Marine & Environmental Sciences Faculty Articles

Cetacean-mediated vertical nitrogen transport in the oceanic realm



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Limnology and Oceanography



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In natural systems, animal-mediated nutrient transport can be a major driver of primary productivity, but the role of marine megafauna such as cetaceans in mediating the transfer and recycling of nutrients has been overlooked. Here, we developed a spatially resolved, stochastic, nutrient-transport model for cetaceans in the oceanic Gulf of Mexico using species−specific foraging depths, distributions, and diets. An estimated 6.4 × 108 mmol N d−1, or 0.06 mt N yr−1 ind−1, is transported to the surface from depths below 100 m by the 19 cetacean species that occur in the oceanic Gulf of Mexico; 75% of this transport occurs seaward of the continental slope, but the per area transported nitrogen is greater on the continental slope (200–1000 m) than in the ocean basin. Benthos to surface transport comprised 6.0 × 107 mmol N d−1 and was much more common on the continental slope than the open basin. Compared to an existing physical-biogeochemical model, the transported nutrients add 8% N d−1 to the estimated ammonium concentration above the nutricline and could add 16% N d−1 to the surface ammonium concentration if expelled nutrients remain at the surface. Through feeding on diel vertical migrants, cetaceans retain an additional 2.7 × 107 mmol N d−1 in the surface waters that would otherwise return to depth via downward diel vertical migration. Cetaceans contribute to nutrient movements and recycling in the oceanic Gulf of Mexico, and may provide one of the few allochthonous sources of nutrients for primary producers in oligotrophic ecosystems.



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This article is a result of research funded by the NationalOceanic and Atmospheric Administration’s RESTORE Science Programunder award NA19NOS4510193 to Nova Southeastern University andThe Gulf of Mexico Research Initiative. We acknowledge CIGoMand PEMX’s for funding the development of the MaxEnt models used inthis study. This is contribution #1613 from the Institute of Environment atFlorida International University. This manuscript was in part supportedthrough thefinancial support of a Florida International University ProvostEmployer Supported Tuition Fellowship.

© 2023 Association for the Sciences of Limnology and Oceanography.

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