The Seasonal Dynamics and Trophic Relations of the Plankton Components in Lake Peipsi (Peipus)

The seasonal dynamics of the biomass and production of phyto-, zoo- and bacterioplankton was investigated during the vegetation periods (from May to November) in 1985 and 1986 in the pelagial of the large eutrophic lake Peipsi (Estonia). The average values of productions per vegetation period for the investigation years were as follows: phytoplanktion − 203.5 gC · m⁻²; bacterioplankton − 37.9 gC · m⁻²; filter-feeding zooplankton − 20.6 gC · m⁻² and predatory zooplankton − 1.5 gC · m⁻². The herbivorous zooplankton production constituted 10.1% of primary production. This ratio indicates a direct relationship between zoo- and phytoplankton in the food chain — filtrators are feeding mostly on living algae and the detrital food chain seems of little importance. The dominance of large forms (Melosira sp., Aphanothece saxicola), in the phytoplankton during the major part of the vegetation period is assumed to be a result of high grazing pressure on small algae. Zooplankton grazing was investigated in situ in a specially constructed twin bathometer. Experimental measurements revealed, that zooplanktion presence in the experimental vessel actually stimulated the phytoplankton growth in many cases — the negative grazing values have been registered. That could be caused by the stimulation effect of nutrients (N, P), excreted by the concentrated zooplankton in the grazing chamber, which led to an increase of the nongrazed phytoplankton production. Bacteria have satisfied the zooplankton food requirements on average by 11%. Grazing on bacteria increased, when grazing on phytoplankton was somehow disturbed.     

Production and Ecology of Benthic Chironomid Larvae (Diptera) in Lake Hayes,New Zealand,a Warm-monomictic Eutrophic Lake

The distribution and abundance of larval chironomids in Lake Hayes were studied from December 1973 to March 1975. The mean annual production of the two dominant species, Chironomus zealandicus and Chironomus sp. a, was 29.2 g m⁻² dry weight which is approximately 4.3 % of the average annual phytoplankton production in the lake. A high annual P/B ratio of 18.5 is consistent with the multivoltine life cycle of C. zealandicus. Larval chironomid production in the second summer when Anabaena blooms were absent was only one quarter of that in the first summer and is consistent with the hypothesis that the production of benthic chironomids in Lake Hayes is closely linked to that of the phytoplankton through the sedimentation of autochthonous organic matter.     

Seston dynamics and tripton sedimentation in the pelagic zone of a shallow eutrophic lake

The transport of organic matter from the water column to the sediment and the relationship between the dynamics of the settleable fraction and that of the total suspended particulate matter were studied in shallow eutrophic Lake Wingra, Wisconsin. Tripton sedimentation was closely related to the dynamics of seston with a lag of 2 to 4 weeks. Sedimentation rate of tripton ranged from 0 to 8 g m^–2 day^–1 (in May and August respectively). Relative t0 the standing crop 0f seston the maximum sedimentation rate was 8% seston per day (in September). The annual tripton sedimentation was estimated at 632 g dry weight or 215 g C per m² which was equivalent t0 55% of the annual phytoplankton production and 42% of the phytoplankton and macrophytes annual production. It was estimated that 70% of the settling organic matter is decomposed annually, consequently only a small fraction 0f tripton is involved in the long term accumulation of bottom deposits. Factors influencing tripton sedimentation are discussed.Research supported by the Eastern Deciduous Forest Biome US-IBP, funded by the National Science Foundation under Interagency Agreement AG-199 BMS69-01147 A09 with the Energy Research and Development Administration-Oak Ridge National Laboratory. Contribution N0. 233 from the Eastern Deciduous Forest Biome US-IBP.Research supported by the Eastern Deciduous Forest Biome US-IBP, funded by the National Science Foundation under Interagency Agreement AG-199 BMS69-01147 A09 with the Energy Research and Development Administration-Oak Ridge National Laboratory. Contribution N0. 233 from the Eastern Deciduous Forest Biome US-IBP.     

Response of plankton to nutrients,planktivory and terrestrial organic matter: a model analysis of whole‐lake experiments

Terrestrial organic matter can be assimilated by aquatic consumers but implications for biomass and production are unresolved. An ecosystem model was fit to estimate effects of phosphorus (P) load, planktivory, and supply rate of terrestrial particulate organic carbon (TPOC) on phytoplankton and zooplankton in five whole‐lake experiments. Phytoplankton biomass increased with P load and planktivory and decreased with TPOC supply rate. Zooplankton biomass increased with P load and responded weakly to planktivory and TPOC supply rate. Zooplankton allochthony (proportion of carbon from terrestrial sources) decreased with P load and planktivory and increased with TPOC supply rate. Lakes with low allochthony (< 0.3) had wide ranges of phytoplankton and zooplankton biomass and production, depending on P load and planktivory. Lakes with high allochthony (> 0.3) had low biomass and production of both phytoplankton and zooplankton. In summary, terrestrial OC inhibits primary production and is a relatively low‐quality food source for zooplankton.     

Contemporary state of the zooplankton in Lake Peipsi

L. Peipsi is one of the richest fish lakes in Europe. Planktivorous smelt dominates in the fish fauna. The abundance of zooplankton fluctuates between 43 600–2241 500 ind m^–3, with the average 974 000 ind m^–3, biomass ranges from 0,09–3,69 g m^–3, with the average 1,86 g m^–3. Since the 1960s the abundance of rotifers has risen considerably while the mean zooplankter weight (B/N) has decreased from 0.005 mg to 0.004 mg. Zooplankton production (herbivores 20.6, predators 1.8, whole zooplankton community 22.4 g C m^–2 per period between May and October) can be considered high. Predatory zooplankton eats on an average 50% of the production of herbivorous zooplankton; about 50% of the whole zooplankton production (P_{Filt + Pred}) reaches fishes. The production of herbivorous zooplankton constitutes 10.1% of primary production. This ratio indicates a direct relationship between zoo- and phytoplankton in the food chain; the detrital food chain seems of little importance. About 6% of phytoplankton energy reaches fishes. The transformation of energy in the food web is efficient. On the basis of zooplankton L. Peipsi can be considered a moderately eutrophic or meso-eutrophic lake.     

Long-term changes in zooplankton abundance and water transparency in Lake Geneva

The water quality of Lake Geneva has declined steadily since the 1960s, due to a continuous increase of external phosphorus loading. Average P level in the lake increased steadily to a peak in 1979, and even 1981 in the case of P content in the trophogenic layer. Since then, reduced external inputs related to the delayed effects of phosphorus removal from waste waters initiated many years previously has led to a decrease in P level, and resulted in present stabilization and even improvement in water quality. Long-term changes in zooplankton abundance correspond quite closely to eutrophication level changes. After increasing since the 1960s, maximum zooplankton biomass was recorded for the first time in 1971; a second main peak appeared in 1981 together with the highest eutrophication level. Over the last seven years, zooplankton abundance has decreased continuously, while water transparency has decreased and phytoplankton production has remained at a high level.     

Experiments with Large Enclosures in a Fertile,Shallow, Brackish Lake,Hickling Broad,Norfolk, United Kingdom

Events in the plankton community of a 120 ha, shallow (1.2 m), brackish lake have been studied with the help of two watertight enclosures, each of which isolated about 300 m³ of water and its underlying sediment. Analyses of soluble reactive phosphorus, total phosphorus, ammonia-N, nitrate-N, silicate-Si, chloride, photosynthetic pigments, phytoplankton and zooplankton counts are reported and are related to inputs of nitrogen and phosphorus into the lake from adjoining basins and the catchment, and to the hydrologic regime. The inputs of phosphorus are budgeted and a very large roost of black-headed gulls appears to provide most of the phosphorus supply. The results are discussed with reference to the eutrophication of the lake and decline of aquatic macrophytes which have occurred in the past ten years.     

An Analysis of the Biotic Community in a Kumaun Himalayan Lake,Nainital (U. P.), India

A comprehensive study of phyto- and zooplankton and macrozoobenthic components in Lake Nainital showed that species richness was high for plankton and low for macrozoobenthos. The algal biomass was dominated by greens (54 %) and blue-greens (31 %), the zooplankton population by copepods (84 %), and the macrozoobenthic community by a Tubifex-Chironomus association constituting≥95 % of the annual number of the macrobenthic invertebrates. Respiration (807.5g C m⁻² year⁻¹) surpassed gross production (630.5 g C m⁻² year⁻¹). The mean annual ratio between phyto- and zooplankton biomass is 3.3 and between phytoplankton and herbivores it is 4.6. If biomass is treated as a measure of crude production, the relationship among the three trophic levels suggests that herbivory is inefficient while carnivory is efficient, because part of the primary production remains unutilized by dominant herbivorous zooplankters, whereas Mesocyclops leuckarti, the sole carnivore, feeds efficiently on rotifers and juveniles of other copepods. The low diversity of different biotic components and the P/R ratio of less than 1 perhaps suggest that the lake is passing through the stage of heterotrophic succession.     

Can results from limnocorral experiments be transferred to in situ conditions?

In 1982–1984 eight limnocorral (LC) experiments, each lasting for two weeks, were performed in mesotrophic Lake Lucerne, Switzerland, to study the effects of biomanipulation (removal of crustaceans by 95 µm filter nets) on zooplankton — phytoplankton relationships and epilimnetic carbon and phosphorus fluxes. Seston concentrations and to a lesser extent primary production rates were reduced in control LCs through zooplankton grazing, and settling flux increased through fecal pellet production. But C and P regeneration were not significantly affected.We found several indications that the LCs, despite of their large size ( 70 m³, 3 m in diameter and 11 m long) were artificial systems when compared to the surrounding lake: The eddy diffusion was diminished by about one order of magnitude, nutrients depleted (but phosphorus was supplied to the LCs), the phyto- and zooplankton showed lower standing crops in the control LCs than in the lake, the phytoplankton showed a shift from nannoplankton to netplankton, the crustacean zooplankton was mostly limited in their vertical migration, and the POC and PP sedimentation rates were increased. Moreover, in our set of experiments we always found outliers, which may have been caused by the different in situ conditions at the beginning of the experiments, and further enhanced by the complexity of the enclosed system.The problems of the LC-technique, such as replicability, scaling (size and time) and data extrapolation are discussed. The impact of crustacean zooplankton on particulate matter, i.e. seston reduction and sedimentation enhancement, can be extrapolated on a qualitative rather than on a quantitative basis for the Lake Lucerne ecosystem.     

Organic Carbon Flux to a Large Salt Lake: Pyramid Lake,Nevada, USA

Energy flux to a large, deep, salt lake from phytoplankton, periphyton and macrophyte primary production as well as fluvial transport and wind-transported terrestrial vegetation and dust were quantified. Average areal phytoplankton net photosynthesis was 511 mg C m⁻² d⁻¹. Highest rates were during water-blooms of the bluegreen alga, Nodularia spumigena. Although areal daily net photosynthesis by periphyton in Pyramid Lake was comparable to other salt lakes, annual carbon influx by periphyton was small due to the lake's graben morphology and moderate euphotic depth (mean, 11.9 m). Macrophytes were uncommon and, therefore a minor source of energy. Truckee River is the only major fluvial discharge to Pyramid Lake and dissolved organic carbon was the principal organic carbon fraction in river water. Large upstream water diversions coupled with several drought years resulted in an average fluvial organic carbon load of only 7.3 g Cm⁻²y⁻¹ or 4% of median phytoplankton net photosynthesis. Tumbleweeds were the most common terrestrial plant material observed in Pyramid Lake comprising a maximum projected importance of 6% of total annual carbon input. Windborne dust represented < .1% of annual carbon input. Phytoplankton primary production is the predominant energy source to Pyramid Lake, accounting for over 80% of annual carbon influx. The relative magnitude of autochthonous and allochthonous vectors to the annual carbon budget of this desert salt lake are comparable to those of the few other large lakes for which detailed energy input budgets have been calculated.     

The Mechanism Controlling Plant Nutrient Concentrations in the Northern Adriatic Sea

A 20 year data set for the northern Adriatic was analyzed and the factors establishing the nutrient environment identified. Concentrations ranged widely (TIN 0.0–78, PO₂ 0.01–1.1, and SiO₄ 0.0–59 mmol m⁻³). In early winter remineralization increased concentrations. Characteristic winter, late spring and fall phytoplankton blooms alternately decreased and increased concentrations, as modified by river input. In summer nutrients were minimal under a semi-closed circulation pattern and high vertical stability, due to closely coupled nitrogen and phosphorus assimilation-regeneration processes and biogenic silica sedimentation. “New” primary production supported mainly by river input of “new” nutrients approximated “regenerated” primary production supported by regenerated nutrients, making the ecosystem especially sensitive to eutrophication pressure from anthropogenic increases in the Po River nutrient load.     

Limnological Studies in a Tropical Man-Made Lake (Lagartijo Reservoir) Venezuela

The purpose of this study was to evaluate the present limnological conditions of Lagartijo reservoir (North central Venezuela) and to compare them with conditions reported in early studies. Lagartijo reservoir supplies an important part of the water demand for Caracas city and wide fluctuations on water volume occur annually. Relevant physical, chemical and biological data were obtained from three sampling stations between July 1990 and April 1992. The reservoir was permanently stratified with a well defined thermocline. The main tributary (Lagartijo river), with a temperature about 6° C colder than the surface temperature of the reservoir, flows through the hypolimnion producing distinct chemical and biological properties. The average of the daily integral phytoplankton photosynthesis was 1550 mg C m⁻² d⁻¹. The present annual average of the net photosynthetic activity is about 40% lower than the reported for 1970 and corresponds to an apparent decrease in phytoplankton biomass and to the reduction of the euphotic zone. Photosynthetic activity was higher for the wet season than for the dry season. Actual chlorophyll a concentration in the euphotic zone averages 4.9 μg l⁻¹. Abundance of zooplankton was significantly decreased in comparison to 1976. Mean zooplankton biomass (dry weight) for the upper 10 m layer was 596 μg l⁻¹. Copepods accounted for most of this biomass, followed by cladocerans and rotifers. For the first time, a freshwater medusa (probably Craspedacusta sowerbyi) was collected from Venezuelan waters.     

Zooplankton and bacteria contribution to phosphorus and nitrogen internal cycling in a tropical and eutrophic reservoir: Pampulha Lake,Brazil

Nutrient regeneration and respiration rates of natural zooplankton from a tropical reservoir were experimentally measured. Excretion rates of ammonia (E_a), orthophosphate (E_p) and community respiration rates (R) were estimated considering the variations in the concentrations of ammonia, orthophosphate and dissolved oxygen between control and experimental units. The ranges obtained for these rates from the 2 h assays were E_a = 1.95–4.95 μg N-NH₄ · mg · DW⁻¹ · h⁻¹; E_p = 0.12–0.76 μg P-PO₄ mg DW⁻¹ · h⁻¹. Respiratory rates were quite constant (R = 0.01–0.02 mg O₂ · mg DW⁻¹ · h⁻¹). The uptake of nutrients due to bacteria can affect the experimental determination of excretion rates of zooplankton. Orthophosphate release increased from 0.28 to 0.82 μg P-PO₄ · mg DW⁻¹ · h⁻¹ when bacterial activity was depleted by antibiotic addition in experimental vessels (Exp IV). This demonstrates that free living bacteria are able to consume promptly most phosphorus excreted by zooplankton. Ammonia excretion rates were lower in experimental units containing antibiotics. Lower excretion rates were also obtained with longer exposure times and higher biomass levels in the experimental units. Finally, this study also showed that zooplankton excretion can affect significantly turn over rates of total phosphorus in Pampulha Reservoir. In some periods, specially during the dry season when zooplankton biomass was very high, phosphorus release by zooplankton, during one single day, can be as high as 40% of the total phosphorus content in lake water (Turn over time = 2.5 days).     

Phytoplankton and zooplankton community structure after nutrient additions to the oligotrophic Lake Hecklan,Sweden

Lake Hecklan, in central Sweden, was fertilized with phosphorus and nitrogen during thermal stratification (late May-early Oct) 1984–1987. The nutrient additions were relatively small and raised the total phosphorus concentrations from 6 to 10 µg l^–1. The working hypothesis was that this moderate increase in the phosphorus concentration could increase the phytoplankton biomass without adverse changes in the planktonic community structure. The fertilization increased the phytoplankton biomass from 0.1 to a maximum of 2 mm³ l^–1. Chrysophyceae and Cryptophyceae dominated throughout the experimental period. Thus, the phytoplankton composition remained typical for a Swedish forest lake and provided a potential for increased zooplankton growth. An increased growth of zooplankton was indicated by increased biomass of Cladocera and Copepoda in 1984 and 1985, and by increased fecundity of herbivorous zooplankton.     

A mathematical model of the phosphorus cycle in Lake Loosdrecht and simulation of additional measures

The phosphorus cycle in the ecosystem of the shallow, hypertrophic Loosdrecht lakes (The Netherlands) was simulated by means of the dynamic eutrophication model PCLOOS. The model comprises three algal groups, zooplankton, fish, detritus, zoobenthos, sediment detritus and some inorganic phosphorus fractions. All organic compartments are modelled in two elements, carbon and phosphorus. Within the model system, the phosphorus cycle is considered as completely closed. Carbon and phosphorus are described independently, so that the dynamics of the P/C ratios can be modelled. The model has been partly calibrated by a method based on Bayesian statistics combined with a Range Check procedure.Simulations were carried out for Lake Loosdrecht for the periods before and after the restoration measures in 1984, which reduced the external phosphorus loading to the lake from ca. 2 mgP m^–2 d^–1 to 1 mgP m^–2 d^–1. The model outcome was largely comparable withthe measured data. Total phosphorus has slowly decreased from an average 130 µgP l^–1 to ca. 80 µgP l^–1, but chlorophyll-a (ca. 150 µg 1^–1, summer-averaged) and seston concentrations (8–15 mgC 1^–1) hardly changed since the restoration measures. About two-thirds of the seston consisted of detritus, while the phytoplankton remained dominated by filamentous cyanobacteria. The P/C ratio of the seston decreased from ca. 1.0% to 0.7%, while the P/C ratios of zooplankton, zoobenthos and fish have remained constant and are much higher. The system showed a delayed response to the decreased phosphorus loading until a new equilibrium was reached in ca. five years. Major reasons for the observed resilience of the lake in responding to the load reduction are the high phosphorus assimilation efficiency of the cyanobacteria and the high internal recycling of phosphorus. A further reduction of nutrient loading, perhaps in combination with additional measures like biomanipulation, will be the most fruitful additional restoration measure.     

The paradox of re‐oligotrophication: the role of bottom–up versus top–down controls on the phytoplankton community

Increases in phytoplankton biomass have been widely observed over the past decades, even in lakes experiencing nutrient reduction. However, the mechanisms giving rise to this trend remain unclear. Here, we unveil the potential mechanisms through quantifying the relative contribution of bottom–up versus top–down control in determining biomasses of phytoplankton assemblages in Lake Geneva. Specifically, we apply nonlinear time series analysis, convergent cross mapping (CCM), to decipher the degree of bottom–up versus top–down control among phytoplankton assemblages via quantifying 1) causal links between environmental factors and various phytoplankton assemblages and 2) the relative importance of bottom–up, top–down, and environmental effects. We show that the recent increase in total phytoplankton biomass, albeit with phosphorus reduction, was mainly caused by a particular phytoplankton assemblage which was better adapted to the re‐oligotrophicated environment characterized by relatively low phosphorus concentrations and warm water temperature, and poorly controlled by zooplankton grazing. Our findings suggest that zooplankton act as a critical driver of phytoplankton biomass and strongly impact the dynamics of recovery from eutrophication. Therefore, our phytoplankton assemblage approach in combination with causal identification of top–down versus bottom–up controls provides insights into the reason why phytoplankton biomass may increase in lakes undergoing phosphorus reduction.     

Long term study on the influence of eutrophication, restoration and biomanipulation on the structure and development of phytoplankton communities in Feldberger Haussee (Baltic Lake District, Germany)

Feldberger Haussee provides a classic example of eutrophication history of hardwater lakes in the Baltic Lake District (Germany) and of changes in their algal flora during the 20th century. The lake originally was regarded as slightly eutrophic. A process of drastic eutrophication from the 1950s until the end of the 1970s caused mass developments of blue-green and green algae. A restoration program was started in the 1980s to improve the water quality of the lake using both diversion of sewage outside the catchment area, and biomanipulation by altering the fish community. This restoration program led to positive changes in the lake ecosystem. Direct effects of biomanipulation resulted in an increase of herbivorous zooplankton, a decrease of phytoplankton biomass, and an increase of water transparency. The recovery of Feldberger Haussee also may have been indirectly enhanced by an increase in nutrient sedimentation as a consequence of intensified calcite precipitation, decrease in phosphorus remobilization due to a pH-decrease, increased NIP-ratio, and recolonization of the littoral zone by macrophytes. This paper concentrates on the long term development of the phytoplankton community as a response to changes in the food web structure as well as to alterations in the chemical environment of the algae. Both are reflected in four major stages passed by the algal assemblage between 1980 and 1994: (1) From 1980-summer 1985 dense green algal populations were found indicating similar conditions as in the 1970s during the period of maximum eutrophication. (2) A diverse phytoplankton community during summer 1985–1989 showed the first effects of a recovery. (3) From 1990–1992 the phytoplankton was characterized by ungrazeable filamentous blue-green algae first of all as a response to increased herbivory of zooplankton on edible species and to increasing N/P-ratios. (4) Finally, the algal species diversity increased in 1993 and 1994 whereas the phytoplankton biomass decreased showing the success of the combined restoration measures.     

Plankton and primary productivity of Lake Manzala,Egypt

Primary production and distribution and abundance of phyto- and zooplankton of lake Manzala were investigated from June 1985 to June 1986.Primary production varied from 4.1 to 28.7 g O₂ m^–2 d^–1 with the highest values 24.2 and 28.7 g O₂ m^–2 d^–1 recorded in the eastern and southern sectors and the lowest value 4.1 g O₂ m^–2 d^–1 recorded in the northern sector. The seasonal mean production for the lake was estimated at 13.3 g O₂ m^–2 d^–1.Mean phytoplankton abundance ranged from 32.7 10⁷ to 76.1 10⁷ cells m^–3 with a mean value of 48.10⁷ cells m^–3. Diatoms were the dominant phytoplankton group comprising 52 to 90 % by number. The greatest relative abundance (87 to 90%) was recorded in the southern sector.Mean zooplankton abundance ranged from 30.1 10³ to 44.4 10³ organisms m^–3 in the eastern sector to 5.5.10³ in the northern sector. In response of eutrophication, the species composition changed significantly over the last 20 years. Cladocerans represented less than 1% of zooplankton during 1959/60, but 75% in 1985/86. Rotifers constituted 40% in 1959/60, and only 1% in 1985/86. Cirriped larvae declined from 21% to 1%.     

Contribution of mathematical modeling to lake ecosystem understanding: Lake Bourget (Savoy,France)

This paper demonstrates how mathematical modeling can contribute to improve understanding of lake behavior. Since the 60's Lake Bourget, one of the largest in France, had been suffering from eutrophication which was checked in 1980 by the diversion of the main sewers entering the lake. A research program was implemented between 1987 and 1990, including an on-site sampling campaign conducted concurrently with thermal and biogeochemical modeling of lake behavior. The model helped provide a better understanding of the ecosystem, displaying some processes hitherto misunderstood: (1) Winter overturn does not reach the bottom of the water column when the weather is mild. This leads to a incomplete reoxygenation of the hypolimnion and to redox conditions inducing the release of orthophosphate from the sediment, (2) Grazing by herbivorous zooplankton is getting more important in the control of spring algal growth as eutrophication of the lake regresses, (3) Settling of particulate phosphorus seems a complex and very important process in Lake Bourget, showing high sedimentation rates for particulate mineral phosphorus.     

The Importance of Lake Morphometry for the Structureand Function of Lakes

This work demonstrates quantitatively and in a comprehensive way that the size and form of lakes regulate many general transport processes, such as sedimentation, resuspension, diffusion, mixing, burial and outflow, which in turn regulate many abiotic state variables, such as concentrations of phosphorus, suspended particulate matter, many water chemical variables and water clarity, which in turn regulate primary production, which regulate secondary production, for example of zooplankton and fish. Such relationships are discussed not qualitatively but quantitatively using a new generation of validated dynamic ecosystem models (LakeWeb and LakeMab) based on mechanistic principles. It has been shown by critical model tests (including blind tests using data covering wide limnological ranges) that these models give predictions that agree well with empirical data. This should lend credibility to the results presented in this work, which would have been very difficult to obtain using traditional methods with extensive field studies in a few lakes. Simulations have been carried out where the inflow of phosphorus is held constant and the consequences simulated for small, large, shallow and deep lakes. There are striking differences in total phosphorus (TP) concentrations and trophic state (from 10 to 100 µg TP/l) and hence also in changes in many variables characterizing lake structure and function, such as Secchi depth, suspended particulate matter, pH, water temperature, chlorophyll, algal volume, macrophyte cover; as well as production and biomasses of benthic algae, bacterioplankton, macrophytes, herbivorous zooplankton, predatory zooplankton, zoobenthos, prey fish and predatory fish. These changes have been quantified in a comprehensive manner in this work and the approach to calculate such changes are basic for an understanding of how different lakes react to changes in nutrient loading (eutrophication). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)