摘要:

Phosphorus plays a central role in the bioenergetics of organisms and ecosystems (recall Adenosine Triphosphate [ATP], substrate level phosphorylation, cyclic and noncyclic photophosphorylation). It is a role which no other atom can duplicate. Phosphorus is of paramount importance in lake management because it most often limits the degree of phytoplanktonic autotrophy (algae growth). However, many other aspects of lake ecosystem structure and function offer substantial promise for the future of lake management and restoration. One such aspect, ecosystem energetics, is too often neglected or misunderstood by the lake manager.

ISSN:1040-2381    

DOI:10.1080/07438149409354462

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Layer aeration (U.S. Pat. 4,724,086) can be described as a depth-discrete artificial circulation technique. Like destratification, it uses both photosynthetic and diffusional sources of oxygen to overcome oxygen demand. Like hypolimnetic aeration, it maintains necessary vertical temperature structure for coldwater fish and zooplankton refugia. Layer aeration alters thermal structure, creating several functional thermoclines, while retaining stratification stability. Persistent metalimnetic anoxia and increased eddy diffusional transport across the thermocline, common problems with hypolimnetic aeration, are overcome by layer aeration.

ISSN:1040-2381    

DOI:10.1080/07438149409354463

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A simple mass balance model, combined with detailed hydrologic and mass balance measurements, yielded accurate predictions of total phosphorus (TP) concentrations in two lakes with no shoreline development. On the other hand, the model based on only natural TP loads predicted TP concentrations lower than observed in four developed lakes; however, in three of the four lakes, predictions and observations were virtually identical if the potential TP contribution from sewage disposal systems associated with shoreline development was included in the budgets. In the exception Harp Lake, the only one of the four with thick deposits of till/soil in its catchment, predicted and observed trophic status were comparable if about a third of the potential TP input from shoreline development reached the lake. The suggestion is that in this case the till/soil was effective in retaining a significant portion of TP transported from septic systems. Lakes with oxic and anoxic hypolimnia were distinguished by using different apparent settling velocities in the TP mass balance model. A lower settling velocity in those lakes with anoxic hypolimnia is consistent with TP release from the sediments under these conditions.

ISSN:1040-2381    

DOI:10.1080/07438149409354464

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Halfmoon Lake is a small, moderately deep, hypereutrophic, hardwater lake with a relatively small (2.4 km2), partially cleared drainage basin situated in the Boreal Mixedwood Ecoregion of central Alberta. The water is often thermally stratified, and average residence time is 60 years. During mid- to late summer 1988 and 1989, 188 metric tons of Ca(OH)2and 58 metric tons of CaCO3were applied to the surface of Halfmoon Lake to decrease total phosphorus (TP) concentration and algal biomass (estimated as chlorophylla[Chla]). Mean summer (July-September) Chlaand TP in the euphotic zone in 1989 and 1990 decreased to 53 and 63%, respectively, of the pretreatment year (1982). Similarly, sediment P release from June through August was 50% lower in 1989 and 1990 than in the pretreatment year. In contrast water quality deteriorated in three nearby reference lake basins, also hypereutrophic, so that average summer euphotic zone Chlaand TP were 217 and 116% higher, respectively, in 1989 and 1990 than in 1982. When these trends were considered, posttreatment corrected Chlaand TP in Halfmoon Lake were 24 and 54%, respectively, of pretreatment values. Decreased summer Chlain Halfmoon Lake was associated with higher winter dissolved oxygen (DO) concentrations, presumably due to a decrease in the oxygen demand in the water column at fall overturn following treatment and hence increased DO at freeze-up. Thus, Halfmoon Lake, a traditional winterkill lake where the water column went completely anoxic by January, had sustainable DO for fish in the posttreatment winters. We further hypothesize that enhanced sediment calcium content was responsible for reduced P loading from bottom sediments during winter and, consequently, lower summer Chla.

ISSN:1040-2381    

DOI:10.1080/07438149409354465

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Comparisons of chlorophyll and phaeophytin measurements performed on field and laboratory cultures of algae showed that fluorometric analyses were comparable to the standard spectrophotometric method over a wide range of phaeophytin, chlorophyll, and chlorophyll-b:chlorophyll-avalues. Inaccurate phaeophytin measurements obtained using a commercially available fluorometer were attributable to an incorrect narrow bandpass excitation filter which can now be replaced by the company. Differences in filtration and extraction technique and in frozen storage time did not result in significant changes in pigment estimates.

ISSN:1040-2381    

DOI:10.1080/07438149409354466

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Four mainstream river impoundments located in Alabama and Georgia were examined in 1989 and 1990 to determine the response of zooplankton and fish to trophic gradient. Mean chlorophyllaconcentrations ranged from 2 μg/L in the mesotrophic lake to 34 μg/L in the highly eutrophic lake. Two of the lakes were moderately eutrophic with mean chlorophyllaconcentrations of 13 and 15 μg/L. Rotifer and total zooplankton densities increased with increasing trophic status, but crustacean zooplankton densities and biomass did not. Estimates of fish abundance and biomass were positively related to trophic state. Forage fish community structure in the mesotrophic lake was numerically comprised of Iepomid sunfish (47%), cyprinid minnows (20%) and shad (Dorosoma) (13%), but shad comprised 45% to 53% of the fish community in the eutrophic lakes. Black bass (Micropterusspp.) growth rates were similar in all lakes, however crappie (Pomoxisspp.) grew faster in the more eutrophic reservoirs. Fishing effort adjusted for lake size was positively related to trophic gradient. Total weight and number of fish harvested was highest in the most eutrophic lake, but highest harvest per unit effort occurred in the mesotrophic lake. Generally, larger fish were caught in the eutrophic lakes than in the mesotrophic lake, and angler-caught black bass size was similar among the three eutrophic lakes. Trophic gradient was not related to angler perception of fishing success nor to where anglers chose to hold their fishing tournaments. Reservoirs with mean growing-season (May-September) chlorophyllaconcentrations between 10 and 15 μg/L may provide black bass and crappie fisheries that are similar to those fisheries of more productive lakes.

ISSN:1040-2381    

DOI:10.1080/07438149409354467

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Mountain Lake, Florida, is augmented with water pumped from the underlying Floridan aquifer to maintain the water level, and a detailed 1990 water budget was developed for this lake to determine how the lake interacts with the surrounding groundwater system. Groundwater interaction with the lake was calculated from flow-net analysis of surficial well data, seepage meter data, and the residual of the water budget equation. Strong leakage through the lake bottom was observed, primarily controlled by the head difference between the lake and the Floridan aquifer and the sediment hydraulic leakance (sediment hydraulic conductivity/thickness). Areas of seepage into the lake (15% of the lake area) were observed at possible sinkhole features in the central portion of the lake. Areas of strong leakage occurred in shore areas where steep outflow gradients and sandy sediments existed. Results from this study indicate that the lake recycles groundwater, as the equivalent of over 90% of augmentation water returns to the groundwater system. Water budget data from this lake dispute the public perception in Florida that lake augmentation is a wasteful practice.

ISSN:1040-2381    

DOI:10.1080/07438149409354468

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Giffin Lake is a shallow, eutrophic lake in south central Washington and the sub ject of an intensive Phase I restoration diagnostic/feasibility study. Water quality problems in the lake have been manifested principally as excessive growth of the floating-leaved macrophyte,Nymphaea odorata, white water lily. Study results indicate that these macrophytes play a central role in chemical, physical, and biological functioning of the lake. The extensive macrophyte canopy prevents diffusion of oxygen to the sediments by inhibiting both gas exchange with the atmosphere and transfer of wind energy to the water column. Anaerobic conditions develop under the summer macrophyte canopy, as do steep nutrient gradients. Phytoplankton seasonal distribution appears to be strongly influenced by competition with macrophytes for nutrients and light. Zooplankton communities are dominated by rotifers which can tolerate low oxygen conditions and which feed on bacteria and detritus prevalent beneath the macrophytes. Fish population distributions, with the exception of carp, are skewed to older and larger individuals, in constrast to those typically observed in lakes with less macrophyte biomass. Fish condition factors are generally below the average for Washington lakes. Recruitment to gamefish populations appears to be poor due to reproductive failures and low growth rates, resulting from the stresses of high temperatures, low summer oxygen concentrations, and predation from carp. Restoration of Giffin Lake would require removal of the majority of the sediments and macrophytes. Currently, the status of Giffin Lake as a wetland may bring such restoration efforts into conflict with wetland protection programs. The need for a means of assessing wetlands value in the management, protection, and restoration of shallow lakes/wetlands is discussed.

ISSN:1040-2381    

DOI:10.1080/07438149409354469

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Zooplanktonic grazing is increasingly recognized as an important component of phytoplankton dynamics and composition in natural, north-temperate lakes. The most efficient grazers are species of the cladoceran genusDaphnia, but in southeastern reservoirs this genus is often sparse in abundance, particularly during summer. Further, the dominant daphnia isDaphnia parvulawhich is a small-bodied species possibly not capable of exerting similar controls on food resources as largerDaphniaspecies. Experimental exclosure of fishes from zooplankton in Jordan Lake, a eutrophic, 55 km2reservoir in Piedmont North Carolina, was undertaken to determine if zooplankton would respond sufficiently to influence phytoplankton. Every major crustacean zooplankton taxon doubled its biomass within 2 weeks after protection from predators in at least 1 of six experiments from May to September. The usual numerical dominant,Skistodiaptomus pallidus, increased in every test by at least two-fold.D. parvulaincreased in four of the tests and rapidly reduced chlorophyll concentrations in each case. Abundance and associated species changes in phytoplankton were negligible without aDaphniaresponse, but whenDaphniaincreased cell densities of all taxa including most blue-green algae decreased. OnlyAnabaenaincreased in proportion to total phytoplankton units. When these results were examined in aD. parvulagrazing model, output suggested phytoplankton declines could be caused solely by increased grazing pressure. These results strongly suggest that fish predation is severely limiting the grazing power of zooplankton in Jordan Lake.

ISSN:1040-2381    

DOI:10.1080/07438149409354470

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Corrected chlorophylladata were gathered for 17 small southeastern piedmont impoundments <648 ha (<1600 a) ranging in trophic state from mesotrophic to hypereutrophic. Working with the managerial concept that water-use impacts are more directly related to frequency of blooms than to mean seasonal values, regression equations were calculated to relate bloom frequency to seasonal mean chlorophyllaconcentrations. The relationship between bloom frequency (chlorophylla≥30 μg/L) and mean chlorophyllaconcentration in this study was very similar to that found for U.S. Army Corps of Engineers (COE) impoundments.

ISSN:1040-2381    

DOI:10.1080/07438149409354471

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor