Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity

Classic marine ecological paradigms view kelp forests as inherently temperate-boreal phenomena replaced by coral reefs in tropical waters. These paradigms hinge on the notion that tropical surface waters are too warm and nutrient-depleted to support kelp productivity and survival. We present a synth...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2007-10, Vol.104 (42), p.16576-16580
Main Authors: Graham, Michael H, Kinlan, Brian P, Druehl, Louis D, Garske, Lauren E, Banks, Stuart
Format: Article
Language:English
Subjects:
Atlantic Ocean
Biodiversity
Biogeography
Biological Sciences
Climate
Ecology
Ecophysiology
Eisenia
Evolution
Forest ecology
Forest habitats
Global climate models
Habitat conservation
Kelp - physiology
Marine
Marine Biology
Marine ecology
Modeling
Oceanography
Pacific Ocean
Refuge habitats
Seawater
Tropical climates
Tropical forests
Tropical regions
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Summary:Classic marine ecological paradigms view kelp forests as inherently temperate-boreal phenomena replaced by coral reefs in tropical waters. These paradigms hinge on the notion that tropical surface waters are too warm and nutrient-depleted to support kelp productivity and survival. We present a synthetic oceanographic and ecophysiological model that accurately identifies all known kelp populations and, by using the same criteria, predicts the existence of >23,500 km² unexplored submerged (30- to 200-m depth) tropical kelp habitats. Predicted tropical kelp habitats were most probable in regions where bathymetry and upwelling resulted in mixed-layer shoaling above the depth of minimum annual irradiance dose for kelp survival. Using model predictions, we discovered extensive new deep-water Eisenia galapagensis populations in the Galápagos that increased in abundance with increasing depth to >60 m, complete with cold-water flora and fauna of temperate affinities. The predictability of deep-water kelp habitat and the discovery of expansive deep-water Galápagos kelp forests validate the extent of deep-water tropical kelp refugia, with potential implications for regional productivity and biodiversity, tropical food web ecology, and understanding of the resilience of tropical marine systems to climate change.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0704778104