Chlorophyll-a

What is it?

Chlorophyll-a is a pigment contained within all phytoplankton and cyanobacteria cells. It is an estimate of algal biomass that is used for mapping the distribution of phytoplankton over time and space.

How does it impact Aquaculture/Fisheries?

Chlorophyll-a is a useful proxy of the biomass of phytoplankton in the water, the food source to filter feeding organisms and zooplankton. This parameter has been utilized for aquaculture siting, Farm Aquaculture Resource Management (FARM) models, harmful algal bloom bulletins, species distribution models (fish, mammals, and top predators), end-to-end ecosystem models, and as a predictor of unregulated fishing activity.

What are the limitations/caveats?

Currently, chlorophyll-a can be confused with other dissolved materials in the water, and it can be over-estimated in coastal regions, particularly in areas with river inputs or resuspension.

Does HYPERSPECTRAL directly improve/enable this product?

Not operationally, but it will soon. Having more information about the other components of the water will help separate the living from non-living components, and will improve the performance chlorophyll-a product substantially. Some efforts at improving chlorophyll-a have been attempted using regional tuning methods, generalized additive models, or applying machine learning techniques, but lack official community endorsement. Currently, NOAA/NASA are working on a dynamic tuning factor to make chlorophyll-a applicable across all water types and regions. Another chlorophyll-a product may soon be offered operationally from PACE that was built using hyperspectral reflectance data and a mixed density network approach.