Opinion: Missing half the picture, focus on stony corals during bleaching events has left critical knowledge gaps in our understanding of reef-scale bleaching and recovery

Abstract

Stony corals make up the bedrock of coral reefs, but they are not the only benthic organisms that contribute to reef diversity. Sponges, ascidians, octocorals, anemones, macroalgae, and more add directly to the complexity and biodiversity of reefs (Figure 1). Addi�onally, they provide food and habitat for many mobile species including specialist to non-stony coral habitat builders (Pratchet 2007;Epstein and Kingsford 2019). The majority of studies on reef impacts focus on how stony corals have been affected and o�en include other groups only when they are nega�vely impac�ng stony coral health, such as compe��on with or overgrown of corals by algae or sponges (Coll et al. 1987;Lapointe et al. 2007;Clements and Hay 2023), or recruitment of stony coral larvae to coralline algae (Webster et al. 2011;Tebben et al. 2015;Tanvet et al. 2022). While it is important to understand how stony corals respond to stressors as they build the founda�on of reef structures, it is also important to understand how all habitat building species may be affected in order to disentangle reef-scale dynamics. This includes so� bodied habitat formers, such as octocorals, anemones, and macroalgae, which leave litle or no trace of mortality a�er an acute stress event (Steinberg et al. 2020) and therefore need to be surveyed and sampled as bleaching events unfold. Coral reef phase shi�s, where reefs that are stony coral dominated become dominated by other taxa a�er disturbance events are becoming increasingly common (Norström et al. 2009;Bell et al. 2013;Baum et al. 2016), as such it is par�cularly important to understand how all habitat-forming taxa on reefs respond to heat stress in order to predict changes to future reef composi�on.