Jing Zhang

The formation of recalcitrant Dissolved Organic Matter (DOM) pools in the ocean has been a longstanding challenge due to the chemical complexity of DOM. Linking nitrogen sequestration and microbial reworking via the production of recalcitrant Dissolved Organic Nitrogen (DON) molecules remains elusive. Here, we characterized intricate molecular composition of DOM using FT-ICR-MS, with a particular emphasis on DON, across three representative regions in the tropical eastern Indian Ocean. Our findings demonstrated the microbial origin of DON in epipelagic waters, with ammonia-oxidizing archaea exerting important control on the enrichment of peptide-like compounds. Microbial respiration was identified as a key driver of DOM transformation throughout the water column. This process enhanced the recalcitrance of DOM and DON by generating molecules with high levels of unsaturation and oxidation, characterized by low bioavailability. These effects were most pronounced in the equatorial region, which demonstrated an exceptional capacity to accumulate nitrogen-rich compounds through microbial processing, thereby facilitating to long-term nitrogen sequestration. Furthermore, we provided a valuable dataset representing microbially derived recalcitrant DON. Our study highlights that a small fraction of DOM with comparatively higher bioavailability is selectively preserved, though the majority of DON persists in the deep ocean due to its recalcitrant nature. This work provides novel molecular-level insights into microbially derived recalcitrant DON molecules, and holds significant implications for the detailed interpretation of global nitrogen sequestration.

Catchment areas on volcanic territories in different regions are of great interest since they are enriched with nutrients that contribute significantly to coastal ecosystems. The Kamchatka Peninsula is one of the most active volcanic regions of the world; however, to date, the chemistry of its river waters and the state of its coastal ecosystems remain understudied in connection with volcanism. The two rivers under study are the largest in this region. The Kamchatka River, unlike the Penzhina River, drains volcanic territories, including the areas of the most active volcanoes of the Klyuchevskaya group of volcanoes and the Shiveluch Volcano. The mouth of the Kamchatka River has been shown to have DIP and DIN concentrations of 2.79–3.87 and 10.0–23.8 µM, respectively, during different seasons, which are comparable to rivers in urbanized areas with sewerage and agricultural sources of nutrients. It has been established that volcanoes form high concentrations of nutrients in the catchment area of the Kamchatka River. The Penzhina River has had very low DIP and DIN concentrations of 0.2–0.8 and 0.17–0.35 µM, respectively, near the mouth during different seasons, but high concentrations of DOC, at 5.9 mg/L in spring, which may be due to seasonal thawing of permafrost. During the period of increasing river discharge, seasonal phytoplankton blooms occur in spring and summer in bays of the same name, as shown using satellite data. The biomass of zooplankton in Penzhina Bay is at a level of 100 mg/L, while in Kamchatka Gulf, it exceeds 2000 mg/L. Thus, the biomass of zooplankton in the receiving basin, which is influenced by the runoff of the Kamchatka River with a volcanic catchment area in eastern Kamchatka, is 20 times higher than in the basin, which has a small nutrient flux with the river runoff in northwestern Kamchatka. This study demonstrates the connection between nutrient fluxes from a catchment area and the formation of seasonal phytoplankton blooms and high zooplankton biomass in the coastal area. We also study seasonal, year-to-year, and climatic variability of water discharges and hydrometeorological conditions to understand how nutrient fluxes can change in the foreseeable future and influence coastal ecosystems.

Some East Asian rivers experienced repeated rearrangements due to Indian–Asian Plates’ collisions and an uplift of the Tibetan Plateau. For the upper Changjiang (Yangtze/Jinsha River), its ancient south-flowing course and subsequent capture by the middle Changjiang at the First Bend (FB) remained controversial. The DNA of freshwater fishes possess novel evolutionary signals of these tectonic events. In this study, mtDNA Cyt b sequences of endemic Schizopygopsis fish belonging to a highly specialized grade of the Schizothoracinae from the eastern Tibetan Plateau were used to infer the palaeo-drainages connectivity history of the upper Changjiang system. Through phylogenetic reconstruction, a new clade D of Schizopygopsis with three genetic clusters and subclusters (DI, DII, DIIIa, and DIIIb) were identified from the upper Yalong, Changjiang, and Yellow Rivers; the Shuiluo River; the FB-upper Changjiang; and the Litang River; respectively. Ancient drainage connections and capture signals were indicated based on these cladogenesis events and ancestral origin inference: (1) the upper Yalong River likely acted as a dispersal origin of Schizopygopsis fish to the adjacent upper Yellow and Changjiang Rivers at ca. 0.34 Ma; (2) the Litang River seemed to have directly drained into the upper Changjiang/Yangtze/Jinsha River before its capture by the Yalong River at ca. 0.90 Ma; (3) the Shuiluo River likely flowed south along a course parallel to the upper Changjiang before their connection through Hutiao Gorge; (4) a palaeo-lake across the contemporary Shuiluo, Litang, and Yalong Rivers was inferred to have served as an ancestral origin of clade D of Schizopygopsis at 1.56 Ma. Therefore, this study sheds light on disentangling ambiguous palaeo-drainage history through integrating biological and geological evidence.

Understanding the factors that control carbonate systems is an important goal due to the complex interactions between the hydrophysical and chemical–biological conditions in coastal basins. The results of this paper present the state of the carbonate system in Penzhina Bay and its adjacent waters—the Shelikhov Gulf—in July 2023, during spring tides with 13 m height. The area we studied included the length of the largest river in the region, the Penzhina River, from the peak of its summer flood to its boundary with the Shelikhov Gulf (the Sea of Okhotsk). This unique dynamic basin, with a length of about 800 km, was studied over 17 days. During this period, the entire water column of Penzhina Bay, down to a depth of about 60 m, and the surface water layer of the Shelikhov Gulf were undersaturated in terms of CO₂, with low levels relative to those of the atmosphere. To explain this observation, the dissolved oxygen, nutrients in mineral and organic forms, humic substances, chlorophyll a, and photic zone thickness are presented for the entire basin under study, together with its hydrological data. The results of daily observations of the carbonate system at fixed anchorage stations characterize two contrasting regions of Penzhina Bay: one that was more exposed to continental runoff, which had salinity levels in the range of 8.0–21.3 psu during one tidal cycle; the second had smaller variations in salinity in the range of 31.6–32.9 psu during one tidal cycle. This study emphasizes the importance of biological processes and continental runoff on the variability of the carbonate system parameters and CO₂ fluxes at a water/atmosphere boundary with extreme tidal conditions in this ecosystem that is barely affected by human activities.

Life satisfaction is vital for a smooth transition to emerging adulthood. However, research on age and gender-related fluctuations in life satisfaction has yielded inconclusive and culture-specific results, which necessitates further investigation in more diverse contexts, including the Chinese culture. Despite the attribution theory and the value-as-a-moderator model highlighting the significance of achievement attribution in this period characterized by the pursuit of success, little is known about the specific impact of internal and external achievement attribution on the development of life satisfaction. This study examined life satisfaction trajectories from adolescence to emerging adulthood and explored the moderating effects of gender and achievement attribution, using five waves of data from the China Family Panel Studies (CFPS). The sample consists of 504 youth (52.2% female), whose life satisfaction was tracked from 2012 (M_age = 16.55, SD = 0.50) to 2020 (M_age = 24.56, SD = 0.50). The multilevel growth models revealed that life satisfaction increased from ages 16 to 18, peaked at age 18, fell until age 20, and then remained stable from ages 20 to 24. No significant association was found between gender or external achievement attribution and life satisfaction development. Youth with higher internal achievement attribution had a greater increase in life satisfaction from ages 16 to 18, but had a larger decrease from ages 18 to 20. Adjusting internal achievement attribution may help alleviate the vulnerability of youth experiencing declining life satisfaction when transitioning to adulthood.