Iron defecation by sperm whales stimulates carbon export in the Southern Ocean

Patricia Lavery, Ben Roudnew, Peter Gill, Justin Seymour, Laurent Seuront, Genevieve Johnson, James Mitchell, Victor Smetacek

    Research output: Contribution to journalArticle

    72 Citations (Scopus)

    Abstract

    The iron-limited Southern Ocean plays an important role in regulating atmospheric CO2 levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of Cexport : Feadded determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 105 tonnes of carbon per year to the deep ocean and respire only 2 × 10 5 tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 105 tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling.

    Original languageEnglish
    Pages (from-to)3527-3531
    Number of pages5
    JournalProceedings of The Royal Society of London Series B: Biological Sciences
    Volume277
    Issue number1699
    DOIs
    Publication statusPublished - 2010

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