Corals

Deep-sea corals are found in the world's oceans on continental shelves, slopes and seamounts where the water temperature ranges from 4 - 13 degrees Celsius.  In the North Pacific, they live at depths from 40 to 5,800 meters. They feed by capturing nutrients from the water column using their tentacles. Some deep sea corals can be hundreds of years old. Because coral is slow growing and lives for a long time, if they are disturbed or destroyed, it can take decades for them to grow back, if they grow back at all.

	A red tree coral (Primnoa pacifica), Dundas Island, at a depth of approximately 200 meters. High abundances of Primnoa pacifica were found at Dundas Island, Portland Inlet, and Juan Perez Sound. Current research indicates that these are  the most important habitat forming corals in the North Pacific. We found dense forests up to one meter high and two meters wide providing habitat, refuge and food for a large number of fish and invertebrates.
	This bamboo coral (family Isididae - in white with an orange deep sea anemone) was encountered at South Moresby Gully at a depth of approximately 438 meters. Bamboo corals are found throughout the world's oceans, and have been recorded in the North Pacific to depths of 3,880 meters.
	Red tree coral (Primnoa pacifica) at Juan Perez Sound were encountered at depths from 90 to 300 meters. Abundant Primnoa up to one meter high and two meters wide were observed to be associated with brachiopods, brittle stars, sea cucumber, decorator crab, stylaster coral, shrimp, anemone, urchin, lingcod  ratfish and rockfish.
	A bubblegum coral (Paragorgia species - in pink in the centre of the shot), Juan Perez Sound, at appproximately 230 meters. Paragorgia are found in the Pacific and Atlantic ocean and are called 'bubblegum' because of their pink/red colour and rounded tips. We found only a few Paragorgia at Goose Trough, South Moresby Gully and Juan Perez Sound.
	White and pink hydrocorals (family Stylasteridae) at 210 meters. Hydrocorals are found worldwide in waters from the intertidal zone to 2,000 meters with many species documented in the waters of B.C. and Alaska. We found these corals at five of the seven sites surveyed.
	This photo of a Sea Fan Coral (Swiftia species) with a brittle star was taken in the lab after being collected at 284 meters in South Moresby Gully.

When you think of corals you might imagine yourself swimming in tropical waters teeming with colourful fish. It has only been a few decades since scientists have been studying deep-sea corals, discovering that many species of corals also live in the dark ocean depths where they are more abundant than in the tropics.

In the northwest Pacific, our most abundant corals are 'gorgonian' and can form ‘forests’ or ‘gardens.’ So far, we know that there are three families of habitat-forming gorgonian corals found in B.C.’s deep waters, all from  the ‘Gorgonian’ order. They are fragile with branching, chalky skeletons that look like trees and grow in clusters resembling forests or groves.

‘Soft’ corals are all part of one living structure and do not form reefs. Stony ‘hard’ corals form reefs by cementing broken coral and sediment together on dead corals. The term 'reef' that we now associate with corals and sponges originally meant 'hazard to navigation.'

More on corals >>