Diurnal Variability in Chlorophyll-a, Carotenoids, CDOM and SO42− Intensity of Offshore Seawater Detected by an Underwater Fluorescence-Raman Spectral System

Jing Chen, Wangquan Ye, Jinjia Guo, Zhao Luo, Ying Li
2016 Sensors  
A newly developed integrated fluorescence-Raman spectral system (λ ex = 532 nm) for detecting Chlorophyll-a (chl-a), Chromophoric Dissolved Organic Matter (CDOM), carotenoids and SO 4 2´i n situ was used to successfully investigate the diurnal variability of all above. Simultaneously using the integration of fluorescence spectroscopy and Raman spectroscopy techniques provided comprehensive marine information due to the complementarity between the different excitation mechanisms and different
more » ... ection rules. The investigation took place in offshore seawater of the Yellow Sea (36˝05 1 40 11 N, 120˝31 1 32 11 E) in October 2014. To detect chl-a, CDOM, carotenoids and SO 4 2´, the fluorescence-Raman spectral system was deployed. It was found that troughs of chl-a and CDOM fluorescence signal intensity were observed during high tides, while the signal intensity showed high values with larger fluctuations during ebb-tide. Chl-a and carotenoids were influenced by solar radiation within a day cycle by different detection techniques, as well as displaying similar and synchronous tendency. CDOM fluorescence cause interference to the measurement of SO 4 2´. To avoid such interference, the backup Raman spectroscopy system with λ ex = 785 nm was employed to detect SO 4 2´c oncentration on the following day. The results demonstrated that the fluorescence-Raman spectral system has great potential in detection of chl-a, carotenoids, CDOM and SO 4 2´i n the ocean.
doi:10.3390/s16071082 pmid:27420071 pmcid:PMC4970128 fatcat:2w6pcglbajcclkaeiytnaqsx7u