Bioaccumulation Dynamics Research Articles

Comparative fate of organohalogen contaminants in two top carnivores in Greenland: Captive sledge dogs and wild polar bears

The limited knowledge and/or the inability to control physiological condition parameters that influence the fate of organohalogen contaminants (OHCs) has been the foremost confounding aspect in monitoring programs and health risk assessments of wild top predators in the Arctic such as the polar bear ( Ursus maritimus). In the present comparative study, we used a potential surrogate Canoidea species for the East Greenland polar bear, the captive sledge dog ( Canis familiaris), to investigate some factors that may influence the bioaccumulation and biotransformation of major chlorinated and brominated OHCs in adipose tissue and blood (plasma) of control (fed commercial pork fat) and exposed (fed West Greenland minke whale ( Balaenoptera acutorostrata) blubber) adult female sledge dogs. Furthermore, we compared the patterns and concentrations of OHCs and their known or suggested hydroxylated (OH) metabolites (e.g., OH-PCBs) in sledge dogs with those in adipose tissue and blood (plasma) of East Greenland adult female polar bears, and blubber of their main prey species, the ringed seal ( Pusa hispida). The two-year feeding regime conducted with sledge dogs led to marked differences in overall adipose tissue (and plasma) OHC residue accumulation between the control and exposed groups. Characteristic prey-to-predator OHC bioaccumulation dynamics for major PCB and PBDE congeners (patterns and concentrations) and biotransformation capacity with respect to PCB metabolite formation and OH-PCB retention distinguished, to some extent, captive sledge dogs and wild polar bears. Based on the present findings, we conclude that the use of surrogate species in toxicological investigations for species in the Canoidea family should be done with great caution, although they remain essential in the context of contaminants research with sensitive arctic top carnivore species such as the polar bear.

Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 2-Polychlorinated biphenyls

The temporal variability and bioaccumulation dynamics of individual PCBs were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the polluted Buenos Aires coastal area. Fish muscles contain high concentrations of total PCBs (11 ± 7.2, 4.6 ± 3.4 or 19 ± 13 μg g −1, dry, fresh and lipid weight, respectively) reflecting chronic bioaccumulation from sewage-industrial particulates. On a temporal basis, lipid normalized PCBs concentrations peaked by the end of 2001–2002 coincident with the rainiest period over the last four decades and shortly after PCB prohibition in the country, reflecting massive discharges to the coastal ecosystem. PCB composition in fish muscles show a prevailing contribution of hexachlorobiphenyls (35 ± 4.2%), followed by hepta (23 ± 3.0%), penta (20 ± 3.6%), tri-tetra (16 ± 4.8%) and minor proportions of octa-decachlorobiphenyls (5.7 ± 3.1%) similar to an Aroclor 1242–1254–1260 1:2:4 mixture. During 2001–2002 maxima fish showed an enrichment in tri-tetrachlorobiphenyls (∼1242–1254–1260 1:1:1 mixture) denoting a fresher signature. Fish/settling material lipid-organic carbon accumulation factors (BSAFs: 2.4–46, average: 21 ± 10) plotted against k ow showed a parabolic trend (BSAFs = −0.38 log k ow 2 + 5.16 log k ow −15.85; R 2 = 0.46) maximizing at hexa, hepta and octachlorobiphenyl 203 with reduced bioaccumulation of a few hepta (170, 191) and most octa-decachlorobihenyls suggesting limited intestinal absorption.

Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 1-Aliphatic hydrocarbons

The temporal variability and bioaccumulation dynamics of C 12–25 n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C 12–25 (165 ± 93, 70 ± 48 or 280 ± 134 μg g −1, dry, fresh and lipid weight, respectively) and UCM (931 ± 560, 399 ± 288 and 1567 ± 802 μg g −1) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001–2002 during the rainiest period over the last four decades (1750 vs. 1083 ± 4.6 mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C 15–17 and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001–2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4–6.4 dry weight or 0.07–0.94 lipid-organic carbon) plotted against K ow showed a parabolic pattern maximizing at n-C 14–18 and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log K ow: 7.2–9.9), intermediate-size C 14–18 n-alkanes and C 15–20 isoprenoids (MW: 198–282; length: 17.9 to 25.4 Å) with melting points ranging from −19.8 to 28 °C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C 25 to above 90% for n-C 14–15 and isoprenoids.

Delineating copper accumulation pathways for the freshwater bivalve Corbicula using stable copper isotopes

Delineation of metal uptake routes in aquatic invertebrates is critical for characterizing bioaccumulation dynamics and assessing risks associated with metal exposure. Here we demonstrate that Cu stable isotopic ratios can be manipulated in both exposure media and algae to determine the efflux rate constant (ke) and to estimate Cu assimilation efficiency (AE) from ingested food in a freshwater bivalve (Corbicula fluminea). The Cu AE in Corbicula fed 65Cu-spiked Cryptomonas ozolini was 38%. Copper uptake routes had no significant influence on efflux; ke of 0.004 per day characterized the slowest component of efflux following short-term exposures to 65Cu in water or in both food and water. Incorporation of the physiological parameters for dietary and dissolved uptake as well as rate constants of loss into a bioaccumulation model allowed for assessing the relative contribution of water and food as Cu sources. At [65Cu2+] of 6.7 microg/L, Corbicula accumulated twice as much Cu from diet as from water. In most freshwater systems, the dietary pathway is likely to act as the major Cu uptake route for Corbicula. Extrapolation of our laboratory results to the San Francisco Bay-Delta (California, USA) indicated that our biodynamic model and the laboratory-derived parameters for dietary 65Cu uptake provided a realistic representation of the processes involved in Cu accumulation by the bivalve Corbicula.

An individual-oriented model for ecological risk assessment of wading birds

The contribution of certain contaminants to reproductive failure in many avian species has been an ongoing concern. Appropriate quantitative techniques have focused either on the individual organisms by providing explicit bioaccumulation dynamics or on whole ecosystems by looking at the fate of the contaminant but fail to make the necessary link via population dynamics of interacting individuals. We used the individual-oriented approach in an effort to quantify effects of chronic contaminant exposure on individual birds. This was made possible by the use of an object-oriented model, where individual birds are interacting objects, and their actions are implemented by passing to them appropriate messages. Using this modeling approach a breeding colony of Great Blue Herons ( Ardea herodias) is simulated as an assemblage of interacting individuals whose daily actions (foraging, growth, feeding of the young) are simultaneously followed over short time intervals for a nesting season. Spatial distribution of the contaminants in prey resources is used on a cell by cell basis and their effects on certain behavior characteristics of adult birds (e.g. foraging efficiency, effects on flying efficiency, parental care) are taken into account. Results showed that sublethal effects could have a considerable effect on colony success. Appropriate selection of endpoints for risk assessment yields a variety of scenarios for colony success.

Seasonal Dynamics of PCB and Toxaphene Bioaccumulation within a Lake Michigan Food Web

Seasonal variations in PCB and toxaphene concentrations were measured in bulk zooplankton, mysid shrimp, benthic amphipods, alewife, and bloater chub collected from Grand Traverse Bay, Lake Michigan between April and September of 1997 and 1998. Concentrations of PCBs in the dissolved phase of the water column were consistent over time; however, seasonal changes in contaminant concentrations within the biota were significant. Seasonal changes were most pronounced in zooplankton, which displayed highest PCB burdens in April and decreased by as much as 75% through September, coincident with changes in phytoplankton biomass, species composition, and changes in the particulate pools of PCBs within the water column. Mysis sp. display a similar PCB trend as zooplankton, while Diporeia sp. displayed maximal PCB concentrations in late summer during 1997. PCB trends in the primary forage fish alewife ( Alosa pseudoharengus) and bloater ( Coregonus hoyi) were correlated more to shifts in lipid content and seasonal diet preferences. PCB concentrations were higher (p < 0.01) in bloater (310 ± 98 ng/g wet weight) than alewife (233 ± 70 ng/g wet weight), however alewife possessed higher toxaphene burdens (198 ± 72 ng/g wet weight) than bloater (88 ± 36 ng/g wet weight). Alewife contaminant burdens were high in spring and fall of both years, decreasing by as much as 60% in midsummer, and were reflective of changes measured in their lipid content associated with gamete production and spawning. These results suggest that despite invariant concentrations of the dissolved pool of PCBs within the lake, accumulation of PCBs by the biota on seasonal scales is controlled appreciably by growth and lipid dynamics, and foraging behavior.

Sediment-associated retene bioavailability of sediment-associated retene to an oligochaete wormlumbriculus variegatus

The bioavailability of retene spiked to two sediment concentrations (50 and 200 µg/g dry weight) was measured in long-term (28-day) bioaccumulation tests performed on the oligochaeteLumbriculus variegatus Muller. Three sediment organic carbon (SOC) concentrations (1.1, 3.0, 23.0% of dry weight) were used. Growth and reproduction, used as endpoints, indicated that retene was chronically nontoxic at the concentrations employed. Retene was clearly bioavailable, but bioaccumulated about 100 times less in the SOC-rich (23.0%) sediment than in the other two (SOC <3.0%). At the lower retene concentration, retene in the worms was undetectable in the high-SOC sediment. Based on final retene present at the end of exposure, the bioaccumulation factors (BAFs) ranged between 1.1–28.2. Normalization to organism lipid and SOC content diminished the variation, so that the biota-sediment accumulation factors (BSAFs) varied from 0.8 to 13.5. When calculated from initial retene concentrations, BAFs within the range of 0.04 to 5.3 and BSAFs from 0.1 to 2.5 were obtained. Results demonstrate that high levels of SOC diminish the bioavailability of sediment-associated retene inL. variegatus considerably. However, the remainder variation in the BSAFs suggests that besides of SOC and worm lipid contents there are also other factors that can affect the bioaccumulation dynamics of sediment-associated retene and the final outcome of its bioavailability.

An optimal trace zinc biomonitor ( Haliotis diversicolor supertexta) control system design in aquacultural ecosystems

The purpose of this paper is to synthesize an optimal trace metal biomonitor control system to efficiently manage aquacultural water quality. A biomonitor organism of gastropod mollusc Haliotis diversicolor supertexta was chosen to estimate zinc (Zn) bioaccumulation. The bioaccumulation dynamics of Zn by H. diversicolor supertexta from an alga Gracilaria tenuistipitata var. liui and ambient water in aquaculture ponds is developed based on a six-compartment pharmacokinetic model. A linear control model based on the dynamic bioaccumulation model is developed to design an optimal feedback biomonitor control system. Linear quadratic regulators (LQRs) with output feedback control of a linear-invariant system are assigned for design algorithm and an optimal proportional plus integral (PI) feedback control strategy is synthesized. Numerical results from the model implementation show that the optimal selection of tuning parameters and the resulting costs vary with desired equilibrium state. The designed optimal feedback biomonitor control system, when suitably tuned, gives a satisfactory monitor of mollusc Zn bioaccumulation. The biomonitor control system developed accounting for bioaccumulation dynamics of Zn in the target tissues of molluscs can be used in the future to evaluate the effects of suspended solid removal devices and biofilters and/or other control scenarios on water quality management in aquacultural ecosystems.

Assessment of the consequences of the radioactive contamination of aquatic media and biota for the Chernobyl NPP cooling pond: model testing using Chernobyl data

The ‘Cooling Pond’ scenario was designed to test models for radioactive contamination of aquatic ecosystems, based on data from the Chernobyl Nuclear Power Plant cooling pond, which was heavily contaminated in 1986 as a result of the reactor accident. The calculation tasks include (a) reconstruction of the dynamics of radionuclide transfer and bioaccumulation in aquatic media and biota following the accident; (b) assessment of doses to aquatic biota; and (c) assessment of potential doses and radiation risks to humans from consumption of contaminated fish. Calculations for the Scenario were performed by 19 participants using 6 different models: LAKECO-B (Netherlands); LAKEPOND (Romania); POSOD (USA); WATER, GIDRO and ECOMOD-W (Russia). For all endpoints, model predictions were compared with the test data, which were derived from the results of direct measurements and independent dose estimates based on measurements. Most of the models gave satisfactory agreement for some portions of the test data, although very few participants obtained good agreement with all criteria for model testing. The greatest level of difficulty was with the prediction of non-equilibrium radioecological processes in the first year after the accident (1986). The calculations 5 for this scenario gave modellers a unique opportunity to test their models using an independent data base and to analyse the advantages and weaknesses of different model approaches. The use of post-Chernobyl data in such a scenario is also recommended for use in training students in the field of radioecology and environmental protection.

Automated quality assurance checks on model structure in ecological risk assessments

Abstract A major criticism routinely leveled against probabilistic risk assessments of putative ecological impacts is that there has been insufficient validation of the model employed in the assessment. The only complete solution to this problem would involve concentrated scientific effort to test and validate the model, which is generally beyond the scope of the risk assessment effort. However, there are several computational checks applicable to all models used in risk analysis that can be employed to ensure the absence of several classes of structural and mathematical errors. Several kinds of profound errors which are routinely committed in practice, including violations of •dimensional and unit concordance•feasibility of correlation matrices, and•single instantiations of a repeated variable, can all be detected using currently available software approaches. Additionally, domain knowledge from ecology can also be marshalled to check the validity of the model in its representation of biological reality. Such knowledge includes facts such as •species abundances cannot be negative,•bioaccumulation dynamics are constrained by trophic interactions, and•food web structure is nonrandom Taken together, these two classes of checks on the model constitute elementary methods of quality assurance for model structure.

Dynamics of dietary bioaccumulation and faecal elimination of hydrophobic organic chemicals in fish

A compilation of available literature data on uptake efficiencies of hydrophobic, organic chemicals from food by fish is presented. It is shown that the uptake efficiency of chemical from food (E O) follows a relationship with the 1-octanol-water partition coefficient (K OW), i.e., 1 E O = 5.3.10 −8 .K OW + 2.3. A model is derived for chemical uptake from food, which is shown to be consistent with the observed food-uptake data. The equations provide an explanation for the phenomenon of food chain accumulation, which is observed in natural ecosystems for several hydrophobic halogenated aromatic hydrocarbons.

Movement and distribution of radionuclides on granitic outcrops within the Georgia piedmont.

From 1962 through 1964, radioactive fallout in parts of the southeastern U.S. has been detected in greater quantity than in many other places of the country. Flatrock ecosystems in Georgia retain very little rainwater; most run-off water flows through a series of communities which filter and retain fallout radionuclides. When fallout-bearing water flowed over barren rocks, lowland communities always held more radionuclides than upland communities. Usually, however, upland communities removed particular isotopes from surplus run-off water. Parmelia conspersa, an “upland” lichen, had higher concentrations of 137Cs (up to 300 pCi/g dry wt.) than any other plant in 1964. Viguiera porteri, an aster, held the largest concentrations of 90Sr (up to 125 pCi/g). Concentrations of fallout were higher in upland Juniperus virginiana than in lowland populations, although the spectrum of isotopes at both sites was similar. Even though each granitic outcrop as a whole is a relatively simple ecological system, it consists of smaller systems wherein the dynamics of radioisotope movements and bioaccumulation can be understood only in terms of intimate familiarity with each little system contributing to the whole. Maximum concentration levels for any component have not been ascertained; nevertheless, accumulation of isotopes within Parmelia and Viguiera may well indicate the extent to which fallout has become an environmental “contaminant” in the Southeast.