Fig. 1

Schematic diagram of multi-functional photosynthetically active radiation (MPAR)"

Fig. 2

Extinction coefficient of 5- and 6-mm light diffusion glass. The influence of optical hole measured by spectrophotometer leads to the waveform not completely overlapping, and the spectral waveform changes greatly in the visible region, which needs to be corrected by subsequent optical elements"

Fig. 3

Photoelectric conversion efficiency of photoelectric inductor at different wavelengths"

Fig. 4

Physical images of MPAR (a), underwater profile support shelves (b), and overall assembly of the marine transmittance meter (c)"

Fig. 5

Cosine response of MPAR"

Fig. 6

Response of the probe to energy in the wavelength range of 400-700 nm, where (a) is the ideal response; (b) is the response result of MPAR; (c) PAR response rate developed for Satlantic, Canada. Taken from the Satlantic PAR specification."

Fig. 7

Operation interface diagram of ocean transmittance meter software (a), and variation with depth in the percentage of radiation in water measured at multiple stations during field experiments in the South China Sea (b)"

Fig. 8

Sampling stations of primary production in the study area. Map of average sea surface height anomaly bases on the data from September 1 to 21, 2018. The negative sea surface height value indicates cyclonic eddy, and positive value denotes anticyclonic eddy. Station A was chosen since it was located at the center of cyclonic eddy"

Tab. 1

Water depth values corresponding to different attenuation ratios at four stations"