Effects of future climate on coral-coral competition

with P. astreoides reduced Fv/Fm at the point of contact by 100%, regardless of climate condi- tions (Fig 1B, climate x contact, p = 0.643). Neither climate condition, nor competition, affected Fv/Fm in non-contact areas (Fig 1C & 1D). Temperature and OA also did not signifi- cantly impact the size of the lesion formed at the point of contact for either coral species (Fig 2). Areas of P. astreoides in contact with O. faveolata exhibited a 62.5% reduction in Fv/Fm under present conditions, but reductions of 100% under future OA and warming conditions at day 7 (Fig 3A, climate x contact, p = 0.036). For O. faveolata, contact with P. astreoides reduced Fv/Fm by 77–84% under both climate conditions (contact: p<0.001), and effects did not vary as a function of OA and temperature (Fig 3B; climate x contact: p = 0.278). At day 14, the patterns for P. astreoides were similar to those on day 7. Contact reduced P. astreoides Fv/ Fm by 45–62% (contact: p<0.001), but there was no longer a significant contact x climate inter- action at day 14 (Fig 3C, p = 0.660). For O. faveolata, patterns on day 7 persisted through day 14; competition reduced Fv/Fm by 84–100% (Fig 3D p<0.001), with no significant difference between climate conditions. As with the P. astreoides-M. cavernosa interaction, negative effects of competition on Fv/Fm were restricted to areas of direct contact. For P. astreoides, areas not Fig 2. Lesion size (means ±SE) for Porites astreoides and Montastraea cavernosa at Day 7. Only corals in direct

contact were included in the analysis. Evaluated via a two-way permutational ANOVA comparing climate and species. Dots represent individual data points. N = 6. https://doi.org/10.1371/journal.pone.0235465.g002 PLOS ONE Climate change alters coral-coral competition PLOS ONE | https://doi.org/10.1371/journal.pone.0235465 August 13, 2020 7 / 16