Nomination for a World Heritage Site 2009 - Phoenix Islands ...

No previous resource surveys have been identified for Carondelet or Winslow reefs, or for
the unnamed reefs in the Phoenix Islands. A survey was attempted at Winslow in August
2008 but the reef could not be located (Jim Maragos, US Fish and Wildlife Service, oral
information). These remote untouched reefs undoubtedly have high species diversity and
populations of endangered species. The draft management plan has an objective to complete
baseline surveys of the reefs of Carondelet and Winslow and of other unnamed reefs in the
Phoenix Islands using standardized quantitative methods. The 2009 expedition by New
England Aquarium is expected to provide more information on these reefs. Establishing notake
zones around Carondelet and Winslow Reefs is foreseen in the new management plan.
More information on the ecology of seamounts is provided later in this nomination in the
chapter on Seamounts.
Oceanography
Sea surface temperatures within PIPA are normally between 28-30°C. There is no significant
thermocline down to 50 m depth. Sea level observations on Kanton show regular four-day
oscillations related to equatorial waves. Oceanographic studies reveal that silicate and
phosphate levels in the waters around the Phoenix Islands are elevated compared adjacent
waters. This may be a result of upwelling and have high importance for the pelagic food
chain in the region. For example in 2000, McKean water temperature was slightly cooler than
that of Nikumaroro. This suggested up-welling and mixing of deeper water on McKean. The
minimum water temperature recorded was 26.7 0 C at Nikumaroro (Obura and Stone 2003).
The Phoenix Islands are adjacent to the equator and are predominantly influenced by the
westward-flowing Equatorial Current (northern equatorial branch of the South Equatorial
Current (BEN) and south equatorial branch of the South Equatorial Current (BES) (TBAP
1993). Offshore currents are generally westward. The strength of the currents varies with the
wind. Usual current speed is 1.9 km per hour (1 knot), with a maximum of 3.7 km per hour (2
knots).
The Phoenix Islands are subject to the ENSO that occurs every two to seven years and lasts
for 18 to 24 months. During ENSO events, the westward trade winds are reduced and the
main water currents experience variations and even reversal. This deepens the eastern Pacific
thermocline. More specifically, the Phoenix Islands are located within the region of the
Central Pacific in which warm pool of surface waters develops at the onset of El Niño phases,
and can experience persistent hotspots lasting 1 year or more, as occurred in 2002-3. This
unique environment of high exposure to warm water pools may exert unusual selective
pressures on marine organisms relevant to climate change adaptation, discussed further in
later sections.
The Tuna and Billfish Assessment Programme (TBAP 1993) provided diagrams (some
shown below) of the seasonal changes in major equatorial surface currents around the
Phoenix Islands.
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