Summer Total Phosphorus Concentrations Research Articles

Habitat distribution of fish in late summer: changes along a nutrient gradient in Danish lakes

Abstract – The horizontal distribution of fish in lakes varies with species, age, predation risk, vegetation coverage and water clarity. Although sporadic data are available for specific lakes, little is known about how habitat distribution generally changes along a gradient in nutrients and clarity. Here we analyse littoral and pelagic fish catch data for 34 Danish lakes (covering 94 lake years) with contrasting total phosphorus (TP) concentrations and mean depth levels (but mainly eutrophic and shallow). Electrofishing was conducted during day along the shore or along the edge of the reed belt if such existed. Gill nets were set overnight for 18 h in open water. We calculated a littoral proportion as: LITPRO = (100 × number caught by electrofishing in the near‐shore area)/(number caught by electrofishing in the near‐shore area and nets in the open water). At all summer TP concentrations LITPRO was high for several ‘littoral’ species such as gudgeon (Gobio gobio), rudd (Scardinius erythrophtalmus) and pike (Esox lucius) and low for more typical pelagic species like pikeperch (Sander lucioperca), ruffe (Gymnocephalus cernuus) and smelt (Osmerus eperlanus). However, for many of these species including the dominant roach (Rutilus rutilus) and perch (Perca fluviatilis) LITPRO increased with TP or lake water chlorophyll a (CHLA) for fish >10 cm, suggesting a more littoral distribution with increasing turbidity. Exceptions are pikeperch and bream (Abramis brama). For bream, LITPRO increased significantly with mean lake depth only. For fish ≤10 cm LITPRO showed only a weak relationship to TP, CHLA or depth. In accordance with the TP‐dependent distribution, major changes occurred in the fish community structure during the monitoring period following nutrient loading reduction. A comparison of LITPRO from the first part of the monitoring period (1989–1993) with a subsequent period (1997–2003) for four abundant species showed a significant decline in LITPRO over time for large‐ and small‐sized roach and perch and large rudd. This suggests a fast response in fish distribution to improved water quality. It further demonstrates that fish monitoring in lakes should cover both littoral and pelagic habitats to describe the recovery process.

The U.S. EPA Lake Erie Indicators Monitoring Program 1983–2002: Trends in Phosphorus, Silica, and Chlorophyll a in the Central Basin

During the past 20 years, Lake Erie has exhibited a series of complex chemical changes resulting from changing anthropogenic influences and introductions of exotic species. Since 1990, some apparent trends in nutrient concentrations have been inconsistent with the predictions of models originally used to guide Lake Erie water quality management. We performed time trend analysis on total phosphorus (TP), chlorophyll a (Chl a), and dissolved reactive silica (DRS) measurements collected during spring and summer in the central basin of Lake Erie between 1983 and 2002. Three distinct time trends in basin-specific, station-averaged open-water TP concentrations were observed over the 20-year period: 1983–1989 decreases, 1990–1997 increases, and 1997–2001 decreases. Exceptionally high levels of turbidity and TP were observed in spring 2002, possibly reflecting increasing frequency of winter storm events. Open-water concentrations of TP declined during the 1980s as annual TP loadings to Lake Erie declined below the 11,000 metric ton target level that had been expected to reduce central basin eutrophication. This was accompanied by a significant increase in available silica and in Chl a concentrations. During the period 1990–2002, when dreissenid mussels were abundant, spring TP concentrations increased but summer TP concentrations declined. Unexpected increases in spring central basin concentrations of DRS (exceeding 1 mg/L) were observed. During the same period, Chl a concentrations declined in the spring and rose slightly during summer.

Effects of Temperature and Other Factors on Summer Phosphorus in the Inner Bay of Quinte, Lake Ontario: Implications for Climate Warming

Summer total phosphorus (TP) concentrations in the inner Bay of Quinte (northeastern Lake Ontario), averaging about five times higher than winter concentrations, were strongly influenced by positive reflux of sediment TP. Several factors potentially influencing the magnitude of the summer peak (1 July to 30 September mean), including seasonal point-source and non-point-source TP loading, seasonal flushing rates, and water temperature, were explored in a multiple regression analysis. Three variables contributed significantly to explanation of the variance in the overall regression (adjusted R 2 = 0.876): June to September water temperature, total daily TP loading rate from three local point-sources (sewage treatment plants) and flow-weighted averaged July to September TP concentrations in the lower Trent and Moira rivers. The strong influence of temperature on summer TP concentrations in the inner Bay of Quinte (where water and air temperatures are nearly 1:1) has important implications for climate change. Summer average water temperature increases of 3 to 4°C are within the range of those predicted by several general circulation models (GCMs with 2x CO 2 end points). The multiple regression model suggests that summer TP concentrations could about double with a water temperature rise of 3 to 4°C above the 1990 to 1994 mean. This would effectively “undo” many benefits achieved to date in point-source TP loading control.

Response of a Shallow, Polymictic Lake to Buffered Alum Treatment

ABSTRACT The first aluminum sulfate (alum) and sodium aluminate lake treatment in Washington State was performed in Green Lake, a shallow (mean depth = 3.9 m), highly eutrophic, polymictic lake in Seattle. During October 1991, 181 tons of alum and 76.5 tons of sodium aluminate were applied to attain a total aluminum dose of 8.6 mg L−1. The use of sodium aluminate as a buffering agent allowed a higher dose of alum to be used, and maintained lake pH (6.7) and alkalinity (28 mg CaCO3 L−1) during treatment Secchi disk transparency increased from 1.9 to 6.1 m following treatment and remained higher throughout 1992 and 1993 than in pretreatment years with summer means of 3.5 and 2.9 m, respectively. Total phosphorus (TP) concentrations decreased from a mean of 40 μg L−1 before treatment to 14 μg L−1 immediately following treatment and remained below 29 μg L−1 during 1992 and below 35 μg L−1 during 1993. The 1992 and 1993 whole-lake, mean summer TP concentrations of 20 and 26 μg L−1. respectively, met the lake m...

Environmental factors influencing chlorophyll v. nutrient relationships in lakes

SUMMARY. 1. A model relating log chlorophyll a concentration to log epilimnetic total phosphorus (TP) concentration was re‐examined based on: (a) comparative and temporal studies of four stratifying Wisconsin and other highly eutrophic temperate lakes; (b) comparative summer lake surveys from Iowa and Alberta.2. Although P‐limited, deeper lakes with long hydraulic residence times and low external and internal nutrient loading in summer had summer chlorophyll a yields below model predictions based on spring and summer epilimnetic TP concentrations.3. For lakes with summer epilimnetic TP between 30 and 80 mg m−3, chlorophyll a concentrations exceeded model predictions based on summer TP. This relationship held even for Lake Delavan, Wisconsin, where the ratio of available N to P was unfavourably low during spring turnover, and where the trans‐thermocline N:P flux ratio was sub‐optimal for algal needs in early summer.4. With increasing summer TP concentrations and/or increasing epilimnetic circulation depth (>5m), chlorophyll a concentrations fell below model predictions—independent of the potential for N‐limitation. This plateauing in chlorophyll a response occurred at lower epilimnetic TP content (<c. 400 mg m−2) in lakes with elevated non‐algal light extinction coefficients. Using Tailing's algorithm for the‘column compensation point’ (algal photosynthesis = algal respiration over diel cycle), light limitation best explains this fall‐off in chlorophyll a yield.5. The failure of the Dillon & Rigler (1974) spring TP v. summer chlorophyll a model for these Wisconsin lakes is unrelated to N‐limitation. Instead, it reflects internal adjustment in take TP in response to stratification and seasonal external P loading.

CONTROL OF INTERNAL PHOSPHORUS LOADING IN TWO SHALLOW LAKES BY ALUM AND AQUATIC PLANT HARVESTING

ABSTRACT Erie and Campbell Lakes are two shallow, nonstratified lakes located in Skagit County, Washington. Both lakes suffered from dense blooms of blue-green algae during late summer. Erie Lake also suffers from occasional fish kills. A Phase I diagnostic study conducted in 1981–82 identified phosphorus as the nutrient controlling algal growth, and internal phosphorus loading via sediment release and aquatic plants was viewed as the most significant controllable sources. The restoration plan recommended aluminum sulfate (alum) to control sediment P release and mechanical harvesting to remove plant phosphorus. Harvesting would also provide recreational benefits and control any increased plant colonization made possible by improved water clarity. Both lakes were treated with liquid alum during Fall 1985, and the harvesting program was implemented in Summer 1986. The 1986 post restoration values indicate a dramatic improvement in the quality of Erie Lake. Mean summer total phosphorus concentrations were re...

Evaluation of the Phosphorus–Chlorophyll Relationship for Lakes Off the Precambrian Shield in Western Canada

Summer chlorophyll (Chl), spring and summer total phosphorus (TP), and total nitrogen (TN) data were collected from 25 lakes off the Precambrian Shield in Alberta. Contrary to the results reported in previous studies in western Canada, the spring TP–summer Chl relationship (n = 29, r2 = 0.67) and TN:TP ratios were similar to those reported for other north-temperate lakes. However, there was less variation in the summer TP–summer Chl relationship (n = 34, r2 = 0.81) than in the spring TP–summer Chl relationship. This is a result of the variability in the summer TP:spring TP ratio which ranged from 0.5 to 2.9 in these lakes. In the shallow productive freshwater lakes TP concentrations increased dramatically between spring and summer (the average summer TP:spring TP ratio was 1.7), whereas in the thermally stratified freshwater lakes (most of which were partially meromictic) summer TP concentrations were much lower than spring TP concentrations (the mean ratio was 0.7). There was less chlorophyll per unit TP in saline lakes (i.e. lakes with more than 500 mg/L total dissolved solids) than in freshwater lakes.Key words: phosphorus, chlorophyll, western lakes, saline lakes, meromictic lakes