To assess distributional shifts of species in response to recent warming, historical distribution records are the most requisite information. The surface seawater temperature (SST) of Kochi Prefecture, southwestern Japan on the western North Pacific, has significantly risen, being warmed by the Kuroshio Current. Past distributional records of subtidal canopy-forming seaweeds (Laminariales and Fucales) exist at about 10-year intervals from the 1970s, along with detailed SST datasets at several sites along Kochi's >700 km coastline. In order to provide a clear picture of distributional shifts of coastal marine organisms in response to warming SST, we observed the present distribution of seaweeds and analyzed the SST datasets to estimate spatiotemporal SST trends in this coastal region. We present a large increase of 0.3°C/decade in the annual mean SST of this area over the past 40 years. Furthermore, a comparison of the previous and present distributions clearly showed the contraction of temperate species' distributional ranges and expansion of tropical species' distributional ranges in the seaweeds. Although the main temperate kelp Ecklonia (Laminariales) had expanded their distribution during periods of cooler SST, they subsequently declined as the SST warmed. Notably, the warmest SST of the 1997–98 El Niño Southern Oscillation event was the most likely cause of a widespread destruction of the kelp populations; no recovery was found even in the present survey at the formerly habitable sites where warm SSTs have been maintained. Temperate Sargassum spp. (Fucales) that dominated widely in the 1970s also declined in accordance with recent warming SSTs. In contrast, the tropical species, S. ilicifolium, has gradually expanded its distribution to become the most conspicuously dominant among the present observations. Thermal gradients, mainly driven by the warming Kuroshio Current, are presented as an explanation for the successive changes in both temperate and tropical species' distributions.
Warming off southwestern Japan linked to distributional shifts of subtidal canopy-forming seaweeds
Kouki Tanaka,S. Taino,H. Haraguchi,Gabrielle Prendergast,M. Hiraoka
Published 2012 in Ecology and Evolution
ABSTRACT
PUBLICATION RECORD
- Publication year
2012
- Venue
Ecology and Evolution
- Publication date
2012-10-12
- Fields of study
Medicine, Environmental Science
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- 1997–98 el niño southern oscillation event
A strong ENSO warm event discussed as a climatic reference point for the kelp decline.
Aliases: 1997-98 ENSO event, El Niño Southern Oscillation event
- ecklonia
A temperate kelp genus in Laminariales that forms canopy vegetation in the study region.
- kochi prefecture
The coastal prefecture in southwestern Japan that forms the geographic setting for the temperature records and seaweed surveys.
Aliases: Kochi
- sargassum spp.
Temperate Sargassum species recorded as canopy-forming brown algae in the coastal surveys.
Aliases: temperate Sargassum
- s. ilicifolium
A tropical Sargassum species observed in the coastal seaweed surveys.
Aliases: Sargassum ilicifolium
- subtidal canopy-forming seaweeds
Seaweeds in subtidal habitats that form the upper canopy and include taxa from Laminariales and Fucales.
Aliases: canopy-forming seaweeds
- surface seawater temperature
Sea surface water temperature measured along Kochi's coastline and used to track long-term thermal change.
Aliases: SST
REFERENCES
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