Occurrence and distribution of chemical pollutants in Lake Mariut,Egypt

Occurrence and distribution of organochlorine pesticides in the water of Lake Mariut, a brackish coastal Egyptian lake suffering from pollution, and their accumulation in the common fish Tilapia were studied. The major pesticides detected in the lake water were lindane, p,p′-DDE, o,p′-DDT, and p,p′-DDT. These compounds, except o,p′-DDT, were detected in the fish samples in exceedingly higher concentrations compared with those found in the lake water.     

Distribution of phosphates in Lake Mariut,a heavily polluted lake in Egypt

In recent years Lake Mariut was subjected to severe pollution. The phosphate content of this Lake was exceedingly higher than that of the other Egyptian Lakes. The distribution of phosphates in Lake Mariut was found to depend upon certain factors which were discussed.     

Occurrence and distribution of chemical pollutants in Lake Mariut,Egypt. II. Heavy metals

The occurrence and distribution of heavy metals in the water of Lake Mariut, a heavily polluted brackish water lake in Egypt, and their accumulation in the different parts ofTilapia fish in this lake were studied. The variations in concentrations of the metals (Zn, Cu, Fe, Mn, and Cd) in the lake water are mostly due to variations in the discharge rate of dumped wastes. The mean concentrations of these metals in different fish parts were much higher than those in the lake water.     

MAN-MADE IMPACT ON THE GEOCHEMISTRY OF THE NILE DELTA LAKES. A STUDY OF METALS CONCENTRATIONS IN SEDIMENTS

Forty two sediment samples were collected from four River Nile northern delta lakes (Mariut, Edku, Burullus and Manzalah) to asses the man-made impact on their environment during the last 20 years. Due to the continuous discharge of agricultural, industrial and sewage waste waters to these lakes, significant variations in the sediment's nature took place, with fine fractions dominating opposite to the outflowing area of the main drains. Organic carbon was elevated at the southern regions, reaching 10.5 ± 4.5% in lake Mariut. Meanwhile, carbonate increased reaching 90% for samples collected at the lake-sea connection areas. The 0.5 N HCl extractable metals indicated enriched levels of different metals at sites affected by sewage and industrial discharge. This fraction constituted 75 and 81% of the total metals in Lakes Mariut and Manzalah, respectively. Extractable Cd for Lakes Mariut and Manzalah constituted 51 and 53%, respectively, while Pb formed 59% of the total digestable metal in Lake Manzalah. Total metals concentrations especially Cd and Pb were elevated 8 to 70 times than those observed in the same lakes 25 years ago. The conversion of the untreated sewage discharge of Alexandria city to Lake Mariut and significant portion of Cairo sewage to Lake Manzalah during the past 10 years lead to the appearance of elevated levels of contaminants in both lakes. Agricultural discharge showed less impact on Lakes Edku and Burullus. Cluster analysis revealed associations between stations located under same types of stress while the correspondence factor analysis displayed that metals distribution pattern in the Nile delta lakes are governed by organic carbon as well as fine grained size fraction distribution.     

Metals and chlorinated hydrocarbons in surficial sediments of three nile Delta lakes,Egypt

Water, Air, & Soil Pollution - Surficial sediment samples from three shallow Nile Delta lakes (Lake Mariut, Hozha hydrodrome, andke Manzalah) were analyzed for PCBs, DDT-group pesticides, and...     

Base neutralizing capacity of sediments from an acidic lake

The base neutralizing capacity (BNC), or alkalinity consumption, of acidic lake sediments may influence the amount of neutralizing agent required to neutralize a lake if the sediment BNC is large relative to the BNC of overlying waters. The extent ofin situ sediment BNC in acidic Bowland Lake (pH 5.0) was inferred by (1) measuring the loss of Ca-45 to acidic sediments from labeled lake water neutralized with CaCO₃, and (2) measuring exchangeable Ca in sediments collected prior to and following neutralization of Bowland Lake with calcite (CaCO₃). The sediment BNC derived from the Ca-45 radiolabeling experiment was 0.01 mg CaCO₃ g^?1 w wt. The mean losses of Ca-45 from the aqueous phase of neutralized and untreated sediment/water mixtures were not significantly different. The mean pH of both neutralized and untreated mixtures decreased to 4.0 during the incubation, possibly because of oxidation of reduced sediments. Sediment BNC estimates derived from literature data for several lakes may be overestimated because of the inclusion of anoxic sediments containing significant amounts of reduced Fe. There was no significant difference in exchangeable Ca between sediments from untreated Bowland Lake and sediments collected 10 m after whole-lake neutralization indicating that little of the supplied alkalinity had been lost to the sediments. Hence,in situ sediment BNC was probably small in Bowland Lake.     

Conserving marginal populations of the food plant (Impatiens noli-tangere) of an endangered moth (Eustroma reticulatum) in a changing climate

Impatiens noli-tangere is scarce in the UK and probably only native to the Lake District and Wales. It is the sole food plant for the endangered moth Eustroma reticulatum. Significant annual fluctuations in the size of I. noli-tangere populations endanger the continued presence of E. reticulatum in the UK. In this study, variation in population size was monitored across native populations of I. noli-tangere in the English Lake District and Wales. In 1998, there was a crash in the population size of all metapopulations in the Lake District but not of those found in Wales. A molecular survey of the genetic affinities of samples in 1999 from both regions and a reference population from Switzerland was performed using AFLP and ISSR analyses. The consensus UPGMA dendrogram and a PCO scatter plot revealed clear differentiation between the populations of I. noli-tangere in Wales and those in the Lake District. Most of the genetic variation in the UK (H_T=0.064) was partitioned between (G_ST=0.455) rather than within (H_S=0.034) regions, inferring little gene flow occurs between regions. There was similar bias towards differentiation between metapopulations in Wales, again consistent with low levels of interpopulation gene flow. This contrasts with far lower levels of differentiation in the Lake District which suggests modest rates of gene flow may occur between populations. It is concluded that in the event of local extinction of sites or populations, reintroductions should be restricted to samples collected from the same region. We then surveyed climatic variables to identify those most likely to cause local extinctions. Climatic correlates of population size were sought from two Lake District metapopulations situated close to a meteorological station. A combination of three climatic variables common to both sites explained 81-84% of the variation in plant number between 1990 and 2001. Projected trends for these climatic variables were used in a Monte Carlo simulation which suggested an increased risk of I. noli-tangere population crashes by 2050 at Coniston Water, but not at Derwentwater. Implications of these findings for practical conservation strategies are explored.     

Biogeochemistry of a forested watershed in the central Adirondack Mountains: Temporal changes and mass balances

Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO₃ ^? concentrations (1.1 μmol _c , L^?1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r²=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO₄ ^2? (831 mol _c ha^?1 yr^?1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO₄ ^2? also contributed to the drainage fluxes of basic cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha^?1 yr^?1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).     

Phosphomonoesterase activity in forest soils

Phosphatases are important in the mineralization of organically-bound phosphorous. Although phosphatases have been studied extensively in agricultural soils, there are few reports on phosphatase activity in forest soils, and no information on the effect of forest management practices, such as thinning and N-fertilization, on phosphomonoesterase (PME) activities. In the present study, the (PME) activity of forest soils from Shawnigan Lake and Jordan River (mg p-nitrophenol released g⁻¹ dry soil h⁻¹ was highest in the forest floor horizon (L-H) and decreased with depth to 60 cm in mineral soil horizons. Addition of orthophosphate and urea during the assay of PME demonstrated these chemicals competitively depressed PME activity. With Shawnigan Lake soil (L-H), the minimum rate (V_max) of PME activity was 5.71 mg p-nitrophenol released g⁻¹ dry soil h⁻¹. For Jordan River, V_max was 3.33 mg p-nitrophenol released g⁻¹h⁻¹. Incubation of L-H horizon of both soils, fumigated or non-fumigated, at 30°C for up to 40 days after rewetting resulted in an initial reduction in PME activity. Comparatively, the PME activity of Jordan River soil recovered faster than that of the Shawnigan Lake soil whose activity remained very low at the end of the incubation. In field plots where trees were thinned and urea and ammonium nitrate fertilizers had been applied 2 yr previously, assays for PME demonstrated that urea fertilization and thinning depressed PME activity while ammonium nitrate did not. This study demonstrated (1) PME activity depended on soil geographic location and depth, and (2) fertilization of forests with phosphates and urea appeared to reduce PME activity and thus may have the potential to depress the mineralization of organic-P.     

Changes in the waterbird community of the Lake Sevan-Lake Gilli area, Republic of Armenia: a case for restoration

Waterbird species richness (Gaviiformes, Podicipediformes, Pelecaniformes, Ciconiiformes, Phoenicopteriformes, Falconiformes, Anseriformes, Gruiformes, Charadriiformes, Passeriformes) has been significantly affected by a 19.5 m lowering of the water level in Lake Sevan (1933-2000), and the complete draining of nearby Lake Gilli (1960-2000) in the Republic of Armenia. Twenty-three former breeders are currently nonbreeders in the area. Four former breeders (black stork Ciconia nigra, glossy ibis Plegadis falcinellus, white-winged scoter Melanitta fusca, little crake Porzana parva) have been extirpated from the area. Four former nonbreeders (cattle egret Bubulcus ibis, red-breasted goose Branta ruficollis, sociable lapwing Chettusia gregaria, lesser black-backed gull Larus fuscus) have been absent from the area for at least 20 years. The red-breasted merganser Mergus serrator is the only former nonbreeder discovered breeding in the Lake Sevan basin. We recommend that management plans of the 1960s and 1970s be used to further develop and enact new efforts to increase the water level of Lake Sevan by at least 6 m, and that Lake Gilli and its surrounding wetlands be restored as a means of increasing waterbird species richness overall, and protecting regional populations of globally threatened or near-threatened species (Dalmatian pelican Pelecanus crispus, red-breasted goose Branta ruficollis, ferruginous pochard Aythya nyroca, white-headed duck Oxyura leucocephala, corn crake Crex crex, great snipe Gallinago media, black-winged pratincole Glareola nordmanni, white-tailed eagle Haliaeetus albicilla).     

Trace element loading of southern Lake Michigan by dry deposition of atmospheric aerosol

Aerosol samples and meteorological data were collected at a mid-southern Lake Michigan site (87° 00′ W, 42° 00′ N) from May through September 1977. Hi-volume samplers with cellulose fiber filters and a digital meteorological data recording system were operated on board the U.S. EPA's R/VRoger R. Simons during four intensive sampling periods. Aerosol samples were analyzed by atomic absorption spectroscopy for seventeen trace elements. A diabatic drag coefficient method was used to determine aerosol deposition velocity (v _d ) overlake. A meanv _d of 0.5 cm s^?1 was found for the 0.1v _d to a long-term climatological record, annual dry deposition loadings to the southern basin for nine elements were estimated. For four elements, Fe, Mn, Pb, and Zn, dry deposition loadings to the southern basin alone of at least 500, 30, 250, and 100 (×10³ kg yr^?1) were found. For Fe and Mn, these loadings represent about 15% of the total of all inputs to Lake Michigan. for Zn and Pb, about one-third to one-half of the annual loading from all sources is from dry deposition of atmospheric aerosol.     

Natural acidification of lakes and rivers in Japan: The ecosystem of Lake Usoriko (ph 3.4–3.8)

Most of the acid lakes and rivers in Japan have been influenced by acid waters of volcanic origin. Acidophilic and acidotolerant organisms are observed in these natural acid lakes and rivers, each of which has its own ecosystem and history. Lake Usoriko (pH 3.4–3.8) is a lake which.has been acidified by strongly acid water containing sulfuric acid and hydrochloric acid. The ecosystem of Lake Usoriko consists of aquatic vascular plants, aquatic bryophytes (Drepanocladus fluitans, etc.), algae, fish (Tribolodon hakonensis), insects, Zooplankton, fungi and bacteria. The paleosediment distributed along Lake Usoriko's northern shore is partly silicified and it contains fossils of a moss (Drepanocladus fluitans) and diatoms such as Pinnularia braunii var. amphicephala which are also distributed in the present lake. ¹⁴C dating of the specimens in the paleosediment, shoots of D. fluitans and the wood and cones of Picea glehnii gave values in the range 11500–34000y B.P. This record shows how long Lake Usoriko has been an acid lake.     

Composition and spectroscopic characteristics of dissolved organic matter extracted from the sediment of Erhai Lake in China

Purpose

The content and composition of dissolved organic matter (DOM) in sediment directly affect nutrient cycling and material exchange in lake ecosystems. This study investigated the content and composition of DOM and its fractions in sediments, as well as the relationship between the different parameters and nitrogen (N) forms in DOM. The main aim of this study was to evaluate the compositional characteristics of DOM, hydrophobic bases (HOB), hydrophobic acids (HOA), hydrophobic neutral fractions (HON), and hydrophilic matter (HIM) in sediments from Erhai Lake, China.

Materials and methods

Seven surface sediment samples with different environmental characteristics were collected. The DOM in the sediment was fractionated into HOB, HOA, HON, and HIM using XAD-8 resin based on compound hydrophobicity. The contents of DOM and its fractions were measured using a TOC analyzer. The structural characteristics of DOM and its fractions were investigated using fluorescence spectroscopy and UV–Vis absorbance. Correlation analyses were carried out to better understand the relationships between the parameters of the spectral characteristics and the contents of the different N forms in DOM and its fractions.

Results and discussion

The content, spatial distribution and structure of DOM and its fractions in Erhai Lake sediment were affected by water depth and aquatic plants. The DOM content in sediment ranged from 0.2 to 0.5 g kg^?1. HON accounted for 41.3 to 85.7 % of DOM, whereas HIM constituted 15.0 to 58.7 % and was significantly negatively correlated with HON (R ² ?=?0.856, P?Conclusions (1) Hydrophobic fractions are the major components of DOM in the sediments from the seven sites in Erhai Lake. (2) DOM and its fractions mainly originated from microbial sources. (3) The A ₂₅₃/A ₂₀₃ ratio is useful for evaluating the contents of N forms. The structure of DOM and its fractions are important in affecting the contents of DON. Nitrate (NO₃-N) contributes to eutrophication, and thus cannot be ignored from studies of Erhai Lake sediment.     

Salinity,chloride, and density relationships in ion enriched Onondaga Lake,NY

The relationship between salinity (S), chlorinity (Cl) and density (d) for the ion polluted (S = 3 to 4.5‰) and stratified Onondaga Lake are presented. The data base includes 220 determinations of the major ionic components collected from ten equally spaced depths. The salinity (S) and ionic strength (I) in the lake can be estimated from S = 1.85 Cl ? 0.28, where Cl is in g kg^?1 and I = 1.456 [Cl^?] ? 0.039, where [Cl] is in mmol L^?1. Due to the high concentration of Ca²⁺ in the lake, the seawater equation of state (Chen and Millero, 1977a) could not be used to estimate reliable densities for the lake (Δd ～ 100 × 10^?6 g cm^?3). A reliable equation of state for Onondaga Lake was derived from the composition data $$d = d_0 + A_v {\text{ }}CL + B_v {\text{ }}Cl^{3/2} $$ where d ₀ is the density of water (g cm^?3), A _v is a temperature dependent parameter related to the infinite dilution apparent molal volumes and B _v is related to the ion-ion interactions of the lake salts. The high ionic content of the lake depresses the temperature of maximum density to 3.18°C and alters the stratification of the lake. The salinity component of the stratification represents 40% of the total density stratification.     

On the possible introduction of non-indigenous zooplankton-feeding fishes into lake Malawi,Africa

It has been proposed that two zooplanktivorous sardines from Lake Tanganyika, Stolothrissa tanganicae and Limnothrissa miodon, be considered for possible introduction into Lake Malawi. Our data indicate that these clupeids, if introduced, would compete directly with the indigenous cichlid fishes, including the commercially important ones, all of which feed preferentially upon zooplankton. We conclude that such an introduction has a high probability of bringing about a collapse of the cichlid fisheries in Lake Malawi without the compensating increase in sardine catch. Such a prediction, of course, cannot be tested without the experiment being conducted. The data suggest that the risk to reward ratio is too large to consider such a drastic biological manipulation of Lake Malawi.     

Ecological Risk Assessment for the Recent Case of DDT Pollution in Lake Maggiore (Northern Italy)

Contamination by DDT of industrial origin was detected in 1996 in Lake Maggiore (Northern Italy) causing concern for wildlife and human health. Starting from 1998 a monitoring programme involving different research laboratories was undertaken to establish the pollution level of the lake. In assessing the ecological risk to Lake Maggiore wildlife during this period, the present study integrates information provided by the Commission for the Protection of Italian and Swiss Waters with further analysis and ecotoxicological tests carried out on some autochthonous target species for this insecticide. Sediments collected at the end of 1997 in the most contaminated bay (total DDT 860.2 ng g^?1 dry weight) caused a decrease in fertility and growth of benthic oligochaetes and chironomids, while the 48 h IC₅₀ for Daphnia galeata (0.76 μg L^?1, c.i. 0.43–1.34) was much higher than the DDT concentration in the lake water. The risk of acute effects on zooplankton should therefore be excluded, while transfer through the trophic web and bioconcentration in fish and fish-eating birds are the most adverse consequences of DDT contamination in Lake Maggiore.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Ecological consequences of invasive lake trout on river otters in Yellowstone National Park

The introduction of lake trout (Salvelinus namaycush) to Yellowstone Lake in Yellowstone National Park has contributed to a significant decline in the endangered Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri), leading to concern over the persistence of this subspecies but also to piscivorous predators in this community. We assessed the impact of lake trout on a key piscivore, the river otter (Lontra canadensis) in two lakes in Yellowstone National Park. Yellowstone Lake continues to support a native cutthroat trout population, although the recent introduction of lake trout has dramatically impacted the cutthroat trout population. Nearby Lewis Lake has an entirely introduced fish fauna of lake trout, brown trout (Salmo trutta), and Utah chub (Gilia atraria) but lacks cutthroat trout. Analysis of otter scat from Yellowstone Lake implicated trout (lake or cutthroat trout) as a major prey item (57% of scat), whereas stable isotopes identified longnose suckers (Catostomus catostomus) as the primary prey there (58% of diet). By contrast, scat from Lewis Lake implicated minnows, presumably Utah chub, as the primary prey for otters occupying that lake (86%), while stable isotopes implicated brown trout (64%) over both lake trout and Utah chub (36% combined). Our data establish the importance of alternative prey to otters and suggest that lake trout-induced reductions in cutthroat trout may not be catastrophic for otter populations here. These data do not necessarily exonerate lake trout, as their impact on other species, most notably grizzly bears (Ursus arctos) and piscivorous birds, has been documented to be substantial, and further data on the nutritional value of alternate prey are required to confirm or refute a working hypothesis that otter populations will continue to thrive in the face of the lake trout invasion.     

Experimental acidification of Little Rock Lake,Wisconsin: The first four years of chemical and biological recovery

Little Rock Lake was experimentally acidified in 1984–1990 during which sulfuric acid was added to one basin, decreasing pH from 6.1 to 5.6, 5.1 and 4.7. The lake has been allowed to recover without manipulation since autumn 1990. By the third year of recovery, ～40% of the change necessary to return to pre-acidification values of pH, acid neutralizing capacity (ANC), sulfate (SO₄ ^2?) and calcium (Ca²⁺) had occurred. During recovery years 1–2, ANC was closely predicted by models based on acidification phase observations, but recovery during years 3–4 was slower than predicted. A possible explanation for the slowed recovery is acidification of the upper 0–5 cm of sediment, which acts as a sink for the ANC generated via SO₄ ^2? reduction, the primary recovery mechanism. Trends for Zooplankton did not follow pH recovery very closely. Species diminished by acidification (e.g. Keralella cochlearis, Daphnia dubia) have not recovered, but species that dominated the community at pH 4.7 (e.g. K. taurocephala, D. catawba) have not maintained high populations. The time required for the Zooplankton community to recover to pre-manipulation conditions is uncertain. Delays also have been observed for the mayfly species Caenis, which had disappeared at pH 4.7. In contrast, reproductive success of largemouth bass (Micropterus salmonides) mirrored that observed during acidification; egg hatch and survival of young-of-the-year to autumn recurred when pH exceeded response levels documented during acidification. Overall, recovery has not closely followed the pattern predicted by acidification responses.     

Age-Dependent Bioaccumulation of Organochlorine Compounds in Fish and their Selective Biotransformation in Top Predators from Lake Maggiore (Italy)

Fish and piscivorous bird eggs collected in 2003 from Lake Maggiore (Italy), were analysed for PCB and DDT contamination. Lake Maggiore has been severely polluted by DDT through production of the pesticide within its catchment. Although agricultural application of DDT was banned in Italy in the 1978, industrial production continued until 1996, with enough contamination of water and soil for serious bioaccumulation in the lake biota. PCB and DDT concentrations in a whitefish (Coregonus macrophthalmus Nusslin 1882) were seen to be dependent on season and fish age, but not on sex. The average increase of the lipid-normalised concentration of DDTs and PCBs was two-fold across season and also across age, resulting in an overall increase of four fold. The seasonal variation was related to the eco-physiological cycle of the fish and to the contamination dynamic of the lake, while the effect of the fish age was explained on the base of biomagnification-related mechanisms. A fugacity model was applied to predict the age-dependent bioaccumulation potential of PCBs, whose concentrations were rather stable in recent years in the lake. Predicted values for compounds with negligible biotransformation were in good agreement with experimental data (calculated vs. experimental mean difference of 14%), and a relationship between the increase of experimental age-dependent concentration and K _ow was observed. The good correspondence between the predicted and the measured values for most PCB congeners confirmed the general inability of fishes to biotransform these compounds. On the contrary, the importance of biotransformation processes was recognised in birds; eggs of a fish eating bird (Podiceps cristatus) from the same area selectively bioaccumulated p,p′-DDE. For PCBs, congener 149 appears to be completely metabolized by the bird species, and congeners 95, 101, 132, 151 and 174 were reduced as well. The role of the meta–para free position on at least one phenyl ring of PCB congeners in biotransformation processes was confirmed.