Polychaete worms play an important role in the seabed ecosystem.

The ecosystem of this lake is very fragile.

He worked hard to accomplish his goals.

His role is the team leader.

Health is very important.

His opinion is very important.

He developed a submarine to explore the seabed.

He developed a new device to explore the seabed.

He is an expert in ecology.

He is working in the information system field.