Internal phosphorus loading in Lake Mendota: response to external loads and weather

1997 ◽  
Vol 54 (8) ◽  
pp. 1883-1893 ◽  
Author(s):  
P A Soranno ◽  
S R Carpenter ◽  
R C Lathrop
Keyword(s):  
Interannual Variability ◽  
Standing Stock ◽  
Internal Loading ◽  
Phosphorus Loading ◽  
External Loading ◽  
Lake Mendota ◽  
Water Column Stability ◽  
Green Algal ◽  
External Loads ◽  
P Budget

We quantified summer internal phosphorus (P) loads and all the major P fluxes in Lake Mendota, Wisconsin, a deep stratified eutrophic lake, during two summers of contrasting external loads to determine (i) whether internal loading by entrainment (mixing at the thermocline) is a significant part of the epilimnetic P budget and (ii) what factors lead to interannual variability in internal loading. We estimated variables for the P budget weekly (standing stock, sedimentation) or daily (outflow, inflow, and entrainment) during a summer of average runoff (1992) and one of higher than average runoff (1993). Entrainment, estimated by calculating the amount of P transported into the epilimnion after the thermocline deepened following storms, was about 10 times higher than external loading during 1992, but was about equal to external loading during 1993. When entrainment was included, the epilimnetic P budget balanced. Interannual variability in internal loading appears to be due to a combination of water column stability, weather, and the P levels accumulated in the metalimnion. External loads to the epilimnion during summer 1993 were much higher than in 1992 (7.0 and 0.9 mg P ·m-2 ·day-1, respectively); however, total loads (internal + external) were more similar (12.5 and 7.8 mg P ·m-2 cdot day-1 in 1993 and 1992, respectively). Although summer chlorophyll concentrations were similar in the two summers, blue-green algal biomass in 1993 was about double that in 1992.

Models of phosphorus turn-over in a hypertrophic lake: the Lake Swarzędzkie case study

2010 ◽  
Vol 39 (3) ◽  
Author(s):  
Katarzyna Kowalczewska-Madura ◽  
Ryszard Gołdyn
Keyword(s):  
Soluble Reactive Phosphorus ◽  
Internal Loading ◽  
Phosphorus Cycling ◽  
Phosphorus Loading ◽  
External Loading ◽  
Lake Ecosystem ◽  
Phytoplankton Primary Production ◽  
Hypertrophic Lake ◽  
Turn Over

Models of phosphorus turn-over in a hypertrophic lake: the Lake Swarzędzkie case studyPhosphorus cycling between components of the ecosystem of the hypertrophic Lake Swarzędzkie was studied in 2000-2003. The results of this study revealed considerable seasonal variation in phosphorus cycling. The main sources of phosphorus load in winter were the tributaries, whereas in summer internal loading prevailed. However, the most effective source of SRP (soluble reactive phosphorus) for phytoplankton primary production in summer was its excretion by organisms from the microbial loop. The share of this source in the total phosphorus pool was 38%, whereas internal loading contributed 23.7%, external loading 16.3%, and regeneration by metazooplankton 22%. This exerted a significant influence on the functioning of the whole lake ecosystem. Limiting both external and internal phosphorus loading is recommended to facilitate water quality improvement in the lake.

Phosphorus loading reductions needed to control blue-green algal blooms in Lake Mendota

1998 ◽  
Vol 55 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Richard C Lathrop ◽  
Stephen R Carpenter ◽  
Craig A Stow ◽  
Patricia A Soranno ◽  
John C Panuska
Keyword(s):  
Algal Blooms ◽  
Management Practices ◽  
Phosphorus Loading ◽  
Balance Model ◽  
Load Reduction ◽  
Lake Water Quality ◽  
Time Step ◽  
Data Set ◽  
Lake Mendota ◽  
Green Algal

We evaluated the reductions in P loading needed to control blue-green algal blooms in Lake Mendota, Wisconsin. After developing a 21-year loading data set, we used a P mass balance model expressed as a difference equation with an annual time step indexed from mid-April. We defined and estimated a loss parameter lambda as the proportion of the lake's April P concentration lost through sedimentation and outflow during the following year. Using the distribution of annual lambda 's and input loadings, we predicted the steady-state distribution of April P concentrations that would result from scenarios of altered inputs due to changes in management practices. These results were then linked to the probability of summer blue-green algal blooms. For no load reduction, the probability of a bloom (>2 mg algae ·L-1) on any summer day is about 60%. This probability decreases to 20% with a load reduction of 50%. Our approach illustrates how managers can consider reducing the frequency of extreme events like algal blooms, which may correspond more to the public's perception of lake water quality than average conditions.

Relative Importance of Phosphorus Supply to Phytoplankton Production: Fish Excretion versus External Loading

1990 ◽  
Vol 47 (2) ◽  
pp. 364-372 ◽  
Author(s):  
Åge Brabrand ◽  
Bjørn Andreas Faafeng ◽  
Jens Petter Moritz Nilssen
Keyword(s):  
Algal Growth ◽  
Perca Fluviatilis ◽  
Rutilus Rutilus ◽  
Phosphorus Release ◽  
Selenastrum Capricornutum ◽  
Phosphorus Loading ◽  
External Loading ◽  
Phytoplankton Production ◽  
Roach Rutilus Rutilus ◽  
Order Of Magnitude

In laboratory tanks with bream (Abramis brama), perch (Perca fluviatilis), and roach (Rutilus rutilus) concentrations of phosphorus and nitrogen increased with time. Phosphorus was mainly released as soluble molybdate-reactive phosphorus (SRP); nitrogen almost exclusively as ammonium. The release increased with the species' tendency to forage on littoral sediments and with a smaller fish size. Bioassays with the test algae Selenastrum capricornutum showed that released phosphorus was readily available to algal growth. The total supply of phosphorus to the epilimnion of Lake Gjersjøen was calculated from the external supply from the tributaries and the estimated phosphorus release from total roach biomass. From May to October 1980 phosphorus release from the roach population contributed about the same order of magnitude as the total phosphorus loading from the watershed. During the period with the most serious phosphorus depletion to the phytoplankton (July, August, and September), the phosphorus supply from fish was about double that of the external phosphorus supply, confirming the important role of sediment-feeding fish populations in the eutrophication processes of lakes.

scholarly journals Retention and Internal Loading of Phosphorus in Shallow, Eutrophic Lakes

2001 ◽  
Vol 1 ◽  
pp. 427-442 ◽  
Author(s):  
Martin Sondergaard ◽  
Peder Jens Jensen ◽  
Erik Jeppesen
Keyword(s):  
Water Quality ◽  
Lake Water ◽  
Recovery Period ◽  
Internal Loading ◽  
External Loading ◽  
Lake Water Quality ◽  
Eutrophic Lakes ◽  
P Release ◽  
P Accumulation

This paper gives a general overview of the nature and important mechanisms behind internal loading of phosphorus (P), which is a phenomenon appearing frequently in shallow, eutrophic lakes upon a reduction of the external loading. Lake water quality is therefore not improved as expected. In particular summer concentrations rise and P retention may be negative during most of the summer. The P release originates from a pool accumulated in the sediment when the external loading was high. In most lake sediments, P bound to redox-sensitive iron compounds or P fixed in more or less labile organic forms constitute major fractions forms that are potentially mobile and eventually may be released to the lake water. The duration of the recovery period following P loading reduction depends on the loading history, but it may last for decades in lakes with a high sediment P accumulation. During the phase of recovery, both the duration and net P release rates from the sediment seem to decline progressively. Internal P loading is highly influenced by the biological structure as illustrated by lakes shifting from the turbid to the clearwater state as a result of, for example, biomanipulation. In these lakes P concentrations may be reduced to 50% of the pre-biomanipulation level and the period with negative retention during summer can thus be reduced considerably. The duration of internal loading can be reduced significantly by different restoration methods such as dredging to remove accumulated P or addition of iron or alum to elevate the sorption capacity of sediments. However, an important prerequisite for achieving long-term benefits to water quality is a sufficient reduction of the external P loading.

Interannual variability of phytoplankton productivity and related parameters in Lake Constance: no response to decreased phosphorus loading?

1991 ◽  
Vol 13 (4) ◽  
pp. 755-777 ◽  
Author(s):  
Max M. Tilzer ◽  
Ursula Gaedke ◽  
Anette Schweizer ◽  
Bärbel Beese ◽  
Thomas Wieser
Keyword(s):  
Interannual Variability ◽  
Phosphorus Loading ◽  
Lake Constance ◽  
Phytoplankton Productivity

scholarly journals The Red Harmful Plague in Times of Climate Change: Blooms of the Cyanobacterium Planktothrix rubescens Triggered by Stratification Dynamics and Irradiance

2021 ◽  
Vol 12 ◽  
Author(s):  
Deborah Knapp ◽  
Bieito Fernández Castro ◽  
Daniel Marty ◽  
Eugen Loher ◽  
Oliver Köster ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Survival Rates ◽  
Standing Stock ◽  
Keystone Species ◽  
Weather Conditions ◽  
High Survival ◽  
Negative Consequences ◽  
Planktothrix Rubescens ◽  
Water Column Stability ◽  
Long Term Study

Planktothrix rubescens is a harmful planktonic cyanobacterium, forming concentrated metalimnetic populations in deep oligo- and mesotrophic lakes, even after successful restoration. In Lake Zurich (Switzerland), P. rubescens emerged as a keystone species with annual mass developments since the 1970s. Its success was partly attributed to effects of lake warming, such as changes in thermal stratification and seasonal deep mixing. However, recent observations based on a biweekly monitoring campaign (2009–2020) revealed two massive breakdowns and striking seasonal oscillations of the population. Here, we disentangle positive from negative consequences of secular lake warming and annual variations in weather conditions on P. rubescens dynamics: (i) despite the high survival rates of overwintering populations (up to 25%) during three consecutive winters (2014–2016) of incomplete deep convective mixing, cyanobacterial regrowth during the following stratified season was moderate and not overshooting a distinct standing stock threshold. Moreover, we recorded a negative trend for annual population maxima and total population size, pointing to a potential nutrient limitation after a series of incomplete winter mixing. Thus, the predication of steadily increasing blooms of P. rubescens could not be confirmed for the last decade. (ii) The seasonal reestablishment of P. rubescens was strongly coupled with a timely formation of a stable metalimnion structure, where the first positive net growth in the following productive summer season was observed. The trigger for the vertical positioning of filaments within the metalimnion was irradiance and not maximal water column stability. Repetitive disruptions of the vernal metalimnion owing to unstable weather conditions, as in spring 2019, went in parallel with a massive breakdown of the standing stock and marginal regrowth during thermal stratification. (iii) Driven by light intensity, P. rubescens was entrained into the turbulent epilimnion in autumn, followed by a second peak in population growth. Thus, the typical bimodal growth pattern was still intact during the last decade. Our long-term study highlights the finely tuned interplay between climate-induced changes and variability of thermal stratification dynamics and physiological traits of P. rubescens, determining its survival in a mesotrophic temperate lake.

Influence of External Loads on Thin Film Cracking

2004 ◽  
Author(s):  
Srinath S. Chakravarthy ◽  
Eric H. Jordan ◽  
Wilson K. S. Chiu
Keyword(s):  
Thin Film ◽  
External Load ◽  
Crack Arrest ◽  
External Loading ◽  
Element Analysis ◽  
Film Cracking ◽  
Two Parameters ◽  
Improved Accuracy ◽  
External Loads

Cracking in thin films under the combined influence of residual stress and an external load is examined. An improved accuracy version of the existing solution for substrate cracking absent the external load is provided. A superposition scheme that uses the solution for substrate cracking and other existing published solutions is presented for the determination of the energy release rate. The superposition scheme is validated using finite element analysis, and conditions under which the superposition scheme is valid are discussed. Crack arrest is examined and two parameters that determine the possibility of crack arrest are identified. The influence of external loading on channelling behavior in the substrate is discussed.

A calculation of the external loading is in the drive of cage of reduction figure

2020 ◽  
pp. 53-54
Author(s):  
L.A. Chumakova
Keyword(s):  
Peak Load ◽  
External Loading ◽  
Rolling Moment ◽  
Pipe Rolling ◽  
Reduction Mill ◽  
Load Action ◽  
External Loads

The calculation of external loads is proposed to determine the rolling moment depending on the time of peak load action at different steady rolling moments in the stand of the reduction mill. Keywords pipe, rolling, algorithm, calculation, stand, moment. [email protected]

Sign in / Sign up

Export Citation Format

Share Document