Fig. 2: Conceptual depiction of the different types of bleaching.
From: Spatially restricted coral bleaching as an ecological manifestation of within-colony heterogeneity
Bleaching can be quantified in terms of the spatial extent (i.e., bleached area, x axis) and the degree of algal symbiont loss (i.e., intensity, y axis). Based on a qualitative literature review and our own field observations (Fig. 1), we argue that different types of bleaching exist. Whole-colony paling is typically a transitory state to whole-colony bleaching triggered by continuous heat stress (green arrows). In contrast, spatially restricted paling and bleaching (purple arrows) may represent an ecologically distinct phenomenon that arises due to coral holobiont and environmental heterogeneity, distinct from whole colony bleaching or paling. Thus, colonies suffering spatially restricted paling/bleaching may not necessarily transition into full colony paling/bleaching and subsequent mortality, as indicated by the dashed lines. Likewise, spatially restricted and whole colony paling may not necessarily lead to bleaching. Quantifying bleaching in terms of the degree of algal symbiont loss (intensity) and spatial extent (bleached area) in conjunction with paling/bleaching dynamics over time will allow to resolve to what extent spatially restricted paling/bleaching results in full colony bleaching and in what cases it represents an ecologically distinct phenomenon. Created with BioRender.com under license number WM275BF87N.
