Browsing by Author "Fossati, Adriano Guido"
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- Unravelling fish communities´ structures in tropical to temperate reefs of eastern AustraliaPublication . Fossati, Adriano Guido; Assis, Jorge; Kim , Catherine J. S.Anthropogenic climate stress events are increasing in frequency and severity, threatening marine environments. Higher temperatures alter habitats of aquatic species, which cope by shifting their ranges poleward to more suitable conditions, referred to as tropicalisation. However, the resulting changes in species, functional group biomass, and thermal affinities are variable, with uncertainties remaining around primary drivers of change. Here, I characterise the structure and temporal changes in communities’ composition, trait-based functional group biomass, and community thermal affinity. I use fish biomass records from 2010-2023 across 33 eastern Australian reefs along a tropical to temperate environmental gradient. Fish community structure is assessed using hierarchical clustering and recursive partitioning with regression trees to infer how environmental conditions (sea surface temperature, primary productivity, wave height, distance to mainland and southern oscillation index) drive the clustering structure. The main community assembly process is assessed using the Dispersal Niche Continuum Index. Functional groups are defined clustering five fish traits, whereas the surveys’ Community Thermal Index is calculated by averaging the thermal mid-points of each species weighted by their mean biomass. Finally, a generalised additive model is applied to quantify the contribution of the same environmental conditions to the changes in the community thermal index. Contrary to expectations, clear tropicalisation patterns are absent at the community level, with limited changes in tropical species biomass. However, communities’ thermal affinities show some increase over time at similar latitudes, suggesting a progression of some tropical species polewards, driven mainly by the harshness of the previous winter as well as distance to land and wave height. Overall, communities display a certain stability in composition, despite the domination of dispersal assembly processes. These results highlight the importance of integrating various spatial resolutions in analyses with extended time series fish biomass data to better detect, predict, and protect marine communities’ alterations under global climate change.