scholarly journals Piscivores, Trophic Cascades, and Lake Management

2002 ◽  
Vol 2 ◽  
pp. 284-307 ◽  
Author(s):  
Ray W. Drenner ◽  
Ray K. David Hambright
Keyword(s):  
Total Phosphorus ◽  
Phytoplankton Biomass ◽  
Field Experiments ◽  
Experimental Testing ◽  
Management Strategies ◽  
Lake Management ◽  
Zooplankton Biomass ◽  
Phosphorus Concentration ◽  
Cascading Trophic Interactions ◽  
Lake Systems

The concept of cascading trophic interactions predicts that an increase in piscivore biomass in lakes will result in decreased planktivorous fish biomass, increased herbivorous zooplankton biomass, and decreased phytoplankton biomass. Though often accepted as a paradigm in the ecological literature and adopted by lake managers as a basis for lake management strategies, the trophic cascading interactions hypothesis has not received the unequivocal support (in the form of rigorous experimental testing) that might be expected of a paradigm. Here we review field experiments and surveys, testing the hypothesis that effects of increasing piscivore biomass will cascade down through the food web yielding a decline in phytoplankton biomass. We found 39 studies in the scientific literature examining piscivore effects on phytoplankton biomass. Of the studies, 22 were confounded by supplemental manipulations (e.g., simultaneous reduction of nutrients or removal of planktivores) and could not be used to assess piscivore effects. Of the 17 nonconfounded studies, most did not find piscivore effects on phytoplankton biomass and therefore did not support the trophic cascading interactions hypothesis. However, the trophic cascading interactions hypothesis also predicts that lake systems containing piscivores will have lower phytoplankton biomass for any given phosphorus concentration. Based on regression analyses of chlorophyll�total phosphorus relationships in the 17 nonconfounded piscivore studies, this aspect of the trophic cascading interactions hypothesis was supported. The slope of the chlorophyll vs. total phosphorus regression was lower in lakes with planktivores and piscivores compared with lakes containing only planktivores but no piscivores. We hypothesize that this slope can be used as an indicator of “functional piscivory” and that communities with extremes of functional piscivory (zero and very high) represent classical 3- and 4-trophic level food webs.

Forest harvest impacts on water quality and aquatic biota on the Boreal Plain: introduction to the TROLS lake program

2001 ◽  
Vol 58 (2) ◽  
pp. 421-436 ◽  
Author(s):  
E E Prepas ◽  
B Pinel-Alloul ◽  
D Planas ◽  
G Méthot ◽  
S Paquet ◽  
...  
Keyword(s):  
Total Phosphorus ◽  
Drainage Basin ◽  
Zooplankton Biomass ◽  
Phosphorus Concentration ◽  
Zooplankton Abundance ◽  
Total Phosphorus Concentration ◽  
Buffer Strip ◽  
Stratified Lakes ◽  
Lake Volume ◽  
Order Of Magnitude

Eleven headwater lakes in Alberta's Boreal Plain were monitored for nutrients and plankton 2 years before and 2 years after variable watershed harvesting (harvesting mean 15%, range 0-35%). After harvesting, variations in annual precipitation resulted in lake water residence times that differed by an order of magnitude from one year to the next. During the first posttreatment year, total phosphorus concentrations increased (overall 40%) in most lakes; however, response was most consistent in lakes that were shallow and the water column mixed or weakly thermally stratified. Chlorophyll a, cyanobacteria (Aphanizomenon-Anabaena), and cyanotoxins (microcystin-LR) increased after harvesting, primarily in shallow lakes. Zooplankton abundance and biomass decreased after harvesting, particularly in stratified lakes where edible phytoplankton biomass declined. In the weakly or nonstratified lakes, declines in zooplankton biomass were associated with higher cyanobacterial biomass and cyanotoxins. Posttreatment change in total phosphorus concentration was strongly related to weather (greatest response in a wet year) and relative drainage basin size (drainage basin area to lake volume, r2 = 0,78, P << 0,01). There was no evidence that buffer strip width (20, 100, and 200 m) influenced lake response. These results suggest that activities within the entire watershed should be the focus of catchment-lake interactions.

Empirical Prediction of Crustacean Zooplankton Biomass in Nutrient-Poor Canadian Shield Lakes

1986 ◽  
Vol 43 (4) ◽  
pp. 788-796 ◽  
Author(s):  
N. D. Yan
Keyword(s):  
Total Phosphorus ◽  
Trophic State ◽  
Zooplankton Biomass ◽  
Canadian Shield ◽  
Phosphorus Concentration ◽  
Trophic State Index ◽  
Entire Study ◽  
South Central ◽  
Wide Range ◽  
Shield Lakes

A comparison of the predictive power of nine existing empirical zooplankton biomass models indicated that lake water phosphorus concentration may be a better predictor of zooplankton biomass in Canadian Shield lakes than phytoplankton biomass, chlorophyll a, midsummer epilimnetic temperature, mean surface water temperature, mean depth, and Carlson's trophic state index. To develop models specifically applicable to nutrient-poor Canadian Shield lakes, a variety of morphometric, chemical, and planktonic parameters were assessed for three consecutive years from 16 Canadian Shield lakes in south-central Ontario. Total nitrogen was the best univariate predictor of zooplankton biomass for data averaged over single ice-free seasons, but total phosphorus was the best predictor when data were averaged over the entire study period. Consideration of pH and maximum depth improved certain models. Total phosphorus is clearly a good predictor of (long-term) average zooplankton biomass in nutrient-poor lakes as it is in lakes exhibiting a wide range in trophic state.

Leaf acid phosphatase isozymes in the diagnosis of phosphorus status in field-grown wheat

1987 ◽  
Vol 38 (1) ◽  
pp. 1 ◽  
Author(s):  
KD McLachlan ◽  
DE Elliot ◽  
DGde Marco ◽  
JH Garran ◽  
Marco DG De
Keyword(s):  
Acid Phosphatase ◽  
Grain Yield ◽  
Total Phosphorus ◽  
Field Experiments ◽  
Phosphorus Deficiency ◽  
Wheat Plant ◽  
Phosphorus Concentration ◽  
Total Phosphorus Concentration ◽  
Residual Phosphorus ◽  
Stages Of Growth

This study examined the inorganic and total phosphorus in wheat plant tops, along with the phosphatase activity and the phosphatase isozymes occurring in the youngest fully expanded leaves, from two field experiments done in 1983 and I984 at two sites in South Australia. Twelve levels of phosphorus were used in the first year, and split plots in the second year allowed the effects of current and/or residual phosphorus treatments to be determined.The inorganic or total phosphorus concentration, or content per plant, could be related to plant and grain yield, but values relative to phosphorus deficiency varied between different stages of growth and between sites. Relationships with inorganic phosphorus were no better than those with total phosphorus.Leaf acid phosphatase assays were a better measure, providing similar values relative to plant deficiency between sites, between seasons and irrespective of whether current or residual phosphorus was the source, but the values varied with plant age.The phosphatase zymograms identified an isozyme which appeared when plants were deficient in phosphorus. It did not appear when they were adequately supplied. The isozyme appeared at all stages of growth to anthesis, and from late tillering through to heading was related to grain yield at both sites, in both seasons and whether freshly applied or residual phosphorus was the source of supply. For diagnostic purposes, specific sets of standards would be required for the phosphorus and phosphatase assays. They would not be required for the phosphatase zymograms.

Empirical Prediction of Crustacean Zooplankton Biomass and Profundal Macrobenthos Biomass in Lakes

1984 ◽  
Vol 41 (3) ◽  
pp. 439-445 ◽  
Author(s):  
John Mark Hanson ◽  
Robert Henry Peters
Keyword(s):  
Surface Area ◽  
Multiple Regression ◽  
Chlorophyll A ◽  
Total Phosphorus ◽  
Zooplankton Biomass ◽  
Crustacean Zooplankton ◽  
Phosphorus Concentration ◽  
Lake Surface ◽  
Total Phosphorus Concentration ◽  
Lake Surface Area

We used data taken from the literature to develop and compare several estimators of crustacean zooplankton biomass (49 lakes) and profundal macrobenthos biomass (38 lakes). Both mean zooplankton biomass (r2 = 0.72, P < 0.001) and mean profundal macrobenthos biomass (r2 = 0.48, P < 0.001) correlated better with mean total phosphorus concentration than with Secchi depth, mean depth, maximum depth, or lake surface area. Mean total phosphorus concentration was also superior to mean chlorophyll a concentration (r2 = 0.57, P < 0.001) as an estimator of zooplankton biomass, but data were insufficient to evaluate chlorophyll a concentration as an estimator of macrobenthos biomass. Inclusion of maximum depth as a variable in a multiple regression resulted in a slight but significant (P < 0.030) improvement in the zooplankton–total phosphorus relationship (R2 = 0.75, P < 0.001). Inclusion of lake surface area as a variable in a multiple regression significantly (P < 0.001) improved the predictive power of the profundal macrobenthos–total phosphorus relationship (R2 = 0.59, P < 0.001).

Seasonal pattern and inferred phosphorus limitation of phytoplankton biomass in two tropical reservoirs in northern Australia

2000 ◽  
Vol 51 (1) ◽  
pp. 91 ◽  
Author(s):  
Simon A. Townsend
Keyword(s):  
Chlorophyll A ◽  
Total Phosphorus ◽  
Phytoplankton Biomass ◽  
Seasonal Pattern ◽  
Phosphorus Concentration ◽  
Wet Season ◽  
Temperate Lakes ◽  
Total Phosphorus Concentration ◽  
River Reservoir ◽  
Annual Range

Manton River Reservoir (MRR) and Darwin River Reservoir (DRR) are two small impoundments in the Australian wet/dry tropics. Over an eight-year period, chlorophyll a concentrations in the mixed layer averaged 3.6 µg L−1 in DRR, and 7.1 µg L−1 in MRR. The seasonal pattern of chlorophyll a at MRR was influenced by wet season wash-out (February average 4.8 µg L−1 ), and dry season destratification and nutrient enrichment of the surface waters (July average 8.4 mg L−1 ). In contrast, DRR exhibited near uniform chlorophyll a concentrations over the year. The seasonal patterns of DRR and MRR chlorophyll a are typical of tropical water bodies which tend to have a smaller annual range than temperate lakes, though this can be modified by significant wash-out. Empirical evidence suggests that the phytoplankton biomass of each reservoir is phosphorus limited, relative to the potential provided by other nutrients and light energy. This conclusion is based on a regression of total phosphorus and chlorophyll a concentrations of pooled DRR and MRR data (P < 0.001; r2 = 0.90), and the high total-nitrogen to total-phosphorus concentration ratios (by weight) of 50 and 37 in DRR and MRR, respectively. Annual chlorophyll a and total phosphorus concentrations for both reservoirs are in accord with the OECD regression for temperate lakes and reservoirs.

Plant tests for diagnosing phosphorus deficiency in barley (Hordeum vulgare L.)

1999 ◽  
Vol 39 (7) ◽  
pp. 857 ◽  
Author(s):  
S. D. Hoppo ◽  
D. E. Elliott ◽  
D. J. Reuter
Keyword(s):  
Total Phosphorus ◽  
Field Experiments ◽  
Lignin Content ◽  
Phosphorus Deficiency ◽  
Plant Age ◽  
Phosphorus Concentration ◽  
Growth Stages ◽  
Hordeum Vulgare L ◽  
Total Phosphorus Concentration ◽  
Phosphorus Fertiliser

Summary. Six field experiments were conducted in the Murraylands and Mid North regions of South Australia between 1986 and 1988 to develop plant tests for diagnosing the phosphorus status of barley. The effects of applied phosphorus level on total phosphorus concentrations in youngest emerged leaf blades or whole shoots, and on shoot yield, were examined and critical ranges were established during vegetative growth. Experiments were conducted on a range of soil phosphorus levels with several methods of phosphorus placement and 2 barley cultivars. During early tillering, shoot yield and phosphorus concentrations in youngest emerged leaf blades and whole shoots were increased more by drilling phosphorus fertiliser with the seed (banded) than by spreading the same phosphorus rate over the soil surface and partially incorporating the fertiliser while sowing (broadcast). However, these methods of phosphorus placement did not affect diagnostic relationships between relative shoot yield and phosphorus concentrations in youngest emerged leaf blades and, as a result, critical total phosphorus concentrations were similar for both methods of applying phosphorus fertiliser. Estimated critical total phosphorus concentrations for both Schooner and Galleon barley were similar at each sampling time when allowances were made for minor differences in growth stages between the cultivars; even though phosphorus concentrations in youngest emerged leaf blades and whole shoots were higher in Schooner than in Galleon at adequate phosphorus supply. Between Zadoks scale 13.5 and 16.5 there was a linear decline in critical total phosphorus concentration in youngest emerged leaf blades with increasing plant age. A more variable, but steeper, decline was found for critical total phosphorus concentration in whole shoots. Critical ranges are proposed for total phosphorus concentrations in youngest emerged leaf blades and whole shoots of barley. The decline in critical total phosphorus concentration in youngest emerged leaf blades with advancing plant age was mainly caused by a higher functional requirement for phosphorus at early stages of growth and by increasing dry weight, cellulose and lignin content of youngest emerged leaf blades as plants age. Changes in the spatial distribution of applied phosphorus in relation to root growth did not seem to be important.

Lake Paranoá, Brasília, Brazil: Integrated Management Plan for its Restoration

1992 ◽  
Vol 27 (2) ◽  
pp. 271-286 ◽  
Author(s):  
Sonia Paulino Mattos ◽  
Irene Guimarães Altafin ◽  
Hélio José de Freitas ◽  
Cristine Gobbato Brandão Cavalcanti ◽  
Vera Regina Estuqui Alves
Keyword(s):  
Total Phosphorus ◽  
Drainage Basin ◽  
Integrated Management ◽  
Algal Growth ◽  
Nutrient Content ◽  
Management Plan ◽  
Cylindrospermopsis Raciborskii ◽  
Phosphorus Concentration ◽  
Limiting Factor ◽  
Total Phosphorus Concentration

Abstract Built in 1959, Lake Paranoá, in Brasilia, Brazil, has been undergoing an accelerated process of nutrient enrichment, due to inputs of inadequately treated raw sewage, generated by a population of 600,000 inhabitants. Consequently, it shows high nutrient content (40 µg/L of total phosphorus and 1800 µg/L of total nitrogen), low transparency (0.65 m) and high levels of chlorophyll a (65 µg/L), represented mainly by Cylindrospermopsis raciborskii and sporadic bloom of Microcystis aeruginosa, which is being combatted with copper sulphate. With the absence of seasonality and a vertical distribution which is not very evident, the horizontal pattern assumes great importance in this reservoir, in which five compartments stand out. Based on this segmentation and on the identification of the total phosphorus parameter as the limiting factor for algal growth, mathematical models were developed which demonstrate the need for advanced treatment of all the sewage produced in its drainage basin. With this, it is expected that a process of restoration will be initiated, with a decline in total phosphorus concentration to readings below 25 µg/L. Additional measures are proposed to accelerate this process.

scholarly journals Genetic variation of seed phosphorus concentration in winter oilseed rape and development of a NIRS calibration

Euphytica ◽  
2021 ◽  
Vol 217 (4) ◽  
Author(s):  
Jakob Eifler ◽  
Jürgen Enno Wick ◽  
Bernd Steingrobe ◽  
Christian Möllers
Keyword(s):  
Genetic Variation ◽  
Field Experiments ◽  
Seed Quality ◽  
Rapeseed Meal ◽  
Quality Analysis ◽  
Phosphorus Concentration ◽  
Genotypic Differences ◽  
Organic P ◽  
P Concentration ◽  
Total P

AbstractPhytic acid is the major organic phosphorus storage compound in rapeseed. Following oil extraction, the defatted meal is used in feed mixtures for livestock. However, monogastric pigs and chickens can only poorly metabolize phytate. Hence, their excrements are rich in phosphorus (P), which when applied as manure may lead to eutrophication of surface waters. The aim of the present study was to analyze the genetic variation for total and organic P concentration (i.e. mainly phytate) in rapeseed and to compare the results with soybean. Two sets of rapeseed material were tested in field experiments in different environments with varying soil P levels and harvested seeds were used for seed quality analysis. Results revealed significant genotypic differences in total seed P concentration, which ranged from 0.47 to 0.94%. Depending on the experiment, the heritability for total P concentration ranged from 52 to 93%. The organic P portion of total P concentration was above 90% for current rapeseed hybrids. In both sets, there was a significant positive correlation between seed protein and P concentration. A NIRS calibration for total P concentration in intact seeds showed in cross validation a standard error of 0.05% and a coefficient of determination of R2 = 0.83. Total P concentration of soybean seeds and meal was between 0.55 and 0.65%, and around 1.1% for rapeseed meal. Rapeseed meal had a twofold higher ratio of total P to nitrogen concentration as compared to soybean which could be considered adverse when the meal is used for feeding livestock.

scholarly journals Farmers’ Demand for Informal Risk Management Strategy and Weather Index Insurance: Evidence from China

2021 ◽  
Author(s):  
Yingmei Tang ◽  
Huifang Cai ◽  
Rongmao Liu
Keyword(s):  
Risk Management ◽  
Field Experiments ◽  
Management Strategies ◽  
Insurance Companies ◽  
Index Insurance ◽  
Insurance Demand ◽  
Weather Index ◽  
Weather Index Insurance ◽  
Risk Management Strategies ◽  
The Government

AbstractIn the absence of formal risk management strategies, agricultural production in China is highly vulnerable to climate change. In this study, field experiments were conducted with 344 households in Heilongjiang (Northeast China) and Jiangsu (East China) Provinces. Probit and logistic models and independent sample T-test were used to explore farmers’ demand for weather index insurance, in contrast to informal risk management strategies, and the main factors that affect demand. The results show that the farmers prefer weather index insurance to informal risk management strategies, and farmers’ characteristics have significant impacts on their adoption of risk management strategies. The variables non-agricultural labor ratio, farmers’ risk perception, education, and agricultural insurance purchase experience significantly affect farmers’ weather index insurance demand. The regression results show that the farmers’ weather index insurance demand and the influencing factors in the two provinces are different. Farmers in Heilongjiang Province have a higher participation rate than those in Jiangsu Province. The government should conduct more weather index insurance pilot programs to help farmers understand the mechanism, and insurance companies should provide more types of weather index insurance to meet farmers’ diversified needs.

scholarly journals PHOSPHORUS NUTRITION OF SOYBEANS AS AFFECTED BY PLACEMENT OF FERTILIZER PHOSPHORUS

1983 ◽  
Vol 63 (2) ◽  
pp. 199-210 ◽  
Author(s):  
C. W. BULLEN ◽  
R. J. SOPER ◽  
L. D. BAILEY
Keyword(s):  
Glycine Max ◽  
Total Phosphorus ◽  
Dry Matter ◽  
Field Experiments ◽  
Seedling Emergence ◽  
Phosphorus Uptake ◽  
Growth Chamber ◽  
Grain Yields ◽  
Chamber Experiment ◽  
Glycine Max L

Growth chamber and field experiments were conducted on Southern Manitoba soils, low in available soil phosphorus, to investigate the effects of various placement methods and levels of phosphorus fertilizer on soybean (Glycine max (L.) Merrill ’Maple Presto’). It was found that soybean responded well to applied phosphorus on low-P soil in growth chamber studies. In the first growth chamber experiment, P was applied in solution to 100%, 50%, 25%, 12.5% and 1% of the total soil volume. Dry matter yields, total phosphorus uptake and utilization of fertilizer P increased at each level of applied P as the size of the phosphated band was decreased. The results were partly attributed to greater chemical availability of P in the smaller zones of P fertilizer reaction. In a second growth chamber experiment, soybeans responded differently to phosphorus banded in six different locations. Placement of the fertilizer 2.5 cm directly below the seed was more effective in increasing dry matter yield, total phosphorus uptake and fertilizer P utilization than placement 2.5 cm and 5 cm away at the same depth or placement 5 cm below the seed, whether the band was directly below, 2.5 cm away or 5 cm away. Soybean yield responses in the field were greatest with P banded 2.5 cm directly below the seed on low-P soils. Placement of P 2.5 cm below the seed resulted in grain yields that were 64% and 50% higher (at the two sites) than those obtained in control plots. Sidebanding P, 2.5 cm below and 2.5 cm away from the seed at the same level of application, improved grain yields of control plots by 40% and 39%. Seed placement and broadcast applications of P were not as effective in increasing grain yields. Broadcasting P in fall or in spring at rates of up to 52.38 kg P/ha did not result in significantly higher grain yields than those obtained in control plots. Placement of P in contact with the seed appeared to reduce seedling emergence, resulting in depressed yields when 52.38 kg P/ha were applied. Key words: Glycine max L. Merrill, ’Maple Presto’

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