Aim: Compare 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. Location: South-Western Australia from Port Gregory to the Recherché Archipelago. Methods: Surveys of Labridae fishes were conducted in 2006 and repeated in 2015across 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. Results:In 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 conclusions:Our 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 warmtemperate assemblages and the potential trajectory of change for cool-temperate assemblages under a warmer future. K E Y W O R D Sassemblage shifts, climate change, endemic fish, Labridae, marine, sea surface temperature, South-Western Australia

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Turning manure into gold The potential of methane-producing bacteria to meet future energy needs At a time of global warming, growing

Climate change is rapidly altering the distributions of species and the composition of communities that have evolved over evolutionary time scales. Quantifying changes in species distributions and abundance in response to warming is critical to understanding how these changes modify structure, function and services provided by recipient communities. Changes in size structure of warm- and cool-affiliated species is an important indicator for climate-driven species redistributions over time, and has received relatively little attention. We quantified changes in length and biomass distributions of 25 species of Labridae fishes from 112 sites spanning 2000 km across a warm-cool temperate transition zone in south Western Australia. Length and biomass data were collected in 2005-2006 and 2014-2015 using diver operated stereo-video. In the decade between sampling events, south Western Australia experienced an extreme marine heatwave followed by repeated summers of anomalously warm ocean temperatures. Biomass of tropical and subtropical species increased 10-fold and 3-fold, respectively, between 2006 and 2015, whereas temperate species biomass remained relatively stable. In 2014-2015, the abundance and biomass of tropical species (e.g. Scarus ghobban) increased in the warmest regions and established multiple size classes poleward of their recorded 2005-2006 distributions, suggesting successful overwintering and recruitment where viable populations were not recorded in 2005-2006. Large, slow-growing temperate species such as Achoerodus gouldii and Bodianus frenchii decreased in small and medium size classes in warm regions. Our findings report a substantial change in the size structure and composition of labrid assemblages over a decade of climatic variability.