摘要:

Lake management practices in Minnesota have included holistic Clean Lakes Projects, extensive remedial methods to control excessive phytoplankton and macrophyte growth, and fisheries improvement projects. Clean Lakes projects have had varying degrees of success, but there has been no systematic evaluation of the overall success of the program. Remedial methods and fisheries management have narrow objectives, and the broader water quality impacts of these management practices have generally not been considered. Future lake management activities in Minnesota include developing better predictive and assessment capabilities, using innovative management techniques such as biomanipulation and community management of macrophytes, and renewing emphasis on controlling nonpoint source inputs to lakes.

ISSN:1040-2381    

DOI:10.1080/07438148909354393

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The development of practical lake management strategies in Minnesota has been greatly facilitated by using the aquatic ecoregion approach and standard assessment methodologies (models). Previous studies have shown the significance of the aquatic ecoregion in determining lake water quality patterns, water quality attainability, and development of nutrient criteria (Heiskary et al. 1987; Heiskary and Walker, 1988). This paper focuses upon the use of ecoregion data for modeling purposes. The Minnesota Lake Eutrophication Analysis Procedure (MINLEAP) is a computer program designed to predict eutrophication indices in Minnesota lakes based upon area watershed, depth, and ecoregion. Ecoregion is used to predict runoff and average stream phosphorus concentration. The program formulates water and phosphorus balances and uses a network of empirical models to predict lake phosphorus, chlorophylla, and transparency values. The program is intended primarily as a screening tool for estimating lake conditions with minimal input data and for identifying “problem” lakes. Included in the program output are: (1) statistical comparisons of observed and predicted phosphorus, chlorophylla, and transparency values; (2) uncertainty estimates; and (3) estimates of chlorophyll a interval frequencies (nuisance frequencies), for observed and predicted conditions. These expressionsof lake condition may be calibrated to citizen preferences using observer surveys (Heiskary and Walker, 1988) to define swimmable and nonswimmable conditions in a locally meaningful manner. The model should be used to approximate lake water quality expectations acknowledging that individual lakes may deviate greatly from regionally defined patterns.

ISSN:1040-2381    

DOI:10.1080/07438148909354394

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A United States–Spanish Cooperative Program is currently being performed between the U.S. Bureau of Reclamation and the Spanish Centro de Estudios y Experimentacion de Obras Publicas applying Landsat satellite digital imagery to eutrophication-related water quality monitoring in Spanish reservoirs. Landsat digital images provided by the thematic mapper sensors were processed with concurrent surface sampling data, to develop regression equations and water surface maps. Limnological parameters selected for the study were related to trophic conditions such as chlorophyll concentrations and Secchi transparency. While thematic mapping based on single-date regression equations has already proved feasible and reliable, more sophisticated processing is needed to develop equations for multiple-date assessment, that is, to enable assessment on any date remote sensing data are available whether concurrent water surface measurements are available or not. The long-term goal of this project is developing updated, cost-effective reservoir surveillance and classification on a regional or nationwide basis.

ISSN:1040-2381    

DOI:10.1080/07438148909354395

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Suspended solids and algal populations were characterized in 16 south central Oklahoma lakes to relate their properties to the spectral reflectances recorded by satellites. The average concentrations of natural suspended solids in the lakes ranged from 7 to 190 g/m3. Ash content increased from about 65 to 90 percent as suspended solids concentrations increased. Mean particle diameter, determined by photon correlation spectroscopy on samples with more than 40 g/m3of suspended solids, ranged from 400 to 2,000 nm. Nutrient concentrations were low; dissolved inorganic nitrogen was less than 0.4 g/m3, and water-soluble phosphorus was less than 25 mg/m3. Algal populations were also low, with chlorophyllaconcentrations averaging 6 mg/m3and rarely exceeding 20 mg/m3. Reflectances in the satellite spectral bands varied only slightly in response to changes in visual color and particle size of suspended solids in the turbid lakes. The relatively low chlorophyll concentrations could not be detected in the satellite spectral bands.

ISSN:1040-2381    

DOI:10.1080/07438148909354396

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

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.Cymbellawas dominant on natural substrate, whileCymbella,Mougeotia, andRhizocloniumwere 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.

ISSN:1040-2381    

DOI:10.1080/07438148909354397

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Whole-lake experiments were conducted on three ponds in interior Alaska to test the effects of calcium magnesium acetate (CMA), an experimental road deicer, on aquatic organisms. The CMA added to the test ponds equalled approximately one chemical application applied to 0.4 km of a typical section of road (one lane) draining entirely to a small pond. Calcium elevation did not persist into the next summer; it may have been flushed out by snowmelt. Acetate from the CMA mixture was apparently rapidly taken up by aquatic organisms and cycled for several months, depleting dissolved oxygen in the water. Dissolved oxygen became extremely low in a small pond of about 2,600 m3treated with 55 mg/L calcium acetate (calculated from calcium elevation). Bacteria and algae both appeared to be stimulated by CMA additions, as indicated by higher standing crops in treated ponds. The algae were probably stimulated by bacterial metabolism products of the acetate, or by phosphorus in the CMA used. Cladocerans were more dense in treated ponds than in control ponds, probably because more food (bacteria and algae) was available. Salmonid fishes, not present in the test ponds, might be stressed by low dissolved oxygen caused by CMA.

ISSN:1040-2381    

DOI:10.1080/07438148909354398

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper is part of a multi-step assessment of the hypothesis that subtropical, semi-arid impoundments may respond differently to increasing nutrient enrichment than similar northern temperate waterbodies (primarily natural lakes) from which the classical lake eutrophication concept has been derived. Common physicochemical indicators of eutrophication are referenced, including nutrient status, phytoplankton biomass (chlorophyll), and hypolimnetic deoxygenation. Data from 89 reservoirs in the southwestern United States and southern Africa were used to examine the eutrophication-related limnology of these lakes. In particular, the effects of a large catchment area:lake surface area ratio (AD:A) on the turbidity, nutrient status, and phytoplankton standing crop were highlighted as distinct features relevant to semi-arid lake classification. The responses of reservoirs in semi-arid regions of the northern and southern hemispheres to nutrient enrichment are contrasted with responses of temperate lakes to highlight their implications for accurately assessing eutrophication of manmade lakes in subtropical, semi-arid areas.

ISSN:1040-2381    

DOI:10.1080/07438148909354399

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Measurement of pollutant loadings is important in any lake management program. The flow interval method is among the most widely used today for this purpose. However, the Baltimore City Water Quality Management Office found this methodology to be extremely sensitive to the unit of flow (e.g. daily average, 15 minute discrete records) used in the computation. In three tributaries monitored, errors attributable to the flow unit used in phosphorus and sediment loading computations were found to be as high as 44 percent and 71 percent, respectively. Potential errors are greatest for streams with flashy hydrographs and a strongly positive flow/concentration relationship. The degree to which phosphorus and sediment loads are underestimated by using daily averaged flows varies with watershed, hydrologic year, and flow-concentration dynamics.

ISSN:1040-2381    

DOI:10.1080/07438148909354400

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Concentrations of soluble and total phosphorus in runoff from 16 grassed and cropped watersheds were measured over the past decade. Six watersheds drained into two flood detention reservoirs, where phosphorus concentrations were also measured at the inflow, within the lake, and at the outflow over a two-year period, to assess the effects of agricultural management practices on water quality. Soluble and total phosphorus concentrations in runoff from the native grass (133 and 343 mgP m−3, respectively) and cropped watersheds (215 and 2423 mgP m−3, respectively) were similar to phosphorus concentrations at the inflows to the reservoirs. Adsorption, biological uptake, and suspended sediment settling reduced soluble and total phosphorus levels 75 and 93 percent, respectively, in outflow from the reservoir with the grassed drainage basin and 72 and 96 percent, respectively, for the cropped drainage basin reservoir. Mean annual chlorophyllaand Secchi depths classified both reservoirs as eutrophic, even though only small amounts of fertilizer phosphorus were applied in their watersheds. Chlorophyll a and Secchi depths predicted from flushing-corrected inflow phosphorus concentrations were within the 95 percent confidence intervals of trophic response curves. Although flushing-corrected inflow phosphorus concentrations from native grass were appreciably lower than from cropped land, all management practices contributed runoff capable of accelerating eutrophication of the reservoirs.

ISSN:1040-2381    

DOI:10.1080/07438148909354401

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Phosphorus is often the principal nutrient limiting primary production in the United States southeastern reservoirs, but its impact on higher trophic levels has not been assessed. A regression analysis was used in this study to examine the relationship between phosphorus concentration and fishes biomass over time in a Virginia reservoir and also in a set of 22 southern Appalachian reservoirs. Both phosphorus and fish biomass concurrently were measured. In the Virginia reservoir, which had experienced a nutrient reduction program, total phosphorus concentration and fish biomass declined together over an 11-year period. Phosphorus concentrations explained two-thirds of the annual variation in fish standing stock. Phosphorus was also the best fish biomass predictor for the southern Appalachian reservoir set, accounting for 75 percent of the variation in standing stock despite great diversity in size, morphometry, chemistry, species composition, and hydrology among impoundments. Predictive power was generally higher for forage fishes than for piscivores–attributed in part to human manipulation, specifically stocking and harvesting, of these sportfish species as well as to a trophic bottleneck in forage-fish availability. The strength and robustness of the regression relationships indicate that, for these systems, reducing phosphorus loading will cause a decline in the fishery. Nutrient abatement programs should be planned with full consideration of the potential trade-off between cleaner water and poorer fishing success.

ISSN:1040-2381    

DOI:10.1080/07438148909354402

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor