摘要:

Trophic state indices (TSIs) have been widely used to rank and classify lakes. Applications and limitations of TSIs are discussed, and types of TSIs developed previously are reviewed. An index is a summary statistic, and most trophic indices have been multivariate metrics, reflecting the complexity of the concept of trophic state. A recently developed TSI scheme for Florida lakes is described. This index includes sub-indices for the major physical, chemical, and biological indicators of trophic conditions (Secchi disk transparency, total P and N concentrations, and chlorophyll a levels), which were developed from a data base of 313 lakes. Use of the index to rank Florida lakes and evaluate problem lakes is described.

ISSN:1040-2381    

DOI:10.1080/07438148409354553

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

We propose that as a first approach the trophic status of natural and artificial lakes having growths of aquatic macrophytes may be assessed by using the total nutrient concentration in the water column (nutrients contained in the macrophytes plus those in the water) in conjunction with existing classification systems. We developed our approach because current approaches for assessing the trophic status of lakes do not adequately classify lakes dominated by aquatic macrophytes. This occurs because conventional sampling and trophic state assessment emphasize conditions in the water and do not consider the nutrients, plant biomass, or organic production associated with macrophytes. Relationships between aquatic macrophytes and other trophic indicators are discussed because changes in macrophyte abundance influence the structural and functional characteristics of lakes. These changes alter perceptions of water quality and overall lake quality.

ISSN:1040-2381    

DOI:10.1080/07438148409354554

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Scientists' role is to separate fact from fiction to assure that decisions be based upon valid evidence rather than emotions and misinformation. The use of chemicals for aquatic vegetation control is one issue commonly surrounded with fear and uncertainty by the general public, environmental groups, and politicians. This has led to restrictive laws in some States which severely limit or prohibit the application of registered aquatic pesticides. In-lake rehabilitation methods and watershed protection measures have achieved mixed results in controlling lake nutrient concentrations to suitably limit macrophyte or algae growth. For many bodies of water, high quality water is not presently economically or technologically feasible. However, symptomatic treatment of nuisance aquatic plant growth with chemicals or through integrated pest management methods can provide waterways acceptable for recreational and functional use. Historically, the chemicals used for aquatic macrophyte and algae control were sodium arsenite and copper sulfate, respectively. These did pose a threat to the environment from overdose and abuse in attempts to eradicate rather than manage aquatic plant problems. Today's chemicals and application techniques are more selective and sophisticated. Toxicity limits, breakdown times, and tolerances are established prior to EPA registration. Organic herbicides that characteristically degrade in the environment or become biologically inactive have replaced persistent chemicals such as sodium arsenite. Formulated, chelated copper compounds are replacing copper sulfate treatments as a safer, more effective approach. Improved application equipment, techniques using spray adjuvants, and granular formulations have helped overcome problems with drift and uneven distribution. The judicious use of chemicals for aquatic vegetation control is imperative. Loss of any of our limited number of tools for maintaining suitable recreational and functional waterways through regulations imposed by the uninformed could severely limit our ability to achieve future water quality objectives.

ISSN:1040-2381    

DOI:10.1080/07438148409354555

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Experimental mechanical barge/conveyor harvesting conducted in June and August of 1981 and 1982 significantly reduced total plant biomass initially, relative to control areas. Regrowth of the predominant species, Eurasian watermilfoil(Myriophyllum spicatum), reached pre-harvest levels within 30 days after June and August harvestings. Total plant andM. spicatumbiomass (g·m−2, dry) in harvested areas peaked later than control area vegetation both years, and was slightly higher. The ratio of the average annual biomass of the harvested area to the control area was the same both years (0.73), despite significant decreases in overall average total biomass in 1982. Similar harvesting resulted in the removal of primarily juvenile fish. Harvesting was conducted in dense littoral zone stands of milfoil (M. spicatum) and curly-leaf pondweed (Potamogeton crispus). The harvesting operation removed primarily bluegill sunfish (Lepomis macrochirus) and to a lesser degree, largemouth bass (Micropterus salmoides), yellow perch (Perca flavescens) and pumpkinseed sunfish (Lepomis gibbosus). Harvesting effectively removed approximately 2–3 percent of the total standing crop of juvenile fish in both June 1981 and 1982, and approximately 2–8 percent in August of both years.

ISSN:1040-2381    

DOI:10.1080/07438148409354556

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Dense carpets of submersed macrophytes in lakes restrict boating and swimming, limit movement of predator fishes, trap fish fry, and contribute to poor fishing. Eliminating plant beds, although good for boating and swimming, removes the plant cover, habitat diversity, and invertebrates needed to support a sport fishery. Fiberglass screens and selective plant harvesting have proven useful in breaking up continuous stands of plants, reducing summer biomass and stored nutrients, and forming boating lanes. The screens kept areas free of vegetation all summer when placed on the lake bed in spring and rapidly removed plants when spread over them in summer. Selective harvesting created islands of vegetation, gave predator fishes access to young fishes hiding among the remaining plants, and opened bottom areas for the spread of new plant species. Although intended to destroy vegetation, these and other methods can be used selectively and economically to rebuild littoral zones to benefit both people and lake biota.

ISSN:1040-2381    

DOI:10.1080/07438148409354557

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Experimental applications of pigmented nylon film were conducted in the Seattle metropolitan area in order to evaluate gas venting characteristics and instalation procedures. The material was highly effective in controlling aquatic plant growth, causing death and decomposition of covered plant materials in 30 to 35 days. Gas entrappment, ballooning, and lifting was observed with unvented material but this was overcome by placing venting slits in the material. A vent slit design of 12/meter2gave the best result. Installation of the film is straightforward and simple. Difficulties encountered with dense plant growth and soft organic sediments are described.

ISSN:1040-2381    

DOI:10.1080/07438148409354558

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Citizen activists participate year after year in the Illinois Volunteer Lake Monitoring Program—providing their own boating equipment and collecting data at least twice monthly from May through October. Over two thirds of the volunteers who started in 1981 continue to be active. The program was initiated by the Illinois EPA in 1981 to help citizens make more informed decisions about lakes' use, protection, and management. Citizens are trained to measure Secchi disk transparency and total depth and record field observations in a systematic manner at designated sites. Secchi disks, special data reporting forms, and postage paid envelopes are provided by the Agency. Morphological data and assessment information are also collected for the lake and watershed. The sampling data are computerized and a statewide summary report is prepared. As resources permit, individual lake reports are also prepared which incorporate physiochemical data obtained under the Agency's Ambient Lake Monitoring Program and include general recommendations for lake protection and management. The program has been very successful: 141 volunteers participated in monitoring 87 lakes in 1981; in 1983 approximately 240 volunteers are scheduled to monitor 160 lakes. The program provides the volunteers with current data on their lake and how its transparency compares to other lakes in the State. It also provides a historic data base for determining seasonal and long-term trends in lake quality. The volunteer monitoring program has resulted in implementation of lake protection/restoration measures for several lakes. Federal, State, and local agencies have used the data collected to help assess the severity of water quality impacts from agricultural runoff and target resources for water quality benefits. Volunteer data have helped document water quality problems, point out critical areas most responsible for water quality degradation, guide the implementation of lake protection/management techniques, and evaluate their effectiveness.

ISSN:1040-2381    

DOI:10.1080/07438148409354559

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Lake conservation begins with grass roots efforts recognizing the needs of the area. The following help foster awareness and effective lake conservation programs: (1)stream cleanups create public awareness and provide case studies to help others; (2) lake conservation symposia at local colleges allow speakers to address the lake conservation needs of local communities; (3) collections of lake resource materials for a local library provide easy citizen access to information; (4) a core contact list of local people most active in lake conservation can be circulated to encourage participation at lake conservation activities; (5) a file of names and addresses of all people interested in the lake community aids their notification of all events; and (6) educational projects for youth groups broaden public awareness of lake problems. Citizens should be encouraged to contact their local Extension Office, Soil & Water District, Health Department, Planning Office, Soil Conservation Service, and other citizens for assistance and advice in lake conservation projects. These efforts which have been implemented in northeastern Illinois are applicable wherever lake conservation is a matter of concern and interest.

ISSN:1040-2381    

DOI:10.1080/07438148409354560

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Greenwood Lake is a 777 ha lake in the suburban New York metropolitan area. The lake lies in New York State (Orange County) and New Jersey (Passaic County) and comes under the jurisdiction of both States. The 6,000 ha watershed is 80 percent forested and 17 percent in residential land use. Greenwood Lake is a headwater of the Wanaque River in the Passaic–Hudson River Drainage Basin. The lake experiences heavy recreational use including boating, fishing, and swimming. Over the course of the last 30 years the lake's water quality has declined appreciably and recreational usage has dropped as a result. Historically, many different citizens organizatons have been formed to address the problems of the lake then gradually died. One major problem with maintaining an active and viable organizaton to coordinate and implement lake management activities on the lake is that the lake is in two States. Although a single lake and a single watershed, local parochial interests prevented coordinated action. In 1979 a group of citizens from New York and New Jersey formed the Greenwood Lake Watershed Management District, Inc., as a bistate committee to address problems of Greenwood Lake. Accepted by the States of New Jersey and New York as a responsible political organization, the GLWMDI applied for and received a grant under Sec. 314 of the Clean Water Act to carry out a lake restoration and watershed management study on Greenwood Lake. The GLWMDI has a 30-member board of directors, an executive director as chairman, and several hundred members. Throughout the 314 study volunteers contributed up to $100,000 worth of hands-on, in-kind services associated with the study. This contribution served as the matching funds needed to obtain the grant. Throughout the 4 years of its existence, the GLWMDI has unified the people in the basin into a powerful action-oriented organization with the welfare of the lake as its primary goal.

ISSN:1040-2381    

DOI:10.1080/07438148409354561

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In 1983 the Massachusetts Division of Water Pollution Control began administering a program of matching grants to municipalities for lake studies and cleanup/restoration activities. Municipalities proposed various projects on 40 lakes and ponds and 35 were able to generate the local match. In some cases lake associations assisted in the process. No correlations were found to exist between cities/towns, their population or economic characteristics and the presence or absence of an association, the size or trophic status of a water body. Apparently lake associations are individual or small group efforts but are not particularly a response to identifiable, repetitive stimuli. It is likely they result from personal, social, and historical factors that are hard to quantify.

ISSN:1040-2381    

DOI:10.1080/07438148409354562

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor