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Exploration and Systematics of Deep-Reef Gorgonian Corals at Pakin Atoll, Micronesia

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Sonia J. Rowley at University of Hawaiʻi at Mānoa
Sonia J. Rowley
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The SRF was specifically requested to support expedition research and the subsequent completion of a monograph describing the gorgonian corals throughout the Islands of Pohnpei (Pohnpei Island, Ant and Pakin Atolls). This has and continues to be achieved, with the outcomes of this project being four-fold: exploratory, systematic, and experimental, leading to unexpected ecosystem management opportunities through local community collaboration.
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Exploration and Systematics of Deep-Reef Gorgonian Corals at Pakin Atoll, Micronesia
Sonia J. Rowley PhD
Dept. Geology & Geophysics, University of Hawai'i at Mānoa, USA
The SRF was specifically requested to support expedition research and the subsequent completion of
a monograph describing the gorgonian corals throughout the Islands of Pohnpei (Pohnpei Island, Ant
and Pakin Atolls). This has and continues to be achieved, with the outcomes of this project being
four-fold: exploratory, systematic, and experimental, leading to unexpected ecosystem management
opportunities through local community collaboration.
EXPLORATION
Tropical coral reefs throughout the Indo-Pacific are central to marine biodiversity. The greater
proportion of these reefs (~80%) exist below 30 m depth, and are among the most diverse, yet most
unexplored realms on the planet. Such deep or ‘Twilight’ reefs (aka. Mesophotic Coral
Ecosystems), and are typically dominated by gorgonian octocorals (Figure 1).
Figure 1. Gorgonian (sea fan) corals on the twilit reefs of Pohnpei Island, Ant and Pakin Atolls
between 98-135 meters depth. Images by S. J. Rowley.
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Figure 2. (a) Project site locations within the Federated States of Micronesia (FSM): (b) Pohnpei
Island, Ant and Pakin Atolls.
Therefore, the primary aim of this project was to explore and describe gorgonian corals on the
unexplored deep-reefs of Pakin Atoll (Figure 2), using technological advances in electronically
controlled rebreathers (Figure 3), data digitization, and dissemination.
The expedition took place from the 17th July to 10th August 2015, and laid the foundation to return in
2016. Long-term collaborations with local community members and officials were also established.
A total of 48 dives were conducted (ave. 16 dives/diver) with 8,691mins (144.85hrs) dive time (ave.
2,897mins, 48.28hrs/diver) to 154m depth. Island and atoll submarine geomorphology consisted of
vertical walls, with low relief slopes and occasional outcrops from 60m at Pohnpei, and wave-cut
ledges ~30, 80, and 130m at Ant and Pakin (Figure 1). Unique benthic communities, particularly
beyond 140m, characterised these deep-reefs. Adverse weather often constrained diving to Pohnpei,
yet provided the opportunity to conduct a gorgonian transplant experiment (see EXPERIMENTAL).
Figure 3. (a) Rebreather dive team and Poseidon test pilots (left to right), Dr. Richard L. Pyle, Dr.
Sonia J. Rowley, and Brian D. Greene. (b) Boosting gas tanks on the way to the dive site on Pakin
Atoll (left to right), Brian D. Greene, Captain, Giovanni, Dr. Richard L. Pyle. Images by K. Kaing. &
S. J. Rowley.
3
Figure 4. Gorgonian coral Astrogorgia sp. at 75 m depth, Pakin Atoll. Image by S. J. Rowley.
SYSTEMATIC
Despite their abundance and diversity, gorgonian octocorals are poorly described throughout
the Indo-Pacific, being notoriously difficult to identify. However, understanding dominant
group systematics, such as gorgonian corals on Twilight reefs, is key for establishing
biodiversity assessments and assisting conservation management efforts. During this expedition,
284 gorgonians were collected (Appendix I) from Pohnpei Island (n=157), Pakin (n=54) and Ant
Atoll (n=73) from 5–154m depth. Individual colonies were recorded in situ (Figure 4) with
associated taxa (e.g., at least 1 new species of Pygmy seahorse) and metadata, and digitized
using QR coding.
Established ichthyologists and team members Pyle and Greene also discovered three new
species of fishes (Appendix II). Taxonomic morphological and molecular analyses are currently
underway for an octocoral monograph.
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Figure 5. Annella reticulata (Ellis & Solander 1786) experimental blocks and project
design conducted on Pohnpei deep reefs between 30-130 m depth. Images by S. J. Rowley.
EXPERIMENTAL
The gorgonian Annella reticulata (Ellis & Solander 1786) was abundant across >20ºC
temperature range, consistent with records within the Indo-Pacific (e.g., between 5-278m depth;
Rowley 2014). Whether such an apparent thermal tolerance, and distributional range is due to a
high physiological capacity, or ecologically and/or geographically isolated species is yet to be
determined. I took the opportunity to test the thermal tolerance of 24 A. reticulata colonies
in a 12-month transplant experiment (Figure 5).
CONSERVATIONbMANAGEMENT
Here, exploration of deep-reef ecosystems has led to the discovery of species and ecological
patterns new to science, providing a natural laboratory to address questions of diversity,
resilience, but also priority conservation. By sharing our experience, data and media with the local
communities (Figure 6, 7), we have been asked to guide regional conservation management
decisions at the governmental level, with an open invitation for ongoing research throughout the
region. In a time of unprecedented marine resource exploitation, the opportunity to share and link
science with policy is more than one could have asked for. Thank you SRF for
supporting this research and facilitating ongoing community and governmental collaboration.
Expedition blogs and summary footage as presented at 3 international and several local intuitions:
https://youtu.be/VNw9WrkEryY
Kalanghan!
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Figure 6. S. J. Rowley teaching chief Sounihrek Pakin and his community how to identify gorgonian
species, and play ‘count the associate brittle stars’ with the children. Image by J. Hartup.
ACKNOWLEDGEMENTS
This expedition would not have been possible without the generous support of the Systematic
Research Fund (SRF). Therefore, sincere gratitude is extended to the SRF selection committee as
supported by The Linnean Society of London, and the Systematics Association. I would like to thank
Dr. Richard L. Pyle and Brian D. Greene for their tireless research and dive support, and most of all,
friendship. Thank you also to the Edmondson Trust of the Bernice Pauahi Bishop Museum,
Honolulu, and Ocean First Education for additional financial support. I am indebted to the local
support provided by Wilbur and Madelaine Walters and KM at the Nihco Marine Park, the late
Sounihrek Pakin and his community, the Office of Fisheries and Aquaculture (OFA), and the
Conservation Society of Pohnpei (CSP). Gratitude is also extended to Valeport for providing
miniCTD fast profiler support facilitating experimental and ongoing environmental monitoring at
depth. Finally, a special thank you to Prof. Steven M. Stanley for enthusiastic mentorship,
stimulating academic discussion, and financial support.
6
Figure 7. Pakin Atoll from sunrise to deep-reef new species discovery and collection. Images by S. J.
Rowley, with B. D Greene catching Parapercis n. sp., at 135 meters depth.
Appendix I. Octocoral specimen inventory collected for SRF supported expedition (2015) as well as
3 years total exploration. n.sp., denotes new species in the process of being described.
Subclass Octocorallia (Alcyonaria), Order Alcyonacea
Family
Genus
species
Alcyoniidae
Alcyoniidae
spp.
Alcyoniidae
Sinularia
sp.
Acanthogorgiidae
Acanthogorgia
n. sp.
Acanthogorgiidae
Anthogorgia
spp.
Acanthogorgiidae
Muricella
spp.
Briareidae
Briareum
stechei
Chrysogorgiidae
Stephanogorgia
spp.
Ellisellidae
Ellisellidae
spp.
Ellisellidae
Dichotella
spp.
Ellisellidae
Ellisella
spp.
Ellisellidae
Heliania
n. sp., x 2
Ellisellidae
Nicella
n. sp.
Ellisellidae
Verrucella
spp.
Ellisellidae
Viminella
spp.
Gorgoniidae
Hicksonella
princeps
Keroeididae
Keroeides
n. sp., x 2
Melithaeidae
Acabaria
spp.
Nephtheidae
Dendronephthya
sp.
Nephtheidae
Nephtheidae
spp.
Nidaliidae
Chironephthya
spp.
Nidaliidae
Siphonogorgia
spp.
Parisididae
Parisis
n. sp.
Plexauridae
Plexauridae
spp.
Plexauridae
Astrogorgia
n. sp., x 2
Plexauridae
Bebryce
n. sp.
Plexauridae
Echinogorgia
spp.
Plexauridae
Echinomuricea
spp.
Plexauridae
Euplexaura
spp.
Plexauridae
Paracis
n. sp., x 2
Plexauridae
Paramuricea
spp.
Plexauridae
Placogorgia
n. sp.
Plexauridae
Rumphella
spp.
Plexauridae
Trimuricea
n. sp.
Plexauridae
Villogorgia
n. sp.
Primnoidae
Plumarella
spp.
Subergorgiidae
Annella
mollis
Subergorgiidae
Annella
reticulata
Subergorgiidae
Subergorgia
spp.
Total
Appendix II. Fish specimen inventory collected for SRF supported expedition (2015) as well as 3 years
total exploration. n.sp., denotes new species described and in the process of being described.
Subclass Actinopterygii, Order Perciformes
Family Genus species
Acanthuridae
Ctenochaetus
striatus
Acanthuridae
Naso
thynnoides
Acanthuridae
Zebrasoma
scopas
Apogonidae
[Unidentified to genus]
sp.
Apogonidae
Cheilodipterus
macrodon
Balistoidea
Sufflamen
bursa
Callanthiidae
Grammatonotus
n. sp., x 2
Callionymidae
Synchiropus
sp.
Chaetodontidae
Chaetodon
sp.
Chaetodontidae
Forcipiger
spp.
Chaetodontidae
Roa
sp.
Cirrhitidae
Cyprinocirrhites
polyactis
Cirrhitidae
Oxycirrhites
typus
Cirrhitidae
Paracirrhites
arcatus
Gobiidae
Amblyeleotris
yanoi
Gobiidae
Tryssogobius
sp.
Holocentridae
Myripristis
spp.
Holocentridae
Neoniphon
spp.
Holocentridae
Sargocentron
spp.
Labridae
Bodianus
neopercularis
Labridae
Cirrhilabrus
earlei
Labridae
Halichoeres
hortulanus
Labridae
Halichoeres
marginatus
Labridae
Halichoeres
melasmapomus
Labridae
Oxycheilinus
arenatus
Labridae
Pseudocheilinus
ocellatus
Labridae
Terelabrus
rubrovittatus
Labridae
Thalassoma
lutescens
Labridae
Xyrichthys
halsteadi
Lethrinidae
Monotaxis
sp.
Malacanthidae
Hoplolatilus
marcosi
Microdesmidae
Ptereleotris
grammica
Mullidae
Parupeneus
barberinus
Mullidae
Parupeneus
crassilabris
Mullidae
Parupeneus
cyclostomus
Mullidae
Parupeneus
multifasciatus
Pempheridae
Pempheris
sp.
Pinguipedidae
Parapercis
n. sp., x 2
Plesiopidae
Calloplesiops
altivelis
Subclass Actinopterygii, Order Perciformes
Family Genus species
Apolemichthys
Centropyge
Centropyge
Centropyge
Centropyge
Centropyge
Centropyge
Centropyge
Centropyge
Centropyge
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacanthidae
Pomacentridae
Pomacentridae
Pomacentridae
Pomacentridae
Pomacentridae
Pomacentridae
Pomacentridae
Pomacentridae
Pseudochromidae
Pseudochromidae
Serranidae
Serranidae
Serranidae
Serranidae
Serranidae
Serranidae
Serranidae
Serranidae
*Syngnathidae
Genicanthus
Pygoplites
Amblyglyphidodon
Amphiprion
Chromis
Plectroglyphidodon
Plectroglyphidodon
Plectroglyphidodon
Pomacentrus
Pomacentrus
Pseudochromis
Pseudoplesiops
Belonoperca
Cephalopholis
Luzonichthys
Odontanthias
Odontanthias
Plectranthias
Pseudanthias
Tosanoides
Hippocampus
Symphysanodontidae Symphysanodon
2
Tetraodontoidea Ostracion
griffisi
aurantia
bispinosa
colini
flavissima
flavissima x vrolickii
heraldi
multicolor
sp.
vrolikii
bellus
diacanthus
aureus
clarkii
sp.
dickii
johnstonianus
lacrymatus
moluccensis
vaiuli
n. sp.
n. sp.
pylei
sp.
seaver, n. sp.
katayamai
n. sp.
sp.
n. sp.
n. sp.
n.sp.
sp.
meleagris
1
3
0
0
0
0
Total
425
*Gorgonian-associated pygmy seahorses
... comm.). More recently, from 2014 to the present, the Association for Marine Exploration (AME) and collaborators have conducted research expeditions annually within the region (Rowley 2016). These expeditions have yielded new fish species at mesophotic depths (Copus et al. 2015; Anderson and Johnson 2017) along with ecological surveys of key MCE benthic components such as fishes , scleractinian and gorgonian corals, as well as monitoring of environmental variables. ...
... MCEs within the Indo-Pacific are typically dominated by a diverse array of gorgonian (sea fan) octocorals (Pyle 1996;Rowley 2014). Of the 65 genera and 15 families currently recorded at mesophotic depths throughout the Indo-Pacific (see Sánchez et al. 2019), 35 genera and 11 families were present within the Senyavin Islands and comprised all higher-order groups (total of 897 specimens collected during four expeditions 2014-2017; see also Rowley 2016). ...
... MCEs within the Indo-Pacific are typically dominated by a diverse array of gorgonian (sea fan) octocorals (Pyle 1996;Rowley 2014). Of the 65 genera and 15 families currently recorded at mesophotic depths throughout the Indo-Pacific (see Sánchez et al. 2019), 35 genera and 11 families were present within the Senyavin Islands and comprised all higher-order groups (total of 897 specimens collected during four expeditions 2014-2017; see also Rowley 2016). The majority of taxa are found at depths below 70 m, consisting of 32 genera within 11 families. ...
Pohnpei, Federated States of Micronesia
Chapter
Full-text available
  • May 2019
The mesophotic coral ecosystems (MCEs) of the Senyavin Islands (Pohnpei Island, and neighboring atolls Ant and Pakin) in the Federated States of Micronesia have received little research attention until recent years. These vibrant, environmentally dynamic ecosystems harbor a reservoir of biodiversity, with species and interactions new to science. Depths of ≥90 m have up to 20 °C annual variance. A strong El Niño event in 2016 resulted in a bloom-forming cyanobacteria smothering the upper MCEs of Pohnpei (25–65 m). Conditions persisted into 2017 with extensive coral bleaching and reef degradation with associated smothering by bloom-forming cyanobacteria and algae in the shallows. The initial bloom signature of 2016 at depth may, therefore, serve as a projected indicator of shallow reef health. Of the 160 reef-building scleractinian corals reported, 28 spanned the full depth range (0–45 m). Differences in irradiance due to geomorphology, as well as reef health, determined the depth transition between two primary benthic groups: photosynthetic scleractinians and filter-feeding azooxanthellate gorgonians, 60 m on low-relief atoll reefs and 45 m at high-relief walls and degraded reefs. Of the 109 gorgonian corals reported, 19 spanned the full depth range (0–140 m) with 70 morphospecies specific to lower mesophotic depths. Similarly, fish assemblages partitioned between shallow and mesophotic depths, characterized by herbivores and planktivores, respectively. Continuously growing marine resource exploitation and terrestrial runoff are heavily influencing reef health. The MCEs of Pohnpei are, thus, unique, yet vulnerable to the exacerbating stresses of man.
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... MCEs throughout the Indo-Pacific are typically dominated by extensive communities of gorgonian (sea fan) octocorals (Rowley 2014). Of the 65 genera and 15 families currently recorded at mesophotic depths throughout the Indo-Pacific, 35 genera and 11 families were present within the Senyavin Islands (total of 897 specimens collected during four expeditions [2014][2015][2016][2017]; see also Rowley 2016). ...
... From 2014-2016, a total of 473 fishes have been collected from the waters of the Senyavin Islands for research (see Rowley 2016). The majority of these fishes are from mesophotic depths with at least 11, collected below 90 m depth that are new species to science. ...
Rowley et al 2018 LAY SUMMARY Community Report[V1]
Technical Report
Full-text available
  • Jul 2018
This is a lay-summary of a larger report and subsequent book chapter (Rowley et al. 2019), for the local communities and governmental agencies of Pohnpei, Federated States of Micronesia. The research presented is a summary of what has been conducted by the University of Hawai'i at Manoa and collaborators since 2014 on the mesophotic coral ecosystems (MCEs) and shallow coral reefs of the Senyavin Islands (Pohnpei Island, and neighbouring atolls Ant and Pakin) in the Federated States of Micronesia (FSM). Annual expeditions have revealed that MCEs are biodiverse, dynamic environments that harbour new species to science (>25 spp.), have species-specific depth distributions, and display remarkable resilience to daily and seasonal fluctuations in temperature. At depths of ≥90 m the annual variability in temperature was up to 20ºC. The strong El Niño event in 2016 and into 2017, extensive coral bleaching occurred on the shallow reefs, with bloom-forming cyanobacteria and algae smothering the reefs. We discovered that reef health could be determined by the depth transition between scleractinians and gorgonians, further revealing areas for conservation management. Reef health is also heavily influenced by the continuously growing marine resource exploitation and terrestrial runoff. Furthermore, the growing $36 million international fishing industry and its associated consequences are contributing to the decline in health of the Pohnpei marine environment. The lush reefs of previous times, therefore, are being replaced by barren reefs, smothered by invasive algae, filamentous cyanobacteria on Pohnpei island, or crustose coralline algae at the atolls. Resource management strategies developed by Pacific Island cultures over hundreds of generations face significant challenges in the modern world. Suggested recommendations may mitigate such challenges. Nonetheless, ocean temperatures have fluctuated over the millennia, a single stressor that reefs may well have the capacity to recover from in our current climate, but the addition of multiple stressors such as eutrophication, local and international fishing exploitation compromise coral reef resilience. In summary, it is essential that both the local communities and the government act now if the reefs of the Senyavin Islands are to recover and survive.
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