Sensitivity of tropical seabirds to El Nino precursors

Devney, Carol, Short, Michael, and Congdon, Bradley C. (2009) Sensitivity of tropical seabirds to El Nino precursors. Ecology, 90 (5). pp. 1175-1183.

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Abstract

Intense El Niño events severely impact seabird populations, often months in advance of peak temperature anomalies. The trophic mechanisms responsible for these impacts are unknown but are assumed to operate at seasonal scales and to be linked to ocean productivity changes. Precursors to El Niño events include changes in both sea-surface temperature and the depth of the 20°C thermocline. Foraging piscivorous seabirds are known to be sensitive to both thermocline depth and sea-surface temperature change, but the potential influence of these phenomena on breeding dynamics is unknown. Using 18 years of data on three seabirds of the western tropical Pacific, we show that pelagic seabird breeding participation is directly and independently related to changes in both surface chlorophyll concentration and thermocline depth that occur well in advance of El Niño generated sea-surface temperature anomalies. In contrast, breeding in an inshore foraging species is not correlated with any environmental/biological parameters investigated. These findings demonstrate that El Niño related phenomena do not affect seabird prey dynamics solely via productivity shifts at seasonal scales, nor in similar ways across different seabird foraging guilds. Our results also suggest that population declines observed in the western tropical Pacific may be directly related to the frequency and intensity of El Niño anomalies over the study period.

Item ID: 5507
Item Type: Article (Refereed Research - C1)
Keywords: 20oC thermocline; Anous stolidus; breeding participation; El Nino southern oscillation; Great Barrier Reef, Australia; precursor impacts; productivity; Sterna bergii; Sterna fuscata; western tropical Pacific, tropical biology
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Reproduced with permission from Ecological Society of America (ESA).

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ISSN: 1939-9170
Date Deposited: 04 Nov 2009 23:52
FoR Codes: 06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060306 Evolutionary Impacts of Climate Change @ 50%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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