___ is an important species of the zooplankton community.

Correct option is A

Euphausiids are small crustaceans that form a crucial part of the zooplankton community. They are commonly known as krill and are found in oceanic ecosystems worldwide. Krill serve as a primary food source for many marine organisms, including whales, seals, penguins, and fish.

• They are heterotrophic organisms that feed on phytoplankton and smaller zooplankton.
• They play a crucial role in the marine food chain and carbon cycle by transferring energy from primary producers (phytoplankton) to higher trophic levels.

Algae (Incorrect): Algae are autotrophic organisms that belong to the phytoplankton group, not zooplankton.

Diatoms (Incorrect): Diatoms are a type of microscopic algae (phytoplankton), known for their silica-based cell walls. They are a primary food source for zooplankton but are not part of the zooplankton community.

Flagellates (Incorrect): Some flagellates are phytoplankton (autotrophic), while others are protozoans that can be both autotrophic and heterotrophic, but they do not form a dominant group in the zooplankton community.