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Toxic anthropogenic pollutants reach the deepest ocean on Earth

S. Dasgupta1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

X. Peng1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

S. Chen1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

J. Li1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

M. Du1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

Y.-H. Zhou2,

2State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China

G. Zhong3,

3State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

H. Xu1,

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

K. Ta1

1Deep Sea Science Division, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan 572000, China

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Dasgupta, S., Peng, X., Chen, S., Li, J., Du, M., Zhou, Y.-H., Zhong, G., Xu, H., Ta, K. (2018) Toxic anthropogenic pollutants reach the deepest ocean on Earth. Geochem. Persp. Let. 7, 22–26.

The Strategic Priority Research Program of the Chinese Academy of Sciences (Grant no. XDB06020000) and the National Key Basic Research Program of China (Grant no. 2015CB755905).

Geochemical Perspectives Letters v7  |  doi: 10.7185/geochemlet.1814
Received 04 February 2018  |  Accepted 18 April 2018  |  Published 14 May 2018
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0


Keywords: persistent organic pollutants, Mariana Trench, PCB, PBDE, anthropogenic pollutants



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Abstract


Persistent organic pollutants (PCBs and PBDEs) were analysed in sediment core samples (0-2 cm) from the southern Mariana Trench at water depths of 7000-11000 m. ∑PCBs concentrations ranged from 931 to 4195 pg/g, far higher than those recorded before in marine sediments from shallower depths. Toxic Equivalence (TEQ) of dl-PCBs ranged from 0.650 – 14.9 pg/g, which is higher than most marine surficial sediments at <500-2500 m ocean depth, recovered from semi-industrial to industrial areas. However, ∑8PBDEs values (averaging ~136 pg/g) were lower than those in surficial sediments from shelf areas recorded in past studies. Evidently, anthropogenic pollutants have reached the deepest realm on Earth, and the Mariana Trench acts as a repository for POPs amplification. The high concentration of PCBs is an eye-opener, which is directly affecting our deep sea ecosystems, considering their pervasiveness and persistence in trench sediments.

Figures and Tables

Figure 1 Sampling location map of Mariana Trench sediments.

Figure 2 Concentrations of PCB congeners (pg/g d.w.) for different sampling locations at various water depths, as represented by coloured stacked bars. Refer to Table S-2 for details.

Figure 3 Concentrations of PBDE congeners (pg/g d.w.) for different sampling locations at various water depths, as represented by coloured stacked bars. Refer to Table S-3 for details.

Figure 4 Comparison of ∑PCBs concentrations in the Mariana Trench sediments with other worldwide marine surface water sediments. Figures in brackets indicate water depth.

Figure 1 Figure 2 Figure 3 Figure 4

View all figures and tables  


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Letter


The deep ocean arguably acts as the largest potential sink for discarded pollutants (Dachs et al., 2002

Dachs, J., Lohmann, R., Ockenden, W.A., Mejanelle, L., Eisenreich, S.J., Jones, K.C. (2002) Oceanic biogeochemical controls on global dynamics of persistent organic pollutants. Environmental Science and Technology 36, 4229-4237.

). However, the hadal zone (~6000 to 11000 m deep), which represents the deepest ocean on Earth, has largely been unexplored due to its remoteness. Of all the toxic anthropogenic pollutants damaging the oceans, persistent organic pollutants (POPs) are of particular concern due to their robust residence time in the environment (Kukučka et al., 2015

Kukučka, P., Audy, O., Kohoutek, J., Holt, E., Kalábová, T., Holoubek, I., Klánová, J. (2015) Source identification, spatio-temporal distribution and ecological risk of persistent organic pollutants in sediments from the upper Danube catchment. Chemosphere 138, 777-783.

), global transport through atmospheric and oceanic currents (Wania and Mackay, 1996

Wania, F., Mackay, D. (1996) Tracking the distribution of persistent organic pollutants. Environmental Science and Technology 30, 390A-396A.

), and their ability to bioaccumulate in marine foodwebs (Lohmann et al., 2007

Lohmann, R., Breivik, K., Dachs, J., Muir, D. (2007) Global fate of POPs: current and future research directions. Environmental Pollution 150, 150-165.

), resulting in organism endocrine disruption (Rhind, 2012

Rhind, S.M. (2012) Anthropogenic pollutants- an insidious threat to animal health and productivity? Acta Veterinaria Scandinavica 54, S2.

) and other adverse health effects. Studies revealing presence of POPs in surface to deep marine sediments are plentiful (e.g., Iwata et al., 1994

Iwata, H., Tanabe, S., Aramoto, M., Sakai, N., Tatsukawa, R. (1994) Persistent organochlorine residues in sediments from the Chukchi Sea, Bering Sea and Gulf of Alaska. Marine Pollution Bulletin 28, 746-753.

; Ma et al., 2015

Ma, Y., Halsall, C.J., Crosse, J.D., Graf, C., Cai, M., He, J., Gao, G., Jones, K. (2015) Persistent organic pollutants in ocean sediments from the North Pacific to the Arctic Ocean. Journal of Geophysical Research: Oceans 120, 2723-2735.

; Combi et al., 2016

Combi, T., Miserocchi, S., Langone, L., Guerra, R. (2016) Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories. Science of the Total Environment 562, 580-587.

; Neira et al., 2018

Neira, C., Vales, M., Mendoza, G., Hoh, E., Levin, L.A. (2018) Polychlorinated biphenyls (PCBs) in recreational marina sediments of San Diego Bay, southern California. Marine Pollution Bulletin 126, 204-214.

), but none of them probed beyond the continental shelf area, leaving the real “depth” of the oceans practically unexplored. In a latest study, Jamieson et al. (2017)

Jamieson, A.J., Malkocs, T., Piertney, S.B., Fujii, T., Zhang, Z. (2017) Bioaccumulation of persistent organic pollutants in the deepest ocean fauna. Nature Ecology and Evolution 1, 0051.

reported high concentrations of POPs in endemic amphipod fauna from the Mariana and Kermadec Trenches. The signature of these pollutants through bioaccumulation could, however, be markedly different from that residing in the sediments.

The Mariana Trench is located in the western Pacific Ocean, where the Pacific Plate subducts beneath the Mariana and Philippine Sea Plates at convergence rates of 4–8 cm/yr. The southern Mariana Trench encloses the deepest point on the Earth's surface-the Challenger Deep, which is 11034 m down, and 2 km deeper than the average depth along the axis of the Mariana Trench (Fujioka et al., 2002

Fujioka, K., Okino, K., Kanamatsu, T., Ohara, Y. (2002) Morphology and origin of the Challenger Deep in the Southern Mariana Trench. Geophysical Research Letters 29, doi: 10.1029/2001GL013595.

).

We detected polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in five sediment samples recovered from the southern Mariana Trench at ocean depths of 6980 m (C1-I-M-S015B02), 8638 m (C1-I-M-S078B10), 9373 m (TS03-S106GT02 (S) and TS03-S106GT02 (D) for top and bottom surface of the core respectively), and 10908 m (TS03-S090LANDER11), (Fig. 1), during TS03 Hadal Trench Cruise carried out via R/V Tansuo Yihao on June, 2017 (See Table S-1 for sampling location details).


Figure 1 Sampling location map of Mariana Trench sediments.
Full size image | Download in Powerpoint

The prominent finding was that, 36 PCB and 10 PBDE congeners (Figs. 2 and 3 respectively) were detected. Lower-chlorinated congeners such as CB-8, CB-37, CB-52 and CB-60 were most abundant (refer to Table S-2), and their concentrations ranged from 1460 to 3300 pg/g. For PBDEs, concentrations ranged from 245 (TS03-S106GT102 (S)) to 591 pg/g (TS03-S090LANDER11) (Table S-3). Low and medium weight PBDEs, such as BDE-47 and BDE-153 were more common in the samples. However, higher weight BDEs 207 and 208 were detected in C1-I-M-S015B02 and TS03-S090LANDER11, with high concentrations of 266 and 280 pg/g respectively.


Figure 2 Concentrations of PCB congeners (pg/g d.w.) for different sampling locations at various water depths, as represented by coloured stacked bars. Refer to Table S-2 for details.
Full size image | Download in Powerpoint


Figure 3 Concentrations of PBDE congeners (pg/g d.w.) for different sampling locations at various water depths, as represented by coloured stacked bars. Refer to Table S-3 for details.
Full size image | Download in Powerpoint

∑PCBs (pg/g) concentrations ranged from 931-4195 pg/g dry weight in all five sediment samples. The Mariana sediments showed higher levels of low- and medium-chlorinated PCB congeners. It is noteworthy that no clear trend of ∑PCB variation with water depth was observed (Fig. S-1).

The seven “indicator PCBs” (Table S-4) chosen following the International Council for the Exploration of the Sea (ICES) convention contributed to 22 % of all PCBs. They showed highest Σ7PCBs values at depths of 8638 m and 9373 m. CB-52 was abundant in most of the samples, except in C1-I-M-S015B02, where it was not detected. These PCBs are indicative of lipophilic contaminants, but their concentrations can vary with the contaminated source (Kim et al., 2004

Kim, M.K., Kim, S., Yun, S., Lee, M., Cho, B., Park, J., Son, S, Kim, O. (2004) Comparison of seven indicator PCBs and three coplanar PCBs in beef, pork, and chicken fat. Chemosphere 54, 1533-1538.

). High concentrations of low-chlorinated CBs, such as CB-52 may be from processes using chlorine oxidation; further, high-chlorinated CBs could be decayed to lighter ones by bacterial decomposition (Kim et al., 2004

Kim, M.K., Kim, S., Yun, S., Lee, M., Cho, B., Park, J., Son, S, Kim, O. (2004) Comparison of seven indicator PCBs and three coplanar PCBs in beef, pork, and chicken fat. Chemosphere 54, 1533-1538.

). Presence of mid-chlorinated CBs, such as Penta-CB (CB-101) and Hexa-CBs (CB-138 and CB-153) could be related to partitioning of these compounds to particulate organic matter. High-chlorinated PCBs, such as CB-180 possibly came from terrestrial pollution in the form of industrial sewage, or from marine traffic (Hong et al., 2005

Hong, S.H., Yim, U.H., Shim, W.J., Oh, J.R. (2005) Congener-specific survey for polychlorinated biphenyls in sediments of industrialized bays in Korea: regional characteristics and pollution sources. Environmental Science and Technology 39, 7380-7388.

). Although no pattern in concentration vs. water depth was evident, deeper trench samples (C1-I-M-S078B10, TS03-S106GT02 (S), TS03-S106GT02 (D), and TS03-S090LANDER11) exhibited higher Σ7PCBs (average 642.2 pg/g) than C1-I-M-S015B02 (129 pg/g) values.

Toxic potency of PCBs was assessed by measuring Toxic Equivalence (TEQ) of twelve dioxin-like (dl-) CB congeners (CB-77, 81, 126, 169, 105, 114, 118, 123, 156, 157, 166, and 189) in all the sediment samples (normalised by multiplying their measured concentrations by the appropriate WHO-TEFs) (Table S-5). The respective TEQPCBs express these analyte concentrations as a single number, which is equivalent to toxicity derived exclusively from 2,3,7,8-TCDD. Mariana dl-PCB-TEQ concentrations ranged from 0.650 – 14.9 pg/g (Table S-6), with the highest TEQPCBs recorded at 9373D. Our results are higher than TEQPCBs values from past studies with sediments from shallow water depths, e.g., a semi-industrial area, Asaluyeh Harbor, Iran (0.001-3.4) (Arfaeinia et al., 2017

Arfaeinia, H., Asadgol, Z., Ahmadi, E., Seifi, M., Moradi, M., Dobaradaran, S. (2017) Characteristics, distribution and sources of polychlorinated biphenyls (PCBs) in coastal sediments from the heavily industrialized area of Asalouyeh, Iran. Water Science and Technology 76, 3340-3350.

); marine sediments from Mediterranean Sea, Catalonia, Spain (0.03-24.8) (Eljarrat et al., 2001

Eljarrat, E., Caixach, J., Rivera, J. (2001) Toxic potency of non- and mono-ortho PCBs, PCDDs, PCDFs, and PAHs in Northwest Mediterranean sediments (Catalonia, Spain). Environmental Science and Technology 35, 3589-3594.

); or Han River, Korea (0.0118-0.626) (Kim et al., 2009

Kim, K.S., Lee, S.C., Kim, K.H., Shim, W.J., Hong, S.H., Choi, K.H., Yoon, J.H., Kim, J.G. (2009) Survey on organochlorine pesticides, PCDD/Fs, dioxin-like PCBs and HCB in sediments from the Han river, Korea. Chemosphere 75, 580-587.

). Surface marine sediments in shallow water are susceptible to organic pollution due to their proximity to industrial areas, as well as from atmospheric interactions. It is however, surprising to witness such contaminants have reached the deepest parts on Earth.

Unlike PCBs, concentrations of PBDEs were lower in the Trench samples. To maintain consistency (since PBDEs are presented as mixtures of congeners), and form a comparable dataset, a total of 8 PBDEs (BDE-28, 47, 99, 100, 153, highlighted in blue in Table S-3; BDE-54, 183, and 209 were not detected) were chosen (Zhang et al., 2016

Zhang, Y., Wang, W., Song, J., Ren, Z., Yuan, H., Yan, H., Zhang, J., Pei, Z., He, Z. (2016) Environmental characteristics of polybrominated diphenyl ethers in marine system, with emphasis on marine organisms and sediments. BioMed Research International 2016, Article ID 1317232, 16 pp, doi: 10.1155/2016/1317232.

), which commonly occur in environmental samples. Their concentrations ranged from 36-289 pg/g. Mid-brominated congener BDE-153 was the most abundant, with concentrations ranging from Yogui and Sericano, 2009

Yogui, G.T., Sericano, J.L. (2009) Polybrominated diphenyl ether flame retardants in the U.S. Marine environment: a review. Environment International 35, 655-666.

), and were found at concentrations of de Wit, 2002

de Wit, C.Y., (2002) An overview of brominated flame retardants in the environment. Chemosphere 46, 583-624.

) and in Qingdao coastal sea sediments (Pan et al., 2007

Pan, J., Yang, Y.-L., Xu, Q., Chen, D.-Z., Xi, D.-L. (2007) PCBs, PCNs and PBDEs in sediments and mussels from Qingdao coastal sea in the frame of current circulations and influence of sewage sludge. Chemosphere 66, 1971-1982.

), China where BDEs 47, 99, and 153 were the most frequently reported congeners. Our results indicate that penta-BDEs could possibly be transported with water in the soluble and particle phases and degradation and fractionation of higher-brominated congeners (such as PBDE 209) may occur during long range transportation. ∑8PBDEs values (range Table S-3) for Mariana Trench sediments are lower than those in shallow water surface marine sediments recorded in past studies. Looking at the research carried in San Francisco Bay sediments, the ∑8PBDEs in each sample area (Suisun Bay, San Pablo Bay, Central Bay, and South Bay) range from 2.46-5.14 ng/g (Klosterhaus et al., 2012

Klosterhaus, S.L., Stapleton, H.M., La Guardia, M.J., Greig, D.J. (2012) Brominated and chlorinated flame retardants in San Francisco Bay sediments and wildlife. Environmental International 47, 56-65.

). In China, samples collected from offshore sediment of northern South China Sea, ∑8PBDEs is 0.93 ng/g and from East China Sea it is below 1 ng/g (Liu et al., 2015

Liu, L., Li, H., Wang, Z., Liu, R., Zhang, Y., Lin, K. (2015) Insights into spatially and temporally co-occurring polybrominated diphenyl ethers in sediments of the East China Sea, Chemosphere 123, 55-63.

). The salient finding is that PBDEs were detected in the deepest Trench sediments with concentrations lower than, or nearing those of, coastal surface sediments adjacent to industrial areas.

We compared the level of ∑PCB concentrations in the Mariana Trench sediments to those reported in past studies at shallower depths (Fig. 4). The overall ∑PCB values from our study (range: 931-4195 pg/g, mean 2424 pg/g) are overwhelmingly higher than those from shallow marine sediments studied in the past (Table S-7); and higher than the world baseline levels for ∑PCBs arising from atmospheric transport found in clean coastal sediments, which is placed at <1 ng/g d.w. (Phillips, 1986

Phillips, D.J.H. (1986) Use of organisms to quantify PCBs in marine and estuarine environments. In: Waid, J.S. (Ed.) PCBs and the Environment Vol. II. CRC Press, Boca Raton, FL., 127-181.

). However, the PCB concentrations in the sediments are markedly lower than those found in endemic amphipod fauna through bioaccumulation from ~7000-10000 m in the Mariana (Jamieson et al., 2017

Jamieson, A.J., Malkocs, T., Piertney, S.B., Fujii, T., Zhang, Z. (2017) Bioaccumulation of persistent organic pollutants in the deepest ocean fauna. Nature Ecology and Evolution 1, 0051.

), since these organisms have been known to rapidly locate and consume any particulate organic matter (POM) from surface-derived carrion falls. Further, pollutants can accumulate in the wax esters of capacious guts of larger amphipods, which are used as energy reserves in times of prolonged food deprivation (Lee et al., 2006

Lee, R.F., Hagen, W., Kattner, G. (2006) Lipid storage in marine zooplankton. Marine Ecology Progress Series 307, 273-306.

).


Figure 4 Comparison of ∑PCBs concentrations in the Mariana Trench sediments with other worldwide marine surface water sediments. Figures in brackets indicate water depth.
Full size image | Download in Powerpoint

Hadal communities, such as Hirondellidae tend to accumulate along the trench axis, where gravity driven down-slope transport of sediments results in a nutrient-rich environment (Ichino et al., 2015

Ichino, M.C., Clark, M.R., Drazen, J.C., Jamieson, A., Jones, D.O.B., Martin, A.P., Rowden, A.A., Shank, T.M., Yancey, P.H., Ruhl, H.A. (2015) The distribution of benthic biomass in hadal trenches: a modeling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor. Deep-Sea Research I 100, 21-33.

). However deep sea lysianassoid amphipods are also recorded from shallower trench depths of nutrient poor environments, thought to be advantageous due to limited competitive interactions (Blankenship and Levin, 2007

Blankenship, L.E., Levin, L.A. (2007) Extreme food webs: foraging strategies and diets of scavenging amphipods from the ocean's deepest 5 km. Limnology Oceanography 52, 1685-1697.

). Post-mortal discharge of pollutants bioaccumulated by these endemic species and stored in the wax esters, or ingestion and faecal release may account for the high concentration of PCBs and PBDEs in the Mariana sediments. In addition, remote trenches encounter seafloor landslides or earthquakes. The funnel-like shape and high fluid dynamics within the Trench favour accumulation of pollutants along the trench axis (Turnewitsch et al., 2014

Turnewitsch, R., Falahat, S., Stehlikova, J., Oguri, K., Glud, R.N., Middelboe, M., Kitazato, H., Wenzhoefer, F., Ando, K., Fujio, S. (2014) Recent sediment dynamics in hadal trenches: evidence for the influence of higher-frequency (tidal, near-inertial) fluid dynamics. Deep-Sea Research I Oceanographic Research Papers 90, 125-138.

), associated with these geotectonic events. However, apart from slightly higher organic carbon content in the Challenger Deep (0.3-0.4 %) (Glud et al., 2013

Glud, R.N., Wenzhöfer, F., Middelboe, M., Oguri, K., Turnewitch, R., Canfield, D.E., Kitazato, H. (2013) High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth. Nature Geoscience 6, 284-288.

), hadal sediments are more depleted in total organic carbon (TOC), often reaching as low as 0.22 % (Luo et al., 2017

Luo, M., Gieskes, J., Chen, L., Shu, X., Chen, D. (2017) Provenances, distribution, and accumulation of organic matter in the southern Mariana Trench rim and slope: Implication of carbon cycle and burial in hadal trenches. Marine Geology 386, 98-106.

). Therefore, the dominance of organic matter-associated POPs in deep sea sediments over surface marine sediments seems paradoxical. We suspect that clay minerals may play a major role in the adsorption of contaminant particles in hadal sediments. Due to the lack of available studies, we conducted a preliminary mineralogical investigation of three sediment samples from deepest points by X-ray diffraction (XRD). Our results indicate clay assemblages (illite, nontronite, clinochlore, and gismondine) are abundant in the deepest sediments (Fig. S-2), with their total relative concentrations ranging from 51.8 to 86.5 % in the three samples (Table S-8) A number of possible mechanisms of sorption of POPs with clay minerals are explained in previous studies (e.g., Li et al., 2015

Li, Z., Fitzgerald, N.M., Albert, Z., Schnabl, A., Jiang, W.-T. (2015) Contrasting mechanisms of metoprolol uptake on kaolinite and talc. Chemical Engineering Journal 272, 48-57.

). For example, hydrogen bonding is demonstrated to bind polar groups of contaminants and basal oxygen atoms or adsorbed water of clay minerals (Wang et al., 2011

Wang, C.J., Li, Z., Jiang, W.T. (2011) Adsorption of ciprofloxacin on 2:1 dioctahedral clay minerals. Applied Clay Science 53, 723–728.

). Binding of POPs in surface or interstitial layers of clays could act towards the agglomeration of pollutants in the hadal sediments. Further, long range transport of these pollutants could be linked to allogenic clays from terrestrial or shallow water origins.

The present discovery serves as evidence as to how far man-made pollutants have reached; and any such contamination will have ecological and toxic effects, long-term or ephemeral, depending on the scale of impact. Possibly, there no longer exists “pure land” that can completely be isolated from human activities in the Earth’s ocean. High concentrations of pervasive pollutants in the trench sediments also imply that the Trench is a repository for POPs amplification, which occurs regardless of the source of these toxic anthropogenic pollutants. Certainly, high concentrations of POPs in the deepest ocean sediments are directly affecting hadal ecosystems, considering their persistent nature. The immediate challenge, therefore, is to assess the impact of anthropogenic pollutants reaching or residing in the deepest ocean. More detailed spatial and ecotoxicological studies on trench sediments will better our understanding of effects of POPs and other pervasive pollutants such as microplastics and litter in such environment.

Editor: Eric H. Oelkers

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References


Arfaeinia, H., Asadgol, Z., Ahmadi, E., Seifi, M., Moradi, M., Dobaradaran, S. (2017) Characteristics, distribution and sources of polychlorinated biphenyls (PCBs) in coastal sediments from the heavily industrialized area of Asalouyeh, Iran. Water Science and Technology 76, 3340-3350.
Show in context

Our results are higher than TEQPCBs values from past studies with sediments from shallow water depths, e.g., a semi-industrial area, Asaluyeh Harbor, Iran (0.001-3.4) (Arfaeinia et al., 2017); marine sediments from Mediterranean Sea, Catalonia, Spain (0.03-24.8) (Eljarrat et al., 2001); or Han River, Korea (0.0118-0.626) (Kim et al., 2009).
View in article


Blankenship, L.E., Levin, L.A. (2007) Extreme food webs: foraging strategies and diets of scavenging amphipods from the ocean's deepest 5 km. Limnology Oceanography 52, 1685-1697.
Show in context

However deep sea lysianassoid amphipods are also recorded from shallower trench depths of nutrient poor environments, thought to be advantageous due to limited competitive interactions (Blankenship and Levin, 2007).
View in article


Combi, T., Miserocchi, S., Langone, L., Guerra, R. (2016) Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories. Science of the Total Environment 562, 580-587.
Show in context

Studies revealing presence of POPs in surface to deep marine sediments are plentiful (e.g., Iwata et al., 1994; Ma et al., 2015; Combi et al., 2016; Neira et al., 2018), but none of them probed beyond the continental shelf area, leaving the real “depth” of the oceans practically unexplored.
View in article


Dachs, J., Lohmann, R., Ockenden, W.A., Mejanelle, L., Eisenreich, S.J., Jones, K.C. (2002) Oceanic biogeochemical controls on global dynamics of persistent organic pollutants. Environmental Science and Technology 36, 4229-4237.
Show in context

The deep ocean arguably acts as the largest potential sink for discarded pollutants (Dachs et al., 2002).
View in article


de Wit, C.Y., (2002) An overview of brominated flame retardants in the environment. Chemosphere 46, 583-624.
Show in context

The PBDE congener distribution of Mariana sediments resembles those reported elsewhere in surface marine sediments from Europe (de Wit, 2002) and in Qingdao coastal sea sediments (Pan et al., 2007), China where BDEs 47, 99, and 153 were the most frequently reported congeners.
View in article


Eljarrat, E., Caixach, J., Rivera, J. (2001) Toxic potency of non- and mono-ortho PCBs, PCDDs, PCDFs, and PAHs in Northwest Mediterranean sediments (Catalonia, Spain). Environmental Science and Technology 35, 3589-3594.
Show in context

Our results are higher than TEQPCBs values from past studies with sediments from shallow water depths, e.g., a semi-industrial area, Asaluyeh Harbor, Iran (0.001-3.4) (Arfaeinia et al., 2017); marine sediments from Mediterranean Sea, Catalonia, Spain (0.03-24.8) (Eljarrat et al., 2001); or Han River, Korea (0.0118-0.626) (Kim et al., 2009).
View in article


Fujioka, K., Okino, K., Kanamatsu, T., Ohara, Y. (2002) Morphology and origin of the Challenger Deep in the Southern Mariana Trench. Geophysical Research Letters 29, doi: 10.1029/2001GL013595.
Show in context

The southern Mariana Trench encloses the deepest point on the Earth's surface-the Challenger Deep, which is 11034 m down, and 2 km deeper than the average depth along the axis of the Mariana Trench (Fujioka et al., 2002).
View in article


Glud, R.N., Wenzhöfer, F., Middelboe, M., Oguri, K., Turnewitch, R., Canfield, D.E., Kitazato, H. (2013) High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth. Nature Geoscience 6, 284-288.
Show in context

However, apart from slightly higher organic carbon content in the Challenger Deep (0.3-0.4 %) (Glud et al., 2013), hadal sediments are more depleted in total organic carbon (TOC), often reaching as low as 0.22 % (Luo et al., 2017).
View in article


Hong, S.H., Yim, U.H., Shim, W.J., Oh, J.R. (2005) Congener-specific survey for polychlorinated biphenyls in sediments of industrialized bays in Korea: regional characteristics and pollution sources. Environmental Science and Technology 39, 7380-7388.
Show in context

High-chlorinated PCBs, such as CB-180 possibly came from terrestrial pollution in the form of industrial sewage, or from marine traffic (Hong et al., 2005).
View in article


Ichino, M.C., Clark, M.R., Drazen, J.C., Jamieson, A., Jones, D.O.B., Martin, A.P., Rowden, A.A., Shank, T.M., Yancey, P.H., Ruhl, H.A. (2015) The distribution of benthic biomass in hadal trenches: a modeling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor. Deep-Sea Research I 100, 21-33.
Show in context

Hadal communities, such as Hirondellidae tend to accumulate along the trench axis, where gravity driven down-slope transport of sediments results in a nutrient-rich environment (Ichino et al., 2015).
View in article


Iwata, H., Tanabe, S., Aramoto, M., Sakai, N., Tatsukawa, R. (1994) Persistent organochlorine residues in sediments from the Chukchi Sea, Bering Sea and Gulf of Alaska. Marine Pollution Bulletin 28, 746-753.
Show in context

Studies revealing presence of POPs in surface to deep marine sediments are plentiful (e.g., Iwata et al., 1994; Ma et al., 2015; Combi et al., 2016; Neira et al., 2018), but none of them probed beyond the continental shelf area, leaving the real “depth” of the oceans practically unexplored.
View in article


Jamieson, A.J., Malkocs, T., Piertney, S.B., Fujii, T., Zhang, Z. (2017) Bioaccumulation of persistent organic pollutants in the deepest ocean fauna. Nature Ecology and Evolution 1, 0051.
Show in context

In a latest study, Jamieson et al. (2017) reported high concentrations of POPs in endemic amphipod fauna from the Mariana and Kermadec Trenches.
View in article
However, the PCB concentrations in the sediments are markedly lower than those found in endemic amphipod fauna through bioaccumulation from ~7000-10000 m in the Mariana (Jamieson et al., 2017), since these organisms have been known to rapidly locate and consume any particulate organic matter (POM) from surface-derived carrion falls.
View in article


Kim, K.S., Lee, S.C., Kim, K.H., Shim, W.J., Hong, S.H., Choi, K.H., Yoon, J.H., Kim, J.G. (2009) Survey on organochlorine pesticides, PCDD/Fs, dioxin-like PCBs and HCB in sediments from the Han river, Korea. Chemosphere 75, 580-587.
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Our results are higher than TEQPCBs values from past studies with sediments from shallow water depths, e.g., a semi-industrial area, Asaluyeh Harbor, Iran (0.001-3.4) (Arfaeinia et al., 2017); marine sediments from Mediterranean Sea, Catalonia, Spain (0.03-24.8) (Eljarrat et al., 2001); or Han River, Korea (0.0118-0.626) (Kim et al., 2009).
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Kim, M.K., Kim, S., Yun, S., Lee, M., Cho, B., Park, J., Son, S, Kim, O. (2004) Comparison of seven indicator PCBs and three coplanar PCBs in beef, pork, and chicken fat. Chemosphere 54, 1533-1538.
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These PCBs are indicative of lipophilic contaminants, but their concentrations can vary with the contaminated source (Kim et al., 2004).
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High concentrations of low-chlorinated CBs, such as CB-52 may be from processes using chlorine oxidation; further, high-chlorinated CBs could be decayed to lighter ones by bacterial decomposition (Kim et al., 2004).
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Klosterhaus, S.L., Stapleton, H.M., La Guardia, M.J., Greig, D.J. (2012) Brominated and chlorinated flame retardants in San Francisco Bay sediments and wildlife. Environmental International 47, 56-65.
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Looking at the research carried in San Francisco Bay sediments, the ∑8PBDEs in each sample area (Suisun Bay, San Pablo Bay, Central Bay, and South Bay) range from 2.46-5.14 ng/g (Klosterhaus et al., 2012).
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Kukučka, P., Audy, O., Kohoutek, J., Holt, E., Kalábová, T., Holoubek, I., Klánová, J. (2015) Source identification, spatio-temporal distribution and ecological risk of persistent organic pollutants in sediments from the upper Danube catchment. Chemosphere 138, 777-783.
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Of all the toxic anthropogenic pollutants damaging the oceans, persistent organic pollutants (POPs) are of particular concern due to their robust residence time in the environment (Kukučka et al., 2015), global transport through atmospheric and oceanic currents (Wania and Mackay, 1996), and their ability to bioaccumulate in marine foodwebs (Lohmann et al., 2007), resulting in organism endocrine disruption (Rhind, 2012) and other adverse health effects.
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Lee, R.F., Hagen, W., Kattner, G. (2006) Lipid storage in marine zooplankton. Marine Ecology Progress Series 307, 273-306.
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Further, pollutants can accumulate in the wax esters of capacious guts of larger amphipods, which are used as energy reserves in times of prolonged food deprivation (Lee et al., 2006).
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Li, Z., Fitzgerald, N.M., Albert, Z., Schnabl, A., Jiang, W.-T. (2015) Contrasting mechanisms of metoprolol uptake on kaolinite and talc. Chemical Engineering Journal 272, 48-57.
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A number of possible mechanisms of sorption of POPs with clay minerals are explained in previous studies (e.g., Li et al., 2015).
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Liu, L., Li, H., Wang, Z., Liu, R., Zhang, Y., Lin, K. (2015) Insights into spatially and temporally co-occurring polybrominated diphenyl ethers in sediments of the East China Sea, Chemosphere 123, 55-63.
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In China, samples collected from offshore sediment of northern South China Sea, ∑8PBDEs is 0.93 ng/g and from East China Sea it is below 1 ng/g (Liu et al., 2015).
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Lohmann, R., Breivik, K., Dachs, J., Muir, D. (2007) Global fate of POPs: current and future research directions. Environmental Pollution 150, 150-165.
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Of all the toxic anthropogenic pollutants damaging the oceans, persistent organic pollutants (POPs) are of particular concern due to their robust residence time in the environment (Kukučka et al., 2015), global transport through atmospheric and oceanic currents (Wania and Mackay, 1996), and their ability to bioaccumulate in marine foodwebs (Lohmann et al., 2007), resulting in organism endocrine disruption (Rhind, 2012) and other adverse health effects.
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Luo, M., Gieskes, J., Chen, L., Shu, X., Chen, D. (2017) Provenances, distribution, and accumulation of organic matter in the southern Mariana Trench rim and slope: Implication of carbon cycle and burial in hadal trenches. Marine Geology 386, 98-106.
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However, apart from slightly higher organic carbon content in the Challenger Deep (0.3-0.4 %) (Glud et al., 2013), hadal sediments are more depleted in total organic carbon (TOC), often reaching as low as 0.22 % (Luo et al., 2017).
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Ma, Y., Halsall, C.J., Crosse, J.D., Graf, C., Cai, M., He, J., Gao, G., Jones, K. (2015) Persistent organic pollutants in ocean sediments from the North Pacific to the Arctic Ocean. Journal of Geophysical Research: Oceans 120, 2723-2735.
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Studies revealing presence of POPs in surface to deep marine sediments are plentiful (e.g., Iwata et al., 1994; Ma et al., 2015; Combi et al., 2016; Neira et al., 2018), but none of them probed beyond the continental shelf area, leaving the real “depth” of the oceans practically unexplored.
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Neira, C., Vales, M., Mendoza, G., Hoh, E., Levin, L.A. (2018) Polychlorinated biphenyls (PCBs) in recreational marina sediments of San Diego Bay, southern California. Marine Pollution Bulletin 126, 204-214.
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Studies revealing presence of POPs in surface to deep marine sediments are plentiful (e.g., Iwata et al., 1994; Ma et al., 2015; Combi et al., 2016; Neira et al., 2018), but none of them probed beyond the continental shelf area, leaving the real “depth” of the oceans practically unexplored.
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Pan, J., Yang, Y.-L., Xu, Q., Chen, D.-Z., Xi, D.-L. (2007) PCBs, PCNs and PBDEs in sediments and mussels from Qingdao coastal sea in the frame of current circulations and influence of sewage sludge. Chemosphere 66, 1971-1982.
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The PBDE congener distribution of Mariana sediments resembles those reported elsewhere in surface marine sediments from Europe (de Wit, 2002) and in Qingdao coastal sea sediments (Pan et al., 2007), China where BDEs 47, 99, and 153 were the most frequently reported congeners.
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Phillips, D.J.H. (1986) Use of organisms to quantify PCBs in marine and estuarine environments. In: Waid, J.S. (Ed.) PCBs and the Environment Vol. II. CRC Press, Boca Raton, FL., 127-181.
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The overall ∑PCB values from our study (range: 931-4195 pg/g, mean 2424 pg/g) are overwhelmingly higher than those from shallow marine sediments studied in the past (Table S-7); and higher than the world baseline levels for ∑PCBs arising from atmospheric transport found in clean coastal sediments, which is placed at <1 ng/g d.w. (Phillips, 1986).
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Rhind, S.M. (2012) Anthropogenic pollutants- an insidious threat to animal health and productivity? Acta Veterinaria Scandinavica 54, S2.
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Of all the toxic anthropogenic pollutants damaging the oceans, persistent organic pollutants (POPs) are of particular concern due to their robust residence time in the environment (Kukučka et al., 2015), global transport through atmospheric and oceanic currents (Wania and Mackay, 1996), and their ability to bioaccumulate in marine foodwebs (Lohmann et al., 2007), resulting in organism endocrine disruption (Rhind, 2012) and other adverse health effects.
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Turnewitsch, R., Falahat, S., Stehlikova, J., Oguri, K., Glud, R.N., Middelboe, M., Kitazato, H., Wenzhoefer, F., Ando, K., Fujio, S. (2014) Recent sediment dynamics in hadal trenches: evidence for the influence of higher-frequency (tidal, near-inertial) fluid dynamics. Deep-Sea Research I Oceanographic Research Papers 90, 125-138.
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The funnel-like shape and high fluid dynamics within the Trench favour accumulation of pollutants along the trench axis (Turnewitsch et al., 2014), associated with these geotectonic events.
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Wang, C.J., Li, Z., Jiang, W.T. (2011) Adsorption of ciprofloxacin on 2:1 dioctahedral clay minerals. Applied Clay Science 53, 723-728.
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For example, hydrogen bonding is demonstrated to bind polar groups of contaminants and basal oxygen atoms or adsorbed water of clay minerals (Wang et al., 2011).
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Wania, F., Mackay, D. (1996) Tracking the distribution of persistent organic pollutants. Environmental Science and Technology 30, 390A-396A.
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Of all the toxic anthropogenic pollutants damaging the oceans, persistent organic pollutants (POPs) are of particular concern due to their robust residence time in the environment (Kukučka et al., 2015), global transport through atmospheric and oceanic currents (Wania and Mackay, 1996), and their ability to bioaccumulate in marine foodwebs (Lohmann et al., 2007), resulting in organism endocrine disruption (Rhind, 2012) and other adverse health effects.
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Yogui, G.T., Sericano, J.L. (2009) Polybrominated diphenyl ether flame retardants in the U.S. Marine environment: a review. Environment International 35, 655-666.
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Penta-BDE mixture components BDE-47 and 99 possibly originated terrestrially from polyurethane foams (Yogui and Sericano, 2009), and were found at concentrations of View in article


Zhang, Y., Wang, W., Song, J., Ren, Z., Yuan, H., Yan, H., Zhang, J., Pei, Z., He, Z. (2016) Environmental characteristics of polybrominated diphenyl ethers in marine system, with emphasis on marine organisms and sediments. BioMed Research International 2016, Article ID 1317232, 16 pp, doi: 10.1155/2016/1317232.
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To maintain consistency (since PBDEs are presented as mixtures of congeners), and form a comparable dataset, a total of 8 PBDEs (BDE-28, 47, 99, 100, 153, highlighted in blue in Table S-3; BDE-54, 183, and 209 were not detected) were chosen (Zhang et al., 2016), which commonly occur in environmental samples.
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Supplementary Information


The Supplementary Information includes:
  • Sampling locations
  • Methods
  • Tables S-1 to S-8
  • Figures S-1 and S-2
  • Supplementary Information References

Download the Supplementary Information (PDF).
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