Accumulation of polychlorinated biphenyls (PCB) associated with bottom sediments in larvae of Chironomus riparius Meigen
Introduction
Polychlorinated biphenyls (PCBs) are organochlorine compounds representing one of the most widespread groups of persistent organic pollutants (POP). Owing to a general resistance to physical, chemical, and biological degradation, PCBs can circulate in the environment for decades (Borlakoglu and Heagele, 1991; Lang, 1992; Safe, 1994; Urbaniak, 2007). PCBs are extremely hydrophobic and in the aquatic environment are readily absorb onto mineral and organic suspended particles including planktonic organisms (Suffet et al., 1994; Niimi, 1996; Jones and de Voogt, 1999). Particle-associated PCBs are transported with water currents over long distances and gradually precipitate to the bottom, accumulating in natural bottom sediments within depositional zones of sedimentation (Choi and Al-Abed, 2009). As such, sediments are primary sinks for PCBs in freshwater bodies. In addition, the above-mentioned properties lead to uneven spatial distribution of PCBs in sediments after entering waterbodies from local sources of pollution (Chuiko et al., 2010). Hence, the main way PCB uptake occurs in aquatic animals is through the alimentary tract, through consumption of food (Rubinstein et al., 1984a, b). From sediments, PCBs are transferred first-of-all to benthic invertebrates, then along food chains to higher trophic levels. High lipophylicity of PCB facilitate their considerable bioaccumulation in aquatic biota (Beyer and Biziuk, 2009; Bettinetti et al., 2012).
Midge larvae of the family Chironomidae are an extremely important component of freshwater benthos in northern temperate lake and riverine ecosystems. In Rybinsk Reservoir, the share of these invertebrates in the community of macrozoobenthos reaches 40 % by number and 70 % by biomass (Perova, 2012). Chironomid larvae dominate the diet of benthivorous fish (Zhiteneva, 1981a, b) and represent one of the primary links in the transfer of PCBs from sediments to biota. However, papers dealing with accumulation of sediment-associated PCB in chironomids are scarce and contradictory. According to some authors, chironomids possess high bioaccumulation capability for PCB (Meier and Rediske, 1984); according to others this capability is low (Zaranko et al., 1997; Bott and Standley, 2000; Yu et al., 2013). To our knowledge, no information is provided in scientific literature about bioaccumulation of PCB homolog groups by chironomid larvae.
The goal of the present paper is to examine under laboratory conditions the patterns of PCB accumulation, their homologous groups, and congeners, by chironomid larvae exposed to sediments from two different locations in Rybinsk Reservoir. The exposures represent sediments contaminated at two different PCB concentrations as well as two different PCB congener profiles.
Section snippets
Test animal cultivation
Laboratory-reared larvae of chironomids Chironomus riparius Meigen were used for the study. The chironomids were cultivated on clean sediment and settled well-water (pH 7.0–7.5, total hardness 4.0–4.5 mM eq/l Ca++and Mg++, dissolved oxygen content at saturation, water temperature 20 ± 2 оC and maintained constant). Larvae were fed daily with yeast suspension.
Test bottom sediments collection
The bottom sediments (0–30 cm layer) were sampled at Rybinsk Reservoir in September 2006 from the board of Papanin Institute for Biology
Results
Calculated from our previous data (425.6 and 24.8 μg / kg dry weight), the sum content of PCBs in sediments were 2503.5 and 145.9 μg / kg TOM, respectively, for NBS I and NBS II (Table 1). Chironomid larvae exposed to these sediments contained PCBs at concentrations of 114.9 and 4.7 μg / kg wet weight, for CG I and II, respectively. Considering that lipid content in chironomid larvae was determined at 1.25 % of total body wet weight, the sum PCB content calculated on a lipid weight basis was
Discussion
It is known that the bioaccumulation of hydrophobic xenobiotics (including PCB) by aquatic organisms depends on the balance of several processes: rate of intake, metabolism, detoxification and elimination, duration of exposure, and level of lipid content in the organism (Mackay and Fraser, 2000). Metabolic detoxification and elimination of PCBs are slow processes. This, along with high lipophylicity of these compounds, determines their high bioaccumulation capacity irrespective of many
Conclusions
In summary, this study revealed that chironomid larvae C. riparius reared for 20 days on sediments from Rybinsk Reservoir, Russia, accumulate PCB in proportion to the content in sediments; however, the BSAF values measured in this study were lower, presumably due to the high organic carbon content in bottom sediments (13–17 %). The BSAF values were 1.11 and 1.59 (dry wt), with the slightly greater value observed at the site with greater PCB concentrations in the sediment. Lastly, the PCB
Author statement
Chuiko G. M. — formulation of goals and objectives, design of the experiment, sampling of bottom sediments, analysis of all data, writing an article, submission to the journal; Tomilina I.I. — cultivation of chironomid larvae and their rearing on bottom sediments; drawing a map-scheme of the Rybinsk reservoir; Brodsky E.S. — analysis of PCB data; Shelepchikov A.A. — determination of PCB in the samples of chironomid larvae and bottom sediments; Mir-Kadyrova E.Ya. — preparing of samples of
Ethical approval
The sampling and cultivation of invertebrates and bioaccumulation experiments were carried out under the ethical approval of the Ethical Committee of the Institute for Biology of Inland Waters of Russian Academy of Sciences.
CRediT authorship contribution statement
Grigorii M. Chuiko: Conceptualization, Methodology, Investigation, Funding acquisition, Formal analysis, Writing - original draft. Irina I. Tomilina: Methodology, Investigation, Formal analysis, Writing - review & editing. Efim S. Brodsky: Methodology, Formal analysis, Writing - review & editing. Andrey A. Shelepchikov: Methodology, Investigation, Formal analysis, Writing - review & editing. Elena Ya. Mir-Kadyrova: Supervision, Resources, Investigation. Dmitry F. Pavlov: Investigation,
Declaration of Competing Interest
The authors report no declarations of interest.
Acknowledgments
The study was performed in the frameworks of the state assignment of FASO Russia (No. 121050500046-8) and long-term international collaboration between IBIW RAS (Russia) and USGS CERC (USA), and financially supported in part by the Russian Foundation for Basic Research (grants RFBR ##08-05-00805 and 12-05-00572). We are grateful to N. N. Nazarova of the laboratory of fish ecology of IBIW RAS who provided the cultivated chironomid larvae. Thanks to Dr. Christopher T. Robinson for assistance on
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