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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Mar. Sci. | doi: 10.3389/fmars.2019.00499

Extreme Marine Heatwaves alter kelp forest community near its equatorward distribution limit

  • 1ARC Centre for Excellence in Convergent Bio-Nano Science and Technology, Monash University, Australia
  • 2School of Earth and Environmental Sciences, University of Queensland, Australia
  • 3Marine Ecology, Conservation, and Resource Management Lab, Oceanological Research Institute, Autonomous University of Baja California, Mexico
  • 4Department of Physical Oceanography, School of Marine Sciences, Autonomous University of Baja California, Mexico
  • 5Global-Change Ecology Research Group, School of Science and Engineering, University of the Sunshine Coast, Australia
  • 6Centre for African Conservation Ecology, Department of Zoology, Nelson Mandela University, South Africa

Climate change is increasing the frequency and severity of marine heatwaves. A recent extreme warming event (2014-2016) of unprecedented magnitude and duration in the California Current System allowed us to evaluate the response of the kelp forest community near its southern (warm) distribution limit. We obtained sea surface temperatures for the northern Pacific of Baja California, Mexico, and collected kelp forest community data at three islands, before and after the warming event. The warming was the most intense and persistent event observed to date, with low-pass anomalies 1°C warmer than the previous extremes during the 1982-1984 and 1997-1998 El Niños. The period between 2014-2017 accounted for ~50% of marine heatwaves days in the past 37 years, with the highest maximum temperature intensities peaking at 5.9°C above average temperatures for the period. We found significant declines in the number of Macrocystis pyrifera individuals, except at the northernmost island, and corresponding declines in the number of fronds per kelp individual. We also found significant changes in the community structure associated with the kelp beds: half of the fish and invertebrate species disappeared after the marine heatwaves, species with warmer affinities appeared or increased their abundance, and introduced algae, previously absent, appeared at all islands. Changes in subcanopy and understory algal assemblages were also evident; however, the response varied among islands. These results suggest that the effect of global warming can be more apparent in sensitive species, such as sessile invertebrates, and that warming-related impacts have the potential to facilitate the establishment of tropical and invasive species.

Keywords: Kelp forest, marine heatwaves, El Niño, Blob, community structure, sentinel areas, tropicalization, trailing edge, extreme warming event

Received: 20 Apr 2019; Accepted: 25 Jul 2019.

Copyright: © 2019 Arafeh-Dalmau, Montaño-Moctezuma, Martinez, Beas-Luna, Schoeman and Torres-Moye. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Mr. Nur Arafeh-Dalmau, ARC Centre for Excellence in Convergent Bio-Nano Science and Technology, Monash University, Brisbane, Australia, n.arafehdalmau@uq.net.au
Dr. Gabriela Montaño-Moctezuma, Marine Ecology, Conservation, and Resource Management Lab, Oceanological Research Institute, Autonomous University of Baja California, Ensenada, Mexico, gmontano@uabc.edu.mx