algal bloom spread in water

I am new to water quality monitoring, I am using ArcGIS so please guide me accordingly. . I have 2 questions:

  1. I want to calculate the algal bloom spread area in the water surface (upper surface). In my study area, I have seen the higher reflectance value is present in the Green band (560nm) as according to literature 705nm peak is used to detect chlorophyll. I don’t know how to calculate only the algal bloom spread area in water
  2. Is there any generalized formula to calculate chlorophyll concentration in water? As I don’t have any insitu data

This forum is about SNAP software, so we can’t provide support for other programs.

But especially as you want to retrieve water chlorophyll, you should consider using Sentinel-2 data and C2RCC:

If you have some information about any special characteristics of your water region, you can look for studies done in other places with similar characteristics. This may give you some idea of how well the available algorithms perform. For areas with low chlorophyll concentration, other factors (e.g., river plumes with suspended sediments) may be important contributers to reflectances. In this case you may need information on the spectral properties of the other contributions to reflectances. In areas of shallow clear water, light reaching the bottom may contribute to the remote sensing reflectances, so you need information on the optical charactistics of the bottom.