Warming-induced changes in reef fish community traits in the Southwestern Atlantic transition zone

Abstract

Marine communities are subject to alterations in environmental conditions, due to both natural variability and climate change. For instance, a rapid increase in sea surface temperature (SST) can modify spatial distribution patterns and abundances of reef fishes and therefore alter the overall diversity, structure, and functioning of these communities. Trait-based approaches may accurately detect community responses to such environmental changes, because species traits should reflect resource and habitat requirements. Here, we investigated temporal variability in reef fish trait composition and thermal affinity and assessed whether shifts are linked to recent ocean warming. We combined species traits related to feeding, growth, and survival with abundance data on reef fish from underwater visual census at 7 islands of the Southwestern Atlantic subtropical transition zone. All islands exhibited gradual trait reorganization from fish assemblages dominated by large-size species at the beginning of the time period to small, cryptobenthic species towards the end. The temporal changes in community weighted mean traits and the community thermal index were related to SST, indicating a numerical response of species to climatic variations. Tropical species are slowly becoming more abundant over time, while temperate species are becoming less abundant, reflecting an initial change in fish composition in this transition zone. These results have ecological implications leading communities to a faster turnover, lower food-chain complexity, and higher vulnerability to change. We highlight the importance of integrating traits and abundance time series data for a holistic understanding of reef dynamics and community responses to environmental variation, including global warming.

Projected climate‐driven shifts in coral distribution indicate tropicalisation of Southwestern Atlantic reefs

“…for most zooxanthellate corals in Brazil. In fact, there is a recent report of functional changes in reef fish assemblages at a subtropical area in Brazil, with an observed increase in the abundance of species with tropical affinity contrasted by a decrease in temperate species abundance over time (Silva et al, 2023). The potential tropicalisation of the SWA was also predicted to impact fish herbivory, that tends to reduce in the tropics, possibly causing a detrimental effect by reinforcing macroalgal dominance, while tends to increase in subtropical areas (Inagaki et al, 2020), which in turn could benefit corals by alleviating their competition with macroalgae since herbivores may reduce macroalgal abundance (Kumagai et al, 2018).…”

Patterns of reef fish taxonomic and functional diversity in the Eastern Tropical Pacific

“…This procedure is analogous to using sample-based rarefaction curves thus allowing for comparisons among locations, while controlling for the difference in sample size based on the MSA (Gotelli andColwell 2001, Magurran andMcGill 2011). This method has previously been used to compare fish assemblages from oceanic (Quimbayo et al 2019) and continental islands (Silva et al 2023).…”

Non-deterministic reef fish community assembly in an upwelling-influenced transitional subprovince of the southwestern Atlantic

“…A flexible diet and enhanced dispersal capability would have made it easier for a relatively large number of species to move around and explore transient environmental states provided by coastal upwelling. In fact, thermal affinity alone may not accurately explain changes in abundance in transitional regions with water stratification, range extension and depth distribution of species also being important (Gomes et al, 2023;Silva et al, 2023). The schematic representation shown in Figure 12 summarizes the assembly process discussed above.…”