the draft Canadian freshwater sediment quality guidelines. Benzo(a)pyrene also exceeded the lower Canadian sediment threshold in 51 (40%) samples. These results indicate a significant level of chemical contamination of Brown Lake as a consequence of four decades of motorized recreational activities and present a significant risk to aquatic biota, particularly benthic and littoral invertebrates associated with the contaminated sediments.
29 citations
TL;DR: The main international lake management problem for the Lake Titicaca/Desaguadero River/ Lake Poopo system involves the use of water resources as discussed by the authors, and water transfer and irrigation projects will have to be strictly prioritized on the basis of environmental, social, economic and hydrological criteria.
Abstract: Lake Titicaca is the largest freshwater lake in South America and the highest of the world’s large lakes. The Desaguadero River links Lake Titicaca to lakes Urur Uru and Poopo and, in wet years to the Coipasa Salt Marsh. Lake Titicaca is bordered by both Bolivia and Peru. The main international lake management problem for the Lake Titicaca/Desaguadero River/Lake Poopo system involves the use of water resources. The maximum usable flow in the Titicaca basin (only 20–25 m3 s–1), is dramatically less than the estimated demand. Water transfer and irrigation projects will have to be strictly prioritized on the basis of environmental, social, economic and hydrological criteria. Establishing the overall volume and demand for water in the Titicaca system has been critical to making good management decisions. Agreements for the study and management of Lake Titicaca between Peru and Bolivia date back to 1955 when both countries signed a document declaring ‘the indivisible and exclusive joint ownership of both countries of the waters of the lake’. Over time, the two countries agreed to create a Binational Autonomous Authority that would have full autonomy for Titicaca–Desaguadero/Poopo system decisions related to implementing the master plan that they had developed. Although it is hard to quantify conservation success in large lake regions, water use projects are being prioritized, city wastewater pollution in the Bay of Puno is being reduced and ameliorated and a large biodiversity project through the Global Environment Facility is underway.
27 citations
TL;DR: In addition, the lakes will become less variable and, so, possibly compromise their character with cascading effects through the ecosystem as discussed by the authors, so that important habitat may be lost, and, therefore, they may become less diverse.
Abstract: Large freshwater lakes in Australia’s arid zone are episodic due to highly variable inflows from allogenic rivers. A few receive enough inflow almost yearly to be permanent, despite large losses from high evaporation. Biodiversity is high, with most taxonomic groups represented, and is largely endemic at the continental scale. There is almost no regional endemism, which is at variance with other major aquatic habitat types in Australia. Abundance fluctuates greatly, with invertebrates and fish booming and busting with floodwater input, but birds generally reach greatest numbers later in the cycle as they gather on the more persistent waters. Invertebrate assemblages are influenced by the degree of lake permanence, turbidity and salinity, providing a temporally variable mosiac of environments throughout a lake system and between systems and with time. Unlike other groups, fish are not speciose, but are important predators in most systems with breeding coinciding with flooding. This favours native species against exotics in the Coongie Lakes but, in the Paroo, exotics are common in permanent waters. Waterbirds are the very obvious components in these variable systems, using their resources for feeding and breeding. Most are extremely nomadic to take advantage of the variable habitat. Two of the most important lake systems, the Coongie Lakes on Cooper Creek and the Paroo lakes in the northwestern Murray Darling catchment, are threatened by water abstraction upstream for irrigation, so that important habitat may be lost. In addition, the lakes will become less variable and, so, possibly compromise their character with cascading effects through the ecosystem. Some smaller lakes are adversely impacted by accelerated sedimentation.
26 citations
TL;DR: Self-shading is seen to have a considerable impact on potential productivity and may affect phytoplankton–cyanobacterial community structure with implications for lake management.
Abstract: Light is the factor that fundamentally determines the level of primary production Primary productivity is controlled by bottom-up factors (nutrient levels), with secondary effects due to biological factors (zooplankton grazing) The light regimen experienced by algae is determined largely by mixing of the water column The processes of photoinhibition and light attenuation combine with the resultant light–dark adaptation to shape the vertical productivity profile and it is important to determine their importance separately because they vary spatially and temporally Daily variations in productivity can be as large as longer-term changes and events causing high productivity may not be important in whole-lake terms At approximately 05 m depth, there is maximal photosynthesis causing depletion of nutrients, but there is vertical homogeneity in productivity control and horizontal similarity in productivity levels There is zero productivity below 5 m depth due to light attenuation but, if the benthos becomes productive due to an environmental change, such as decreased turbidity, overall productivity may rise appreciably Self-shading was investigated by incubating serial dilutions of whole lakewater with filtered water to reduce the density of algal cells Photosynthetic efficiency was calculated as productivity per unit of chlorophyll a Self-shading showed different responses for conditions of ‘low’ and ‘high’ productivity With low productivity, there was a shading loss of 17%, while for high productivity this was 46% Thus, self-shading is seen to have a considerable impact on potential productivity and may affect phytoplankton–cyanobacterial community structure with implications for lake management
TL;DR: In this paper, the authors address the problem of what social needs must be met to sustain society, and the contribution of lakes to each need is discussed, including aesthetics, education, economic opportunity, emotional security, cultural opportunity, individual freedom and spirituality.
Abstract: Lake management is typically approached from a biophysical perspective. Lake managers ask how lakes can be managed to sustain their ecological functions. The social value of lakes is usually given less attention. The present paper begins the analysis at the other end of the lake and society connection by posing the question: what social needs must be met to sustain society? The primary social needs of sustainable societies are outlined and then the contribution of lakes to each need is discussed. Lakes can only provide optimal social benefits if management decisions recognize the full set of potential contributions lakes can make to society and those management decisions are integrated to provided balanced attention to all values that lakes provide. The present paper expands the domain of values beyond the traditional environmental and recreational contributions of lake management to also include aesthetics, education, economic opportunity, emotional security, cultural opportunity, individual freedom and spirituality. Citizen involvement is essential in broadening the conceptualization of the lake values and in implementing integrated management plans.
TL;DR: In this article, the authors developed a historical orthophosphate balance in Lake Chapala, quantifying the main point and non-point sources that contribute to the enhancement of this nutrient in the lake.
Abstract: Lake Chapala, the most important lake in Mexico, has suffered from cultural eutrophication problems for many years, manifested by the growth of aquatic vegetation and an increase in primary productivity. It was found that about 70% of the total phosphorus entering Lake Chapala is orthophosphate, thus increasing the biological availability of nutrients in the lake. In addition, the hydrologic imbalance in the lake, caused by the over-use of water resources along the Lerma–Chapala basin, has significantly increased the hydraulic residence time of the inflow waters, thus increasing the effects of the added phosphorus, and creating conditions that increase the lake’s eutrophication status.
The shallow characteristics of the lake and the action of the wind forces produce rapid changes in water quality, especially in the distribution of phosphate. The focus of this paper is on the development of a historical orthophosphate balance in Lake Chapala, quantifying the main point and non-point sources that contribute to the enhancement of this nutrient in the lake. The estimation of the amount of phosphate in the lake can be used to determine appropriate management practices to reduce the phosphate loads on the lake.
TL;DR: Variations in catches could be caused by cyclical changes in fish populations, by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long-term studies of catch variation.
Abstract: The Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha ‐1 year ‐1 ), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12-fold and fourfold, respectively. The species present in the gill-net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined (Quiros 1990) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991), a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations (Wooton 1991), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long-term studies of catch variation.
TL;DR: The conclusion is that the IMC fishery of Kaptai Reservoir is an overexploited fish stock and the existing policy needs to be strengthened and more effectively implemented to stabilize the fishery.
Abstract: Interannual variation in yield per species from a freshwater reservoir in Bangladesh was analysed by using long-term landing data. Each species was categorized according to characteristics in interannual yield variation. The characteristics were defined with respect to size of the interannual variation in terms of absolute and relative variation around the mean yield and long-term trends in catch levels. Annual variation was directly (t18 = 7.84; P < 0.01) related to the yield and can serve as a good indication of the status of the fishery when catches are low. The target fish, Indian major carps (IMC) Labeo rohita, Labeo calbasu, Catla catla and Cirrhinus mrigala, showed large variation in annual yield. This might have occurred because of variation in annual recruitment. Illegal use of gears is mostly related to variation in year class strength, and is assumed to be the most important source of change of stock variation. An increase in catch rate was recorded for Corica soborna. Such a stable combination may only be possible for a certain period without a long-term trend. Trends in the yield rate of the major fish category for three decades reveal a sharp decline in the catch of IMC. In contrast, small clupeid-like C. soborna have the highest yield rate. Fishing gears can play a crucial role in this fishery. Fisheries managers must always be alert when issuing fishing licenses and on the control on gears. The conclusion is that the IMC fishery of Kaptai Reservoir is an overexploited fish stock. In this fishery, the same gears are usually employed indiscriminately for different species and size classes. To stabilize the fishery, the existing policy needs to be strengthened and more effectively implemented. Also, some fishing gears and traps need to be restricted. An effective stock protection policy is suggested. Further study on catch size of individual species is essential prior to the development and implementation of any management scheme.
TL;DR: In this article, the effects of introduced artificial reefs on the diversity of freshwater fish communities in lentic and lotic zones of a very impacted river in southeastern Brazil were investigated. And they showed that the higher environmental complexity in the lotic zone, as compared to the reservoir, is incremented in areas where artificial reefs were introduced; also, diversity is mainly affected by the introduction of artificial reefs.
Abstract: This paper deals with the effects of introduced artificial reefs on the diversity of freshwater fish communities in lentic and lotic zones of a very impacted river in southeastern Brazil. To accomplish this goal, artificial reefs were introduced, in December 1997, in the Barra Bonita reservoir and in the lotic zone immediately below the dam. Fish diversity was always higher in the lotic zone than in the reservoir. Accordingly, fish diversity near the artificial reefs was consistently higher than in the control areas. We propose that the higher environmental complexity in the lotic zone, as compared to the reservoir, is incremented in areas where artificial reefs were introduced; also, we present that, in both areas, diversity is mainly affected by the introduction of artificial reefs.
TL;DR: In this article, the response of the phytoplankton of a Patagonian Reservoir to the additional nutrients generated by the production of salmon in cages was investigated. And the results were discussed in relation to a 7 year study of the reservoir and the possible directions of trophic development.
Abstract: Bioassays were undertaken in order to test the response of the natural late-summer inoculum of the phytoplankton of a Patagonian Reservoir to the additional nutrients generated by the production of salmon in cages. The results are discussed in relation to a 7 year study of the reservoir and the possible directions of trophic development. The main consequences of fish farming activities in Alicura are likely to lead to an increase in both nutrient concentrations, algal density and phytobiomass. The composition of the sediment close to the fish farm is affected. With regard to phytoplankton, we observed changes in species composition and temporal changes in their associations. The additional nutrient sources of fish food and faeces from salmonid production create an internal load that leads to a decrease in the N/P, Si/P and Ca/P ratios of the water column. The trophic level of Alicura Reservoir remains unchanged at present and the impact of fish farming operation remains localized.
TL;DR: In this article, optical and biological measurements were performed in Lake Ulemiste in the summer of 1997 (four measurement days), and from May to October in 1998 (12 measurement days).
Abstract: Optical and biological measurements were performed in Lake Ulemiste in the summer of 1997 (four measurement days), and from May to October in 1998 (12 measurement days). This kind of data, describing the type and amount of optically active substances in the water, phytoplankton characteristics, the underwater light field, and temperature–oxygen situation in the lake are necessary when estimating the ecological state of the lake. Lake Ulemiste is the main drinking water reservoir of Tallinn, the capital of Estonia. Phytoplankton abundance and biomass, chlorophyll a and suspended matter were determined from collected Lake Ulemiste water samples in the laboratory. Spectrophotometrical processing of the filtered and unfiltered water was carried out to describe the beam attenuation coefficient spectra and optical influence of yellow substance in the water. Vertical profiles of downwelling irradiance of the PAR (400–700 m) region of the spectrum (and from these data the averaged over depth diffuse attenuation coefficient) were determined. The relative transparency of the water was estimated by using a Secchi disk. Passive optical remote measurements were episodically made from aboard a boat. Results obtained confirmed that Lake Ulemiste is turbid (almost hypertrophic), comparable with most turbid lakes in Estonia (e.g. Lake Vortsjarv) and Finland (Lake Tuusulanjarvi). Its chlorophyll a content varied within the range 13–121 mg m–3, phytoplankton biomass 3–107 mg L–1, phytoplankton abundance 65 000–999 000 mL–1, suspended matter 8–34 mg L–1, effective concentration of the yellow substance 6–30 mg L–1, diffuse attenuation coefficient of light in the PAR region 1.0–3.3 m–1 and a Secchi disk depth of 0.5–1.75 m. The temporal variation of the spatial averages of these parameters during 1998 was analysed. Almost all characteristics showed an increase from May to midsummer with a maximum in late July or in August (correspondingly the Secchi depth values were minimal in late summer). The amount of yellow substance was an exception, which was nearly constant during the observation period. The maximum level of chlorophyll a content in July and August 1998 markedly exceeded that in 1997, despite the fact that the summer of 1997 was sunny, but the summer of 1998 was cold and rainy. The correlative relationships between the different parameters were investigated together with the respective data for other lakes. They show that the data of Lake Ulemiste supplemented the correlation graph in the region of turbid lakes, whereby in all cases the correlation coefficient increased following the addition of Lake Ulemiste data. The highest correlation coefficient was obtained when light attenuation coefficient values were correlated with a sum of weighted concentrations of chlorophyll a, yellow substance and suspended matter (multiple regression analysis).
TL;DR: The three most challenging environmental issues facing the Lake Champlain basin are reducing phosphorus pollution, preventing toxic contaminants from entering the lake and managing invasive aquatic species that are not native that threaten native flora and fauna.
Abstract: Lake Champlain is the sixth largest freshwater lake in the USA. Lake Champlain’s watershed is shared by Vermont and New York in the USA, and Quebec in Canada. The lake’s remarkable drainage area to surface area ratio is 19:1. More than 600 000 people live in the Lake Champlain basin and millions visit each year. The lake’s relatively healthy natural resources sustain a thriving economy. The three most challenging environmental issues facing the Lake Champlain basin are reducing phosphorus pollution, preventing toxic contaminants from entering the lake and managing invasive aquatic species that are not native that threaten native flora and fauna. To effectively address these issues, the Lake Champlain Basin Program (LCBP) believes that all decisions about the lake must be based on accurate, ongoing scientific research and that citizen involvement and inter-jurisdictional cooperation is vital. The programme has worked hard to identify all citizens and organizations that have a stake in Lake Champlain and draw them into a cooperative, sustainable management process. A 1990 Act of Congress (Public Law 101-596) established a coordinated framework to study and understand the diverse systems of Lake Champlain and its basin in order to develop a comprehensive management plan to protect and restore lake and watershed resources. A 31-member multi-stakeholder board was established to develop the plan, a process that took 5 years and included numerous public meetings. Today, a Steering Committee oversees the implementation of the plan and the activities of the LCBP.
TL;DR: The Lake Toba Heritage Foundation (LHTF) as discussed by the authors is a non-government organization dedicated to the management of the lake watershed in South-east Asia and the largest volcanic lake in the world.
Abstract: Lake Toba is the largest year-round lake in South-East Asia and the largest volcanic lake in the world. The Lake Toba catchment area faces an environmental crisis characterized by widespread deforestation, drought, decline of the water level, water quality degradation, invasive species and loss of biological diversity. More than half of the Lake Toba catchment area is classified as land at high erosion risk. Widespread poverty gives people little room to think beyond day-to-day needs and is an instrument for unsustainable methods of fishing and growing food. The Lake Toba catchment area is not managed as an integrated whole, but rather as four separate districts. Guidelines and orders tend to come from the government in Jakarta rather than being developed locally with stakeholder involvement. Differences in approach between government and non-governmental organizations (NGOs) have resulted in friction and mistrust between the two. Local, national and international NGOs have been the biggest contributors to increasing the awareness of the need for an integrated approach to managing the lake. Technical exchanges with Lake Champlain have facilitated an exchange of experience of managing a large lake watershed, the transfer of low-cost alternative technologies for managing waste water in small communities and development of new approaches to pulp and paper mills on both lakes. The Lake Toba Heritage Foundation’s priorities include establishing a research and monitoring programme, creating a science and education centre, and developing better coordination among central, provincial and district levels of government.
TL;DR: In this article, the advantages and disadvantages of various analytical techniques used for monitoring of cyanobacteria in lakes, optimized or developed at the Institute of Nutrition, Jena, Germany, are discussed.
Abstract: The toxins of cyanobacteria include potent neurotoxins and hepatotoxins. Deaths after exposure by ingestion of cyanobacterial cells and toxins from freshwater sources have been reported. The hepatotoxins are cyclic peptides, which comprise microcystins (MC) and nodularin (NOD), and they cause poisonings with an established syndrome of human and animal illnesses. The identification and determination of these hepatotoxic peptides are challenges for analytical chemists. Methods based on solid phase extraction and size exclusion chromatography are available for the clean up of raw extracts. Both principles are also used for the enrichment of MC from low contaminated sample material. The separation of MC is achieved by high-pressure liquid chromatography methods with ultraviolet (UV) detection or mass spectrometric detection. The unambiguous identification of MC not available as standards is possible by mass spectrometry (MS) or, under optimal conditions, by UV spectrometry using diode array detection. To date, 60 different MC and four NOD have been described, but new compounds are frequently identified. Therefore, powerful tools for the elucidation of the structure of unknown MC are an important need. In addition to classical methods for structure elucidation (e.g. nuclear magnetic resonance spectrometry), microwave-assisted hydrolysis of cyclic peptides followed by enantio-selective determination of the amino acid profiles can be used. More recently, MS with collision-activated dissociation has become an important tool for obtaining structure information. The present paper discusses the advantages and disadvantages of the various analytical techniques used for monitoring of cyanobacteria in lakes, optimized or developed at the Institute of Nutrition, Jena, Germany. A pathway for handling MC-containing samples with regard to different analytical tasks (i.e. the identification and elucidation of structure followed by qualitative and quantitative determination) is proposed.
TL;DR: In this article, the attenuation of light in the waters of Lake Ulemiste is rather high, with a diffuse attenuation coefficient of photosynthetically active radiation, spectral region 400-700 nm (PAR) being 1.0-3.3 m.
Abstract: Underwater light climate in strongly eutrophic Lake Ulemiste was studied by applying in situ measurements and model calculations. The attenuation of light in the waters of Lake Ulemiste is rather high, with a diffuse attenuation coefficient of photosynthetically active radiation, spectral region 400–700 nm (PAR) being 1.0–3.3 m–1. From the subsurface irradiance, only 3–13% reaches the depth of 1 m. However, in most cases, 1% from the irradiance just under the surface of water is available at the average depth (2.5 m) of the lake. A simple model is used for an approximate description of the temporal variation of underwater PAR at different depths. The initial data are the episodically determined values of the diffuse attenuation coefficient of PAR, Kd,PAR and the values of continuously recorded incident irradiance. Light is limiting phytoplankton growth in Lake Ulemiste only for a very short time each year: in early spring and late summer. The study should be continued to investigate the effect of artificially regulated influx and outflow of water and nutrients to toxic cyanobacteria blooms in this lake.
TL;DR: In this article, the authors discuss the basic structures, principles and components of ELS models and demonstrate what can actually be done in water management in terms of remediation of the effects asociated with acidification (lake liming), eutrophication and contamination by mercury and radiocaesium.
Abstract: Lake ecosystems throughout the world are threatened by numerous chemicals. Most people have heard about the major chemical threats to aquatic systems, such as mercury, radionuclides, sulphur and acid rain, and nutrients causing eutrophication effects. How are these threats manifested in ecosystems? What is threatened and why? What can be done for remediation? The complexity of ecosystems has often led to the predictive failure of ecosystems models, and a decade ago these models were rightly regarded with suspicion. At that time, many lake models predicted target variables, such as mean concentrations of toxins in water, sediments and fish, within a factor of 10. There has been very rapid development in predictive modelling for water pollutants during recent years. Today, lake models for water pollutants predict as well as can be measured (i.e. within a factor of 0.25–0.5). One major reason for this rapid development is the Chernobyl accident. Large quantities of radiocaesium were released in a pulse during April–May 1986. In order to follow the radiocaesium along ecosystem pathways, the identification of fundamental transport processes and the structuring of models has been developed. To obtain a high predictive power in ecosystem models, it is crucial to include only the key processes (the optimal size problem). Effect-load- sensitivity (ELS) models play a paramount role in the environmental sciences and lake management. The aim of ELS models is to provide quantitative predictions relating operationally defined ecological effect variables to load and environmental sensitivity variables. Validated ELS models provide a tool to simulate practically feasible remedial measures, and important concepts like critical load, natural load and guideline limits/values can be defined from ELS models. The first objective of this paper is to discuss some basic structures, principles and components of ELS models. Empirical (static) and dynamical (time-dependent) ELS models exist for mercury, radiocaesium and phosphorus in lakes. These models have high predictive powers for a wide range of validation lakes. The second objective of this paper is to demonstrate what can actually be done in water management in terms of remediation of the effects asociated with acidification (lake liming), eutrophication and contamination by mercury and radiocaesium.
TL;DR: For instance, in the Irkutsk region, stakeholders have worked together to reduce the flow of unpurified drainage into the lake by 10 million m3 year-round as discussed by the authors.
Abstract: Created 20–30 million years ago, Lake Baikal is one of approximately 13 ancient lakes in the world. Lake Baikal is also the deepest lake in the world with 365 rivers flowing into it and holding a full 20% of the liquid fresh water on the surface of the Earth. The lake stretches from the south-eastern section of Siberia to portions of northern Mongolia. Administratively, it is divided between three members of the Russian Federation: the Republic of Buryatia, Irkutsk Oblast and Chita Oblast. Lake Baikal and its catchment area are characterized by considerable biodiversity and by a vast richness of natural resources. Well over half of the 2615 plant and animal species found in the Baikal region are endemic. Lake Baikal’s unusual biota includes the Baikal seal (Phoca sibirica) which lives nowhere else on Earth and is separated by 3220 km from its nearest relative. These freshwater seals give birth to their young in snow dens on the lake’s ice. The Baikal region is a spectacular example of coexistence among different cultures and faiths over centuries. Over 1000 archaeological remains of past cultures have been found near Lake Baikal shores. Preserving the unique lake culture, values and ecological, ethnic and cultural traditions of the local people is one of the key elements in developing a model for sustainable development in the Baikal region. Lake Baikal is currently still considered clear and healthy overall, however the number and type of pollution sources are growing, and local pollution can be severe. The main sources of pollution in Lake Baikal are industrial wastes and atmospheric emissions from the Baikalsk pulp and paper mill, atmospheric emissions from nearby industrial facilities, excessive nutrient loads from farming and sediment and wastes that flow into Lake Baikal through the Selenga River. In May 1999, protection of Lake Baikal was codified in federal law for the first time. Progress is being made on a number of fronts despite the turbulent political transformations in Russia in the last 10 years. For instance, in the Irkutsk region, stakeholders have worked together to reduce the flow of unpurified drainage into the lake by 10 million m3 year–1.
TL;DR: The epifluorescence technique was used to quantify the total bacterial population in two dams and in anatural lagoon, which have different geographical locations and physicochemical characteristics, and it is shown that plate counts underestimate the population.
Abstract: The epifluorescence technique was used to quantify the total bacterial population in two dams (Neusa and Prado) and in anatural lagoon (Fuquene), which have different geographical locations and physicochemical characteristics. Bacterial abundance was similar in the three water-bodies (8.4810 cellsL –1 ), but the density of plateable heterotrophs was alwayslower (1.4 –110 6 CFUL ) when obtained by the plate count method. Results obtained during validation of the epifluorescencetechnique show: (i) that there are no statistically significant differences between counts of samples fixed in the field and unfixe dsamples; (ii) that the median count of samples fixed and observed periodically over a period of 8 months was similar; (iii)that plate counts underestimate the population; and (iv) that epifluorescence counts were similar in the three water-bodiesstudied, despite their different ecological conditions. Key words Andean region, bacterioplankton, epifluorescence, plate counts. *Corresponding author. Email: amparo.canosa@utadeo.edu.coAccepted for publication 17 December 2000.
TL;DR: In this paper, the recent (1992-1997) evolution of the phytoplankton communities analysed by sample clustering was analyzed by analyzing two large groups of samples (1992−1993 and 1995−1997).
Abstract: Lake Orta became heavily polluted in 1926 by ammonium sulphate and copper. After a couple of years the biological communities became extremely simplified and were composed of a few resistant species. This acute copper pollution was followed by a chronic acidification of the water, brought about by in-lake biochemical oxidation of ammonium. Since the 1960s, heavy metals discharged from some plating factories became an additional source of pollution. After the reduction of ammonium discharge in 1982 and from May 1989 to June 1990 the lake was limed: the pH at overturn increased from pH 4.4 to 5.9, the metals’ concentration decreased and the number of planktonic taxa rapidly increased.
The present paper deals with the recent (1992–1997) evolution of the phytoplankton communities analysed by sample clustering: the cluster analysis indicates the separation of two large groups of samples (1992–1993 and 1995–1997). Such clustering is because of the gradual decline of the chlorophytes (for a long period the most important group in Lake Orta) between 1992 and 1994, followed by their marked decrease between 1995 and 1997, during which they were replaced by blue–green algae.
Also noticeable was the increase in diatoms, which had disappeared from the phytoplankton community from the 1930s until 1994, but during spring and summer 1997 they amounted to 40% of community abundance. Although it is now possible to describe a phytoplanktonic seasonal succession in Lake Orta, the dissimilarities shown by the cluster analysis seem to indicate the existence of a certain year-to-year variability inside the dominant species assemblage, meaning that the phytoplankton community is still evolving.
In spite of the phytoplankton’s fast recovery after liming, it is only since 1994 that the algal community started to change toward a phytoplankton assemblage more typical of deep subalpine lakes.
TL;DR: The Laguna Lake Development Authority (LLDA) as mentioned in this paper is a national government agency that was given the power to control and abate pollution within the Laguna de Bay watershed.
Abstract: Laguna de Bay is the largest lake in the Philippines and the second largest freshwater lake in South-East Asia. The lake is shallow with a mean depth of only 2.8 m. Rice paddies, sugar cane fields, coconut plantations and other agricultural fields make up large portions of the catchment area, although there is also extensive urbanization and industrialization. As industry and population around the lake have grown, the lake and its tributaries have become overwhelmed by industrial, commercial, agricultural and domestic pollution resulting in massive fish kills and polluted water. Laguna de Bay is under the management and protection of a national government agency known as Laguna Lake Development Authority (LLDA). In 1983, the LLDA was given the power to control and abate pollution within the Laguna de Bay watershed. The mandate of the LLDA includes the environmental regeneration and sustainable development and use of the lake’s waters, fisheries and wetlands. The LLDA receives no federal funds but it retains and uses collected fees from regulated industries. The LLDA has instituted an environmental-user fee or pollution-charge system that has given corporations an incentive to construct and use wastewater treatment plants at a lower cost than the required fees for dumping waste into Laguna de Bay. User fees provide more flexibility about how and when a user or industrial facility cleans up its manufacturing process. Many medium- and large-sized domestic and multinational corporations have achieved at least 30–50% reductions in pollution loads. The user fees also encourage industry water conservation. Other creative approaches to conserving Laguna de Bay include ‘Environmental Armies’ that consist of volunteers who clean up river banks, demolish illegal fish pens and install low-cost garbage traps at the river’s mouth. ‘Poison Awards’ are given annually and publicly to companies that continue to dump large amounts of waste into lake tributaries. Organizers also name a ‘Most Improved Company’ to provide a positive incentive. Laguna de Bay stakeholders face a severe shortage of resources to continue their work. Innovative strategies are needed to achieve pollution reductions from smaller industries
TL;DR: In this article, the concepts and principles for integrated environmental management (IEM), which is based on a strategic and participatory approach to environmental and regional planning, has been successfully applied to a large lake system in the southern region of Thailand.
Abstract: The concepts and principles for integrated environmental management (IEM), which is based on a strategic and participatory approach to environmental and regional planning, has been successfully applied to a large lake system in the southern region of Thailand. The application was achieved through the Danish Cooperation for Environment and Development funded project ‘Environmental Management in the Songkhla Lake Basin’ (EmSong Project) in the Office of Environmental Policy and Planning within the Ministry of Science, Technology and Environment. Through the application of the methods and tools for IEM, including the use of a participatory and strategic planning approach, and the establishment of a comprehensive database and an integrated surface water model for the lake system, an environmental action programme (EAP) has been developed. This action programme, which is based on a broad consensus at the local and regional level, includes vision and mission statements, resource objectives and strategies for management from an economically and ecologically important lake system in Thailand. The operational part of the EAP is a project catalogue, which contains immediately needed projects described to an international pre-feasibility level. The former is the tangible output of the EmSong Project. A more intangible output from the EmSong Project is committed and informed local and regional government and community-based organizations.
TL;DR: By studying early benthic P-diagenesis it remains to be demonstrated whether this procedure can contribute to a re-availability of P-binding sites to guarantee the long-term effect of the measure.
Abstract: After the reduction in external phosphorus-load (P-load), in-lake measures became practicable for eutrophic Lake Jabel. The benthic release of phosphorus (P) was efficiently suppressed by a significant nitrate supply via its main tributary. The in-situ stimulation of P-release as a result of the temporary decrease in this nitrate load, and the simultaneous P-removal by deep-water siphoning and external P-elimination was primarily designed for the faster deprivation of P from lake sediment. This new strategy was aimed at exhausting the ‘P-surplus’, that is, the mobile redox-sensitive iron-bound P-portions of the uppermost sediment layers, where a re-supply from deeper layers is needed within the stratification period of 2 consecutive years of operation of the P-elimination system. By studying early benthic P-diagenesis it remains to be demonstrated whether this procedure can contribute to a re-availability of P-binding sites to guarantee the long-term effect of the measure.
TL;DR: The Centre for Transboundary Cooperation facilitates international communication and cooperation between the Estonian and Russian governments and promotes public participation in environmental, social and economic development and decision-making as mentioned in this paper.
Abstract: Lake Peipsi is the fourth largest lake in Europe and the largest international lake in Europe. Lake Peipsi is shallow, eutrophic, biologically very productive and is bordered by many wetland areas along its coasts. Large peat deposits in the Lake Peipsi basin are protected under national legislation. The lake is most important as a resource for recreation and fisheries. The fish stock in Lake Peipsi is one of the richest in Europe. The most critical environmental issues for the Peipsi watershed are eutrophication and unregulated fishing in the lake. During the Soviet period, large collective farms dramatically accelerated eutrophication. Despite the drop in fertilizer use during the last 10 years and a decrease in the number of domestic animals in the watershed, the impact of the earlier agricultural pollution is still significant. Untreated sewage has also been dumped in the Narva River tributary as a result of an international dispute concerning water supply and wastewater treatment. People living in the Lake Peipsi region have faced traumatic changes as a result of the re-establishment of the border between Russia and Estonia in 1992. The establishment of an international border on the waters of the lake has resulted in fishermen losing access to many of their traditional fishing areas. Political and economic transformations of the last 10 years have seriously interrupted information exchange between different institutions and organizations concerned with the health of the lake. The Centre for Transboundary Cooperation facilitates international communication and cooperation between the Estonian and Russian governments and promotes public participation in environmental, social and economic development and decision-making. The centre is in the process of guiding the development of a watershed management plan for the Lake Peipsi watershed and a vision for watershed development that is truly sustainable.