摘要:

Diverse, moderately dense stands of aquatic plants in a lake's littoral zone benefit fish and wildlife and the functioning of the littoral ecosystem. Certain plant species are aesthetically pleasing and do not hamper recreational water uses. The technology is available to manipulate community structure, to increase diversity, and to select for desirable species. However, this technology has not been used in community manipulation strategies. This paper discusses the beneficial and negative attributes of a number of aquatic species common to the north central United States, discusses the technologies available for community manipulation, proposes a management scheme for University Bay of Lake Mendota, and urges field testing of ideas so that community manipulation may provide consistent, predictable, and beneficial results.

ISSN:1040-2381    

DOI:10.1080/07438148609354637

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In British Columbia, Canada, managing Eurasian water-milfoil (Myriophyllum spicatumL.) integrates harvesting, tillage, bottom barrier applications, and diver-operated dredging methods in annual control programs in nine lakes. Two tillage technologies developed in British Columbia for removing plant roots in high use public areas are not known to have been applied in other jurisdictions. Barge-mounted rototillers achieve 80 to 97 percent reductions in stem densities in water depths up to 3.5 m. An amphibious cultivator is operated in water up to 1.25 m deep with similar effectiveness at lower unit cost and several times higher treatment rates. Both tillage machines may be operated in fall and spring and are particularly suitable during periods of lake drawdown. An independent researcher is developing applications of high power ultrasound to control Eurasian watermilfoil. Effects of laboratory experiments include damage to plant cells and tissues with single exposures of ultrasound for several seconds. This technology promises advantages for management and high levels of effectiveness in treatment of shoot and root tissues; current research is concentrated on reducing the exposure time required to kill meristematic tissues.

ISSN:1040-2381    

DOI:10.1080/07438148609354638

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Moderation of aquatic plant growth by changing the primary growth control factor, light, is an economically viable and ecologically acceptable technique for many lake and stream habitats. In open unshaded waters, great potential exists for plant growth either by large plants (macrophytes) or algae. Although other factors such as nutrients affect growth,without lightno plant growth would occur. Attempts to eradicate macrophytes are likely to be unsuccessful and may lead to unstable or extreme situations such as dense algal blooms or monotypic plant stands. The absence of macrophytes, particularly in streams, also can lead to a poor aquatic community. Techniques for moderating plant growth include (1) intercepting light above the water by bank vegetation or at the water's surface by opaque materials, or by redesigned lake or stream margins; (2) reducing light penetration of the water by the action of bottom-feeding fish or of boats, the addition of dyes, or the redesign of waterbodies to maintain materials in suspension; (3) confining macrophytes to deeper water (redesigning margins, protecting marginal plants, and using netting); and (4) combining the detrimental effects of environmental factors on plants with their physiological responses (differential cutting to maintain very dense and very sparse plant stands). Surveys to identify the extent of the problem and potential solutions must be emphasized. No universal solution exists and apparently similar sites may vary subtly but significantly.

ISSN:1040-2381    

DOI:10.1080/07438148609354639

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Macrophyte transplant experiments were conducted between 1981 and 1985 in Chautauqua Lake, N.Y., to evaluate the feasibility of reestablishingPotamogeton amplifoliusand increasing its abundance in the lake. Transplants with attached rhizomes and cuttings without rhizomes grew readily following transplanting. In the summer, growth rates of established plants ranged from 0.1 to 0.9 cm/day and new propagules grew from 0.7 to 0.8 cm/day. Three to four years after transplanting, numbers ofP. amplifoliusplants at both sites remained constant at 60 to 68 percent of the original number of transplants. Although the plants actively propagated by rhizomal and stem vegetative reproduction, the stands of transplantedP. amplifoliusfailed to spread more than a meter beyond the original transplant sites after four years. Heavy encroachment by other macrophyte species may have prevented expansion of the transplant stands.

ISSN:1040-2381    

DOI:10.1080/07438148609354640

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The computer program HARVEST deterministically simulates all important aspects of an aquatic macrophyte harvesting operation. It runs on a personal computer and can simulate any current or proposed harvesting system operating in any realistic aquatic macrophyte-infested environment. The inputs, logic, assumptions, and outputs of the model are described. Its application in evaluating the cost and effectiveness of harvesting programs is demonstrated.

ISSN:1040-2381    

DOI:10.1080/07438148609354641

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Lake Eureka, III., was created in 1942 primarily to serve as a water supply source for the city of Eureka. Because of complaints about taste and odor in the finished waters, the city abandoned the lake and switched to ground water as the water supply source in 1979. A detailed taste and odor investigation indicated that high concentrations of iron and manganese, and the dominance of blue-green algae in the lake waters, contributed to the problems in the finished waters. Lake destratification using a low-energy mechanical destratifier in the deepest part of the lake in combination with chelated copper sulfate application to control blue-green algae was tried in 1981 to enhance the lake water quality characteristics. The aerator has been found capable of destratifying the lake and maintaining adequate oxygen levels. Iron and manganese concentrations in the deep waters have been reduced by 95 to 97 percent from the predestratification levels. Chlorine demand values have been reduced by more than half, and problem-causing blue-green algae have been brought under control. The city reverted back to the lake as its water supply source in April 1982, saving 50 to 60 percent in the water treatment plant's annual operating costs over the past three years.

ISSN:1040-2381    

DOI:10.1080/07438148609354642

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Lake Ballinger is a 40 ha (100 acres) eutrophic lake in the city of Mountlake Terrace, Wash. The lake's very poor water quality characteristics have been brought about by excessive nutrient loadings from the watershed and internal cycling of phosphorus during periods of hypolimnetic anoxia. A two-phase restoration project was undertaken to improve the water quality of the lake. Phase I was the restoration of Hall Creek (the major surface water inlet) by establishing two sedimentation basins and rehabilitating the stream bank. Phase II was the construction of a hypolimnetic injection/withdrawal system to enhance the dissolved oxygen levels in that strata and remove phosphorus-rich hypolimnetic waters. The internal cycling of phosphorus has been reduced from an annual loading of 109 kg in 1980 to 17 kg in 1984. Data analysis indicates that further watershed management efforts are needed to control the increasing loading of nutrients into Lake Ballinger and achieve a long-term improvement in the lake's water quality.

ISSN:1040-2381    

DOI:10.1080/07438148609354643

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In an attempt to create lake-type fishing in northwestern Minnesota, legislative funds were provided to construct a lake near the Canadian border by damming the north fork of the Roseau River. The lake was to serve as a focus for Hayes Lake State Park. Soon after the creation of this impoundment, winterkill conditions developed from incomplete burning of the vegetation in the reservoir basin prior to flooding. Limnological sampling conducted between 1979 and 1983 confirmed the winterkill conditions, with dissolved oxygen levels of 4 ppm at the surface to 0.4 ppm at lake bottom. In January 1984, a bottom water drawdown device was installed. Tests conducted after its installation showed that the dissolved oxygen level had been restored to 6.7 ppm at the surface and 3.5 ppm at the lake bottom. After the installation of the pipe, winter fishing activity increased along with other recreational uses.

ISSN:1040-2381    

DOI:10.1080/07438148609354644

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Seasonal and annual variation in the biochemical oxygen demand of the water column (WBOD) and the sediment (SBOD) are described for two small central Iowa lakes based on sampling over 57 consecutive months, 1977–82. A correlation analysis was done to determine the relationship between WBOD and SBOD to 15 physical and chemical variables using composite values for the whole lake and for the top, middle and bottom-most strata on each sampling date. The best single variable model for predicting volume-weighted WBOD was mean lake chlorophyllaconcentration: WBOD = 1.79 + 0.032 (chlorophylla). There were no significant correlations between SBOD and any of 15 environmental variables, but in the control lake, not artificially destratified, SBOD and chlorophylla(−) and ammonia (+) showed significant correlations. Artificial destratification increased the vertical distribution of oxygen and chlorophylla, reduced peaks of algal blooms, increased near-bottom water temperature and oxygen concentration, and reduced SBOD and ammonia.

ISSN:1040-2381    

DOI:10.1080/07438148609354645

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Accuracy of thein vivomethod for estimating chlorophyll was evaluated on two Oklahoma reservoirs that are morphometrically and hydrologically dissimilar. The coefficients of correlation between chlorophyll a contents estimated fluorometrically and determined spectrophotometrically on Overholser and Lawtonka Reservoirs were 0.767 and 0.970, respectively. The mean of the error distribution on Overholser Reservoir was 0.07 ±3.12 μg/L (n = 30), and 0.52 ±2.11 μg/L (n = 150) on Lawtonka Reservoir. Regression equations were developed to permit prediction of chlorophyll a content from fluorometric measurements, and experiments were conducted to determine the factor(s) responsible for observed error. With proper calibration of the fluorometer, accuracy of the fluorometric estimates was equivalent to spectrophotometric precision. Therefore,in vivofluorometry is uniquely suited for synoptic analysis of distribution of algal biomass and has wide application for reservoir management (Grimshaw and Shapiro, in prep.).

ISSN:1040-2381    

DOI:10.1080/07438148609354646

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor