HY-1C/D Reveals the Chlorophyll-a Concentration Distribution Details in the Intensive Islands' Waters and Its Consistency with the Distribution of Fish Spawning Ground

Chlorophyll-a (Chl-a) change details derived from HY-1C/D images in the waters of the Zhoushan archipelago were analyzed. A new Chl-a inverse model was built based on the relationship between the in situ Chl-a and the combination of red, blue and green bands of the coastal zone imager (CZI). Chl-a as well as fishery resources were analyzed. The results showed the following. (1) The Chl-a concentration in the waters of the Zhoushan archipelago was mainly in the range of 0.5 similar to 6 mu g/L. High Chl-a area distributed in the west side of the study area, with a value of 3.5 similar to 5.5 mu g/L. The Chl-a concentration in the east side of the study area was relatively lower, with a value of 0.5 similar to 2 mu g/L. Chl-a around the islands was higher than that in the area far away from the islands. In addition, Chl-a concentration increased obviously downstream of the island. (2) The spawning ground of many fish in the waters of the Zhoushan archipelago was abundant, and its spatial-temporal variation was consistent with the change of Chl-a. (3) The islands interacted with the current, inducing upwelling upstream and vortex streets downstream. The complex hydrodynamic environment promoted a vertical exchange of water bodies, thereby resulting in an increase in suspended sediment concentration, nutrients, Chl-a and attracting fish.