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ver the millennia, perpetual these little-studied reefs. Here, as part geological sea level changes have of a collaborative research team sup- Ocontinuously shaped coral reef ported by the Seaver Institute, our mis- environments. Coral reef biodiversity, sion as the Bishop Museum rebreather considered at its peak within the Coral team was twofold: to test-pilot the Triangle, is most notable throughout Poseidon next generation rebreather; the Philippine archipelago largely and to discover, document and due to it having among the highest characterize mesophotic reefs within number of islands (more than 7,100) the Batangas region of the Philippines. per geographical area. The origin of Descending to depths unexplored, such diversity remains the subject of away from the bustle of the shallows, much controversy and investigation is not without risks. As inquisitive generating hypotheses of speciation explorers we are caught in peace and and migration from within or outside exhilaration between the enticing the region. Nevertheless, central to attenuation of the deep slope and the determining reef biodiversity and bio- mesophotic reef before us. To me these geographical distributions are species reefs are akin to being transported back responses to environmental change, in time. Not only do MCEs harbour particularly as human impacts acceler- a myriad of new species, behaviours ate and/or exacerbate natural processes. and interactions just waiting to be Coral reefs in the ‘twilight zone’ discovered, they also hold the keys to between 40 and 200 m are termed questions of persistence, polyphyly, ‘mesophotic coral ecosystems’ (MCEs). and the evolution of structure–func- MCEs are classified as conservation tion relationships over geological the Philippines priority ecosystems (e.g. IUCN) time. What fauna and even flora are and posited to act as refugia against present, how do they survive, how environmental disturbances. Until are they beneficially connected to the recent technological advances, such surrounding habitats if at all, and are mesophotic reefs were largely inacces- such patterns duplicated in other areas? sible or overlooked, being too precari- With the exception of reefs within ous for conventional SCUBA and too Hawai’i which are often dominated by shallow to justify the cost of a deep-sea members of the zooxanthellate genus submersible. However, exploration Leptoseris, low-light habitats throughout using advanced closed-circuit the Pacific are typically charac- rebreather technology terized by gorgonian has enabled us sea fans, soft Refugia in the ‘twilight Refugia in the to penetrate corals, zone’: discoveries from discoveries zone’: the mys- sponges teries and of As inquisitive explorers we are caught in peace and exhilaration By Sonia J. Rowley Science letters black corals, the majority of which are depth. The swim bladders of sampled unknown to science. The Philippines fish are vented with needles as we are no exception; on this trip alone ascend (the notorious ‘Pyle’ stop). At we have discovered at least seven new the surface, specimens are catalogued fish and 20 new gorgonian species at and preserved, whilst digital imagery is depth, the latter providing substrate systematically documented for immedi- for fish to lay their eggs. Our diving ate dissemination in the web-based experience tells us that it is at around archive Explorers Log. The discovery 80 m depth that the temperature of the twilight zone is not exclusive— Images: Opposite: A typical mesophotic drops, a shelf emerges, and where such everyone can immediately enjoy! assemblage from the Solomon Islands with characteristic ‘twilight’ assemblages Are shallow reefs being seeded by the deep-reef Griffis’ AngelfishApolem - begin to be found. Dynamic sea-level deep reefs? Are certain taxa habitat spe- ichthys griffisi. Carlson & Taylor 1981. This changes produce extreme variations in cialists or bathymetric migrators? These page, from top left: Chromis n. sp.. Plectran- shallow water habitats of up to 80–100 questions remain to be elucidated, thias n.sp.. Dr. Luiz Rocha with the pinecone m, with these deeper reefs remaining but when they are, key evolutionary fishMonocentris sp.. Mesophotic reefs of gorgonians in the Philippines. Mesophotic relatively unchanged, and less than mechanisms facilitating survival over reefs of gorgonians in Fiji. Dr. Brian Bowen. 50% species overlap with shallow taxa. geological time will undoubtedly be The PI team: Brian Greene, David Pence, Therefore, gorgonian corals and reef unveiled. So even though as humans Dr. Richard Pyle, Joshua Copus, Dr. Sonia fish are key taxonomic groups within we are challenged to save habitats Rowley, Robert Whitton, with Poseidon deep-reefs with some taxa spanning from their ongoing destruction, prototypes and Inspiration Rebreathers. considerable depths (e.g. 5–2,000 m). ‘twilight’ reefs of refugia may likely At depths greater than 100 m we replenish many of their inhabitants. work against time, determined by the Dr. Sonia Rowley (soniajrowley@ ratio between the saturation of our gmail.com) is an invertebrate mortal tissue with dissolved gas and zoologist at the Bernice Pauahi Bishop Museum, and the University the safety gas that we carry. Yet no of Hawai’i, USA. part of what we encounter is lost; all Funding and collaborations: digital imagery is synchronized with Bernice Pauahi Bishop Museum, the rebreathers’ advanced electronics, Hawai’i, USA; Hawai’i Institute of capturing time, depth and specimen Marine Biology, Hawai’i, USA information. I continue to collect California Academy of Sciences, gorgonians as we ascend—intrigued by California, USA; Seaver Institute, their dynamic patterns of diversity with California, USA Spring 2014 | The Marine Biologist 19.

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