Abstract
The equatorial Pacific Ocean atoll islands of Kiritimati and Teraina encompass great physical, chemical and biological variability within extreme lacustrine environments. Surveys of lake chemistry and sediments revealed both intra- and inter-island variability. A survey of more than 100 lakes on Kiritimati found salinities from nearly fresh to 150 ppt with the highest values occurring within the isolated, inland portions of the island away from the influence of groundwater or extreme tides. Dissolved oxygen (DO) and pH values also showed considerable variability with a less regular spatial pattern, but were both generally inversely related to salinity. Series of lakes, progressively more isolated from marine communication, present a modern analog to the chemical and morphologic evolution of presently isolated basins. Sediments on both islands consist of interbedded red and green silt, possibly degraded bacterial mat, overlying white, mineralogenic silt precipitate. Variability may be indicative of shifts in climatological parameters such as the El Niño Southern Oscillation (ENSO) or the Pacific Intertropical Convergence Zone (ITCZ).
Highlights
The equatorial Pacific coral atoll lakes and lagoons of Kiritimati (Christmas) and Teraina (Washington) Islands, Republic of Kiribati (Figure 1), possess a breadth of lacustrine environments from fresh to hypersaline in which a range of tropical limnologic conditions can be examined within a small geographic area
R: R: R1 R R: FMiagpuoref t1he central North Pacific Ocean showing the location of Kiritimati and Teraina islands Map of the central North Pacific Ocean showing the location of Kiritimati and Teraina islands
The saline lakes of Kiritimati show remarkable variability, and because local geology and evaporation minus precipitation are relatively uniform across the island, the primary factor influencing salinity distribution is likely location
Summary
The equatorial Pacific coral atoll lakes and lagoons of Kiritimati (Christmas) and Teraina (Washington) Islands, Republic of Kiribati (Figure 1), possess a breadth of lacustrine environments from fresh to hypersaline in which a range of tropical limnologic conditions can be examined within a small geographic area. Salinity in shallow hypersaline lacustrine environments is extremely sensitive to climatic changes that influence salt concentrations via changes in the evaporation minus precipitation balance, and the hydrologic variability of Kiritimati and Teraina lakes has been attributed to the El Niño Southern Oscillation (ENSO) [1]. Long proxy records of lacustrine hydrology have the potential to elucidate ENSO behavior over centennial to millennial timescales, but require a baseline of modern variability against which past changes can be compared. An extensive description of the lakes of Kiritimati and Teraina that expands upon past work is critically needed to more completely define this baseline variability
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