HONOLULU — Scientists made new discoveries while recently diving to deep coral reefs in the remote atolls of northwest Hawaii.

The Papahanaumokuakea Marine National Monument says a research expedition returned last week with specimens of previously unknown deep-water algae. The scientists also brought back the first recorded specimens of black coral from Johnston Atoll.

The researchers visited Nihoa, Mokumanamana, French Frigate Shoals and Laysan Island. They later went to the Johnston Atoll National Wildlife Refuge.

Scientists collected fish, coral and algae samples for genetic analysis and searched for invasive alien species. At Johnston Atoll, they conducted archaeological surveys of the Howland, a whaling ship wreck from the late 1800s.

The monument said Monday the expedition included 26 days of diving to deep coral reefs more than 200 feet below the surface.