Lake Color Research Articles

Unraveling long-term changes in lake color based on optical properties of lake sediment

A number of boreal surface waters have become browner over the last two decades. Recovery from acid rain is regarded as an important driver for this lake color increase, indicating a general browner lake color in preindustrial times. However, the lack of long-term monitoring data makes it challenging to unravel historical changes in lake color. In this study, we estimated long-term development in lake color (1800 to 2015) based on the optical properties of alkaline extractable dissolved organic matter (DOM) from sediment using UV–Vis and fluorescence spectroscopy. We found that the present lake color (2015) was significantly browner (four times higher in absorption coefficient) than for the period from 1800 to 1915 when lake color was at a lower and more stable level. Fluorescence excitation–emission matrices combined with parallel factor analysis (EEM-PARAFAC) indicate that terrestrially derived DOM was the main source of sediment DOM. However, the importance of in-lake source of DOM has significantly increased with time. The long-term trend in DOM burial was not consistent with the anthropogenic sulfur (S) deposition pattern. However, along with the increased sediment DOM, there has been increased precipitation, temperature and forest growth with time, which affect the production and degradation of DOM. Even though S deposition might have delayed the runoff of terrestrial DOM for a certain period, it comes in addition to other color-regulating factors. Thus, there is no single driver for the observed lake browning, but rather an interplay between different drivers varying in strength over time, such as afforestation, changes in areal use, declined S deposition, and increased temperature and precipitation.

Comparison of LISAT and Landsat imagery for estimating chlorophyll-a (case study: Jatiluhur Reservoir)

Jatiluhur Reservoir located in Purwakarta Regency, West Java is one of the largest reservoirs in Indonesia. Various studies have been done to determine the quality of water in the reservoir. The presence of locally made satellites, LISAT, can be a tool for monitoring the reservoir’s water constituent using satellite imagery. Our purpose here is to define the spectral reflectance properties on Jatiluhur Reservoir and determine the water column constituents that correlate with the observed lake color. In addition, this study also aims to compare the spatial, temporal, and spectral resolutions of LISAT imagery and Landsat imagery in the Jatiluhur Reservoir region. Based on the table of the relationship between TSI with chlorophyll a parameter, the TSI value is in the range of 80 - 90. TSI 80 value> falls into the category of hypereutrophic waters. The estimated result from Landsat and LISAT imageries still show different results. Chlorophyll-a value from image processing also show significance differences from Chlorophyll-a value derived from laboratory analysis.

Colour Classification of 1486 Lakes across a Wide Range of Optical Water Types

Remote sensing by satellite-borne sensors presents a significant opportunity to enhance the spatio-temporal coverage of environmental monitoring programmes for lakes, but the estimation of classic water quality attributes from inland water bodies has not reached operational status due to the difficulty of discerning the spectral signatures of optically active water constituents. Determination of water colour, as perceived by the human eye, does not require knowledge of inherent optical properties and therefore represents a generally applicable remotely-sensed water quality attribute. In this paper, we implemented a recent algorithm for the retrieval of colour parameters (hue angle, dominant wavelength) and derived a new correction for colour purity to account for the spectral bandpass of the Landsat 8 Operational Land Imager (OLI). We used this algorithm to calculate water colour on almost 45,000 observations over four years from 1486 lakes from a diverse range of optical water types in New Zealand. We show that the most prevalent lake colours are yellow-orange and blue, respectively, while green observations are comparatively rare. About 40% of the study lakes show transitions between colours at a range of time scales, including seasonal. A preliminary exploratory analysis suggests that both geo-physical and anthropogenic factors, such as catchment land use, provide environmental control of lake colour and are promising avenues for future analysis.

A Novel Approach on Dehazing Volcanic Crater Lake Hazy Scene Videos Based on Color Attenuation Prior

A crater lake of Mt. Kelud active volcano formed after the eruption on February, 2014. Real time surveillance has been conducted for 24 hours using a CCTV camera on the top of the summit. The primary purpose of this observation is monitoring the volcanic activity, such as degassing and discoloration of crater lake water. These phenomenons became the symptoms of the volcanic activity. The weather condition is continuously changes between clear, cloudy, and hazy. Obviously, camera vision is obscured or even blocked by haze. Another problem is that airlight source is hard to estimate because the lake color tends to be brighter in clear conditions. In this paper, a dehazing technique is proposed based on color attenuation prior and contrast enhancement. In contrast enhancement, the transmission map was enhanced using adaptive gamma correction. Our data were analyzed using referenceless fog density estimation (FADE). Our experimental results give the best result when it comes to fog density (by 1.60912 density) compared to previous algorithms.

Phytoplankton of lakes in different types of landscape in Southern Karelia (Vendyurskaya group and Zaonezhye)

The phytoplankton of nine lakes located in different types of landscapes in the southern part of the Republic of Karelia was studied in spring and summer seasons of 20112012. In seven of the lakes phytoplankton was studied for the first time (lakes Gizhozero, Lelikozero, Myagrozero, Kondozero, Korytovo (Zaonezhsky Peninsula), lakes Koverjarvi, Rapsudozero (Vendyurskaya group). The highest species diversity in lakes of all types of landscapes was demonstrated by diatoms (20-42 % of the total number of species) and green algae (17-42 %). Each lake had its specific algal flora, and degree of their similarity measured by the S0rensen index was low. Quantitative indicators of phytoplankton in the lakes varied over a wide range of values. Phytoplankton abundance ranged within 5.8-1060.5 thousand cells/L (with an average of 160.1 ± 29.1), and biomass ranged from 0.010 to 1.374 g/m 3 (0.209 ± 0.04 g/m 3 on average). Data clustering using 26 variables showed different levels of relationship both between lakes and between their groups. It was found that the main factors influencing the total abundance and total biomass of phytoplankton, as well as the abundance and biomass of different groups of algae are the catchment area/water surface area ratio, total nitrogen and phosphorus, water catchment area, mineralization, lake surface area, pH and color. We obtained significant positive correlations (at a level of p < 0.05) between the structural indicators of phytoplankton and nutrients (total nitrogen and phosphorus).

Beyond the color: A structural insight to eosin-based lakes

Motivated by the fugitive and undisclosed nature of eosin-derived pigments as used by Vincent van Gogh, this paper presents the syntheses of monometallic and historical bimetallic eosin-based lakes and structural elucidation by MS, ATR-FTIR and NMR. Specifically two monometallic (Al, Pb) and several bimetallic lakes (on varying Al and Pb constituents) have been synthesized and examined alongside two reference compounds: eosin disodium salt and eosin Y. Resulting monometallic lake complexes are 2:1 adducts (dye:metal) with the carboxylic group coordinating the metal. In historical lake preparations, no correlation between the coordinating metals and the resulting lake color can be made.On production and investigations of different eosin lake substrates, two main anchored species have been distinguished: H-bonded for eosin onto Pb-substrates and a further bridged bidentate for eosin onto alumina. A prominent tendency to form 2:1 eosin:Pb adducts emerged in each Pb-containing recipe. Evidence concerning historical lakes suggests that eosin can diversely coordinate to metals thus producing a variety of nuances in according to experimental pH and reaction conditions. This behavior may well explain observed discrepancies between historical recipes and experimental findings regarding the coordination of eosin to one or more metals.

Formulation and Charcterization of Lake Color Obtained From Red Cabbage

Colorants are mainly used to impart a distinctive appearance to the pharmaceutical dosage forms. The present study was carried out to develop aluminium lake color of a dye obtained from red cabbageusing different adsorbent (s) (Aluminium oxide or aluminium hydroxide or combination of both) in different ratio by simply mixing them to get dye adsorbed onto the surface of adsorbent.Batch Mode studies were carried out for 60 minutes. Aluminiumhydroxide at a concentration level of 30% w/v found to be the choice of adsorbent after optimization because maximum adsorption of dye from reaction mixture after 60 minutes and maximum % yield.After optimization of adsorbent the effect of pH and temperature also studied by formulating lake by varying these two parameters. It was observed that a higher temperature (50oC) and a slight acidic pH (6) favor the adsorption. The lake then characterized for various physicochemical properties like angle of repose, Carr’s index, hausner’s ratio, loss on drying, particle size and limit test for heavy metals. The lake was found to follow pseudo second order kinetics.

Brownish discoloration of the summit crater lake of Mt. Shinmoe-dake, Kirishima Volcano, Japan: volcanic–microbial coupled origin

A drastic change in lake water color from blue-green to brown was observed in the summit crater lake of Mt. Shinmoe-dake, Kirishima Volcano about 8 months after its 2008 eruption. The color change lasted for about 2 months (April–June 2009). The discoloration was attributed to a brownish color suspension that had formed in the lake water. X-ray fluorescence and Fourier transform infrared analyses of a sample of the suspension identified schwertmannite (Fe8O8(OH)6(SO4)). A cultivation test of iron-oxidizing bacteria for the sampled lake water with lakebed sediment revealed that the crater lake hosts iron-oxidizing bacteria, which likely participated in schwertmannite formation. We suggest that pyrite (FeS2) provided an energy source for the iron-oxidizing bacteria since the mineral was identified in hydrothermally altered tephra ejected by the August 2008 eruption. From consideration of these and other factors, the brownish discoloration of the summit crater lake of Mt. Shinmoe-dake was inferred to have resulted from a combined volcanic–microbial process.

The impacts of prescribed moorland burning on water colour and dissolved organic carbon: A critical synthesis

Discolouration of natural surface waters due to the humic component of dissolved organic carbon (DOC) is a costly problem for water supply companies. This paper reviews what is known about the impacts of prescribed moorland vegetation burning on water colour. Relevant research has taken place at three scales: laboratory experiments on peat cores, plot scale sampling of soil waters and catchment scale sampling of stream waters. While laboratory studies suggest burning increases colour production, the evidence from catchment and plot studies is contradictory. Plot studies suggest colour production may decrease or remain unchanged following burning although there is evidence for some transient changes. Catchment studies suggest prescribed moorland burning causes stream water colour to increase, although in most cases the evidence is not clear cut since most studies could not clearly disentangle the effects of burning from those of vegetation cover. The differences in findings between plot and catchment studies may be explained by: i) the short-term nature of some studies which do not measure long-term response and recovery times to burning; ii) the lack of colour measurements from shallow soil depths which contribute more to streamflow than soil water from deeper in the peat; and iii) the possibility of hydrological interactions occurring between different experimental plots at some sites. Additionally, the increase in recent patch burning in some catchments that has been statistically attributed by some authors to increases in stream water colour cannot be reconciled with theoretical calculations. When dilution with waters derived from other parts of the catchment are taken into account, large values of colour have to be theoretically derived from those recently burnt areas that occupy a small proportion of the catchment area in order to balance the change in stream water colour observed in recent years. Therefore, much further process-based work is required to properly investigate whether prescribed vegetation burning is a direct driver of enhanced colour and DOC in upland streams, rivers and lakes.

Differences of Lake Color between Mapangyongcuo Lake and La'angcuo Lake Based on Remote Sensing

Lake color is an important index of water optical properties.Because of its special geographical conditions,color of lakes in Qinghai-Tibet Plateau is significantly different.In this paper,Mapangyongcuo Lake and La'angcuo Lake in the south of Tibet were chosen as research.Starting from the image representation of the two lakes' color,remote sensing technology was used to analyze the differences.As shown in the results that,evaporation and recharge of the two lakes were different,so the substance deposition such like salt were different,and then influenced the lake color.This is a new method to research on lakes in Qinghai-Tibet Plateau that are lack of observed data.

The formation and evolution of Hule and Río Cuarto maars, Costa Rica

The Hule and Río Cuarto maars are respectively located 11 and 18 km northward of the active crater of Poás volcano, on the Caribbean side of the Central Volcanic Range of Costa Rica. They lie on the northern part of Poás volcano massif, along a N–S trending, ~ 27 km-long volcanic fracture crossing the Poás volcano. The volcanic products from Hule maar (2.3 km × 1.8 km, area ~ 3.5 km 2) are mainly pyroclastic surges (poorly vesiculated andesites with very small plagioclases), silica-rich andesitic pumice flows, air-fall deposits, ballistic blocks, and reworked deposits that overlie the regional Pleistocene volcanic basement. They were produced during three main explosive phases. Two overlapping pyroclastic cones have developed within the Hule maar, and at least three lava fields are related to them (high-Al basalt to basaltic andesite). Another maar, Pata de Gallo (400 m across), is located less than 1 km off the SE rim of Hule. Río Cuarto is a nearly circular maar (700–850 m across) with a surface area of 0.33 km 2. Río Cuarto products include surges, ballistics and air-fall tephra, produced during three main explosive phases. These deposits show a narrow fan oriented westward, according to westerly wind direction. They indicate a westerly-directed surge (first 2 km), followed by air-fall deposits (up to 5 km away). Radiocarbon dating has shown that Hule was formed ~ 6.2 ka ago and Pata de Gallo probably formed ~ 2.8 ka ago, while the intra-maar products could have ages of ~ 1.7 ka or ~ 0.7 ka, indicating that Hule is a polygenetic maar. There are no radiocarbon ages yet for dating the formation of Río Cuarto maar, but archaeological data suggest that it erupted between 3–4 ka ago. The volume of pyroclastic deposits associated to Hule maar is estimated to be 0.51–0.53 km 3, from which ~ 20% is juvenile material, therefore 0.07–0.08 km 3 of new dense rock equivalent (DRE) magma, after subtracting 20–30% of porosity. The tephra from Río Cuarto is estimated to be 4.4 × 10 7 m 3, of which 0.008 m 3 correspond to DRE magma. The Hule and Río Cuarto maars are occupied by lakes and, in the last decades, several lake-overturn events have taken place, with a repeat cycle of six to seven years. The main outcome of these events has been the mass death of fish accompanied by changes in the lake color. In these systems, the hazard related to the possible occurrence of Nyos-type gas eruptions can be considered negligible or very local, but significant for tourists who camp by the lakes.

Long-term patterns in pH and colour in small acidic boreal lakes of varying hydrological and landscape settings

Changes in water pH and colour since the late 1980s were studied in 35 small boreal lakes of varying hydrological and landscape settings but similar climate and acid deposition. The data was collected during the autumnal overturn on the annual basis except in lake with weekly sampling during the ice-free period. In addition to the deposition data information about catchment soil types as well as local meteorological and hydrological conditions were used for the long-term data interpretation. The lakes are situated in a small area in southern Finland, 130 km north from Helsinki, where sulphate deposition declined by >60% in one decade since the mid-1980s. The results showed that water colour increased in most lakes while pH did not. In lakes dominated by surface runoff there was a distinct upward shift in colour, with an initial increase after the mid-1990s and a second increase in 2004. The first shift appeared when the sulphate deposition reached a level ca. 25% of that in 1988. However, the upward shift in colour also coincided with a change in hydrological conditions after several dry summers. In contrast, the second shift in colour clearly coincided with a switch in hydrology due to the abnormally wet summer of 2004 after severe drought in 2002–2003. Although the hydrological conditions indisputably had a key role in determining the annual variability in colour, a distinct negative relationship between acid deposition and water colour in 90% of the lakes strongly suggested that reduction in sulphate deposition fostered the leaching of coloured organic substances from the catchment soils. Increase in colour, in turn, strongly influenced lake water pH, and the present day higher organic matter concentrations seemingly depress pH values more than in the 1980s, before the reduction in acid deposition.

Variations in colored dissolved organic matter between boreal lakes studied by satellite remote sensing

There have been major improvements in our understanding of the role of lakes and impoundments in global carbon cycle. Estimating the true role of lakes as sentinels, regulators and integrators of climate change requires analyzing carbon content of vast number of lakes. This is not realistic without using remote sensing methods. There are no satellite sensors at the moment that provide full global coverage and at the same time have spatial and radiometric resolutions suitable for lake color dissolved organic matter (CDOM) mapping. Therefore, the global study has to be performed using more sensitive sensors to create regional lake CDOM statistics for as many sites as possible and extrapolating the results on global lake map that can be created from less sensitive sensor data with full global coverage (Landsat). As a first step towards the global lake carbon mapping we show that the Advanced Land Imager (ALI) allows to study regional variations in lake CDOM content and consequently estimate closely correlated DOC (dissolved organic carbon) and CO2 saturation values. The results show also that there may be regional differences in lake CDOM content even if the study sites are geographically relatively close to each other and occupying zones with similar land cover and annual runoff. In one occasion the difference can be explained with human impact that has caused acidification of lakes but the other occasion needs further studies.

The impacts of thawing permafrost on the chemistry of lakes across the subarctic boreal‐tundra transition, Mackenzie Delta region, Canada

AbstractIn the lake‐rich tundra uplands east of the Mackenzie Delta, almost one in ten lakes has been affected by retrogressive thaw slumping. In this study, we assessed water chemistry for 34 slump‐affected and 39 undisturbed upland lakes across this region and found that environmental factors typically evoked to explain variation in tundra lake water quality including surficial geology and proximity to the treeline or coast were subordinate to the main driver, permafrost degradation. Thaw slump‐affected lakes had elevated ionic concentrations and water clarity in comparison with undisturbed lakes. The strength of the ionic impact was positively associated with the proportion of catchment affected by slumping and inversely related to disturbance age. Slumping did not have a significant effect on total organic carbon (TOC) concentrations, although water clarity increased significantly with decreasing age of disturbance. In lakes undisturbed by slumping, fire‐induced active‐layer deepening had a detectable influence on lake water ionic strength. Surficial deposits influenced TOC concentrations with the highest concentrations and colour in undisturbed lakes with lacustrine catchments. In a warming Arctic, thermokarst processes may increase in importance as a driver of ionic chemistry and optical properties of small lakes and ponds, and shifts in aquatic food webs can be anticipated. Copyright © 2009 John Wiley &amp; Sons, Ltd. and Her Majesty the Queen in right of Canada.

Influence of Chlorophyll and Colored Dissolved Organic Matter (CDOM) on Lake Reflectance Spectra: Implications for Measuring Lake Properties by Remote Sensing

Light reflected from lake surfaces can convey much information about water quality, especially algal abundance, humic content, turbidity and suspended solids. Light reflectance from lakes is complicated, and detailed spectra are needed for analysis of controlling factors. We obtained detailed reflectance spectra from the water surfaces of 15 lakes in east-central Minnesota and found patterns related to chlorophyll a (chl a), turbidity and humic matter (colored dissolved organic matter, CDOM). Increasing chl a and turbidity generally resulted in higher reflectance across the visible and near-infrared spectrum. Increasing CDOM led to low reflectance, especially below ~500 nm. Spectra of lakes with high chl a were distinguishable from those of lakes low in chl a, and lakes with low or high CDOM had readily distinguishable spectra. Several optical characteristics of lake water can be estimated from reflectance intensities measured over narrow wavelength bands. The ratio of reflectance at 700 nm to that at 670 nm was the best predictor of chl a over a wide range of conditions, including high turbidity and CDOM. Several relationships involving reflectance at 412, 443, 488, and 551 nm, the wavelengths used to calculate oceanic chl a from MODIS satellite data, also yielded a high R2. The ratio of reflectance at 670 nm to 571 nm provided the best estimates of humic color despite the low absorbance of CDOM at these wavelengths. Relationships involving reflectance for all 15 lakes in the range 400–500 nm, where CDOM absorbs light, had low r2 values; none was high enough for reliable estimates of lake color. For 10 lakes with low to medium chl a levels (≤10 mg m−3), regressions involving 412 and 443 nm yielded moderately good relationships. Airborne and satellite remote sensing thus might be used to identify lakes high in CDOM, and may provide reasonable estimates of humic color in lakes with low chl a levels.

Determinants of seston C : P‐ratio in lakes

Summary1. The ratio of carbon to phosphorus (C : P) in seston is a major determinant of energy transfer in aquatic food webs and may vary more than an order of magnitude owing to various extrinsic and intrinsic factors. In this study, the determinants of C : P‐ratios in lake particulate matter (seston) was assessed in 112 Norwegian lakes, covering a C : P (atomic ratio) from 24 to 1842 (mean 250).2. No overall effects of lake area, season or latitude on C : P was detected. Particulate P, but not particulate C, correlated with C : P. Multivariate analysis including a range of lake properties revealed total dissolved P, as the major determinant of sestonic C : P, with the fraction of detritus in total seston, chlorophyll or Secchi depth and lake colour as significant contributors. Together these parameters explained 30% of observed variance if using dissolved P and 81% if using total P as input variable to the multivariate model.3. Chlorophyll and Secchi depth were highly correlated and substitutable in the analysis. Phytoplankton community composition did not affect seston C : P, probably reflecting the fact that live phytoplankton generally contributed &lt;25% of the seston pool.4. Total P correlated positively with C : P and is the key determinant of phytoplankton biomass and thus Secchi depth; the latter parameters contributed negatively to seston C : P, probably owing to increased light attenuation. These lake data thus support the light : nutrient ratio hypothesis, i.e. that high light and low P cause skewed uptake ratios of C to P.5. Zooplankton biomass in general and Daphnia biomass in particular, was negatively correlated with C : P, probably reflecting a negative impact of poor seston quality at high C : P. Zooplankton grazing and nutrient recycling may also have contributed to a negative correlation between zooplankton biomass and sestonic C : P.

Photography in limnology: documentation of lake color using a CCD camera

During a survey of Norwegian lakes, photographic records were made of lake color as reflected by a white Secchi disk positioned at half of the depth of extinction. The pictorial distinction between different lakes is documented in this article. The pictures recorded can readily be transferred to a color model [e.g., Commission Internationale de L’Eclairage (CIE)-Lab]; from there, numerical color parameter values such as hue (h*, the quality of color) and chroma (C*, the intensity of color) may be assigned to each record. There are, however, limitations and obstacles connected with the transformation of color values recorded by a CCD camera (or film digitizers) to absolute numerical values comparable between different cameras and systems. A single CCD camera may be useful for documenting lake color, but there are technical limitations restricting its use as a scientific instrument for quantitative purposes.

Increased colour and organic acid concentrations in Norwegian forest lakes and drinking water ? a result of increased precipitation?

Recently there have been major increases in water colour and dissolved organic carbon (DOC) in many forest lakes that serve as drinking water reservoirs in the southern part of Norway. We studied changes in the physical and chemical properties in (I) a selected group of lakes and (II) raw water from the municipal waterworks of Oslo since 1983 and 1976, respectively. The largest increase in DOC and water colour occurred between 1997 and 2001. Statistically significant correlations are seen between water colour and accumulated amounts of precipitation, while variation in temperature had no apparent effect. Despite significant reduction in sulphate concentrations in precipitation and lake waters since 1980, the lakes were more acidic in 2000 and 2001 than in previous years. Increases in colour and acidity, together with somewhat minor changes in DOC concentrations, indicate changes in the physical and chemical properties of the natural organic matter (NOM). Alteration in properties of NOM is most probably caused by increased precipitation that has changed the water pathways in the catchments and increased the leaching of organic components from the upper forest floor.

Surface water chemistry of burned and undisturbed watersheds on the Boreal Plain: an ecoregion approach

The water chemistry of the euphotic zone in 12 lakes within burned and reference watersheds on Alberta's Boreal Plain was surveyed two years post-fire. Five burned and four reference lakes were located in the Boreal Foothills (mean elevation = 1048 m) and three reference lakes were situated at lower elevations in the Boreal Mixedwood ecoregion (748 m). Mean dissolved organic carbon (DOC) concentration in lake water from burned watersheds was 1.4-fold higher than in lake water from reference Foothills watersheds, whereas lake colour increased with the area of catchment burned divided by lake volume (r = 0.98). Reference Mixedwood lakes had higher mean total phosphorus (TP, 1.8-fold) and chlorophyll a (chl a; 4.4-fold) concentrations than reference Foothills lakes. Ten additional lakes from a previous study in boreal Alberta were used to further compare water chemistry between ecoregions. Boreal Mixedwood lakes (n = 13) had higher TP (2.3-fold), chl a (3-fold), and Ca2+ + Mg2+ (3.3-fold) concentrations than Boreal Foothills lakes (n = 9). Our data suggest an influence of forest fire on lake chemistry in the Boreal Foothills, and demonstrate the need for an ecoregion approach to detect the impacts of watershed disturbance on the Boreal Plain. Key words: watershed disturbance, forest fire, lake nutrients, lake elevation, phosphorus, chlorophyll a, anions, cations, dissolved organic carbon.

Modelling production and biomasses of herbivorous and predatory zooplankton in lakes

This work presents a dynamic model to predict two fundamental functional categories of zooplankton in lakes, herbivorous and predatory zooplankton. The model has been developed as an integral part within the framework of a more comprehensive lake ecosystem model, LakeWeb, which also accounts for phytoplankton, bacterioplankton, two types of fish (prey and predatory), as well as zoobenthos, macrophytes and benthic algae. The new model is based on ordinary differential equations, the ecosystem scale and gives seasonal variations (the calculation time is 1 week). It is meant to account for all important factors regulating the production and biomass of zooplankton and the predation on zooplankton in lakes. The model has not been calibrated and tested in the traditional way using data from a few well investigated lakes. Instead, it has been tested using empirical regressions based on data from many lakes. We have also presented new data sets and regressions based on those data for zooplankton. The basic aim of the dynamic model is that it should capture general functional and structural patterns in lakes. We have demonstrated by several model tests along limnological gradients (total phosphorus concentrations, pH, lake colour, latitude and lake size) that the new model gives predictions that agree well with the values given by the empirical regressions, and also expected and requested divergences from these regressions when they do not provide sufficient resolution. It would have been very difficult indeed to carry out such tests regarding ecosystem responses using traditional methods with extensive field studies in a few lakes. We have given algorithms for (1) production of herbivorous and predatory zooplankton, (2) elimination (related to the turnover time of zooplankton), (3) zooplankton consumption by prey fish, and the factors influencing these processes/rates. The model is driven by data easily accessed from standard monitoring programs or maps and meant to be of practical use in lake management.