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Innovation to Learn More About Alaska's Deep-Sea Corals and the Species that Live There Post #8

July 29, 2022

Some of our observations during this survey of deep sea coral ecosystems in the Gulf of Alaska

A soft fan shaped coral sits surrounded by the rocky structures that have built upon each other for years as part of this unique ecosystem. Credit: NMFS/NOAA. Color correction applied by NOAA Fisheries

During our most recent dive we encountered more interesting deep sea creatures whose relationships with each other create the deep sea ecosystems of the Gulf of Alaska.

Vulnerability to Disturbance

Deep-sea corals are widespread throughout Alaska, including the continental shelf and upper slope of the Gulf of Alaska, the Aleutian Islands, the eastern Bering Sea, and extending as far north as the Beaufort Sea. Many grow very slowly. During the survey, as mentioned in post 4, we found tentacled bamboo coral. Changes due to both natural disturbance and some human activities can affect their rate of growth and may have profound effects that can linger for decades.

The Gulf of Alaska seafloor is littered with diverse populations of sea stars below and within tentacled bamboo coral. In the distance other unidentified brightly colored corals can only stir the imagination. Credit: NOAA Fisheries
This tentacled bamboo coral (Isidella tentaculum), seen on the right, grow at a rate of only 14 mm per year. Changes affecting their rate of growth may have profound effects that can linger for decades. Image courtesy of NMFS, NOAA. Color correction applied by NOAA Fisheries.

Groundfish Habitat

Arrowtooth flounder (Atheresthes stomias) is a relatively large flatfish and one of the most abundant fish in the Gulf of Alaska. It plays an important role in Alaska's complex marine food chain. It feeds extensively on the commercially important walleye pollock and in turn is an important part of the diet of Steller sea lions. In Alaska, NOAA Fisheries scientists and the flatfish fishing industry collaborated to develop changes to fishing gear that would reduce effects of flatfish trawling on seafloor habitats of the central Gulf of Alaska and the eastern Bering Sea shelf. The modified gear they developed –Bering Sea flatfish gear– not only reduced impacts to seafloor habitat and the animals living there but also reduced the fishery’s impacts on crabs. In the central Gulf of Alaska and Bering Sea areas, flatfish fishermen are now required to use this modified fishing gear.

An arrowtooth flounder (so named because of the shape of its teeth) swims along the muddy bottom of the Gulf of Alaska. Credit: NMFS/NOAA. Color correction by NOAA Fisheries
Arrowtooth flounder (Atheresthes stomias) is a relatively large flatfish and one of the most abundant fish in the Gulf of Alaska. It plays an important role in Alaska's complex marine food chain. Image courtesy of NMFS, NOAA. Color correction applied by NOAA Fisheries.

Dusky rockfish (Sebastes variabilis) have one of the most northerly distributions of all rockfish species in the Pacific. They range from southern British Columbia north to the Bering Sea and west to Japan, but are abundant only in the Gulf of Alaska (GOA).

A school of dusky rockfish swim over a unique rocky and coral covered bottom in the Gulf of Alaska - their scales reflecting light and flashing brightly. Credit: NOAA, NMFS; Color correction by NOAA Fisheries
Dusky rockfish (Sebastes variabilis). Image courtesy of NMFS, NOAA. Color correction applied by NOAA Fisheries.

Sea Stars

Callogorgia compressa is a type of soft coral in the family Primnoidae. Callogorgiahave a fan shaped body structure that often serves as a habitat for other organisms.

Certain brittle stars have a commensal relationship with these corals. The brittle stars benefit from the elevation provided by Callogorgia allowing them to suspension feed.

Cat sharks use Callogorgia as a nursery habitat by depositing their egg cases on the branches. Callogorgiahas also formed associations with copepods, zoanthids, and scale worms.

A soft fan shaped coral sits surrounded by the rocky structures that have built upon each other for years as part of this unique ecosystem. Credit: NMFS/NOAA. Color correction applied by NOAA Fisheries
Callogorgia compressa, is a type of soft coral in the family Primnoidae. Callogorgia have a fan shaped body structure that often serves as a habitat for other organisms. Certain brittle stars have a commensal relationship with these corals. The brittle stars benefit from the elevation provided by Callogorgia allowing them to suspension feed. Cat sharks use Callogorgia as a nursery habitat by depositing their egg cases on the branches. Callogorgia has also formed associations with copepods, zoanthids, and scale worms. Image courtesy of NMFS, NOAA. Color correction applied by NOAA Fisheries.

A slime star (Pteraster tesselatus). The slime star feeds on various benthic invertebrates, including sponges, the false jingle shell, scallops, clams, and colonial sea squirts. If attacked by a predator such as a sunflower star (Pycnopodia helianthoides), the slime star emits great quantities of repellent mucus and can often evade the predator.

A slime star rests on the bottom of the Gulf of Alaska with other types of sea stars seen in the background. Credit: NMFS/NOAA; color correction applied by NOAA Fisheries
A slime star (Pteraster tesselatus). Image courtesy of NMFS, NOAA. Color correction applied by NOAA Fisheries.

Thanks for checking out this blog! If you got this far, you’re likely hungry for more. If so, check out another blog: EcoFOCI's Spring Mooring Cruise.

Are there other topics you’d like to see us share? Let us know at afsc.info@noaa.gov.

Fair winds and following seas!

Previous: Innovation to Learn More About Alaska's Deep-Sea Corals and the Species that Live There Post #7