摘要:

The Clean Lakes staff of the Tennessee Division of Water Management have undertaken three separate projects since the inception of the Federal 314 program. The first project was the creation of a Trophic State Index and Priority Ranking System for the publicly owned lakes of Tennessee. This project was completed in 1979. During this inventory of public lakes, attention was drawn to Acorn Lake, a highly eutrophic, highly used public lake located in Montgomery Bell State Park. In 1980, it was decided that the second Clean Lakes project would be a diagnostic/feasibility study of Acorn Lake. The lake was monitored for 23 months in an attempt to discover the source or sources of the nutrients causing the eutrophic conditions at the lake. The Acorn Lake study revealed that a variety of problems within the watershed had created a nutrient sink in the sediments of the lake. Watershed management and lake drawdown were recommended as restoration techniques. While researching this project, the Clean Lakes staff discovered that a significant number of similar public lakes were being routinely artificially fertilized for a variety of reasons. In response to this problem, the Acorn Lake Report contained not only recommendations for Acorn Lake, but also a new Division of Water Management policy against the application of artificial fertilizers in lakes. The third Clean Lakes project, begun in 1982, is a diagnostic/feasibility study with major emphasis on sedimentation and macrophytes of the Upper Buck Basin of Reelfoot Lake. The multiple problems at Reelfoot Lake of siltation, excess macrophyte encroachment, heavy metal and pesticide pollution, and eutrophication have been highly documented, but no one has yet been able to accurately predict the rate of sedimentation in the lake, although it is known to be filling rapidly. The Clean Lakes staff, assisting Dr. J. Roger McHenry of the Agricultural Research Service, U.S. Department of Agriculture, will use cesium-137 dating techniques in an attempt to determine this rate.

ISSN:1040-2381    

DOI:10.1080/07438148409354493

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

An EPA sponsored lake restoration feasibility study afforded the opportunity to examine the applicability of conventional temperate zone indices and management approaches to tropical Puerto Rican lakes. Major problems in using temperate zone guidelines are anticipated in Puerto Rico because lake events are relatively aseasonal, nitrogen rather than phosphorus may be limiting, heavy rainfall and steep topography result in naturally high loading, and mountainous terrain results in protection from wind driven mixing. Data for 26 lakes were examined; two of these lakes had been studied in detail. Trophic state indices using chlorophyll, nitrate, total phosphorus, transparency, net productivity, and other parameters were calculated and used in lake ranking. Some comparisons with Florida lakes suggest that Puerto Rican lakes receive more nutrients without developing objectionable blooms. We suggest a series of recommendations for study and management of Puerto Rican lakes.

ISSN:1040-2381    

DOI:10.1080/07438148409354494

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Observations over a 14-year period at Liberty Lake, Wash., have indicated a close relationship between the seasonal decline of aquatic macrophyte populations and the onset of planktonic Cyanobacteria blooms. Tracer methods, using radiophosphorus, have been employed in laboratory and inin situexperiments to investigate the ability ofElodea canadensis, an important component of the Liberty Lake macrophyte community, to translocate phosphorus from sediments to the open water. Results of these experiments showed good agreement between release rates determined in the laboratory andin situfor senescing macrophytes. Experiments with actively growingElodeaplants indicate some release or leakage of phosphorus from healthy plants. Nutrient budgets and a phosphorus model for Liberty Lake indicate that internal cycling of sediment phosphorus by aquatic macrophytes is an important source of phosphorus to planktonic primary production as well as direct sediment/water exchange. Indeed, in Liberty Lake, it is possible that macrophyte influence on the dynamic cycling of phosphorus in the lake may not only influence, but also control the pattern, timing, and community composition of planktonic production. A conceptual framework that can be applied by lake managers for determining the potential contribution of macrophyte phosphorus cycling in lakes is discussed.

ISSN:1040-2381    

DOI:10.1080/07438148409354495

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The effect of injecting different dosage rates of calcium nitrate into the bottom sediments of Long Lake in New Brighton, Minn., was observed in a laboratory study. The purpose of the study was to determine the minimum dosage necessary to reduce phosphorus release rates from the sediments to satisfactory levels. The study included measurement of sediment phosphorus release rates under both aerobic and anaerobic conditions, and evaluated the effect of adding ferric chloride to the sediments along with the calcium nitrate. The addition of ferric chloride was included in the study to determine if the iron available in the sediment was adequate to sorb the PO4−3when oxidized conditions were provided. The study concluded that at least for the short term (90 days), injection of calcium nitrate could eliminate virtually all phosphorus release from the sediments previously releasing phosphorus at a rate of 7 mg P/m2/day, and actually result in the sediments becoming a sink for phosphorus in the water column. The study also concluded that although the addition of iron enhanced the calcium nitrate treatment's effectiveness, similar results could be achieved by increasing the calcium nitrate dose slightly and not adding the iron, which was a more cost-effective alternative.

ISSN:1040-2381    

DOI:10.1080/07438148409354496

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Under conditions of anoxia, lake sediments will liberate sorbed phosphorus compounds into the overlying water. The magnitude of the sediment-liberated phosphorus load will be a function of the concentration of phosphorus in the sediments, the area of lake bottom overlayed by anoxic water, and the temporal duration of anoxic conditions. In some cases the resulting phosphorus load may be a substantial component of the lake's annual phosphorus budget. This may have serious implications in the restoration and management of such lakes. The importance of internally-generated phosphorus loads in the nutrient budget of New Jersey's two largest lakes, Lake Hopatcong and Greenwood Lake, was assessed. The formation and depth of the thermocline were established from temperature profiles. The volume of the hypolimnion and the area of lake bottom overlayed by the hypolimnion were calculated. Following stratification, water column profiles of total phosphorus and dissolved oxygen concentrations were monitored. These data were used to compute the internally generated phosphorus load. In both lakes, a 10-fold increase in the concentration of total phosphorus was observed following the depletion of oxygen in the hypolimnion. The internally generated load associated with this phenomenon represents 5.9 percent and 29.3 percent of the annual total phosphorus budget of Lake Hopatcong and Greenwood Lake, respectively. The relevance of endogenous phosphorus loading is discussed for each lake in relation to its existing trophic status and future restoration and management.

ISSN:1040-2381    

DOI:10.1080/07438148409354497

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Complaints of declining water quality and increasing macrophyte growth resulted in a 3-year study to determine the feasibility of phosphorus control on recreationally important Lake Wabamun, Alberta. All nutrient inputs including groundwater were measured or estimated to assess the importance of each source. A preliminary phosphorus loading calculation suggested that the sediment may supply a large quantity of phosphorus during the annual cycle. Sediment release was estimated using a mass balance approach and by phosphorus analysis of sediment cores taken at biweekly intervals. The mass balance suggested that release occurred in late summer, and represented a gross input that exceeded annual external supplies. This was supported by a decline in non-apatite inorganic phosphorus in cores during the same time. These results led to the conclusion that major phosphorus control projects in the watershed were not warranted.

ISSN:1040-2381    

DOI:10.1080/07438148409354498

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Aeration with the commercially available LIMNO aerator has now been in use for about 10 years. Over 40 aerator units have been installed and successfully operated in nine different projects. From the abundant experience gathered during this relatively long period some examples are chosen to illustrate the efforts on increased mineralization capacity of allochthonous and autochthonous organic material. The ubiquitous eutrophication problems especially degrade water quality in lakes and reservoirs. Excessively produced algal material in the hypolimnetic layer leads to serious anoxia, preventing higher life and aerobic respiration processes. Furthermore, internal recycling processes connected with the metabolic and geochemical cycles of manganese and iron enable the multiple use of recycled phosphorus. All of these processes are possible to control by aeration. On the other hand, necessary treatment for drinking water preparation, such as filtration, flocculation, and chlorination can be reduced if a sufficient oxygen balance is maintained in the hypolimnetic water body. Results are presented from two drinking water reservoirs and some lakes where drastic improvements were observed.

ISSN:1040-2381    

DOI:10.1080/07438148409354499

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Lakes and reservoirs in agricultural watersheds are often turbid with suspended sediments. The interactions among suspended sediments, dissolved organic matter, bacteria, algae and zooplankton will continually modify water quality. Our object was to evaluate the effects of dissolved organic matter (DOM) source, bacteria, and suspended sediments on the survival and growth in body length ofDaphnia pulex. We grewDaphnia in vitrowith different DOM sources (bur oak and hackberry leaf leachate), with and without suspended sediments. Daphnids grown in hackberry leaf leachate, with or without sediments, grew more than those in the corresponding bur oak leaf leachate treatments (P < 0.01). Bacterial density also was higher in the hackberry treatments compared to the bur oak treatments. Daphnids grew more in treatments with DOM plus suspended sediments than in the corresponding treatments without suspended sediments (P < 0.01), although bacterial density was lower in treatments with suspended sediments. Suspensions without daphnids had lower bacterial densities than those with daphnids. This experiment reveals some of the complexity of the interactions among the sediments, DOM, bacteria, and zooplankton that influence water quality. The results may have some applications to lake and reservoir management, particularly the biomanipulation of water and wastewater.

ISSN:1040-2381    

DOI:10.1080/07438148409354500

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Square Lake, Minn., mimics an ideal of the biomanipulation approach. The lake's zooplankton community is dominated by large (body size) herbivorous cladocerans (Daphnia pulicaria) whose collective grazing abilities have maintained a reduced standing crop of algae, apparently since 1926. The physical and chemical environmental factors that defineDaphnia'sniche in Square Lake are discussed and include stable stratification, a large hypolimnetic volume, and phosphorus concentrations within certain threshold limits. These environmental limitations seem to be generally important for providing a metalimnetic refuge forDephnia. Future biotic reconstructions that aim to encourage large-bodiedDaphniashould consider these environmental limitations.

ISSN:1040-2381    

DOI:10.1080/07438148409354501

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The feasibility of using the zooplankton speciesDaphnia pulexas a biological control agent of nuisance algal blooms was investigated experimentally in two Illinois lakes. Two questions were posed: (1) Can grazing byDaphnia pulexbuffer the effects of increased nutrient loading to an initially low-nutrient lake? and (2) CanD. pulexsignificantly reduce algal biomass when introduced into a lake that already exhibits excessive phytoplankton growth? These questions were answered by introducingD. pulexindividuals into large enclosures (1,000 liters) suspended in the lakes, which do not naturally containD. pulex. The first question was addressed in Dynamite Lake, an oligo-mesotrophic quarry lake that does not normally exhibit algal blooms. Four treatments were employed within the enclosures: (1) a control, (2)D. pulexadded, (3) nutrients (nitrogen and phosphorus) added, and (4)D. pulexand nutrients added. Nutrients were not added until theD. pulexpopulations became established and were added at weekly intervals after initial addition. In an experiment performed in 1982D. pulexdisplayed the ability to substantially buffer the effects of increased nutrient loading. Although addition of nutrients increased phytoplankton biomass in all enclosures to which they were added, by the end of the experiment enclosures withoutD. pulexhad phytoplankton densities (measured as chlorophyll a concentration) greater than those withD. pulex. The second question was addressed in Larimore Pond, a highly eutrophic farm pond with a dense summer surface bloom of phytoplankton. One experiment in the summer of 1982 was performed with a control and withD. pulexadded. The results were quite striking: by the end of the experiment (roughly 6 weeks) enclosures withoutD. pulexexhibited phytoplankton densities an order of magnitude greater than those withD. pulex. These results demonstrate thatD. pulexcan effectively control phytoplankton biomass even in lakes in whichD. pulexis not a natural inhabitant. Therefore, management strategies designed to facilitate introduction and survival ofD. pulexor other large grazers should be encouraged as a viable within-lake technique for mitigating the symptoms of eutrophication.

ISSN:1040-2381    

DOI:10.1080/07438148409354502

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor