Abstract
Vertical variability in the bio-optical properties of seawater in the northern South China Sea (NSCS) including inherent optical properties (IOPs) and chlorophyll a concentration (Chl) were studied on the basis of in situ data collected in summer 2008 using an absorption/attenuation spectrophotometer. An empirical model was developed to estimate Chl profiles based on the absorption line height at long wavelengths, with a relative root mean square error of 37.03%. Bio-optical properties exhibited large horizontal and vertical spatial variability. As influenced by coastal upwelling and the Zhujiang River (Pearl River) discharge, both IOPs and Chl exhibited high values in the surface waters of the inner shelf, which tended to decrease with distance offshore. Subsurface maximum layers of IOPs and Chl were observed in the middle and outer shelf regions, along with significantly higher values of attenuation coefficients beneath this layer that rapidly increased towards the bottom. In the open ocean, both IOPs and Chl exhibited consistent variability, with the subsurface maximum layer typically located at 34–84 m. Phytoplankton were found to be one of the major components in determining the vertical variability of bio-optical properties, with their vertical dynamics influenced by both physical forcing and light attenuation effects. The depth of the subsurface maximum layer was found to be closely related to the fluctuation of the oceanic thermocline and the depth of the euphotic zone, which also affected the total integrated biomass of the upper ocean. Typically high values of attenuation coefficients observed in the bottom waters of the continental shelf reflected the transport of particulate matter over the bottom boundary layer. Our results reveal large spatial differences in bio-optical profiles in response to complex marine ecodynamics in the NSCS. From the perspective of marine research, high-resolution optical measurements are clearly advantageous over conventional bottle sampling.
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References
Barnard A H, Pegau W S, Zaneveld J R V. 1998. Global relationships of the inherent optical properties of the oceans. Journal of Geophysical Research, 103(C11): 24955–24968, doi: https://doi.org/10.1029/98JC01851
Behrenfeld M J, Boss E. 2003. The beam attenuation to chlorophyll ratio: an optical index of phytoplankton physiology in the surface ocean?. Deep Sea Research Part I: Oceanographic Research Papers, 50(12): 1537–1549, doi: https://doi.org/10.1016/j.dsr.2003.09.002
Behrenfeld M J, Boss E, Siegel D A, et al. 2005. Carbon-based ocean productivity and phytoplankton physiology from space. Global Biogeochemical Cycles, 19(1): GB1006
Bishop J K B. 1999. Transmissometer measurement of POC. Deep Sea Research Part I: Oceanographic Research Papers, 46(2): 353–369, doi: https://doi.org/10.1016/S0967-0637(98)00069-7
Boss E S, Collier R, Larson G, et al. 2007. Measurements of spectral optical properties and their relation to biogeochemical variables and processes in Crater Lake, Crater Lake National Park, OR. Hydrobiologia, 574(1): 149–159, doi: https://doi.org/10.1007/s10750-006-2609-3
Boss E, Pegau W S, Gardner W D, et al. 2001. Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf. Journal of Geophysical Research: Oceans, 106(C5): 9509–9516, doi: https://doi.org/10.1029/2000JC900077
Boss E, Picheral M, Leeuw T, et al. 2013. The characteristics of particulate absorption, scattering and attenuation coefficients in the surface ocean; Contribution of the Tara Oceans expedition. Methods in Oceanography, 7: 52–62, doi: https://doi.org/10.1016/j.mio.2013.11.002
Brewin R J W, Dall’Olmo G, Pardo S, et al. 2016. Underway spectrophotometry along the Atlantic Meridional Transect reveals high performance in satellite chlorophyll retrievals. Remote Sensing of Environment, 183: 82–97, doi: https://doi.org/10.1016/j.rse.2016.05.005
Buesseler K O. 2001. Ocean biogeochemistry and the global carbon cycle: an introduction to the U.S. joint global ocean flux study. Oceanography, 14(4): 5, doi: https://doi.org/10.5670/oceanog.2001.01
Chang G C, Dickey T D. 2001. Optical and physical variability on timescales from minutes to the seasonal cycle on the New England shelf: July 1996 to June 1997. Journal of Geophysical Research: Oceans, 106(C5): 9435–9453, doi: https://doi.org/10.1029/2000JC900069
Chen C C, Shiah F K, Chung S W, et al. 2006. Winter phytoplankton blooms in the shallow mixed layer of the South China Sea enhanced by upwelling. Journal of Marine Systems, 59(1–2): 97–110, doi: https://doi.org/10.1016/j.jmarsys.2005.09.002
Claustre H, Fell F, Oubelkheir K, et al. 2000. Continuous monitoring of surface optical properties across a geostrophic front: Biogeochemical inferences. Limnology and Oceanography, 45(2): 309–321
Cui Wansong, Wang Difeng, Gong Fang, et al. 2016. The vertical distribution of the beam attenuation coefficient and its correlation to the particulate organic carbon in the north South China Sea. In: Remote Sensing of the Ocean, Sea Ice, Coastal Waters, and Large Water Regions. Edinburgh, United Kingdom: SPIE, 2016
Cullen J J. 1982. The deep chlorophyll maximum: Comparing vertical profiles of chlorophyll a. Canadian Journal of Fisheries and Aquatic Sciences, 39(5): 791–803, doi: https://doi.org/10.1139/f82-108
Cullen J J. 2015. Subsurface chlorophyll maximum layers: Enduring enigma or mystery solved?. Annual Review of Marine Science, 7: 207–239, doi: https://doi.org/10.1146/annurev-marine-010213-135111
Dickey T D. 2001. The role of new technology in advancing ocean biogeochemical research. Oceanography, 14(4): 108–120, doi: https://doi.org/10.5670/oceanog.2001.11
Fennel K, Boss E. 2003. Subsurface maxima of phytoplankton and chlorophyll: Steady-state solutions from a simple model. Limnology and Oceanography, 48(4): 1521–1534, doi: https://doi.org/10.4319/lo.2003.48.4.1521
Fujii M, Boss E, Chai F. 2007. The value of adding optics to ecosystem models: a case study. Biogeosciences, 4(5): 817–835, doi: https://doi.org/10.5194/bg-4-817-2007
Gardner W D, Gundersen J S, Richardson M J, et al. 1999. The role of seasonal and diel changes in mixed-layer depth on carbon and chlorophyll distributions in the Arabian Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 46(8–9): 1833–1858, doi: https://doi.org/10.1016/S0967-0645(99)00046-6
Gernez P, Antoine D, Huot Y. 2011. Diel cycles of the particulate beam attenuation coefficient under varying trophic conditions in the northwestern Mediterranean Sea: Observations and modeling. Limnology and Oceanography, 56(1): 17–36, doi: https://doi.org/10.4319/lo.2011.56.1.0017
Gong Xiang, Shi Jie, Gao Huiwang, et al. 2014. Modeling seasonal variations of subsurface chlorophyll maximum in South China Sea. Journal of Ocean University of China, 13(4): 561–571, doi: https://doi.org/10.1007/s11802-014-2060-4
Gong Xiang, Shi Jinhui, Gao Huiwang, et al. 2015. Steady-state solutions for subsurface chlorophyll maximum in stratified water columns with a bell-shaped vertical profile of chlorophyll. Biogeosciences, 12(4): 905–919, doi: https://doi.org/10.5194/bg-12-905-2015
Kara A B, Rochford P A, Hurlburt H E. 2000. An optimal definition for ocean mixed layer depth. Journal of Geophysical Research, 105(C7): 16803–16821, doi: https://doi.org/10.1029/2000JC900072
Kheireddine M, Antoine D. 2014. Diel variability of the beam attenuation and backscattering coefficients in the northwestern Mediterranean Sea (BOUSSOLE site). Journal of Geophysical Research: Oceans, 119(8): 5465–5482, doi: https://doi.org/10.1002/2014JC010007
Kitchen J C, Zaneveld J R V. 1990. On the noncorrelation of the vertical structure of light scattering and chlorophyll a in case I waters. Journal of Geophysical Research: Oceans, 95(C11): 20237–20246, doi: https://doi.org/10.1029/JC095iC11p20237
Knap A, Michaels A, Close A, et al. 1996. Protocols for the Joint Global Ocean Flux Study (JGOFS) core measurements. Reprint of the IOC Manuals and Guides No. 29, UNESCO, Paris
Lavigne H, D’Ortenzio F, D’Alcalà M R, et al. 2015. On the vertical distribution of the chlorophyll a concentration in the Mediterranean Sea: a basin-scale and seasonal approach. Biogeosciences, 12(16): 5021–5039, doi: https://doi.org/10.5194/bg-12-5021-2015
Li Q P, Dong Y, Wang Y. 2016. Phytoplankton dynamics driven by vertical nutrient fluxes during the spring inter-monsoon period in the northeastern South China Sea. Biogeosciences, 13: 455–466, doi: https://doi.org/10.5194/bg-13-455-2016
Li Q P, Franks P J S, Landry M R, et al. 2010. Modeling phytoplankton growth rates and chlorophyll to carbon ratios in California coastal and pelagic ecosystems. Journal of Geophysical Research, 115(G4): G04003
Lin Junfang, Cao Wenxin, Wang Guifen, et al. 2014. Inversion of biooptical properties in the coastal upwelling waters of the northern South China Sea. Continental Shelf Research, 85: 73–84, doi: https://doi.org/10.1016/j.csr.2014.06.001
Lin Peigen, Cheng Peng, Gan Jianping, et al. 2016. Dynamics of wind-driven upwelling off the northeastern coast of Hainan Island. Journal of Geophysical Research: Oceans, 121(2): 1160–1173, doi: https://doi.org/10.1002/2015JC011000
Liu K K, Chao S Y, Shaw P T, et al. 2002. Monsoon-forced chlorophyll distribution and primary production in the South China Sea: observations and a numerical study. Deep Sea Research Part I: Oceanographic Research Papers, 49(8): 1387–1412, doi: https://doi.org/10.1016/S0967-0637(02)00035-3
Liu Fenfen, Tang Shilin, Chen Chuqun. 2013. Impact of nonlinear mesoscale eddy on phytoplankton distribution in the northern South China Sea. Journal of Marine Systems, 123–124: 33–40, doi: https://doi.org/10.1016/j.jmarsys.2013.04.005
Lu Zhongming, Gan Jianping, Dai Minhan, et al. 2010. The influence of coastal upwelling and a river plume on the subsurface chlorophyll maximum over the shelf of the northeastern South China Sea. Journal of Marine Systems, 82(1–2): 35–46, doi: https://doi.org/10.1016/j.jmarsys.2010.03.002
Ma Jinfeng, Zhan Haigang, Du Yan. 2011. Seasonal and interannual variability of surface CDOM in the South China Sea associated with El Niño. Journal of Marine Systems, 85(3–4): 86–95, doi: https://doi.org/10.1016/j.jmarsys.2010.12.006
McGillicuddy D J Jr. 2016. Mechanisms of physical-biological-biogeochemical interaction at the oceanic mesoscale. Annual Review of Marine Science, 8(1): 125–159, doi: https://doi.org/10.1146/annurev-marine-010814-015606
McGillicuddy D J Jr, Johnson R, Siegel D A, et al. 1999. Mesoscale variations of biogeochemical properties in the Sargasso Sea. Journal of Geophysical Research: Oceans, 104(C6): 13381–13394, doi: https://doi.org/10.1029/1999JC900021
Mignot A, Claustre H, D’Ortenzio F, et al. 2011. From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-a concentration. Biogeosciences, 8(8): 2391–2406, doi: https://doi.org/10.5194/bg-8-2391-2011
Mignot A, Claustre H, Uitz J, et al. 2014. Understanding the seasonal dynamics of phytoplankton biomass and the deep chlorophyll maximum in oligotrophic environments: A Bio-Argo float investigation. Global Biogeochemical Cycles, 28(8): 856–876, doi: https://doi.org/10.1002/2013GB004781
Mitchell B G, Kahru M, Wieland J, et al. 2003. Determination of spectral absorption coefficients of particles, dissolved material and phytoplankton for discrete water samples. In: Mueller J L, Fargoin G S, McClain C R, eds. Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, revision 4, Vol. IV (Chapter 4), NASA/TM-2003-211621/Rev4-vol. 4. Greenbelt, MD: NASA Goddard Space Flight Center, 39–64
Mobley C D. 1994. Light and Water: Radiative Transfer in Natural Waters. San Diego, CA, USA: Academic Press
Morel A. 1988. Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters). Journal of Geophysical Research: Oceans, 93(C9): 10749–10768, doi: https://doi.org/10.1029/JC093iC09p10749
Morel A, Maritorena S. 2001. Bio-optical properties of oceanic waters: A reappraisal. Journal of Geophysical Research: Oceans, 106(C4): 7163–7180, doi: https://doi.org/10.1029/2000JC000319
Nencioli F, Chang G, Twardowski M, et al. 2010. Optical characterization of an eddy-induced diatom bloom west of the island of Hawaii. Biogeosciences, 7(1): 151–162, doi: https://doi.org/10.5194/bg-7-151-2010
Ning Xiuren, Chai Fei, Xue Huijie, et al. 2004. Physical-biological oceanographic couplinginfluencing phytoplankton and primary production in the South China Sea. Journal of Geophysical Research: Oceans, 109: C10005, doi: https://doi.org/10.1029/2004JC002365
Oubelkheir K, Claustre H, Sciandra A, et al. 2005. Bio-optical and biogeochemical properties of different trophic regimes in oceanic waters. Limnology and Oceanography, 50(6): 1795–1809, doi: https://doi.org/10.4319/lo.2005.50.6.1795
Oubelkheir K, Sciandra A. 2008. Diel variations in particle stocks in the oligotrophic waters of the Ionian Sea (Mediterranean). Journal of Marine Systems, 74(1–2): 364–371, doi: https://doi.org/10.1016/j.jmarsys.2008.02.008
Pan Xiaoju, Wong G T F, Tai J H, et al. 2015. Climatology of physical hydrographic and biological characteristics of the Northern South China Sea Shelf-sea (NoSoCS) and adjacent waters: Observations from satellite remote sensing. Deep Sea Research Part II: Topical Studies in Oceanography, 117: 10–22, doi: https://doi.org/10.1016/j.dsr2.2015.02.022
Parsons T, Takahashi M, Hargrave B. 1984. Biological Oceanographic Processes. 3rd ed. England: Pergamon Press, 330
Pérez V, Fernández E, Marañón E, et al. 2006. Vertical distribution of phytoplankton biomass, production and growth in the Atlantic subtropical gyres. Deep Sea Research Part I: Oceanographic Research Papers, 53(10): 1616–1634, doi: https://doi.org/10.1016/j.dsr.2006.07.008
Platt T, Bouman H, Devred E, et al. 2005. Physical forcing and phytoplankton distributions. Scientia Marina, 69(S1): 55–73, doi: https://doi.org/10.3989/scimar.2005.69s155
Roesler C S, Barnard A H. 2013. Optical proxy for phytoplankton biomass in the absence of photophysiology: Rethinking the absorption line height. Methods in Oceanography, 7: 79–94, doi: https://doi.org/10.1016/j.mio.2013.12.003
Shang Shaoling, Li Li, Li Jun, et al. 2012. Phytoplankton bloom during the northeast monsoon in the Luzon Strait bordering the Kuroshio. Remote Sensing of Environment, 124: 38–48, doi: https://doi.org/10.1016/j.rse.2012.04.022
Stramski D, Reynolds R A, Babin M, et al. 2008. Relationships between the surface concentration of particulate organic carbon and optical properties in the eastern South Pacific and eastern Atlantic Oceans. Biogeosciences, 5(1): 171–201, doi: https://doi.org/10.5194/bg-5-171-2008
Sullivan J M, Twardowski M S, Zaneveld J R V, et al. 2006. Hyperspectral temperature and salt dependencies of absorption by water and heavy water in the 400–750 nm spectral range. Applied Optics, 45(21): 5294–5309, doi: https://doi.org/10.1364/AO.45.005294
Uitz J, Claustre H, Morel A, et al. 2006. Vertical distribution of phytoplankton communities in open ocean: An assessment based on surface chlorophyll. Journal of Geophysical Research: Oceans, 111(C8): C08005
Wang Guifen, Cao Wenxi, Yang Dingtian, et al. 2008. Variation in downwelling diffuse attenuation coefficient in the northern South China Sea. Chinese Journal of Oceanology and Limnology, 26(3): 323–333, doi: https://doi.org/10.1007/s00343-008-0323-x
Wang Lei, Huang Bangqin, Chiang K P, et al. 2016. Physical-biological coupling in the western South China Sea: The response of phytoplankton community to a mesoscale cyclonic eddy. PLoS One, 11(4): e0153735, doi: https://doi.org/10.1371/journal.pone.0153735
Wang Lei, Huang Bangqin, Laws E A, et al. 2018. Anticyclonic eddy edge effects on phytoplankton communities and particle export in the northern South China Sea. Journal of Geophysical Research: Oceans, 123(11): 7632–7650, doi: https://doi.org/10.1029/2017JC013623
Wang Dongxiao, Shu Yeqiang, Xue Huijie, et al. 2014. Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea. Journal of Geophysical Research: Oceans, 119(4): 2550–2567, doi: https://doi.org/10.1002/2013JC009172
Wang Guifen, Zhou Wen, Cao Wenxi, et al. 2011. Variation of particulate organic carbon and its relationship with bio-optical properties during a phytoplankton bloom in the Pearl River estuary. Marine Pollution Bulletin, 62(9): 1939–1947, doi: https://doi.org/10.1016/j.marpolbul.2011.07.003
Wong G T F, Pan Xiaoju, Li Kuoyuan, et al. 2015. Hydrography and nutrient dynamics in the Northern South China Sea Shelf-sea (NoSoCS). Deep Sea Research Part II: Topical Studies in Oceanography, 117: 23–40, doi: https://doi.org/10.1016/j.dsr2.2015.02.023
Xing Xiaogang, Claustre H, Uitz J, et al. 2014. Seasonal variations of bio-optical properties and their interrelationships observed by Bio-Argo floats in the subpolar North Atlantic. Journal of Geophysical Research: Oceans, 119(10): 7372–7388, doi: https://doi.org/10.1002/2014JC010189
Xiu Peng, Chai Fei. 2014. Connections between physical, optical and biogeochemical processes in the Pacific Ocean. Progress in Oceanography, 122: 30–53, doi: https://doi.org/10.1016/j.pocean.2013.11.008
Xiu Peng, Liu Yuguang, Li Gang, et al. 2009. Deriving depths of deep chlorophyll maximum and water inherent optical properties: A regional model. Continental Shelf Research, 29(19): 2270–2279, doi: https://doi.org/10.1016/j.csr.2009.09.003
Xu Wenlong, Wang Guifen, Zhou Wen, et al. 2018. Vertical variability of chlorophyll a concentration and its responses to hydrodynamic processes in the northeastern South China Sea in summer. Journal of Tropical Oceanography (in Chinese), 37(5): 62–73
Ye H J, Sui Y, Tang D L, et al. 2013. A subsurface chlorophyll a bloom induced by typhoon in the South China Sea. Journal of Marine Systems, 128: 138–145, doi: https://doi.org/10.1016/j.jmarsys.2013.04.010
Zaneveld J R V, Kitchen J C, Moore C C. 1994. Scattering error correction of reflecting-tube absorption meters. In: Ocean Optics XII. Bergen, Norway: SPIE
Zhang Wenzhou, Wang Haili, Chai Fei, et al. 2016. Physical drivers of chlorophyll variability in the open South China Sea. Journal of Geophysical Research: Oceans, 121(9): 7123–7140, doi: https://doi.org/10.1002/2016JC011983
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Foundation item: The National Natural Science Foundation of China under contract Nos 41776045 and 41576030; the Fundamental Research Funds for the Central Universities under contract No. 2017B06714; the Open Project Program of the State Key Laboratory of Tropical Oceanography under contract No. LTOZZ1602; the Science and Technology Program of Guangzhou, China under contract No. 201607020041.
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We thank all contributors to the dataset in the South China Sea Open Cruise by the R/V Shiyan3, South China Sea Institute of Oceanology, CAS and Qian Li for his constructive suggestions on the initial version of the manuscript. We also thank Guy Evans from Liwen Bianji, Edanz Editing China (www.liwenbianji.cn/ac), for editing the English text of a draft of this manuscript.
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Wang, G., Zhou, W., Xu, Z. et al. Vertical variations in the bio-optical properties of seawater in the northern South China Sea during summer 2008. Acta Oceanol. Sin. 39, 42–56 (2020). https://doi.org/10.1007/s13131-020-1535-y
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DOI: https://doi.org/10.1007/s13131-020-1535-y