scholarly journals Biophysical controls on seasonal changes in the structure, growth, and grazing of the size-fractionated phytoplankton community in the northern South China Sea

2021 ◽  
Vol 18 (24) ◽  
pp. 6423-6434
Author(s):  
Yuan Dong ◽  
Qian P. Li ◽  
Zhengchao Wu ◽  
Yiping Shuai ◽  
Zijia Liu ◽  
...  
Keyword(s):  
Growth Rate ◽  
South China Sea ◽  
South China ◽  
Phytoplankton Community ◽  
Northern South China Sea ◽  
Grazing Rate ◽  
Phytoplankton Growth ◽  
Small Cells ◽  
Grazing Impact ◽  
China Sea

Abstract. The size-fractionated phytoplankton growth and microzooplankton grazing are crucial for the temporal change of community size structure, regulating not only trophic transfer but also the carbon cycle of the ocean. However, the size-dependent growth and grazing dynamics on a monthly or an annual basis are less addressed in the coastal ocean. In this paper, the seasonal responses of the size-fractionated phytoplankton growth and grazing to environmental change were examined over 1 year at a coastal site of the northern South China Sea. We found a nanophytoplankton-dominated community with strong seasonal variations in all size classes. Phytoplankton community growth rate was positively correlated to nutrients, with community grazing rate correlating to the total chlorophyll a at the station, reflecting a combined bottom-up and topdown effect on phytoplankton population dynamics. Further analyses suggested that the specific growth rate of microphytoplankton was significantly influenced by phosphate, and that of nanophytoplankton was influenced by light, although picophytoplankton growth was controlled by both nitrate and temperature. In addition, the specific grazing rate of nanophytoplankton was well correlated to phytoplankton standing stock, while that of micro- and pico-compartments was negatively influenced by ciliate abundance and salinity. Finally, a lower grazing impact for micro-cells (38 %) than nano- and pico-cells (72 % and 60 %, respectively) may support size-selective grazing of microzooplankton on small cells at this eutrophic system.

scholarly journals Biophysical controls on seasonal changes in the structure, growth, and grazing of the size-fractioned phytoplankton community in the northern South China Sea 

2021 ◽  
Author(s):  
Yuan Dong ◽  
Qian Li ◽  
Zhengchao Wu ◽  
Yiping Shuai ◽  
Zijia Liu ◽  
...  
Keyword(s):  
Growth Rate ◽  
South China Sea ◽  
South China ◽  
Phytoplankton Community ◽  
Northern South China Sea ◽  
Grazing Rate ◽  
Phytoplankton Growth ◽  
Small Cells ◽  
Grazing Impact ◽  
China Sea

Abstract. The size-fractionated phytoplankton growth and microzooplankton grazing are crucial for the temporal change of community size-structure, regulating not only trophic transfer but also carbon cycle of the ocean. However, the size-dependent growth and grazing dynamics on monthly or an annual basis are less addressed in the coastal ocean. In this paper, the seasonal responses of the size-fractionated phytoplankton growth and grazing to environmental change were examined over a one-year period at a coastal site of the northern South China Sea. We found a nanophytoplankton dominated community with strong seasonal variations of all size classes. Phytoplankton community growth rate was positively correlated to nutrients with community grazing rate correlating to the total chlorophyll-a at the station, reflecting a combined bottom-up and top-down effect on phytoplankton population dynamics. Further analyses suggested that the specific growth rate of microphytoplankton was significantly influenced by phosphate with that of nanophytoplankton by light, although picophytoplankton growth was controlled by both nitrate and temperature. In addition, the specific grazing rate of nanophytoplankton was well correlated to phytoplankton standing stock, while those of micro- and pico-compartments were negatively influenced by ciliate abundance and salinity. Finally, a lower grazing impact for micro-cells (38 %) than nano- and pico-cells (72 % and 60 %, respectively) may support a size-selective grazing of microzooplankton on small cells at this eutrophic system.

scholarly journals Seasonal and spatial comparisons of phytoplankton growth and mortality rates due to microzooplankton grazing in the northern South China Sea

2012 ◽  
Vol 9 (11) ◽  
pp. 16005-16032
Author(s):  
B. Chen ◽  
L. Zheng ◽  
B. Huang ◽  
S. Song ◽  
H. Liu
Keyword(s):  
South China Sea ◽  
Mixed Layer ◽  
South China ◽  
Surface Waters ◽  
Northern South China Sea ◽  
Phytoplankton Growth ◽  
China Sea ◽  
Grazing Effect ◽  
Basin Surface ◽  
Microzooplankton Grazing

Abstract. We conducted a comprehensive investigation on the microzooplankton herbivory effect on phytoplankton in the northern South China Sea (SCS) using the seawater dilution technique at surface and deep chlorophyll maximum (DCM) layers in two cruises (July–August of 2009 and January of 2010). We compared vertical (surface vs. DCM), spatial (onshore vs. offshore), and seasonal (summer vs. winter) differences of phytoplankton growth (μ0) and microzooplankton grazing rates (m). During summer, both μ0 and m were significantly higher at the surface than at the layer of DCM, which was below the mixed layer. During winter, surface μ0 was significantly higher than at DCM, while m was not significantly different between the two layers, both of which were contained within the mixed layer. Surface μ0 was, on average, significantly higher in summer than in winter; while average surface m was not different between the two seasons. There were no significant cross-shelf trends of μ0 in summer or winter surface waters. In surface waters, μ0 was not correlated with ambient nitrate concentrations and the effect of nutrient enrichment on phytoplankton growth was not pronounced. There was a decreasing trend of m from shelf to basin surface waters in summer, but not in winter. Microzooplankton grazing effect on phytoplankton (m/μ0) did not increase with distance offshore, suggesting that the importance of microzooplankton as grazers of phytoplankton may not decrease in onshore waters. On average, microzooplankton grazed 73% and 65% of the daily primary production in summer and winter, respectively.

Phytoplankton community at warm eddies in the northern South China Sea in winter 2003/2004

2010 ◽  
Vol 57 (19-20) ◽  
pp. 1792-1798 ◽  
Author(s):  
Bangqin Huang ◽  
Jun Hu ◽  
Hongzhou Xu ◽  
Zhenrui Cao ◽  
Dongxiao Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
Phytoplankton Community ◽  
Northern South China Sea ◽  
China Sea

scholarly journals Phytoplankton growth and physiological responses to a plume front in the northern South China Sea

2017 ◽  
Author(s):  
Qian P. Li ◽  
Weiwen Zhou ◽  
Yinchao Chen ◽  
Zhengchao Wu
Keyword(s):  
South China Sea ◽  
South China ◽  
Bottom Water ◽  
Frontal Zone ◽  
Northern South China Sea ◽  
River Estuary ◽  
Phytoplankton Growth ◽  
Frontal System ◽  
China Sea ◽  
Plume Water

Abstract. Due to a strong river discharge during April–June 2016, a persistent salinity front, with freshwater flushing seaward on the surface but seawater moving landward at the bottom, was formed in the coastal waters west of the Pearl River Estuary (PRE) over the Northern South China Sea (NSCS) shelf. Hydrographic measurements revealed that the salinity front was influenced by both river plume and coastal upwelling. Shipboard nutrient-enrichment experiments with size-fractionation chlorophyll-a measurements were performed on both sides of the front as well as the front zone to diagnose the spatial variations of phytoplankton physiology across the frontal system. We also assessed the size-fractionated responses of phytoplankton to the treatment of plume water at the frontal zone and the seaside of the front. Biological impact of vertical mixing or upwelling was further examined by the response of surface phytoplankton to the addition of local bottom water. Our results suggested that there was a large variation of phytoplankton physiology on the seaside of the front driven by dynamic nutrient fluxes, although P-limitation was prevailing on the shore-side of the front and at the frontal zone. The spreading of plume water at the frontal zone would directly improve the growth of micro-phytoplankton, while nano- and pico-phytoplankton growths could become saturated at high percentages of plume water. Also, the mixing of bottom water would stimulate the growth of surface phytoplankton on both sides of the front by altering the surface N / P ratio closer to the Redfield stoichiometry. In summary, phytoplankton growth and physiology could be profoundly influenced by physical dynamics of the frontal system during the spring–summer of 2016.

Monsoon-driven dynamics of environmental factors and phytoplankton in tropical Sanya Bay, South China sea

2012 ◽  
Vol 41 (1) ◽  
Author(s):  
Mei-Lin Wu ◽  
Yan-Ying Zhang ◽  
Jun-De Dong ◽  
Chuang-Hua Cai ◽  
You-Shao Wang ◽  
...  
Keyword(s):  
Environmental Factors ◽  
South China Sea ◽  
South China ◽  
Phytoplankton Community ◽  
Northern South China Sea ◽  
Factors Affecting ◽  
China Sea ◽  
Sanya Bay ◽  
Monsoon Winds ◽  
Physical And Chemical

AbstractIn this work, we analyze environmental (physical and chemical) and biological (phytoplankton) data obtained in Sanya Bay during four cruises, carried out in January, April, August, and October. The main objective of this study was to identify the key environmental factors affecting phytoplankton structure and bacterioplankton in the bay. Results suggest that spatial variations in the phytoplankton community and bacterioplankton biomass are the result of nutrients. Temporal variation in the abundance of bacterioplankton and phytoplankton are affected by a combination of physical and biological factors, such as temperature and nutrients. The silicate, phosphate, and nitrogen phytoplankton require for growth may be co-limited. Monsoon winds (a southwestern monsoon during summer and a northeastern monsoon during winter) play important roles in controlling the phytoplankton community and bacterioplankton abundance in Sanya Bay, northern South China Sea.

scholarly journals Variation of phytoplankton absorption coefficients in the northern South China Sea during spring and autumn

2007 ◽  
Vol 4 (3) ◽  
pp. 1555-1584 ◽  
Author(s):  
J. Wu ◽  
H. Hong ◽  
S. Shang ◽  
M. Dai ◽  
Z. Lee
Keyword(s):  
South China Sea ◽  
South China ◽  
Phytoplankton Community ◽  
Northern South China Sea ◽  
Outer Shelf ◽  
Pearl River ◽  
China Sea ◽  
Shelf Slope ◽  
Phytoplankton Absorption ◽  
The Pearl River

Abstract. We examined the temporal and spatial variabilities of phytoplankton absorption coefficients (αphλ)) and their relationships with physical processes in the northern South China Sea from two cruise surveys during spring (May 2001) and late autumn (November 2002). A large river plume induced by heavy precipitation in May stimulated a phytoplankton bloom on the inner shelf, causing significant changes in the surface water in αph values and B/R ratios (αph(440)/αph(675)). This was consistent with the observed one order of magnitude elevation of chlorophyll α and a shift from a pico/nano dominated phytoplankton community to one dominated by micro-algae. At the seasonal level, enhanced vertical mixing due to strengthened northeast monsoon in November has been observed to result in higher surface αph(675) (0.002–0.006 m−1 higher) and less pronounced subsurface maximum on the outer shelf/slope in November as compared that in May. Measurements of αph and B/R ratios from three transects in November revealed a highest surface αph(675) immediately outside the mouth of the Pearl River Estuary, whereas lower αph(675) and higher B/R ratios were featured in the outer shelf/slope waters, demonstrating the respective influence of the Pearl River plume and the oligotrophic nature of South China Sea water. The difference in spectral shapes of phytoplankton absorption (measured by B/R ratios and bathochromic shifts) on these three transects infers that picoprocaryotes are the major component of the phytoplankton community on the outer shelf/slope rather than on the inner shelf. In addition, a regional tuning of the phytoplankton absorption spectral model (Carder et al., 1999) demonstrated a greater spatial variation than seasonal variation in the lead parameter a0(λ). These results suggest that phytoplankton absorption properties in a coastal region such as the northern South China Sea are complex and region-based parameterization is mandatory in order for remote sensing algorithms.

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