Trophic structure of micronekton in the Northwest Pacific Ocean

IntroductionStable isotope analysis has been widely used in the study of the trophic structure of marine micronekton in recent years. MethodsIn this study, the carbon and nitrogen stable isotope values of fish, cephalopod, shrimp and zooplankton species were measured from samples collected in the Northwest Pacific Ocean in March and September 2019 to construct a continuous trophic spectrum and to compare isotope niches among species. In addition, we compared the variation of isotopic niches of micronekton among different groups and among different species, respectively. ResultsSignificant differences of delta C-13 and delta N-15 values were detected among fish, cephalopod and shrimp groups with delta C-13 value ranges of -21.9 parts per thousand to -18.7 parts per thousand, -21.3 parts per thousand to -17.7 parts per thousand and -20.4 parts per thousand to -19.5 parts per thousand, respectively and the range of delta N-15 values was 7.0 parts per thousand to 12.4 parts per thousand, 8.2 parts per thousand to 12.2 parts per thousand and 7.6 parts per thousand to 10.6 parts per thousand, respectively. Using copepods as the baseline for estimating the average trophic level (TL) of micronekton, the TLs ranged from 2.67 to 4.80 and the average TLs for cephalopods, fishes and shrimp were 3.3 +/- 0.3, 3.7 +/- 0.6 and 4.0 +/- 0.3, respectively. Myctophidae and Stomiidae occupied higher TLs. In addition, Oplophorus gracilirostris, Enoploteuthis chunii and Abralia similis had wide isotopic niches. DiscussionOur results show that Myctophidae, Stomiidae, Oplophorus gracilirostris, Enoploteuthis chunii and Abralia similis play important roles in maintaining the stability of the Kuroshio-Oyashio ecosystem in the Northwest Pacific Ocean.

Automated summary

Stable isotope analysis was used to study the trophic structure of marine micronekton in the Northwest Pacific Ocean. The results showed significant differences in carbon and nitrogen stable isotope values among different species, with average trophic levels of 3.3±0.3 for cephalopods, 3.7±0.6 for fishes, and 4.0±0.3 for shrimps.