Zhuoyi Zhu - Academia.edu (original) (raw)

Papers by Zhuoyi Zhu

Marine Pollution Bulletin

Under eutrophication background, the increasing dinoflagellates blooms relative to diatoms blooms... more Under eutrophication background, the increasing dinoflagellates blooms relative to diatoms blooms off the Changjiang Estuary has caused much concern. We have provided sediment evidence for the first time that the time window of diatoms-to-dinoflagellates shift off the Changjiang Estuary in the East China Sea is early 1990s. Investigations to the water column revealed different surface-bottom concentration matchup patterns between peridinin (dinoflagellates) and fucoxanthin (diatoms), which suggests that the diatoms-dinoflagellates shift recorded in the sediment may have come from more dinoflagellate blooms since 1990s. Physical-biogeochemical 3D numerical simulations for the past decades suggest that the effect of increasing spring sea surface temperature and increasing N/P ratio on the diatoms-dinoflagellates shift is dominant and recessive, respectively.

Goldschmidt Abstracts, 2020

Lipid classes and fatty acids of the particulate and the dissolved organic matter were investigat... more Lipid classes and fatty acids of the particulate and the dissolved organic matter were investigated in the Krka River estuary (Adriatic Sea) in autumn (September 2008) and spring (May 2009) to get insight on different freshwater/marine processes taking place during different seasons. Krka River is one of the most pristine European rivers. The sampling strategy included sampling of freshwater, halocline and seawater at stations of different trophic status. Total particulate lipids showed large variations, from 12.6 to 55.4 μg/l, while total dissolved lipids varied only from 20.7 to 40.0 μg/l. Autumn was characterized by processes oforganic matter degradation, while new organic matter production takes place during spring. Fatty acid distribution patterns are used to distinguish between various sources. Bacterial branched fatty acids were very low in May. The halocline appeared to be the layer suitable for phytoplankton accumulation as revealed from higher contribution of phytoplankton polyunsaturated fatty acids (PUFA), compared to freshwater and marine layer. The comparison between estuarine and marine stations revealed that PUFA were more important at marine station although organic matter pool (DOC+POC) was lower there.

Journal of Experimental Marine Biology and Ecology, 2011

This paper reports for the first time upon the effects of increasing CO 2 concentrations on a nat... more This paper reports for the first time upon the effects of increasing CO 2 concentrations on a natural phytoplankton assemblage in a tropical estuary (the Godavari River Estuary in India). Two short-term (5-day) bottle experiments were conducted (with and without nutrient addition) during the pre-monsoon season when the partial pressure of CO 2 in the surface water is quite low. The results reveal that the concentrations of total chlorophyll, the phytoplankton growth rate, the concentrations of particulate organic matter, the photosynthetic oxygen evolution rates, and the total bacterial count were higher under elevated CO 2 treatments, as compared to ambient conditions (control). δ 13 C of particulate organic matter (POM) varied inversely with respect to CO 2 , indicating a clear signature of higher CO 2 influx under the elevated CO 2 levels. Whereas, δ 13 C POM in the controls indicated the existence of an active bicarbonate transport system under limited CO 2 supply. A considerable change in phytoplankton community structure was noticed, with marker pigment analysis by HPLC revealing that cyanobacteria were dominant over diatoms as CO 2 concentrations increased. A mass balance calculation indicated that insufficient nutrients (N, P and Si) might have inhibited diatom growth compared to cyanobacteria, regardless of increased CO 2 supply. The present study suggests that CO 2 concentration and nutrient supply could have significant effects on phytoplankton physiology and community composition for natural phytoplankton communities in this region. However, this work was conducted during a non-discharge period (nutrient-limited conditions) and the responses of phytoplankton to increasing CO 2 might not necessarily be the same during other seasons with high physicochemical variability. Further investigation is therefore needed.

Frontiers in Marine Science

How the microbial community response to carbon degradation is unclear, while it plays an essentia... more How the microbial community response to carbon degradation is unclear, while it plays an essential role in predicting microbial community shift and determining carbon cycling. Surface sediments in two contrasting aquacultural tidal flat sites in Fujian Province, China, were collected in October, 2020. In addition to 16s rRNA gene high-throughput sequencing for determining bacteria and archaea biodiversity, an amino acids-based molecular degradation index DI was used to quantify the carbon degradation status. The results revealed that the microorganism response to DI at the family level was community competition. Specifically, the winning microbes that grew under carbon degradation (i.e., operational taxa unit numbers negatively related with the degradation index) accounted for only 18% of the total family number, but accounted for 54% of the total operational taxa unit numbers. Network analysis confirmed the oppressive relation between winners and the rest (losers + centrists), and ...

Journal of Agricultural and Food Chemistry

Aquatic Ecology, 2020

Phospholipid (PL) composition has a tremendous influence on the cell integrity and physiological ... more Phospholipid (PL) composition has a tremendous influence on the cell integrity and physiological competency. At the same time, plankton PL make important metabolic fuels for higher trophic levels. The goal of this study was to identify environmental control on PL production and their molecular identity of the suspended particles in two different estuaries. We conducted research in subtropical, eutrophic Wenchang River Estuary in China and temperate pristine, mesotrophic Krka River Estuary in Croatia. In agreement with the more abundant phytoplankton, PL concentrations were much higher in the Wenchang River Estuary (30.3-178.2 lg L-1) than in the Krka River Estuary (8.4-18.8 lg L-1). Given that six PL classes investigated (phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidic acid (PA), phosphatidylinositol (PI), and phosphatidylserine (PS)) have different roles in the cell, we expected their different fatty acid composition in different environments. We found small differences in the fatty acid composition of PC, PG, and PI between two estuaries. These results suggest that the essential Handling Editor: Télesphore Sime-Ngando.

Biogeochemistry, 2021

The northern slope water of the South China Sea (SCS) is oligotrophic. The regenerated nitrogen f... more The northern slope water of the South China Sea (SCS) is oligotrophic. The regenerated nitrogen from dissolved organic nitrogen (DON) has been suggested to play a pivotal role in sustaining primary productivity; however, DON cycling has not been investigated there. Dissolved free amino acids (DFAAs) and polyamines (DFPAs) are two major groups of labile DON that are used rapidly by heterotrophic bacteria, and important in nitrogen cycling. Here, we measured turnover rates and concentrations of representative DFAAs (arginine and glutamic acid) and DFPAs (putrescine) in waters of the northern slope of the SCS, to estimate uptake rates and evaluate their potentials to fulfill carbon and nitrogen demands of bacterial production. Furthermore, homologs of genes encoding transporter systems for arginine ( aotJ ) and putrescine ( potD / potF ) were quantified in metagenomes from four depths at two sampling stations. The taxa encoding these genes were identified to gain insight into the composition of microbial communities potentially utilizing DFAAs and DFPAs. We found that uptake rates of two DFAAs and putrescine were more rapid than measured previously in seawater with similar environmental characteristics. The uptake of arginine and glutamic acids was estimated to account for 2.4-51% (19 ± 14%) and 2.7-59% (24 ± 20%) of bacterial carbon and nitrogen demand, respectively, and putrescine uptake contributed 4.4-100% (27 ± 33%) and 13-293% (80 ± 96%), respectively. Spatial variation in uptake rates indicated that biogeochemical cycling of DFAAs was distinct from that of DFPAs. Redundancy analysis and metagenomes demonstrated that environmental variables and distinction in bacterial assembleges using DFAAs and DFPAs could both affect their dynamics in the northern slope water of the SCS.

Science of The Total Environment, 2021

Submarine groundwater discharge (SGD) and associated nutrient have long been received insufficien... more Submarine groundwater discharge (SGD) and associated nutrient have long been received insufficient attention in the aquaculture areas of Lianjiang, East China Sea. In this study, we used 224Ra mass balance model to evaluate the importance of SGD in the aquaculture areas of Lianjiang in different seasons. The results showed that SGD fluxes were 0.14 ± 0.070 m3 m-2 d-1 in July and 0.077 ± 0.040 m3 m-2 d-1 in October 2019, which corresponded to approximately 22% and 32% of the river discharge, respectively. Nevertheless, the dissolved inorganic nitrogen (DIN) and phosphorus (DIP) fluxes contributed by SGD over total nutrient inputs were approximately 58% and 73%, respectively in July, 11% and 33%, respectively in October 2019. The ratio of DIN to DIP in seawater was slightly higher than that derived from SGD in July and significantly lower than that derived from the river and SGD in October, which was prone to profound modulated by shellfish (e.g., clam Ruditapes philippinarum and Sinonovacula constricta) and nori (e.g., Pyropia haitanensis) that selectively acquire nitrogen and phosphorous, suggesting that SGD could affect the nutrient structure and aquaculture activities in Lianjiang. Moreover, the new primary production via SGD yielded (2.47 ± 1.32) × 103 mg C m-2 d-1 in July and (3.52 ± 1.76) × 102 mg C m-2 d-1 in October 2019, which were approximately 8-25% and 10-31% of the production in the entire study area. These meaningful discoveries indicated that SGD and associated nutrient are the predominant regulator of nutrient and aquaculture structure under significant seasonal differences.

Journal of Cleaner Production, 2021

Journal of Geophysical Research: Oceans, 2020

Acta Oceanologica Sinica, 2021

Quantifying the gross and net production is an essential component of carbon cycling and marine e... more Quantifying the gross and net production is an essential component of carbon cycling and marine ecosystem studies. Triple oxygen isotope measurements and the O2/Ar ratio are powerful indices in quantifying the gross primary production and net community production of the mixed layer zone, respectively. Although there is a substantial advantage in refining the gas exchange term and water column vertical mixing calibration, application of mixed layer depth history to the gas exchange term and its contribution to reducing indices error are unclear. Therefore, two cruises were conducted in the slope regions of the northern South China Sea in October 2014 (autumn) and June 2015 (spring). Discrete water samples at Station L07 in the upper 150 m depth were collected for the determination of δ17O, δ18O, and the O2/Ar ratio of dissolved gases. Gross oxygen production (GOP) was estimated using the triple oxygen isotopes of the dissolved O2, and net oxygen production (NOP) was calculated using O2/Ar ratio and O2 concentration. The vertical mixing effect in NOP was calibrated via a N2O based approach. GOP for autumn and spring was (169±23) mmol/(m2·d) (by O2) and (189±26) mmol/(m2·d) (by O2), respectively. While NOP was 1.5 mmol/(m2·d) (by O2) in autumn and 8.2 mmol/(m2·d) (by O2) in spring. Application of mixed layer depth history in the gas flux parametrization reduced up to 9.5% error in the GOP and NOP estimations. A comparison with an independent O2 budget calculation in the diel observation indicated a 26% overestimation in the current GOP, likely due to the vertical mixing effect. Both GOP and NOP in June were higher than those in October. Potential explanations for this include the occurrence of an eddy process in June, which may have exerted a submesoscale upwelling at the sampling station, and also the markedly higher terrestrial impact in June.

Progress in Oceanography, 2021

Please note that this is an author-produced PDF of an article accepted for publication following ... more Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Limnology and Oceanography, 2020

The effects of bottom water oxygen concentration on sediment oxygen uptake, oxygen penetration de... more The effects of bottom water oxygen concentration on sediment oxygen uptake, oxygen penetration depth, nitrate and ammonium fluxes, anammox, denitrification, dissimilatory nitrate reduction to ammonium, nitrification, and mineralization were investigated off the Changjiang estuary and its adjacent East China Sea, by combining a seasonal comparison with three artificially induced bottom water oxygen conditions (oxic, ambient, and severe hypoxia). A 50% decrease in in-situ bottom water oxygen concentrations between May and August, led to decreases in the average sediment oxygen uptake and oxygen penetration depth by 23% and 29%, respectively. Anammox rates decreased by a factor of 2.5, and the relative contribution of anammox to the total benthic N-loss decreased from 20% to 7.4%. However, denitrification rates increased, leading to an overall benthic N-loss rate of 0.85 mmol N m −2 d −1. At the same time, an increasing contribution of dissimilatory nitrate reduction to ammonium to total nitrate reduction led to higher recycling of inorganic nitrogen during hypoxia in August. Under artificially induced conditions of severe hypoxia, there was a sharp decrease in both sediment oxygen uptake and benthic N-loss rates by 88% and 38%, respectively. Nitrate and ammonium fluxes showed complex behavior at different sites which could be related to the repression of sedimentary nitrification below a bottom water oxygen threshold of 9.7 μM and increasing dissimilatory nitrate reduction to ammonium. Taken together, our results indicate that changes in benthic nutrient cycling under seasonal hypoxia enhance the retention of both organic and inorganic nitrogen, thereby exacerbating oxygen deficiency.

Earth and Planetary Science Letters, 2021