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In order to have a deep understanding of the role of ocean squid in Northwest Pacific Ocean food web, samples were collected during the comprehensive scientific survey launched by the Ministry of Agriculture and Rural Affairs in 2021 and 2022. Carbon and nitrogen stable isotope technology was used to analyze the muscle stable isotopes and nutritional niches of two cephalopod species, Ommastrephes bartramii and Onychoteuthis borealijaponicus, in Northwest Pacific Ocean. The results show that O. bartramii δ13C and δ15N values between sites were significantly different. O. borealijaponicus δ13C values between the two sites showed significant differences, while the δ15N values were not significant. Muscle δ13C and δ15N values between O. bartramii and O. borealijaponicus showed significant differences. During ontogeny, the δ13C and δ15N values of O. bartramii and O. borealijaponicus were not significantly associated with carcass length. The nutrient niche width of O. bartramii (SEAc=0.35‰²) is greater than that of O. borealijaponicus (SEAc= 0.20‰²), with a moderate overlap between the two squids (0.314) . The high niche overlap between males and females is 0.988 and 0.76, respectively. The analysis shows that the δ13C values of O. bartramii and O. borealijaponicus are influenced by SST and feeding effects, while the δ15N values are influenced by feeding effects. The utilization of food and habitat resources was highly similar in both female and male cephalopod groups. [ABSTRACT FROM AUTHOR]

In order to better understand the nutritional niche changes during the ontogeny period of Ommastrephes bartramii and Onychoteuthis borealijaponicus, 36 O. bartramii and 30 O. borealijaponicus samples were collected from "Songhang" fishery resources survey ship in 2021-2022, and stable isotopic analysis was conducted on their eye crystals. The results show that: the variation in individual δ13C and δ15N values for O. bartramii ranged from 0.10‰ to 1.68‰ and 0.79‰ to 7.51‰, respectively; and the variation in individual δ13C and δ15N values for O. borealijaponicus ranged from 0.15‰ to 1.20‰ and 0.81‰ to 7.05‰, respectively. The niche area change range for O. bartramii and O. borealijaponicus was 0.40‰²-5.85‰² and 0.27‰²-5.36‰², respectively. GAM model analysis showed that the δ13C and δ15N values of O. bartramii eye crystals had a significant correlation with crystal diameter, with deviation interpretation rates of 31.9% and 34.3%, respectively. Similarly, the δ13C and δ15N values of O. borealijaponicus eye crystals were significantly correlated with crystal diameter, with deviation interpretation rates of 12.9% and 19.4%, respectively. According to the analysis, O. bartramii and O. borealijaponicus feeding flexibility is responsible for the irregular change of δ13C and δ15N values with increasing carcass size. The larger magnitude of individual isotopic changes reflects the greater magnitude of baseline isotopic values in the Kuroshio-Oyashio transition zone in Northwest Pacific Ocean. Additional 83% of the O. bartramii samples and 80% of the O. borealijaponicus samples niche amplitude of δ13C was small, but niche amplitude of δ15N was larger, so the feeding level of O. bartramii and O. borealijaponicus in this area is different. The GAM model showed that individual growth and baseline values were factors affecting the tissue δ13C and δ15N values. [ABSTRACT FROM AUTHOR]

Zooplankton is an important link between primary producers and lower trophic level organisms in the marine food web, and is an important biological basis for the formation of fishing grounds. Based on the Zooplankton samples collected by the fishery resources survey vessel "Songhang" of Shanghai Ocean University during the comprehensive scientific survey of fishery resources in the high seas of the Northwest Pacific Ocean from June to August in 2021 and 2022, the Zooplankton samples were analyzed in terms of their species composition, distributional characteristics, and their relationship with the environment. The results showed that a total of 174 Zooplankton species were collected in the surveyed area over the two years, belonging to 10 groups. Copepoda and planktonic larvae were the most abundant Zooplankton, with 95 and 22 species identified respectively, accounting for 54.6% and 12.6% of the total number of species, followed by ScyphoZoa, with 18 species identified, and Ostracoda, Tunicata, Chaetognatha, Euphausiacea, and Gastropoda with 11, 9, 6, 4 and 3 species respectively. Additionally, two species each of Polychaeta, Amphipoda, and Cladocera were identified. The dominant genes (species) included seven categories: Clausocalanus sp., Oncaea sp., Paracalanus sp., Calocalanus sp., Oithona plumifera, Oithona decipiens and Metridinidae larvae. The species diversity and dominant genes (species) composition were similar in both years. The mean Zooplankton abundance in 2021 was 732.89 ind./m³, lower than that in 2022 (1 418.88 ind./m³). The Shannon-Wiener index in 2021 was 1.57-3.16, the Evenness index was 0.54-0.91, and the abundance index was 0.84-3.36. All three indices were higher than those in 2022, which ranged from 0.66 to 2.92, 0.26 to 0.94, and 0.77 to 3.11, respectively. GAM analyses showed that Zooplankton abundance was significantly and negatively correlated with the sea-surface salinity and the water temperature in the 200 m layer, and the analyses suggested that the Kuroshio current and the Oyashio also had a certain effect on the temporal and spatial distributions of the abundance. The results of this study will provide basic information for the study of Zooplankton in the high seas of the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

In order to explore the effects of potassium fertilizer types and dosage on the cold resistance of alfalfa, and to reveal the antioxidant physiological mechanism of potassium fertilizer to improve the cold resistance of alfalfa, ' Gibraltar' alfalfa was as the material, and a two-factor (potassium fertilizer application amount and type) randomized block experiment was designed, which 3 types of potash fertilizers (potassium chloride, potassium sulfate and potassium dihydrogen phosphate ) were used and the applying amounts were set according to 0, 100, 200, 300 kg K2O⋅hm-2. The overwintering organs of alfalfa were excavated to simulate low temperature stress treatment (4, -10, -20 and -30 °C) in the early stage of overwintering, and the content of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activity in the root crown of alfalfa were determined.The results showed that, under the low temperature freezing stress treatment, the MDA contents of alfalfa treated with 3 kinds of potassium fertilizers were lower than that of the control, and the decreased range of K2SO4 treatment was the most significantly (P<0.05). With the increase of potassium fertilizer application, MDA decreased first and then increased. Under the treatment of 200 kg K2O⋅hm-2, the difference between MDA content and CK in root crown of alfalfa was the most significant (P<0.05).The changes of antioxidant enzyme activities in the alfalfa materials treated with different application rates of the 3 potassium fertilizers were opposite to those of MDA under low temperature stress treatment. The activity of SOD, POD and CAT were the highest and both had the most significant difference with CK (P<0.05).It showed that the alfalfa treated with K2SO4 in autumn and the application rate of 200 kg K2O⋅hm-2 had the strongest cold resistance. The results showed that potassium fertilizer with appropriate dosage could improve the antioxidant properties of alfalfa root and neck under low temperature stress, reduce the degree of membrane lipid peroxidation, improve the cold resistance of alfalfa, and be more conducive to the safe overwintering of alfalfa. [ABSTRACT FROM AUTHOR]