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Tropicalization of temperate reef fish communities facilitated by urchin grazing and diversity of thermal affinities


Schuster, JM and Stuart-Smith, RD and Edgar, GJ and Bates, AE, Tropicalization of temperate reef fish communities facilitated by urchin grazing and diversity of thermal affinities, Global Ecology and Biogeography, 31, (5) pp. 995-1005. ISSN 1466-822X (2022) [Refereed Article]

Copyright Statement

2022 John Wiley & Sons Ltd

DOI: doi:10.1111/geb.13477



Global declines in structurally complex habitats are reshaping both land- and seascapes in directions that affect the responses of biological communities to warming. Here, we test whether widespread loss of kelp habitats through sea urchin overgrazing systematically changes the sensitivity of fish communities to warming.


Global temperate latitudes.

Time period


Major taxa studied



Community shifts in thermal affinity related to habitat were assessed by simulating and comparing fish communities from 2271 surveys across 15 ecoregions.


We found that fishes in kelp and urchin barrens differed in realized thermal affinities and range sizes, but only in regions where species pools had high variability in the thermal affinities of species. Barrens on warm temperate reefs host relatively more warm-affinity fish species than neighbouring kelp beds, highlighting the acceleration of tropicalization processes facilitated by urchin grazing. In contrast, proportionally more cool-affinity fishes colonize barrens at high temperate latitudes, contributing to community lags with ocean warming in these regions.

Main conclusions

Our findings implicate urchins as drivers of ecological change, in part by affecting ecological resilience to warming.

Item Details

Item Type:Refereed Article
Keywords:climate change, community temperature index, habitat change, kelp forest, species distribution, thermal sensitivity, urchin barren
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Understanding climate change
Objective Field:Global effects of climate change (excl. Australia, New Zealand, Antarctica and the South Pacific) (excl. social impacts)
UTAS Author:Stuart-Smith, RD (Dr Rick Stuart-Smith)
UTAS Author:Edgar, GJ (Professor Graham Edgar)
ID Code:150886
Year Published:2022
Deposited By:Ecology and Biodiversity
Deposited On:2022-07-04
Last Modified:2022-11-09

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