## 3 Results and Discussion
### Ecotoxicological Risk for Wharf Road  
Normally, heavy metal and \(\mathrm{PCDD/F}\) toxicities depend on the species. However, significant concentrations of heavy metals and \(\mathrm{PCDD/F}\) were detected in wharf roach, which suggest a risk of \(\mathrm{PCDD/F}\) toxicity to this isopod. Pb, Cd, and Cr (particularly hexavalent chromium) have a high toxicity. However, due to arthropod exoskeleton molting, isopods can reduce the risk from excessive heavy metal contamination [45]. In this study, the concentrations of these three heavy metals were lower compared with the other heavy metals. In particular, Cr was detected at low concentrations (0.02-0.21 \(\mathrm{\SIUnitSymbolMicro g}\)/g-dw), which is comparable to a previous study that showed 0.18-1.68 \(\mathrm{\SIUnitSymbolMicro g}\)/g-dw in _L. italica_[26]. However, the detected concentrations of Cu, Cd, and Pb (33.1-129, 0.46-6.85, and 0.22-1.46 \(\mathrm{\SIUnitSymbolMicro g}\)/g-dw, respectively) are slightly higher than reported in _L. cinascens_ (23.1-35.6, 0.319-0.893, and 0.0220-0.218 \(\mathrm{\SIUnitSymbolMicro g}\)/g-wet, respectively) from China [27]. [PERSON] et al. [46] reported that the 96 h-LC50 of Cu and Cd on _Sphaeroma serratuun_ (marine isopod) was 4.60 mg/L and 4.79 mg/L, and on _Ilodea bultica_ (marine isopod) it was 1.45 mg/L and 1.29 mg/L. [PERSON] and [PERSON] [47] reported that the 96 h-LC50 in sea water on _Jaeropsis_ sp. and _Limnoria tripunctata_ (both marine isopods) was 0.41 and 7.12 mg/L. These heavy metal concentrations in sea water were in almost the same range as those in wharf roach in this study. These heavy metals can accumulate in crustacean bodies from environmental media [48; 49], having high bioconcentration factors (BCFs): Cd 17000, Pb 31000, Cu 120000, and Zn 9200 for freshwater isopod _Asellus aquaticus_ (L.) [50];  
Figure 5: Hierarchical dendrogram for 11 sampling sites obtained using hierarchical cluster analysis with an average linkage method: (**a**) calculated using heavy metal concentrations and (**b**) calculated using \(\mathrm{PCDD/F}\) and DL-PCB concentrations. and Cu 2060 and Cd 311 for marine amphibod _Paramorea walkeri_[51]. Even though the sensitivity to heavy metals differs among isopod species, the contamination level of heavy metals in this study poses an ecological risk to the wharf roach. The total TEQs of the PCDD/Fs and DL-PCBs in the total dried body weight were discussed to assess the ecological risk (Table 2). MAT's sample had the highest PCDD/Fs (2.33 pg-TEQ/g-dw), followed by GAM's sample (1.86 pg-TEQ/g-dw). Compared with these two sampling sites, the other site had a lower PCDD/Fs level (<LOD-0.72 pg-TEQ/g-dw). DL-PCBs were detected at a higher level (0.64-27.79 pg-TEQ/g-dw) compared with the PCDD/Fs. The GAM sample contained the highest amount of DL-PCBs (27.79 pg-TEQ/g-dw), followed by HAC's sample (11.72 pg-TEQ/g-dw). Other samples contained slightly lower levels (0.64-5.37 pg-TEQ/g-dw). The total TEQs of the PCDD/Fs and those of DL-PCBs in the total dried body weight were correlated significantly ([PERSON]'s rank correlation test, \(p\) = 0.04), and this correlation trend was retained in the total TEQ value in the lipid (\(p\) = 0.03). The TEQ of the DL-PCBs was dominant in the total TEQ (65%-100%, Figure 6). However, the contribution ratios of the PCDD/Fs in the total TEQ in NOT and MAT were higher than in the other nine sampling sites (34% and 35%, respectively). These detected levels of dioxins were higher than those detected previously in mussels [43; 52] and small marine arthropods [53]. However, currently detected levels in the wharf roach were similar and/or lower than in marine crabs [54; 55; 56]. These differences may be caused by trophic level, species differences on feeding habitat, and metabolism. Due to a lack of toxicological information, it is difficult to estimate the ecotoxicological risk of dioxins on the wharf roach. [PERSON] et al. [56] detected a relatively higher level of dioxins on crab _Carcinus mediterraneus_ and estimated a significant risk from dioxins.