The frequency distribution of individual body sizes in animal communities (i.e. the size spectrum) provides powerful insights for understanding the energy flux through food webs. However, studies of size spectra in rocky and coral reef communities typically focus only on fishes or invertebrates due to taxonomic and data constraints, and consequently ignore energy pathways involving the full range of macroscopic consumer taxa. We analyse size spectra with co-located fish and mobile macroinvertebrate data from 3,391 reef sites worldwide, specifically focusing on how the addition of invertebrate data alters patterns. The inclusion of invertebrates steepens the size spectrum, more so in temperate regions, resulting in a consistent size spectrum slope across latitudes, and bringing slopes close to theoretical expectations based on energy flow through the system. These results highlight the importance of understanding contributions of both invertebrates and fishes to reef food webs worldwide.

Proactive and coordinated action to mitigate and adapt to climate change will be essential for achieving the healthy, resilient, safe, sustainably harvested and biodiverse ocean that the UN Decade of Ocean Science and sustainable development goals (SDGs) seek. Ocean-based mitigation actions could contribute 12% of the emissions reductions required by 2030 to keep warming to less than 1.5ºC but, because substantial warming is already locked in, extensive adaptation action is also needed. Here, as part of the Future Seas project, we use a “foresighting/hindcasting” technique to describe two scenarios for 2030 in the context of climate change mitigation and adaptation for ocean systems. The “business-as-usual” future is expected if current trends continue, while an alternative future could be realised if we were to effectively use available data and knowledge to push as far as possible towards achieving the UN SDGs. We identify three drivers that differentiate between these alternative futures: (i) appetite for climate action, (ii) handling extreme events and (iii) climate interventions. Actions that could navigate towards the optimistic, sustainable and technically achievable future include:proactive creation and enhancement of economic incentives for mitigation and adaptation;supporting the proliferation of local initiatives to spur a global transformation;enhancing proactive costal adaptation management;investing in research to support adaptation to emerging risks;deploying marine-based renewable energy;deploying marine-based negative emissions technologies;developing solar radiation management approaches; anddeploying existing and new solar radiation management approaches to help safeguard critical ecosystems.