摘要:

During summer (May-October), a positive relationship was evident between lake water levels and chlorophyllaconcentrations in littoral and littoral:pelagic interface regions of Lake Okeechobee. High water levels in synergy with the large size (1830 km2), shallow depth (Zx= 2.7 m), and unique bottom configuration of Lake Okeechobee appeared to facilitate greater horizontal mixing and circulation which resulted in higher phosphorus concentrations in a portion of the littoral zone. In shallow littoral regions where light penetration was sufficient, an empirical link between phosphorus and chlorophyllawas evident. East-to-west and north-to-south gradients of phosphorus extended from hard-bottom littoral regions to the open-water pelagic zone located over soft, phosphorus-laden flocculent muds, and these gradients were more pronounced at low lake levels. Phosphorus loading from tributaries only affected algal concentrations in a small portion of the lake. A higher water level regulation schedule was implemented in 1978 to augment water supplies and this increased lake levels when precipitation was sufficient. A slightly lower lake level regulation schedule might reduce the frequency of hypereutrophic algal blooms in nearshore and littoral areas.

ISSN:1040-2381    

DOI:10.1080/07438149309354453

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Seasonal means of chlorophyll (Chl), total phosphorus (TP), total and non-volatile suspended solids (TSS, NVSS), and Secchi depth from 28 reservoirs and natural lakes in Iowa, Kansas, and Oklahoma were used to test predictions of log-log regression models developed from Missouri reservoirs by Jones and Knowlton (1993). Water-bodies in Iowa, Kansas, and Oklahoma exhibited a curvilinear relation between log-Chl and log-TP similar to that for Missouri reservoirs. These data fit the Missouri regressions for Chl-TP and Chl-(TP NVSS) fairly well; although the Missouri models usually underpredicted Chl for Iowa waterbodies. Missouri models provided an excellent fit to outstate transparency data.

ISSN:1040-2381    

DOI:10.1080/07438149309354454

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Data from 94 Missouri reservoirs demonstrated a large interregional variation in total phosphorus (TP), total nitrogen (TN), algal chlorophyll (Chl), and suspended solids among the four physiographic provinces with numerous reservoirs. The interprovincial pattern for nutrients, algal biomass, and mineral turbidity was Ozark Highlands < Ozark Border ≃ Glacial Plains < Osage Plains corresponding to an interregional gradient between forest and agriculture as the dominant land cover. On the basis of TP most Missouri reservoirs were eutrophic (61%) or mesotrophic (21%) with few hypereutrophic (7%) or oligotrophic (11%). Statewide, water clarity was low (median Secchi depth 1.0 m) and more strongly related to non-volatile suspended solids (NVSS, R2= 0.80) than algal Chl (R2= 0.30). Summer mean values showed a curvilinear relation between Chl and TP (log10transformed) reaching an asymptote above ≃ 50 μg/L TP/L — a range where most reservoirs have high NVSS and low TN:TP. Nitrogen limitation, light limitation, or binding of phosphorus by non-algal suspended material may explain reduced Chl:TP ratios in turbid reservoirs. Survey data, however, do not distinguish the roles of differing limiting nutrients and light limitation in reservoirs with > 10 mg NVSS/L. Conventional lake management scenarios based on phosphorus control seem appropriate for Missouri reservoirs of low to moderate turbidity.

ISSN:1040-2381    

DOI:10.1080/07438149309354455

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In-situ decomposition and P release (litter bags) in Lake Okeechobee forVallisneria, Hydrilla, andPotamogetonfollowed a simple exponential decay model.VallisneriaandHydrilladecomposed at rapid rates (k = 32–42/yr) so that only 9–14% of initial dry wt remained after 3 weeks;Potamogetondecomposed at a rate of 9.9/yr with 57% of the dry wt remaining during this period. Phosphorus was readily mobilized from decomposing plants: rates of phosphorus loss were 37.2, 25.2, and 9.1/yr forHydrilla, Vallisneria, andPotamogeton, respectively (>75% of initial phosphorus was lost after 3 weeks forHydrillaandVallisneria). Laboratory experiments confirmed that the loss of phosphorus from desiccated submersed aquatic vegetation is fast (within 4 hr) and readily bioavailable. Yield coefficients of 564–665 mg dry wt of algal cells (Selenastrum) or 1.4–5.6 mg chlorophyllaper mg P released were obtained.

ISSN:1040-2381    

DOI:10.1080/07438149309354456

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Lake Patzcuaro is a tropical, high-altitude, freshwater lake (130 km2surface area) located on the Mexican plateau. The lake originated from tecto-volcanic processes associated with the Mexican Neovolcanic Axis. Maximum depth (12 m) occurs in the northern part of the lake, whereas shallow areas are developing in the south. Its indigenous fish fauna and the presence of P'urhépecha Indian settlements around its shoreline identify Lake Patzcuaro as a unique natural resource having ecological, historical, and cultural value. The lake is endorheic and the annual water balance is controlled by differences among rainfall, seepage, watershed runoff, and evaporation. A mass-balance model indicates that hydrologic inputs from the watershed are being reduced as a result of watershed deterioration. High turbidities result from volcanic silt, raw sewage, and increasing erosion loads to the lake. Lake Patzcuaro is light-limited due to scattering and attenuation from suspended inorganic materials. The lake has high concentrations magnesium, sodium, carbonates, total phosphorus, chlorophylla, and suspended solids. Lake Patzcuaro is mostly eutrophic with some less productive areas. Proposed lake management strategies focus on the watershed and include: erosion control and reforestation, basin-wide sewer systems and wastewater treatment, and preservation of the indigenous fishery.

ISSN:1040-2381    

DOI:10.1080/07438149309354457

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A laboratory comparison of the effectiveness of two sediment phosphorus (P) inactivation techniques (aluminum sulfate and calcium nitrate) was made using intact sediment cores collected from Green Lake, WA. Additional treatments with Na2S, NaOH, and glucose were performed to assess effectiveness of the treatments under conditions of 1) reduced availability of Fe, 2) increased pH, and 3) organic matter enrichment, respectively. Under warm, dark, quiescent conditions both aluminum sulfate (alum) and calcium nitrate (nitrate) were equally effective in controling P release from the sediments when compared to a control. Addition of Na2S resulted in an increase in P release, but again alum and nitrate were equally effective compared to the control. Addition of NaOH resulted in an increase of P release, but alum was not as effective as nitrate in controling P release, possibly due to pH sensitivity of the aluminum hydroxy-P complex. Addition of glucose resulted in an increase of P release, perhaps due to increased gas evolution, but nitrate was not as effective in controling P release, possibly due to the availability of nitrate for degradation of organic matter and subsequent release of methane and nitrogen gas. Sediment oxygen demand (SOD) of Green Lake sediments was determined to be much less than that of sewage polluted Lake Lillesjön, Sweden, and similar to the SOD of Lake Lillesjön sediments following nitrate treatment. Sediment profiles of Fe, Mn, P, N, S, water content, and organic matter suggest that anaerobic processes were operational in the sediments. Although a recent study indicates that the overlying water does not experience episodes of reduced oxygen content, and that much of the water column increase in P can be attributed to migrating phytoplankton (primarilyGloeotrichia echinulata), possible links between sediment chemical and microbial processes and P uptake by benthic stages of phytoplankton at the sediment-water interface have not been investigated. More well planned and monitored in-lake treatments or limnocorral experiments of both alum and nitrate are needed to improve our predictions of the effectiveness and longevity of these two chemical treatments.

ISSN:1040-2381    

DOI:10.1080/07438149309354458

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Major phosphorus (P) fluxes to and from the pelagic zone (i.e., open water region including epilimnion, metalimnion, and hypolimnion) were estimated from data collected over a 6 year period during the summer in Eau Galle Reservoir, Wisconsin. P inputs to the pelagic zone included profundal sediments, the watershed, groundwater, and transport of P from the littoral zone. P outputs from the pelagic zone included discharge from the reservoir, deposition, and transport of P to the littoral zone. Nighttime convective circulation was assumed to be the dominant mechanism of P exchange between the littoral and pelagic zones. Littoral P inputs, often neglected from budgetary analyses, accounted for 15% of the total measured P input and 25% of the internal P input to the pelagic zone. External P inputs were greatest, accounting for 42% of the total measured P input to the pelagic zone. These results emphasize the need for control of various sources of P inputs in the development of lake and reservoir management strategies.

ISSN:1040-2381    

DOI:10.1080/07438149309354459

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We use data gathered since 1971 on Douglas Lake, Michigan to illustrate the use of temperature and depth adjusted oxygen deficits to assess changes in the rate of lake eutrophication. The method of calculation with adjustments is presented. By comparing different hypolimnia in the multidepression lake, we show that localized lakeshore land use produces regional patterns of production that are detected by comparison of oxygen deficits. For some lake regions, the increase in oxygen deficit has had a linear doubling since 1971. Using historical data, this rate of change is much greater than for the previous 50 years. The oxygen deficits in the lake region farthest from lakeshore development averaged 60% of those in the region nearest lakeshore development.

ISSN:1040-2381    

DOI:10.1080/07438149309354460

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Walker Pond Size Model is a widely used spreadsheet approach to the design of storm water treatment ponds. The user inputs the Soil Conservation Service curve number for the pervious areas and the fraction of impervious area. Input parameters must be correctly determined by the user. One commonly made error is to enter the weighted curve number in place of the pervious curve number, which can result in overestimation of dead storage volume by as much as 8.89 mm (0.35 inch). Using the weighted curve number only and not the model's equation can underestimate the required volume as much as 19.56 mm (0.77 inch). Proper use of the Walker Model is essential to obtain a beneficial, cost-effective design.

ISSN:1040-2381    

DOI:10.1080/07438149309354461

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor