Which of the following organisms are known as chief producers in...

Diatoms are chief producers in the oceans, and they contribute to 40% of the ocean's primary productivity. They constitute a major group of unicellular eukaryotic microscopic algae and are among the most common types of phytoplanktons found floating on the surface of the seas.
The other given organisms also exhibit an autotrophic mode of nutrition, however, their productivity is lesser as compared to diatoms.