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Notes From the Field: SE7EN Rebreathers in Pohnpei by Sonia Rowley and Richard Pyle

Notes From the Field: SE7EN Rebreathers in Pohnpei

Sonia J. Rowley Ph.D & Richard L. Pyle Ph.D




The water clarity at Pohnpei and Ant Atoll in the Federated States of Micronesia (FSM) is astounding. On the first dive we are greeted by a soiree of barracuda, sharks, rays, jacks, a myriad of fish and benthic delights - clearly we’re on for an amazing trip! In collaboration with the University of Hawai’i, and Hawai’i Institute of Marine Biology, we at the Bishop Museum are here to investigate the unchartered ‘Twilight Zone’ reefs of Pohnpei and the nearby Ant Atoll. Our continuous mission is to 1) investigate the origins of coral reef biodiversity throughout the tropical Pacific, 2) discover species new to science whilst simultaneously characterising the twilight-zone reefs, and 3) test-pilot new innovative features of the POSEIDON SE7EN.




Pohnpei: Someplace with a Mountain

As part of our mission to investigate the origins of coral-reef biodiversity throughout the tropical Pacific, we aim to target some of the most remote, untouched and exciting locations. Pohnpei and its surrounding reefs and atolls fill that bill, with one of our key team members, Brian Greene, fortuitously raised in Micronesia. What Brian doesn’t know about this region simply is not worth knowing and throughout the course of our adventure it becomes increasingly clear the significance of our research, both from a scientific and technical perspective. 




The reefs he selects are untouched, unimpeded by man’s influence. It’s breathtaking; no sediment run off, no fishing gear, no trash items penetrate these reefs and depths -- just light beams attenuating deeply facilitating the existence of calcifying algae and curious-looking forams! We even find zooxanthellate gorgonians beyond 75 m (246 ft), which is unheard of! The reefs below 60 m (~200 ft) are quite literally littered with sea fan corals and interweaving fish, blissfully unaware of the impending invasion our collecting prowess. These so-called “Mesophotic Coral Ecosystems” support countless species new to science, and once again each dive is a treasure trove of wonder, curiosity and excitement.




In order to accurately catalogue our catch, it is essential to document depth, temperature and location. All cameras, computers and Beta Poseidon SE7EN rebreathers are time-synched, therefore, no information is lost! For example, with the sea fans, as each one is collected the SE7EN paddle is photographed, further enabling a real-time interaction and update of all the information that keeps us alive! Primarily, PO2 gas content, time to surface (TTS) and depth…. where is everybody, double check, and continue. The fish are a different matter, taking more time and skill to capture yet easier to recall depth and location through prior filming. The direct integration of the SE7EN with our research in addition to its light and ease of use truly make this an amazing rig - its hard to know its there half the time! Through the extensive data logged by our rebreathers, synchronized with time codes on video clips and digital images, we can capture the exact depth, water temperature, and other parameters. We can also see where and at what depth research equipment has been deployed (e.g., plankton light traps), where quantitative surveys have taken place, and the gathering of specific information for puzzling scientific questions!




Naturally, it is worth noting that not even the SE7EN can save us from ourselves on occasion as we always arm ourselves with back up computers and dive timers with and without independent oxygen tracking and, therefore, PO2. Key to our work is awareness. 


In our quest for insights on the origin of coral reef biodiversity, the timeless twilight reefs are invariably unique ranging from the shear walls of the outer atolls to the sloping inclines of many islands. Overhangs, ledges, cryptic crevices and caves invoke curiosity peppered with a little danger! Its here we typically find something different, new and out of conventional understanding. Such structures and associate fauna and flora can be indicative of dynamic sea level change over time. Making species inventories enables us to track biodiversity throughout the tropical Pacific, but what’s specifically unique to Pohnpei and the Marshall Islands per se is the urgent need to discover and document nature. As climate change increasingly impacts our daily lives the effects of sea level rise are much more dramatic. For over 3000 years settlers, originally from Papua New Guinea, have made these islands and atolls their home. Living off the land and ocean it seems idyllic, however for the first time in their history their homes are in peril, with sea level rising 2-3 feet (~1 m) in recent decades. These climatic refugee’s are forced to seek Someplace with a Mountain - higher ground from the flooding atolls of their former homes of 3000 years standing! Our work here helps to understand past sea level patterns, what and where animals survived and can survive, how we can predict future changes to assist the local communities, in addition to delving into the fascinating realms of biological evolution which may or may not be able to keep up in many species with climate and subsequent sea level changing at such an alarming rate! Therefore it is not only the value of the technology, but also the for the environment and local people, that motivates what we do. Here we aim to set up a species inventory specific to this region allowing you, to contribute to its conservation - more on this to come…….




Pohnpei SE7EN

As scientists and explorers, we are using the Poseidon SE7EN rebreathers well below their rated depths. This is not because we are reckless and irresponsible; we are, in fact, fulfilling several missions simultaneously. Part of the reason these rebreathers represent the perfect tool for deep exploratory dives in remote locations is that we have been contributing to their design and development. As official test divers for the SE7EN, it is our job to ensure that the units continue to function even below their rated depth. We already know through extensive structural analysis and chamber testing under controlled conditions by Poseidon and other independent testing consultants that these rebreathers will function properly at such depths, but it is still important to know how reliable they will perform under real-world conditions. Our research projects serve as the perfect opportunity for this, not only because we are highly trained on these systems, but also because our scientific diving protocol is particularly rigorous in terms of contingency and emergency bailout planning. More importantly for us, we need to know that these systems will meet our needs, in our diving environment. We’re happy to report that our needs are, in fact. 




HPR Radio interview: Into the Twilight Zone with Richard Pyle and Sonia Rowley:


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