Dataset: Percent tissue mortality of corals in experimental plots (Coral Biodiversity project)

Methodology: 

To evaluate the potential role of intraspecific competition in suppressing P. verrucosa growth in monocultures versus interspecific competition in polycultures, we conducted a subsequent experiment at the same backreef location (17°28′37″S 149°50′21″W) using a similar experimental approach to that described above. We assembled 60 plots (six by six grid space, 18 soda bottle caps embedded) that contained one of five treatment configurations (n = 12 plots per treatment, 576 P. verrucosa total):

1) six live P. verrucosa; 12 bottle tops with epoxy but lacking coral

2) 12 live P. verrucosa; six bottle tops with epoxy but lacking coral

3) 18 live P. verrucosa

4) six live P. verrucosa, six P. rus, and six A. hyacinthus (hereafter live polyculture)

5) six live P. verrucosa; six dead P. rus and six dead A. hyacinthus (hereafter dead polyculture)

Corals were attached to plots at randomized locations by screwing the corals into the bottle caps embedded within each plot. At two and seven months, we assessed the percentage growth and tissue mortality of individual corals in each plot as described above. At seven months, four plots were excluded from our analyses where corals had been heavily predated by the pin cushion star Culcita novaeguineae. We observed this event in the field, it occurred for only four of our 60 plots, and it occurred only on these adjacent plots, so we considered it to be a nontreatment-related disturbance that should be excluded. Colonization of each plot by benthic macroalgae was assessed at two months but not at seven months, due to macroalgae absence among plots at that time. As above, percent cover of macroalgae was determined via photographs using ImageJ (version 1.8.0_121), coral tissue mortality was estimated visually, and corals and their epoxy/bottle-top base were wet-weighed in the field to determine changes in mass. At the end of the experiment, corals were successfully separated from their respective epoxy/bottle-top base and were used to determine, via subtraction, the percent coral mass change throughout the experimental period.

Sampling and analytical procedures:

We used permutation-based, LME models in the R package predictmeans to compare differences in the percentage mass change and tissue mortality of P. verrucosa corals in each treatment. In each analysis, plot type (e.g., 18 live P. verrucosa) was treated as a fixed factor, and individual replicate plots were treated as a random effect nested within plot type.