Gorgonians élixir de vie!!

The typical image of a tropical coral reef is that of shallow reef-building (hermatypic) corals and an abundance of reef fish. The origins of such coral reef biodiversity is the subject of much scientific intrigue and investigation, yet beyond 30 m (100 ft) depth these vibrant ecosystems give way to dynamic unknown environments that harbour a wealth of species and species interactions completely new to science. DSC08334[ps] 2_BANNER.jpgFigure 1. Beautiful colonies of Acropora spp. and Pocillopora spp., amongst others at 8 m (26 ft) depth, Pohnpei. Their relatively small size gives a patch-work quilt of 'teenagers' hanging together in the pack, yet this also reveals a remarkable recovery from the damage of the 2008 Typhoon Chataan, which devastated much of Micronesia. This holds promise for future times (see Rowley et al. 2018). Image by SJ. Rowley.

With increasing technological advances in electronically controlled rebreathers and redundancy, we have the ability to penetrate these unexplored depths. In the least destructive and most cost-effective way, we can gain access to cryptic species (physically and biologically speaking) and behavioural observations otherwise obscure to submersibles or remotely operated vehicles

SoniaAloneLarge_BLOG.jpgFigure 2. Sonia J. Rowley collecting a colony of Ellisella sp., at 120 m (394 ft) depth, Pohnpei. Image by RL. Pyle.

Documenting our respective taxonomic groups at these mesophotic depths necessitates precision, awareness, and speed, all nested within experience. On our descent we scan the reef for potential collecting spots, aware yet unfazed by depth and with no time to loose. At a very early age it became clear to me that whilst diving it was unwise to have an imagination beyond the present moment. Besides, why would one need to when you're living the reality of your imagination! I have come to see that an errant mind at depth and in life, leads to difficulties. The peace of mind I seek on the surface can be found here at depth.New_Species_135mDSC06959[PS]_THUMBNAIL.jpgFigure 3. A delicate new species of gorgonian coral (more information to follow) from 135 m (445 ft) depth, Pohnpei. Image by SJ. Rowley.

My fish-collecting dive buddies are kept both in view and at a safe distance - as not to disturb the fish - whilst I select specific sea-fan colonies; these look new!Sonia_Bag[PS]_THUMBNAIL_FREE.jpgFigure 4. Sonia J. Rowley sampling gorgonian colonies at 120 m (394 ft) depth, Pohnpei. Images by RL. Pyle.

Collection proceeds in the following manner: first a scaled photograph of the colony, then a sample of the colony, which is then placed into a pre-labeled Ziploc bag, which is then placed into a large mesh bag attached to my utility belt and pouch. For precision, I photodocument my rebreather computer (see Figure 4 & 5). This enables me to time-synch each specimen collected environmental loggers for depth, temperature, and other variables. Thereafter, it's time to select another colony. Seldom is it necessary to travel far. The mesophotic depths are where I can be situated in a single spot for considerable time without the need to move due to the sheer abundance and diversity of gorgonian corals. In short, as with most taxa, gorgonian research is fascinating and is most certainly a labour of love.Slide1.jpgFigure 5. Documentation of depth, dive time, and temperature (not shown on this make of rebreather), as well as key safety information such as TTS (time to surface), PO2 (partial pressure of oxygen), and ceiling (first decompression stop). Image by SJ. Rowley.

On ascent into the shallows, we again see the silhouette of the boat; we can but look for an hour or two at the very least. Stuck, on a coral reef with a great camera! Over the years I have taken to conducting photo-transects to monitor the reefs. DSC06385_surface_boat_Ant.jpgFigure 6. Silhouette of the boat at Ant Atoll. Image by SJ. Rowley.

With all this time at shallower depths how could you not? This data is proving invaluable, particularly to the local communities in terms of quantitatively and qualitatively documenting the change in reef health over time and in relation to disturbance, whether anthropogenic or not. After each transect is completed it is time for some fun. I chase fish, others, and anything mildly photogenic. With a macro-lens, I spend hours studying the filter-feeding creatures on the reef and notice trait similarities with the gorgonians - this is where some of my best research ideas take place. Decompression, therefore, is another opportunity to ensconce myself into this amazing environment, to learn and document it as much as possible. In a cipher, I whip off my fins for some moonwalking and somersaults, bouncing from one dead coral head to the next - serious science I'll have you know!

DSC06713_Fillstation_2014.jpgFigure 7. RL. Pyle filling the oxygen tanks and preparing to mix the gasses for the following day's dive. It's also a good opportunity to write! Image by SJ. Rowley.

We surface, and it's back to base for cylinder filling, gas mixing, and sample processing. This latter part can take upwards of seven hours. Each bag is drained with the specimen gingerly placed on a black background (aka. a t-shirt) for a scaled image with associated hand-written labels each bearing a unique identifier code that is specific to each colony.

Gorgonian_Sampling_Bay![PSs].jpgFigure 8. Sonia J. Rowley processing gorgonian specimens: photographing, sub-sampling for molecular analyses, and ensuring that all the data is synchronised with the in situ images and rebreather unit. Sometimes this can all be all a bit too much for the specimens, who just need to relax a little! Images by ​RL. Pyle.

Molecular sub-samples are made with the remainder of the colony preserved in 95% ethanol. Specimen preservation is paramount, however, ethanol can be a limiting resource. Here, Hana Bay Rum (60% proof) saved the day when our specially shipped 95% EtOH leaked from the base of the bottles. Nevertheless, the preservation properties of rum, are in fact historical, with Quoy and Gaimard having committed the cardinal sin of denying the crew of their élixir de vie during the 1826-29 French Expedition L’Astrolabe! ……Sacré bleu!!

1826-29 French Expedition L’Astrolabe.jpgFigure 9. The French expedition L’Astrolabe and Dumont d'Urville during 1826-29, where rum was used to preserve the specimens much to the crew's distress!

Seldom a dull moment on expedition research.

DSC05598_New_species_105m.jpgFigure 10. New gorgonian species [who's DNA refuses to extract!] at 105 m (345 ft) depth, Pohnpei. Image by SJ. Rowley.

Gorgonian corals are notoriously difficult to identify, particularly in the field. Their traits can be cryptic leading to much confusion, necessitating other research skills to discern species differences and what is new to science. Therefore, the real species identification begins on our return, where multiple character traits are investigated: morphology, genetics, and a thorough taxonomic investigation of each specific group. 

DSC05658_Astrogorgia_Seriatopora_70m_SGB.jpgFigure 11. Astrogorgia colony with Seriatopora at it's base at 105 m (345 ft) depth, Pohnpei. Image by SJ. Rowley.

Gorgonian research, particularly of the Indo-Pacific, is not an easy task. The taxonomic information alone is largely sourced from expeditions conducted one or two centuries ago. This is where the work begins and the true evolutionary patterns unfold. For me this is extremely fascinating and nearly as exciting as diving to get them in the first place. I'm under no illusion of what a privilege it is to do what I do and to share as much information as possible.  

This research was generously supported by: 

The Seaver Foundation


Adapted from Rowley SJ. 2014. Gorgonians élixir de vie. Bernice P. Bishop Museum. 8th July 2014.