The vertical attenuation of irradiance as a function of turbidity: a case of the Huanghai(Yellow) Sea in spring

The planar photosynthetically available radiation (PAR), turbidity and concentration of chlorophyll a (chl a), were measured at 26 stations in the Huanghai (Yellow) Sea during a cruise of China SOLAS from 19 to 27 March 2005. Due to low chl a (<0.35 mg·m~(-3)) in upper layers (above 5 m),suspended particulate matter became the major factor that influenced the turbidity in early spring.The calculated vertical diffuse attenuation coefficient of PAR, K_(PAR), varied with water depths with a maximum value in the upper 5 m layer. The mean K_(PAR) in survey area was 0.277±0.07 m~(-1) that is considerably higher than most of the other case 2 waters. Within the survey area, K_(PAR) also showed distinct regional characteristics, corresponding to the distribution of turbidity. Based on measurements, the relationship between K_(PAR) and turbidity as well as chl a was established.It was suggested that suspended particulate matter plays an important role in light attenuation in the Huanghai (Yellow) Sea in spring.