Temperate reefs from around the world are becoming tropicalised, as warm‐water species shift their distribution towards the poles in response to warming. This is already causing profound shifts in dominant foundation species and associated ecological communities as canopy seaweeds such as kelp are replaced by tropical species. Here, we argue that the cascading consequences of tropicalisation for the ecosystem properties and functions of warming temperate reefs depend largely on the taxa that end up dominating the seafloor. We put forward three potential tropicalisation trajectories, that differ in whether seaweeds, turf or corals become dominant. We highlight potential gains to certain ecosystem functions for some tropicalisation endpoints. For example, local benthic fish productivity may increase in some tropicalised reefs as a higher proportion of primary production is directly consumed, but this will be at the expense of other functions such as carbon export. We argue that understanding these changes in flows of energy and materials is essential to formulate new conservation strategies and management approaches that minimise risks as well as capture potential opportunities. Regardless of which trajectory is followed, tropicalised systems represent largely novel ecosystem configurations. This poses major challenges to traditional conservation and environmental management approaches, which typically focus on maintaining or returning species to particular locations. We outline management practices that may either mitigate predicted structural and functional changes or make the most of potential new opportunities in tropicalised reefs. These include marine protected areas to increase resilience and connectivity, the development of new fisheries that target range‐expanding invaders, and assisted evolution and migration strategies to facilitate the dominance of large habitat formers like corals or seaweeds. We highlight important ecological and ethical challenges associated with developing novel approaches to manage tropicalised reefs, which may need to become increasingly interventionist. As technological innovations continue to emerge, having clear goals and considering the ethics surrounding interventions among the broader community are essential steps to successfully develop novel management approaches. A plain language summary is available for this article.

Knowledge about the coastal zooplankton of the south-eastern Indian Ocean is limited, with few studies having compared assemblages across the latitudinal range of the western seaboard of Australia. The dominant oceanographic feature in this region is the Leeuwin Current, which transports warm, lower-salinity, tropical waters southward along the shelf-edge. This study examined data collected by Australia’s Integrated Marine Observing System at three coastal National Reference Stations located at 22°S 114°E, 32°S 115°E and 34°S 122°E. Spatial and temporal patterns in zooplankton abundance, composition and diversity were investigated, and differences in assemblage structure, particularly with respect to copepods, were related to oceanographic conditions. Clear dissimilarities among copepod assemblages were observed, becoming weaker in winter owing to enhanced connectivity of species driven by alongshore and cross-shelf transport in the Leeuwin Current. Both physical and biogeochemical factors were significant in structuring copepod assemblages, with seawater density, incorporating temperature and salinity, exerting the greatest influence. The results suggest that both broad-scale latitudinal gradients and mesoscale events contribute to variation in zooplankton assemblages in these waters. This study provides the first detailed comparison of zooplankton assemblages among the north-west, south-west and southern coastal waters of Western Australia, and enhances understanding of the processes influencing zooplankton distribution and structure.

The cover image relates to the Research Article https://doi.org/10.1111/ddi.13484 “Sea temperature and habitat effects on juvenile reef fishes along a tropicalizing coastline” by McCosker et al. A tropical vagrant blue‐spine unicornfish (Naso unicornis) juvenile swims among kelp in the temperate waters of Sydney, Australia. Photo credit: John Turnbull.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.