Abstract:Organochlorine pesticides (OCPs), including chlordanes, endosulfans, and dichlorodiphenyltrichloroethanes (DDTs), have been gaining much visibility in ecotoxicological studies due to their growing reported harmful effects. In this study, muscle and adipose tissue samples from five Great Knots (Calidris tenuirostris) and five Red Knots (C. canutus) at stopover sites (Table 1) along the East Asian-Australasian Flyway (EAAF) were extracted using Soxhlet extraction method and further analyzed using gas chromatography (GC) to determine residues of OCPs in tissues. Among 19 OCPs that we examined in this study, a total of 14 OCPs were detected. The highest concentration of total OCPs in tissues was 1 573.5 ng/g lipid weight (Table 2), much higher than similar work from other countries (Table 3), and seven OCPs had 100% detection frequencies. The highest concentration of detected compound was p, p′-DDE in muscle samples of Great Knots as well as muscle samples and adipose tissue samples of Red Knots, while endosulfan sulfate and/or p, p′-DDT had the highest concentration in adipose tissue samples of Great Knots. We used Wilcoxon Signed-Rank Test to compare the difference of OCPs contamination between species, and the results showed that concentration of HCHs in muscles of Red Knots were significantly higher than Great Knots (P = 0.05), while the concentration of endosulfan sulfate and/or p, p′-DDT were higher in adipose tissue of Great Knots than Red Knots (P < 0.05). Paired T-test indicated that residues of OCPs were generally higher in adipose tissues than muscles (P < 0.05), suggesting that OCPs mainly concentrated in adipose tissue rather than muscle. We compared OCPs compositional profiles (Fig. 1) in this study with previous studies on OCPs in sediments in the Yellow Sea region, and found that OCP profiles of the two knot species were similar with that in sediments. Spearman Test further indicated that OCPs detection frequencies in the two knot species were positively related to that in the sediments (P < 0.05, Fig. 2), suggesting that there are close relationship between OCPs in bird body and in the sediments in the Yellow Sea region. Although it′s still unclear of the lethal threshold of OCPs in shorebirds, this study indicated that OCPs might have profound effects on the shorebirds along the EAAF.