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Notes From the Field: Adventures in Anilao - New Species found while diving on POSEIDON SE7EN Rebreather

Notes From the Field: Adventures in Anilao

Searching for New Species on Deep Philippine Reefs

By Sonia J. Rowley Ph.D and Richard L. Pyle Ph.D


The origins of coral reef biodiversity, considered at its peak within the Coral Triangle, is the subject of much scientific intrigue and investigation. The Philippine archipelago is no exception, possessing over 7,100 islands per geographic area, it lends itself to some of the most biodiverse coral reefs on this planet. Yet the majority (up to 80%) of these reefs and abundance of life appears to exist between 30 - 150 m (100 - 500 ft) depth. Only in recent times have we begun to penetrate this largely unexplored ‘twilight zone’, with increasing technological advancements in electronically-controlled rebreathers. These advancements facilitate the most cost efficient and least destructive method of deep-reef discovery, as well as invaluable access to cryptic species otherwise inaccessible by submersibles. Spearheading such technological advancements in electronically-controlled rebreathers is the unprecedented intelligence of the POSEIDON SE7EN rebreathers, which enable our scientific exploration and discovery, whilst we simultaneously assist in refining and ensuring safer units for future explorers!


Here our research takes us to Anilao, and the Island of Lubang, in the Philippines, home to some of the most vibrant coral reef communities within the coral triangle. It is here whilst testing various prototype features for the POSEIDON SE7EN, that we safely discovered many new species to science in habitats previously unexplored.


Mission Twilight

Tropical coral reefs within the ‘Twilight Zone’ (known to scientists as ‘Mesophotic Coral Ecosystems’, or MCEs) are classified as conservation priority ecosystems (e.g. IUCN). It is predicted that MCEs act as a refuge for reef animals to re-populate shallow coral reefs, particularly in the face of destructive environmental and human disturbances. However, our preliminary investigations over the last decade show that more than 50% of species found in the Twilight Zone are specific to these depths and geographic locations. On shallow reefs, the total diversity of shallow reefs declines as one moves eastward across the Pacific from the Coral Triangle. However, this pattern does not seem to be as evident on deeper reefs, where diversity tends to be more consistent across the Pacific. These intriguing patterns of biodiversity are only partially understood. As part of a collaborative research project with the California Academy of Sciences and the Hawai’i Institute of Marine Biology, our mission as the Bishop Museum rebreather team was twofold: 1) discover, explore, and characterise deep-reefs within the Philippine archipelago; and 2) test-pilot new and existing features of the POSEIDON SE7EN rebreather.


As we descend into the Twilight Zone, characteristic depth zonations emerge, and it’s akin to being transported back in time. Sea levels have risen and fallen by about 100-120 m (330-400 feet) in cycles perpetuated over the millennia (approximately every 100,000 yrs) and these sea-level changes have shaped the reefs we enjoy so much today. Therefore, as we glide past these depth-specific habitat zones, what we are in fact seeing are former shallow coral reefs that have been submerged through melting glaciers over time - an aquatic museum if you will! The fauna, and even flora, change with each depth-specific biogenic feature; and its these patterns that we turn our attention to, as we work toward discovering the origins of Indo-Pacific coral reef biodiversity over geological time.   


As a research and POSEIDON SE7EN test team, we at Bishop Museum are uniquely equipped with effective tools and experience to discover, explore and capture new species and species interactions at depths of up to 150 m (500 ft). It must be made clear, however, that we DO NOT ENDORSE THE USE OF POSEIDON REBREATHERS BEYOND THEIR STATED DEPTH LIMIT. Our equipment and electronics are specifically designed for these expeditions. Each diver possesses equivalent on- and off-board gases, back up electronics and staged cylinders that we each deposit at specific depth intervals relative to the gas content, along a vertical transect on the reef. Surface and in-water safety support are always at hand! As we work against the clock, our focus is parsed between our mission, our team members and ourselves; for every passing minute we are at depth we accumulate lengthy decompression obligations. Our ability to be autonomous yet function as a team is paramount, with each expedition dive providing ‘proof of concept’ for, 1) an increased diversity and new species discovery with depth through efficient sampling of two key deep-reef groups, gorgonian corals and fishes; and 2) the ultimate utility of the POSEIDON SE7EN as a safe and reliable expedition rig.



Whilst descending down to the depths, we never quite know what we are going to find, it really is pure discovery, and we ALWAYS want more time at depth! Nevertheless, during our explorations of Anilao, we have discovered as many as ten new species of fishes below 100 m (330 ft). The most stunning species, discovered and collected by our fellow SE7EN test diver Brian Greene at depths up to 147 m (485 ft), is in the genus Grammatonotus, a member of the little known Splendid Perches. This beautiful and rarely encountered group of fishes are specific to the Twilight-Zone depths and below. In the dark and gloomy depths, these fish swim freely among the increasingly silty ledges and sea fan corals. Yet why swim so freely, what other species eat them, how do they reproduce, where else can they be found? To us, these and many other fascinating questions barely scratch the surface of a huge wealth of biological evolution and information at these depths, just waiting to be explored.


Figure 4_Brian_D


Although the fish are both popular and charismatic, they represent only a small part of coral-reef biodiversity. Another, arguably more interesting part of reef diversity are the gorgonian corals. These corals are conspicuous, diverse and often dominant reef components found throughout the oceans, from the shallows to depths in excess of 4,000 m (13,123 ft). Some are zooxanthellate (possessing symbiotic algae), but most are not and it is these that we are most likely to encounter in the Twilight Zone. Colonies can be anything up to 6 m (20 ft) tall with certain deep-ocean species recorded to be thousands of years old! As we continue to explore, it is clear that gorgonian corals are typical, often dominant members of the deep-reef communities, most of which are unknown to science. The Philippines are no exception and one of us (Rowley) systematically selects, photographs and collects specific colonies from the depths up into the shallows. Each digital image is synchronized with the SE7EN rebreathers’ advanced data logging system, capturing time, depth and essential specimen information. The differences at each depth and dive site are both fascinating and remarkable; always offering something new!




Of the 730 gorgonian specimens collected during our visits to Anilao, likely more than 40 species from the deep reefs are new to science. However, gorgonian corals - and numerous invertebrate groups per se - are notoriously difficult to identify in the field, and generally in a state of taxonomic confusion. At an easier level we can identify 43 genera found from this research trip alone, with 39 of those being at depths below 50 m (164 ft), and a further 23 genera below 100 m (330 ft). As the research continues it is very clear that numerous gorgonians down at mesophotic depths, particularly here in the Philippines, have not previously been encountered.


Notable, however, are that few gorgonians are present on shallow reefs, particularly around Anilao. There may be numerous reasons for this conspicuous absence, one of which became apparent after we were made aware of a prolific illegal jewelry trade throughout the Philippine archipelago, of which gorgonian and black corals are key collection targets! Such corals provide secondary space to other organisms (e.g., fish, flatworms, brittle stars and many invertebrates), often acting as nurseries and areas of protection to many species of fish, and a haven for new pharmaceuticals. Through mapping the distribution of gorgonian corals and other reef animals, our work can help to define and select areas of conservation management, as we discover which species can seed to the shallows and which are specific at depth.



Testing the Limits, and the Limits of Testing


Figure 7_Brian DWe need to reiterate that neither we, nor Poseidon, advocate the use of these rebreathers to such extreme depths. While it may seem to be a contradiction, our use of the POSEIDON SE7EN rebreathers to depths approaching 150m / 500 ft  is part of a very specific and carefully crafted protocol. Poseidon has conducted extensive manned and unmanned testing on all of its equipment, and especially its rebreathers, and they rate the SE7EN to a depth of 100m / 330 ft.  So…. if we have demonstrated that they work well much deeper than the rated depth, then why does Poseidon limit its rating as it does?  There are several reasons -- some involving the physical characteristics of the rebreather itself (such as work of breathing at such pressures); others are related to a corporate responsibility to ensure adequate conservatism in formal ratings.  And, of course, there’s the cold reality that diving to such depths is extremely risky no matter what sort of life-support system (open-circuit or closed-circuit), and it would arguably be irresponsible of any rebreather manufacturer to formally rate its equipment for use in such extreme conditions.


Perhaps a more appropriate question is: why do we trust our lives to this equipment at depths well below the manufacturer’s rated depth? The fact of the matter is that most commercially available rebreathers (at least those made by responsible manufacturers) are rated to similar maximum depths, for similar reasons. No matter which rebreather we used to conduct these dives, we would need to make a conscious decision to exceed the manufacturer’s stated depth limit. Not all rebreathers have the same characteristics for deep diving.  Some have better work of breathing than others.  Some have better carbon dioxide absorbent characteristics than others. Some have better oxygen control systems than others.  Some are more ergonomic than others. The reality is that no rebreather design (including the SE7EN) is the best in every single aspect of underwater life-support. But for what we do, and how we do it, we have weighed the alternatives, and the choice for us is obvious.


Despite the fact that we are official Poseidon test divers and share all of the data from these dives with Poseidon, and the fact we have full blessings of and extensive consultation with Poseidon engineers when planning and conducting these dives; the only reason we do them is for us, and for our science. No one at Poseidon has ever asked us to make any dives beyond the rated limits, and we are not in any way compensated for conducting these dives.  When we make dives to such extreme depths, we have two primary objectives.  The first and foremost objective is to make sure that we all return from the dive alive and healthy.  The second is to scientifically explore this environment.


Figure 8_Rich_Sonia_Brian_TeamPoseidon-Small


As part of the overarching goal of unveiling the origins of Indo-Pacific coral reef biodiversity, we aim to continuously explore these undescribed deep-reefs at remote geographic locations. This is largely made possible through Poseidon and the continual evolution for intelligent, safe, deep-reef exploration.





Next Installment: Exploring the Deep Coral Reefs of Pohnpei


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