Researchers' Diaries

Dr. Merrick Ekins

Collection Manager of Sessile Marine Invertebrates, Queensland Museum

Kimberley Coast – Soft Corals

The 2010 Western Australian Museum Kimberley trip was my first trip to the Kimberley region of Australia. It is a spectacular place with interesting islands and reefs, off the sandstone coast. I was joining fellow Queensland Museum scientist Monika Schlacher-Hoenlinger to record and collect octocorals. Octocorals are corals that have eight tentacles but are more commonly known as soft corals. These include the huge gorgonian fans (Figure 1), whips (Figure 2), big mushrooms (Figure 3) and my favourite the genus Xenia (Figure 4).

Fig 1. Beautiful fans of the family Melithaeidae

Fig 2. Whip garden (Juncella sp.).

Fig 3. Giant Mushroom (Sarcophyton sp.)

Fig 4. Xenia sp.

If you carefully watch them closely underwater, you can see them opening and closing like delicate little flowers. We collected what appeared to be 3 different species of Xenia, but on closer examination we concluded they are most likely variations in colour and gross morphology of the same species. These specimens will require further investigation in the laboratory to detect if they really are different species. We collected 194 specimens comprising 81 different species of octocorals. This number is likely to increase as we spend time in the laboratory examining the morphology of the polyps and sclerites under the microscope (Figure 5). In addition, the use of DNA will help to reveal differences between these cryptic species.

Fig 5. Microscopic sclerites of Paraplexaura sp.

It was a privilege to be able to do research in an area that has been largely untouched by human activities. The reefs surrounding Cassini Island provided some fantastic SCUBA diving. Diving straight off the back of the boat and into the water, unsure of what the underwater world would look like was a wonderful daily experience. One of my roles was to videotape each transect before sampling was done. Since this involved being one of the first people in the water, it was always interesting to see the sharks and big fish before they took off. Then I would settle down to examining the pretty sessile marine life. I didn’t have to worry about the soft corals swimming off, they patiently waited for the photographs and sampling.

The reef’s surrounding Cassini Island appeared to have a higher diversity of octocorals than Long Reef; however this could be a result of a larger number of intertidal sites at Long Reef and the higher amount of sampling at Cassini Island. In the shallow water habitats, the octocoral fauna was dominated by Sarcophyton and Sinularia forming sheet like layers over the substrate.

However, as the depth increased Dendronephthya (Figure 6 opposite) and Stereonephthya predominated with their very pretty displays of colour and sharp spicules.

Fig 6. Dendronephthya sp. displaying large macroscopic sclerites

But it was below 15 m and in regions of high current flow that the gorgonian fans (Family Melithaeidae) and sea whips come into their own, providing wonderful forests to dive in. The family Melithaeidae is one group that requires revision and on this trip we collected specimens that shared characteristics of different genera.

The presence of Dampia pocilloporaeformis (Figure 7) was an interesting discovery as this has previously only been recorded from Rowley Shoals and Ningaloo earlier this year. Dampia pocilloporaeformi is very hard and rubbery and looks just like a hard coral so it is difficult to detect and it’s always like a “ah ha” when I find it underwater, and that’s one of the things I like best about marine biology...the thrill of discovery.

Fig 7. Dampia pocilloporaeformis

During the expedition whilst erecting a satellite transmitter on Cassini Island, I had the opportunity to observe bird wildlife. I observed and photographed a bird I had never seen before, with Glenn Moore’s assistance it has been identified as an Island Monarch (Monarcha cinerascens) (Figure 8). If accepted it will be a new record for mainland Australia, other than on the external territory of Ashmore Reef. This observation has been submitted to Birds Australia Rarities Committee and Australia Field Ornithology.

Fig 8. Island Monarch (Monarcha cinerascens)

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