A Steady Supply of Food

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Science  23 May 2008:
Vol. 320, Issue 5879, pp. 987
DOI: 10.1126/science.320.5879.987a

The environmental and anthropogenic factors affecting leatherback turtle populations are generally unknown and cannot explain why populations are increasing in the Atlantic yet declining in the Pacific. By analyzing reproductive success rates, migratory patterns, and oceanographic variables, Saba et al. demonstrate that turtle populations are most likely regulated by the abundance of zooplankton where they forage, as measured by the net primary productivity (NPP) estimated from satellite data. NPP was shown to vary among oceanic regions and to be affected by regime shifts that typically enhance ocean productivity; however, both the total NPP and overall consistency in NPP over time were much lower in the Pacific regions examined than in the Atlantic. In turn, these differences in local resources appear to affect turtle size and overall egg production—larger females that have matured faster lay more eggs than smaller females. These differences, coupled with anthropogenic impact and the effects of climatic shifts on NPP, may explain the discrepancy in demography between the Atlantic and Pacific leatherback populations. — LMZ

Ecology 89, 1414 (2008).

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