Limnological Studies Research Articles

Development of a 10-year Limnological Study of Crater Lake, Crater Lake National Park, Oregon, USA

ABSTRACT This paper summarizes the development of a limnological study of Crater Lake conducted between 1983 and 1992. The program was mandated by Congress in the fall of 1982 after a panel of limnologists found the lake data base (1896–1981) to be inadequate to determine if the phytoplankton community had changed and if the lake was decreasing in clarity as suggested from independent studies between 1978 and 1981. Congress authorized and directed the Secretary of the Interior to promptly instigate studies and investigations as to the status and trends of changes of water quality and to immediately implement such actions as necessary to assure the retention of the lake's natural pristine water quality. Program goals were to develop a detailed data base and an understanding of physical, chemical, and biological characteristics and processes of the lake. Ecological relationships among trophic levels and environmental conditions were stressed to evaluate the hypothesis that the lake had changed in water qual...

Limnological studies of Amarga Lagoon, Chile: A saline lake in Patagonian South America

Amarga Lagoon, lat. 50°29′ S and long. 73°45′ S, it is located at the Torres del Paine National Park, Chile. The physical, chemical, and biological features of the lake were studied. According to salinity, the lake is mesosaline. Sodium and chloride were the dominant ions. Nitrogen was potentially limiting for phytoplankton growth. One Cyanophyceae species andArtemia were the predominant species in the plankton.Artemia provided abundant food for flamingoes.

Vltava cascade as teaching grounds for reservoir limnology

The empirical and modelling limnological studies of the reservoirs of the Vltava Cascade spanning over 30 years have demonstrated the major differences between stratified throughflowing reservoirs and lakes. The most significant limnological differences are caused by the generally deep outflows due to the extreme position of the maximum depths, and high flow rates causing flow-driven gradients. Limnological conditions in dam reservoirs are very sensitive to the theoretical retention time of water in the reservoir (RT), in particular in the range RT < 200 days. The primary effect of the high inflow rates is the weakening of stratification, due mainly to increasing bottom temperatures leading to deeper mixing, which results in lower surface temperatures. The hydrophysical changes subsequently affect the fate of chemical constituents and the primary production; the effects are propagated to higher levels and fed back to both chemical and physical water quality. A reservoir being second or successive in a cascade differs limnologically in that it is affected by the dominantly hypolimnetic releases of the upperlying reservoir. The differences in hydrophysics, hydrochemistry and hydrobiology have been specified and the findings are, in general, supported by modelling studies.

The Contours of Vegetation Change and Human Agency in Eastern Africa's Great Lakes Region:ca. 2000 BC toca. AD 1000

Elsewhere I have set forth a basic outline for charting histories of vegetation change through the use of paleoenvironmental data (Schoenbrun 1991). This essay builds on the previous one by laying out the contours of vegetation change and human agency in the Great Lakes region (Map 1) over the roughly three millennia afterca. 2000 BC.The history of the vegetation in eastern Africa's Great Lakes region brings into focus several important features of long-term environmental change—human action, climatic shift, and internal successional patterns. The primary sources for this history come from a variety of published palynological and limnological studies from Burundi, Rwanda, Uganda, and Zaire. Perhaps the most rewarding data for reconstructing climatic and vegetational change come from palynological studies. Pollen studies often reflect detailed changes in the constitution of plant communities, and their value for reconstructing the vegetational and climatic contexts for Holocene human history has provoked the development of a rigorous method for their analysis. Contemporary studies of plant community succession and human-vegetation relationships are a secondary source for the history of land clearance in the Great Lakes region. These works provide a means to determine the different imprints of human and climatic action on the paleoenvironmental record.In this study I combine the full range of paleoenvironmental evidence to reconstruct the form and pace of vegetation change. I focus on a part of eastern Africa famous for its great ecological diversity. One of the rewards of this endeavor is to demonstrate to paleoecologists, archaeologists, and historians alike the value of a truly interdisciplinary approach to environmental change.

Limnology Project at Mahaweli Reservoirs; it a Limnological Study at Kotmale, Victoria and Randenigala Reservoirs

The objective of this study was to collect basic data to ascertain status of Kotrnale, Victoria and Randenigala reservoirs and to understand the trophic evolution of the reservoirs. The transparency values changed with the reservoirs. The highest frequency percentage of secchi depth observed at each reservoir are; Victoria 1.21--1.6Im, Randenigala 2.51-3.0Im and Kotmale 2.10-2.30 indicating highest value at Randenigala and the lowest value at Victoria. All three reservoirs are thermally stratified and the highest differences in temperature gradients were observed from surface to about 25m depth. In the deeper layers the temperature gradient is distin.ctly low. The highest conductivity values were observed closer to the dams of the three reservoirs indicating accumulation of dissolved ions towards the dams. In all three reservoirs the pH gradient was higher at the surface compared to the values bellow 10m depths. The high dissolved Oxygen concentrations are closely linked with the euphotic zones. Oxygen concentrations were markedly low below the depth of 20m. However there is no completely deoxygenated layers at the bottom of the reservoirs. Data on chemical substances also proves the development of a strong chemocline below 20m depth level. Water hardness values are high when water retention levels of the reservoirs are low. High levels of Hydrogen Sulfide concentrations have been observed at the bottom layers of Randenigala reservoir from time to time. Sulfide concentration increased with the increasing depth of the reservoirs. The range of Nitrite concentrations recorded for Victoria is 0.005-D.l ppm and for Randenigala 0.01-D.08 ppm. Ammonia was recorded only in deeper layers below the 45m level at Randenigala. The zooplankton community of the three reservoirs consists of Copepods, Rotifers and Cladocerans. The phytoplankton community of the three reservoirs consist mainly of green and blue green algae.

Thermal Stratification Modeling of Lakes with Sediment Heat Flux

A sediment heat flux submodel was developed, based on the findings of related limnological studies, and incorporated into a mixed‐layer (integral‐energy) lake‐stratification model. The basic and modified versions of the mixed‐layer model were applied to three years of field data for four different lakes. The inclusion of the submodel was necessary to adequately calibrate the model to the stratification conditions observed in the two shallow transparent lakes. The stratification regimes of the two other deeper lakes were accurately simulated without accommodating sediment heat flux. These results suggest that the accurate simulation of thermal stratification in shallow transparent lakes requires consideration of sediment heat flux. Sediment and water budgets calculated with the modified model support the developed sediment heat flux submodel.

Oligotrophication after a nutrient reduction in a shallow sand-pit lake (Créteil Lake, Paris suburbs, France) : a case of rapid restoration

A limnological study was performed out, over 8 years from 1979 to 1986, in a shallow recently created sand-pit lake, Lake Creteil (Paris suburb, France). The lake is mainly supplied by phreatic waters. Typical of shallow waters, thermal stratification which occurred from May to October was intermittently broken by wind, leading to high seasonal fluctuations and allowing a reoxygenation of the total water column. The interannual development of the lake was characterized by a regular increase in transparency (from 1 m in 1979 to 2.7 m in 1985) which was partly due to not only stabilization of the bottom sediment and the banks, but also to a reduction of the biological component. A decrease in chlorophyll a concentrations resulted from nutrient diversion of domestic inputs collected through the rainwater pipe coming into the lake. The rapid restoration of water quality shows that this small artificial lake is very sensitive to human interventions.

Ecological and limnological studies of Lake Tanganyika and its adjacent regions between African and Japanese scientists: An introduction

Ecological and limnological studies of Lake Tanganyika and its adjacent regions between African and Japanese scientists: An introduction

Limnological Studies of the Tank in Vedanthangal Water-Bird Sanctuary, with Special Reference to Impact of Guano on Water and Soil Quality

Limnological Studies of the Tank in Vedanthangal Water-Bird Sanctuary, with Special Reference to Impact of Guano on Water and Soil Quality

The Aral Sea: Recent limnological changes and their conservation significance

Abstract1. Limnological changes to the Aral Sea, a large saline lake in central Asia, are considered. Important changes include the decreased water‐level (c. 15 m), the recession of the shoreline (up to 120 km in places), the exposure of large areas of lake bed, the increased salinity (from c. 10 to 30 g 1−1), and the marked alteration in the nature of the lacustrine biota involving decreases in diversity and biomass and the introduction of species.2. Fish have virtually disappeared from the lake and the diversity of associated bird and wildlife communities has decreased.3. The major cause of the limnological changes is the diversion of water, mainly for agricultural purposes, from inflowing rivers (the Amu‐ and Syr‐Darya), and, to a lesser degree, species introductions.4. Limnological changes have been accompanied by changes to regional rivers and terrestrial environments, groundwaters, climate, and to agricultural productivity.5. It is concluded that four major values of the lake (economic, cultural, scientific, and environmental) have been seriously diminished by recent changes to it. The need to continue limnological studies is stressed.

Limnological studies on the Rhine and two of its tributaries in Basel

Limnological studies on the Rhine and two of its tributaries in Basel

15 years of limnological studies in Bolivia

(1991). 15 years of limnological studies in Bolivia. SIL Proceedings, 1922-2010: Vol. 24, No. 2, pp. 1197-1197.

Can macrophytes be useful in biomanipulation of lakes? The Lake Zwemlust example

Lake Zwemlust (area 1.5 ha, Zm 1.5 m) has been the object of an extensive limnological study since its biomanipulation involving removal of planktivorous fish (bream) in March 1987 and emptying of the lake. In the subsequent summer period of 1987 the Secchi depth increased to the lake bottom (2.5 m), compared withca 30 cm in the earlier summers. The reaction of submerged macrophytes to improving under-water light climate was rapid. In summer 1987, besides the introducedChara globularis, 5 species of submerged macrophytes occurred and colonized 10% of the lake area. In 1988 and 1989 only quantitative changes were observed; new species did not appear, but the area colonized by macrophytes increased by 7 and 10 times, respectively.Elodea nuttallii was dominant among the macrophytes andMougeotia sp. among the filamentous green algae. Their abundance, contributed to transient N-limination of phytoplankton causing a persistent clear water phase in 1988 and 1989, unlike in 1987 when zooplankton grazing contributed chiefly to the water clarity. Laboratory bioassays on macrophytes confirmed nitrogen limitation.

A contribution to the study of biogeochemical cycling in an english lake by PIXE: The flux of barium and strontium in the phytoplankton

The Oxford scanning proton probe has been used to analyse a range of phytoplankton organisms for Ba and Sr. This is part of an on-going study of the biogeochemical cycling of these elements in Esthwaite Water in the English Lake District. Previous studies have indirectly suggested that dinoflagellates and cyanobacteria may be implicated in such cycles. Present results fail to confirm this suggestion but point to members of the Chlorophyta as being Ba accumulators. Some also accumulate Sr. The paper demonstrates the potential value of PIXE in limnological studies.

Limnological study of lake Todos Los Santos (Chile) Morphometry, physics, chemistry, plankton, and primary productivity

Limnological study of lake Todos Los Santos (Chile) Morphometry, physics, chemistry, plankton, and primary productivity

Perlphyton as Indicators of Enrichment in Lake Pend Oreille, Idaho

ABSTRACT Periphyton in the littoral zone of Pend Oreille Lake, a large (383 km2, deep (Zmax — 380 m)) meso-oligotrophic lake in northern Idaho, were studied to compare with pelagic productivity and to identify areas of inshore degraded water quality. Periphyton growth was determined on artificial tiles and natural substrates at 0.5 and 1.5 m depths. Means for all measures of production on natural substrates were higher than means for artificial substrate. Indicators of biomass were higher on 0.5 m tiles than those at 1.5 m; exposed sites, however, showed less difference between depths than did the more sheltered sites. Because of inorganic interference, ash-free dry weight provided a better measure of periphyton biomass than dry weight. Significant differences existed between sites, indicating greater algal growths in developed and relatively confined bays. Cymbella was dominant on natural substrate, while Cymbella, Mougeotia, and Rhizoclonium were co-dominant on artificial substrate. Blue-green algae biomass comprised only a small part of the total biomass on either artificial or natural substrates. Periphyton biomass in Pend Oreille Lake was comparable to other lakes showing accelerated eutrophication. Despite Pend Oreille Lake's great depth and large profundal area, littoral productivity was similar to lakes more shallow in nature with higher overall productivity. In-shore water quality degradation was documented at a time when open-lake conditions indicated the lake was meso-oligotrophic. Given that changes in lake trophic status would first show up in littoral areas–compared to the relatively slow changes taking place in the phytoplankton of pelagic areas–periphyton monitoring should provide valuable refinement to in-depth limnological studies on open waters of lakes.

PHYSICAL, CHEMICAL AND BIOTIC RESPONSES TO DECREASING WATER DEPTH IN A HIGHVELD PAN FOLLOWING WET AND DRY SUMMERS

SUMMARY The classification of highveld pans by Geldenhuys (1982) emphasized the spatial diversity of morphology, vegetation and fauna. However, since the characteristics of individual pans also change seasonally and over longer term wet/dry cycles, he called for more detailed limnological studies to improve predictive and management potential. Marked changes occurred in the physical, chemical and biological characteristics of Rolfes pan in response to winter drawdown following dry (1983) and wet (1986) summers. The constancy of physical and chemical conditions during 1986 contrasted with rapid changes in temperature, turbidity, conductivity and salinity as benthic plants disappeared in 1983. The abundance of emergent vegetation provided breeding sites for certain wetland birds in 1986 but shallow water and submerged plants attracted wading birds in 1983. Changes within and between years highlighted the importance of three distinctive limnological characteristics of pans; large surface area to volume ratio...

Methodology for studies of carbon dynamics between phytoplankton primary production and heterotrophic bacterial secondary production

The SCENTO-System was used to study the carbon dynamics between phytoplankton primary production and heterotrophic bacterial secondary production. Most of the methods used nowadays in situ for limnological synecology studies were applied. Primary production measurement showed an increasing tendency with increasing content of chlorophylla. It provided a true photosynthetic rate lying within the range of eutrophic lakes. Net EOC released from the algae ranged from 8.5 to 27.5 μg C l−1(6h)−1. Accompanying the algal products the number of bacteria increased from 1.475 ×109 to 8.074×109 cells l−1. The bacterial mean cell volume was small, between 0.0315 and 0.0548μm3. Bacterial carbon production from direct growth estimates was compared with independent calculations of bacterial growth from EOC uptake and3H-thymidine incorporation. Direct estimates were 2.97–10.0 μg Cl−1 (24h)−1 with the exception of a zero-growth on the third day. EOC uptake was 123.5–191.0 μg Cl−1 (6h)−1. That calculated from3H-thymidine incorporation was 0.2–0.5 μg Cl−1 (6h)−1.14C-glucose dark uptake ran parallel to the increasing bacterial biomass. The respiration of glucose was 6.5% (avg.) of the gross uptake. Since the system operated without grazing pressure, a real carbon flow from primary production to bacterial secondary production could be observed.

Limnological and Ecological Considerations for Hydropower Development in Honduras

ABSTRACT The recently commissioned EI Cajon dam is the third major hydroelectric project to be built in Honduras, but the first to include detailed limnological and ecological studies, in the near future, ecological and sociological studies may play a significant role in deciding the next site for hydropower generation, since initial evaluations of three possible future sites suggest that their economic value is similar. The authors describe limnological and ecological aspects of existing and future hydroelectric projects in Honduras, and then use the example of watershed management in the EI Cajon basin to illustrate some of the problems associated with impoundment planning and management in Honduras.

Limnología del Lago Petén Itzà, Guatemala

Limnological studies of Guatemalan lakes are scarce, Since 1978, flooding caused by increasing of lake Peten Itza water level has been a serious problem. This lake is warm monomictic with thermocline around 20 meters and with a maximum depth of 60 m. Stratification lasts from February to November. Water chemical characteristics since 1969 to 1985 were subject to a preliminary investigation. Calcium doubled since 1975, the rest of ions remained constant. Probably, the increase of calcium was related with the plugging of the groundwater outflow, which causes the increasing of the water level. Sulfate was the main anion. Lyngbya and Mycrocystis were the dominant algae in 1969 and 1983, respectivelly.