Composting is a major method to produce organic fertilizers, and the variation in antibiotic resistance genes (ARGs) during composting is crucial for the safe utilization of mature compost. The effects of different bulking agents (cellulose-rich cornstalk and lignin-rich garden waste) on ARGs variations during swine manure composting were investigated. The results showed that composting thermophilic could effectively reduce ARGs (58–61 %), whereas ARGs rebounded and were enriched with decreasing temperature during the maturation stage. Compared to their initial abundance, ARGs were enriched 6.97 times (cornstalk) and 22.27 times (garden waste) during the maturation period. The ARGs enrichment mechanism in swine manure composting differed for cornstalk and garden waste amendments. The cornstalk was used as the bulking agent, the selective pressure of continuous high temperature resulted in the proliferation of spore-forming bacteria (Bacillus, Sporosarcina and Psychrobacillus), which are potential host bacteria of ARGs and cause ARGs enrichment through vertical gene proliferation. In the garden waste treatment, the enriched ARGs in the final compost were related to horizontal gene transfer mediated by mobile genetic elements (intl1), with the primary potential host bacteria being Bacillus, Saccharomonospora, and Caldicoprobacter. The types of enriched ARGs were consistent across different bulking agents composting process, and the risk genes enriched in the final mature compost included ermB, ermF, sul1, sul2, tetO, and tetX.
Abstract Based on investigation data on Pb in Jiaozhou Bay waters in May, August and October 1992, the author introduces horizontal and vertical variation models of matter content to calculate the horizontal loss amount, vertical dilution amount and vertical sediment amount of the Pb content in both surface and bottom waters and establishes modeling chart of its horizontal and vertical variation. The results show that the absolutely and relatively horizontal loss amount of the Pb content in the bottom waters were 6.23μg/L and 59.73% respectively in May. Absolutely horizontal increase amount of the Pb content in the bottom waters varied from 4.14 to 5.51μg/L, and relatively horizontal increase amount varied from 22.59% to 35.59% in August and October. In May, August and October, the Pb content in both surface and bottom waters had an absolutely vertical dilution amount of 2.18μg/L and a relatively vertical dilution amount of 22.54% in the waters of the southeast of the bay. Besides, the absolutely vertical sediment amount of the Pb content in both surface and bottom waters ranged from 4.89μg/L to 7.58μg/L and the relatively vertical sediment amount ranged from 40.14 to 46.88% in the same waters. As for in the central waters of the bay, the absolutely and relatively vertical dilution amount were 3.17μg/L and 43.01% respectively, the absolutely and relatively vertical sediment amount were 1.18-18.86μg/L and 10.14-77.32% respectively during the same period. The variation model of matter content reveals that the Pb content transported by the main sea currents settled as sediment in the waters of the southeast of the bay, and it continued to accumulate in the bottom waters from May to August. The Pb content in that area was transported to the bottom waters of the center of the bay through the bottom of ocean floor so that a large amount of the Pb content was accumulated there from August to October. The author introduces the transferring process of the matter content in the center of Jiaozhou Bay: matter content brought by the main sea currents settles as sediment in the offshore waters and keeps accumulating in its bottom layer under the tidal effect and current action then moves through the bottom layer of the ocean floor to the bottom waters of the center of the bay. As a result, the matter content accumulates a lot there, and keeps rising to reach its surface waters.
Small yellow croaker Larimichthys polyactis is an important commercial fish species; however, industrial-scale fishing has largely contributed to the changes in its biological characteristics, such as individual miniaturization, faster growth, and younger average age. Robust understanding of the pivotal life history of L. polyactis , a typical oceanodromous species, is needed for its conservation and restoration. However, L. polyactis fidelity to natal or spawning sites is not well understood and, at present, there is no effective management strategy to guarantee the sustainable exploitation of L. polyactis . This study used laser ablation inductively coupled plasma-mass spectrometry to analyse the elemental composition of otoliths from 60 adult yellow croakers caught in the southern Yellow Sea, including two spawning groups with 1- and 2-year-old fish (S1 and S2, respectively) sampled close to China and one overwintering group including two-year-old fish (O2) sampled close to South Korea. The ratios of elements (Li, Na, Sr, and Ba) to Ca in the otolith core zones were significantly higher ( P < 0.05) than in those of the year one (Y1) and year two (Y2) annual rings, but there were no significant differences in the elemental ratios between the Y1 and Y2 zones. Principal component analysis (PCA) of the elemental otolith signatures of the core, Y1, and Y2 zones in the three groups revealed two distinct clusters (cluster 1: S1-core, S2-core, and O2-core zones; cluster 2: S2–Y1, O2–Y1, S2–Y2, and O2–Y2 zones) and one zone (S1–Y1), suggesting spawning-site fidelity and natal-site fidelity uncertainty, especially considering the dispersal by current in prolonged period (50 h) from fertilized eggs to hatching and internal effect, such as yolk sac and maternal effect. Furthermore, these results indicated that the S2 and O2 groups could represent the same population, suggesting a stable migratory route for L. polyactis in Chinese and South Korean waters, whereas the S1 group could represent another population. This suggests the possibility a mixed L. polyactis population in the southern Yellow Sea. Characterization L. polyactis spawning-site fidelity is a crucial step toward linking spawning-site fidelity of this overexploited species with thorough conservation and management strategies.
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