In 2012 we conducted an integrated ecological assessment of the marine environment of the Pitcairn Islands, which are four of the most remote islands in the world. The islands and atolls (Ducie, Henderson, Oeno, and Pitcairn) are situated in the central South Pacific, halfway between New Zealand and South America. We surveyed algae, corals, mobile invertebrates, and fishes at 97 sites between 5 and 30 m depth, and found 51 new records for algae, 23 for corals, and 15 for fishes. The structure of the ecological communities was correlated with age, isolation, and geomorphology of the four islands. Coral and algal assemblages were significantly different among islands with Ducie having the highest coral cover (56%) and Pitcairn dominated by erect macroalgae (42%). Fish biomass was dominated by top predators at Ducie (62% of total fish biomass) and at Henderson (35%). Herbivorous fishes dominated at Pitcairn, while Oeno showed a balanced fish trophic structure. We found high levels of regional endemism in the fish assemblages across the islands (45%), with the highest level observed at Ducie (56% by number). We conducted the first surveys of the deep habitats around the Pitcairn Islands using drop-cameras at 21 sites from depths of 78 to 1,585 m. We observed 57 fish species from the drop-cams, including rare species such as the false catshark (Pseudotriakis microdon) and several new undescribed species. In addition, we made observations of typically shallow reef sharks and other reef fishes at depths down to 300 m. Our findings highlight the uniqueness and high biodiversity value of the Pitcairn Islands as one of the least impacted in the Pacific, and suggest the need for immediate protection.
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Friedlander AM, Caselle JE, Ballesteros E, Brown EK, Turchik A, Sala E (2017): The Real Bounty: Marine Biodiversity in the Pitcairn Islands. v1.2. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Dataset/Occurrence. https://nzobisipt.niwa.co.nz/resource?r=pitcairn&v=1.3
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Pitcairn Island (and surround islands)
|Bounding Coordinates||South West [-25.5, -131], North East [-23.8, -125]|
No Description available
|Title||Marine Biodiversity in the Pitcairn Islands|
|Funding||We are grateful to the persons and institutions that supported or collaborated on this Pristine Seas expedition and made it successful: Spain's National Research Council, US Geological Survey, University of Hawaii, US National Park Service, University of California Santa Barbara, Nitrox Solutions, Poseidon Diving Systems, Mares, the Pew Environment Group, Nigel Jolly and the crew of the Claymore II. We are very grateful to the Pitcairners at large, who hosted us in their homes and showed to us the secrets of their island and ocean. Heartfelt thanks to the Pitcairn Island Council and the Government of the Pitcairn Islands for authorizing our stay and providing research permits.|
|Study Area Description||Pitcairn Islands|
The personnel involved in the project:
Sampling sites were haphazardly selected around all four islands to incorporate representative wave exposures, habitats, and oceanographic conditions. At each site, SCUBA surveys were conducted at both 10 and 20 m depth. In addition, two sites at 30 m were surveyed at Pitcairn to characterize the deeper reef community, as well as surveys conducted on the patch reefs (∼5 m) in the shallow lagoon of Ducie.
|Study Extent||The Pitcairn Islands are the only emergent parts of an ancient chain of volcanoes that rose from the seafloor between 0.9 and 16 Myr ago, and are geologically connected to the Tuamotu and Gambier islands of French Polynesia. The four islands differ in their size, geological age, and isolation. Pitcairn is a high volcanic island of 450 ha with lava cliffs and rugged hills rising to a peak at 335 m. Henderson (200 km ENE of Pitcairn) is the largest island in the group with an area of 4,310 ha. Henderson was formerly an atoll, but the formation of Pitcairn 0.8–0.9 Myr ago caused an uplift of the crust, which elevated Henderson 33 m above sea level . Henderson was declared a UNESCO World Heritage site owing to its unique terrestrial natural history and ecological intactness. Ducie (472 km E of Pitcairn), the most southerly coral atoll in the world, consists of a central lagoon surrounded by four islets covering 70 ha. Oeno (120 km NW of Pitcairn) is a low coral atoll of 65 ha comprising a central low-lying island surrounded by a shallow lagoon and fringing reef (diameter ca. 4 km).|
|Quality Control||Species names were matched against the World Register of Marine Species (WoRMS).|
Method step description:
- Characterization of the benthos was conducted along a 50 m-long transect parallel to the shoreline at each sampling depth strata. For algae, corals, and other sessile invertebrates we used a line-point intercept methodology along transects, recording the species or taxa found every 20 cm on the measuring tape. Point contact data were expressed as percent cover. For sea urchins, we counted and sized individuals in fifteen, 50×50 cm quadrats haphazardly placed along each 50 m transect line. Quadrat placement was stratified with three quadrats per 10 m segment of transect line.
- At each depth stratum within a site, one diver counted and estimated lengths for all fishes encountered within fixed-length (25-m) belt transects whose widths differed depending on direction of swim. Transect bearings were set along isobaths within homogeneous habitats with each transect separated by at least 5 m. All fish ≥20 cm total length (TL) were tallied within a 4 m wide strip surveyed on an initial “swim-out” as the transect line was laid (transect area = 100 m2). These included large-bodied, vagile fishes. All fishes <20 cm TL were tallied within a 2 m wide strip surveyed on the return swim back along the laid transect line (transect area = 50 m2). This included small-bodied, less vagile and more site-attached fish. In addition, all species observed outside of the transect area at each station were recorded to estimate total species richness at a site.
- National Geographic's Remote Imaging Team developed deep ocean drop-cams, which are high definition cameras (Sony Handycam HDR-XR520V 12 megapixel) encased in a borosilicate glass sphere that are rated to 10,000 m depth. Viewing area per frame was between 2–6 m2, depending on the steepness of the slope where the drop-cam landed. Cameras were baited with frozen fish and deployed for ca. four hours. The cameras remained sealed during the entire expedition with communications through a Subconn connector. Lighting at depth was achieved through a high intensity LED array directed using external reflectors. Depth gauging was conducted using an external pressure sensor. The drop-cams were ballasted with a 22 kg external weight that resulted in a descent rate of 1.5 m s−1. The primary release mechanism was a burn wire that was activated using onboard battery voltage. The drop-cams are positively buoyant resulting in an ascent rate of 0.5 m s−1. Drop-cams have an onboard VHF transmitter that allows for recovery using locating antennae with backup location achieved via communication with the ARGOS satellite system.
- Friedlander AM, Caselle JE, Ballesteros E, Brown EK, Turchik A, Sala E (2014) The Real Bounty: Marine Biodiversity in the Pitcairn Islands. PLoS ONE 9(6): e100142. doi:10.1371/journal.pone.0100142