Shifts in Labridae geographical distribution along a unique and dynamic coastline

Jack R C Parker,Scott Bennett,Joseph D Dibattista,Tanika C Shalders,Euan S Harvey,Benjamin J Saunders,Maria Beger

doi:10.1111/ddi.12980

Jack R C Parker, Scott Bennett + Show 5 more

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https://doi.org/10.1111/ddi.12980

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Abstract

AbstractAimCompare the distribution and composition of temperate Labridae (wrasse) assemblages on shallow water coastal reefs in South‐Western Australia between 2006 and 2015, after a decade characterized by both gradual ocean warming and severe heatwave events.LocationSouth‐Western Australia from Port Gregory to the Recherché Archipelago.MethodsSurveys of Labridae fishes were conducted in 2006 and repeated in 2015 across 112 reefs spanning 2,000 km of coastline, using diver‐operated stereo‐video systems (stereo‐DOVs). We used a hierarchical design with seven regions, four locations in each region, four reef sites in each location and twelve transects in each site.ResultsIn 2015, we found an increase in abundance of tropical and subtropical labrid species that were rarely observed in 2006. Three temperate species declined in abundance, which tended to be large and slow growing fish. Twenty‐two labrid species increased in abundance. There was also a discernible poleward shift in 20 of the 25 most abundant and representative labrid species from 2006 to 2015. The labrid community composition was explained predominantly by sea surface temperature (SST), physical reef structure and kelp (Ecklonia radiata) cover.Main conclusionsOur study reveals that labrid assemblages associated with the shallow water temperate reefs of South‐Western Australia have undergone rapid changes across almost 2,000 km of coastline, with warm‐temperate waters showing the strongest change. However, cool‐temperate waters on the south coast also showed significant changes in the composition of the labrid assemblages. Our findings provide important insights into the effects of warming and habitat loss on warm‐temperate assemblages and the potential trajectory of change for cool‐temperate assemblages under a warmer future.

Highlights

Temperate reef ecosystems sit at the interface of several vectors of rapid global change, making them important environments in which to quantify the response of biotic communities to a changing environment (Bennett et al, 2016)
Climate‐driven species redistribution, for example can lead to increased diversity and abundance of tropical species in temperate reef ecosystems, while at the same time driving the poleward retreat of temperate species (Bennett, Wernberg, Harvey, Santana‐Garcon, & Saunders, 2015; Cheung et al, 2012; Day, Stuart‐Smith, Edgar, & Bates, 2018; Vergés et al, 2014)
Our study has found that a significant change in the marine assemblage persists in the mid‐west, 4 years after this same heatwave, and can be observed in the south‐west fish assemblages too

Summary

Introduction

Temperate reef ecosystems sit at the interface of several vectors of rapid global change, making them important environments in which to quantify the response of biotic communities to a changing environment (Bennett et al, 2016). Climate‐driven species redistribution, for example can lead to increased diversity and abundance of tropical species in temperate reef ecosystems (i.e. tropicalization), while at the same time driving the poleward retreat of temperate species (Bennett, Wernberg, Harvey, Santana‐Garcon, & Saunders, 2015; Cheung et al, 2012; Day, Stuart‐Smith, Edgar, & Bates, 2018; Vergés et al, 2014). This can have important implications for the functioning of temperate reef ecosystems (Bennett, Wernberg, Harvey, et al, 2015; Wernberg et al, 2016). Benchmarking marine assemblages is important (Dayton, Sala, Tegner, & Thrush, 2000), as is re‐visiting these benchmarks periodically to gauge changes in marine assemblages over time

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