Dataset: Coral growth data

Methodology:

To create standardized units of coral, nine ~6-8 cm length branches of Acropora millepora were collected from twelve separate colonies (108 branches total) within Votua’s MPA during October 2014 and individually epoxied (Emerkit) into the cut-off necks of inverted plastic bottles. These were then anchored on the reef by screwing them individually into an upturned bottle cap embedded within the substrate (see Video S1 at http://www.int-res.com/articles/suppl/m586p011_supp/ for an example of this experimental method) and allowed to acclimate for ~1 month. Following the acclimation period, corals were detached from the substratum and weighed in the field using an electronic scale (OHAUS Scout Pro) enclosed within a plastic container that was mounted to a tripod holding it above the water surface. Eighteen to 24 hrs before the weighing session, each coral’s bottle-top/epoxy base was brushed with a toothbrush to remove fouling organisms. Before weighing, each coral was gently shaken 30 times to remove excess water, and then weighed, immediately placed back into the water, and reattached to the substrate. 

Initial mass of coral branches did not differ among treatments (Linear mixed effect (LME) model, p = 0.328; mean mass ranged from 13.4–18.9 g).

Corals were subjected to one of nine experimental treatments for 33 days: (1) direct contact with four thalli of Galaxaura rugosa (live seaweed), (2) close proximity (i.e. ~1.5cm away, no contact) to four thalli of Galaxaura, (3) direct contact with four Galaxaura mimics (microfiber dust cloth), (4) close proximity to four Galaxaura mimics, (5) direct contact with four Sargassum polycystum thalli (live seaweed), (6) close proximity to four Sargassum thalli, (7) direct contact with four Sargassum mimics (plastic aquarium plants), (8) close proximity to four Sargassum mimics, or (9) no seaweed or mimic exposure (control) (n = 9-13 per treatment).  

Sampling and analytical procedures:

At day 33, corals were detached from the substratum and reweighed in the field as previously described. Following the weighing session, corals were separated from their bottle/epoxy base and were weighed separately to determine changes in coral mass alone during the 33-day period (i.e. without the weight of the epoxy and bottle neck base).

Differences in relative growth (as a percentage of initial weight) among treatments were analyzed using LME models in the R package nlme [Pinheiro et al, 2017], with coral colony used as a random factor in all analyses. When necessary, the varIdent argument was used to control for heteroscedasticity. Subsequent pairwise comparisons were performed using the generalized linear hypothesis test (glht) in the R package multcomp [Hothorn et al, 2008].