PMC

Conceptual diagram of the loss of coral cover owing to climate-change-related disturbances and the indirect and direct effects of OA on reef-associated macroinvertebrates.

Ratios of the densities or number of taxonomic units of macroinvertebrates at high-CO₂ relative to control sites (n = 35 surveys). Circles mark the estimated ratios, error bars show lower and upper 95% CIs (see electronic supplementary material, tables S5 and S6). Differences are significant (p < 0.05) if the error bars do not include the value 1.0.

Indo-Pacific reef communities with contrasting structural complexity. (a) Structurally complex reef (complexity rating value 4–5) with branching, tabulate and foliose coral morphologies. (b) Structurally simplified communities dominated by massive coral morphologies (complexity 2–3), as found in areas of chronic disturbance as shown here from one of the PNG CO₂ seeps. (c) Flattened reef lacking three-dimensional structure (complexity 0–1), as found after major disturbance. (Online version in colour.)

Partial effects plots showing the relationships of macroinvertebrates to CO₂, complexity and substratum type (HC: quadrats dominated by living hard corals; DS: substrata devoid of macrofauna). Circles indicate estimated marginal mean densities or number of taxonomic classes per 0.25 m⁻² (total counts = all organisms combined; mobile/sessile and calcifying/non-calcifying = densities of all mobile/sessile and calcifying/non-calcifying organisms combined). Error bars are lower and upper 95% CIs. Estimated percentage change (high CO₂ to control, complexity rating = 0 to complexity rating = 5, and DS to HC) and their 95% CIs are shown in the panels.