Data COTS density & reef substrate rugosity

Field surveys of crown-of-thorns seastar (COTS) population densities on 9 reef locations around Moorea, French Polynesia. Paired day and night surveys were performed every 6 months in triplicate 200m2 permanent-transects over a 2 year period. Reef substrate rugosity was also quantified

Estimation of the uncertainty in the three hierarchical stages of the model.

<p>The measurement error <i>σ_ε</i> corresponds to the uncertainty at the data stage, and all other variance components <i>σ</i> account for uncertainty in the process model, decomposed into the variability in trend (intercept and slope) of coral cover at the three spatial scales of habitat, reefs and sites.</p

Sampling design of the Long Term Monitoring Program showing the hierarchical levels of observation for the Cooktown-Lizard Island sub-region, one of six sub-regions of Australia's Great Barrier Reef.

<p>The sub-region is divided into three shelf-positions or habitats (inner reef (red arrows), mid-shelf reef (orange arrows), and outer reef (green arrows)). Each habitat is sampled on three sites (green dots) in each of two or three reefs. We highlight three sites at Carter reef from the outer reef habitat. Modified from original satellite images © Landsat and MODIS satellite imagery courtesy of NASA Goddard Space Flight Center and US Geological Survey.</p

Observed (dots) and fitted (curves) <i>Acropora</i> dynamics and associated parameter estimates and uncertainties.

<p>Coral dynamics are modelled at the three spatial scales within the sub-region of Cooktown-Lizard Island; with plotted lines for: habitats (top); reefs (middle); and sites (bottom). Shaded areas encompass 95% posterior predictive intervals around estimated coral trajectories and 95% credible intervals around model parameters. Top-right inserts on plots illustrate the linear and non-linear components of coral trajectories extracted from equations for <i>f_h</i>, <i>f_r</i> and <i>f_i</i>. Top-left inserts illustrate posterior distributions of linear parameters (from the top to the bottom, plotted lines are for: <i>θ₀</i> and <i>θ₁</i>, <i>δ₀</i> and <i>δ₁</i> respectively; refer to Fig. 2, see equations in main text). Intercept terms were indexed by 0 and slope terms by 1 and shown with their 95% credible interval. Thin black lines on reef- and habitat-scale plots (mid- and top-line) show the fitted dynamics of nested individual sites. Note different y-axis scales in inserted graphs. Estimates of coral cover trajectories are illustrated at the three sites at Carter Reef from the outer reef habitat depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110968#pone-0110968-g001" target="_blank">Figure 1</a>.</p

Directed Acyclic Graph showing how <i>Acropora</i> cover <i>y_ij</i> at a site <i>i</i> and time <i>j</i> is fitted in three stages.

<p>Here, the transformed data <i>y_ij</i> are modelled using a normal distribution with an expected value <i>µ_ij</i> and variance σ_ε. The expected value <i>µ_ij</i> is a function of four spatial scales (sub-region <i>f_s</i>, habitat <i>f_h</i>, reef <i>f_r</i>, and site <i>f_i</i>). Linear trends at sub-region and habitat scale are modelled using fixed effects (<i>β</i>, <i>γ</i>). At the site and reef scale, trend parameters (<i>θ</i>, <i>δ</i>) are considered as random. Trend parameters are denoted with the subscript 0 corresponding to the intercept and 1 corresponding to the slope. Random effects require specification of a variance component (<i>σ</i>), specified for each spatial scale of the model. Refer to the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110968#s2" target="_blank">methods</a> section for equations.</p

Dynamics of various communities surveyed at the reference reef locations.

<p>These nine locations consist of three sites (Haapiti: H, Tiahura: T, Vaipahu: V) × three water depths (6, 12, 18 m). Y-axes on the left indicate cover values (mean ± SE) of the sessile communities: reef-building corals and other benthic components. Y-axes on the right indicate densities (mean ± SE) of coral-predators: populations of the outbreaking seastar <i>Acanthaster</i> and butterflyfish assemblages. Arrows on the x-axes indicate the occurrence of the tropical cyclone <i>Oli</i>. Refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047363#pone-0047363-g005" target="_blank">Figure 5</a> for correlations between the dynamics of different communities. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047363#pone-0047363-g002" target="_blank">Figure 2</a> for an illustration of the changes observed on reefs.</p

Distributions and densities of <i>Acanthaster</i> feeding-scars as observed around Moorea through time.

<p>The dimensions of the circles are proportional to the abundance of scars (n scars per 2 min-towing section), and a color code is used to distinguish different abundance classes (refer to the legend). A mean relation of 8.6±1.7 SE scars per individual seastar was estimated during the outbreak (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047363#pone.0047363.s001" target="_blank">Table S1</a>). The positions of the three reference sites where reef communities were surveyed are also displayed on the graphs: Haapiti (H), Tiahura (T), Vaipahu (V). Original satellite image from © Google Earth.</p

A portion of Moorean outer-reef (6 m-depth on the site Vaipahu) is shown through time.

<p>(<b>A</b>) Corals dominate the healthy reef (coral cover >40%). (<b>B</b>) Algae have colonized dead coral skeletons following severe predation by the seastar <i>Acanthaster</i> (∼10% coral cover). (<b>C</b>) Mostly dead and weakened coral skeletons were swept away by a cyclone occurring at the end of the seastar outbreak (Lison de Loma et al. <i>unpublished data</i>) and colonizing algae once again dominate the devastated reef (∼5% coral cover). © Photos Mohsen Kayal.</p

Photographs illustrating the outbreaking seastar <i>Acanthaster</i> and its feeding-scars as found on colonies preyed upon.

<p>(<b>A</b>) An <i>Acanthaster planci</i> observed on a living tabular coral from the genus <i>Acropora</i>. (<b>B</b>) A partially-killed coral from the genus <i>Acropora</i> bearing feeding-scars left by successive predation events by <i>Acanthaster</i>: <b>1</b>) live portion of the colony bearing the pigmented coral tissue, <b>2</b>) freshly killed portion of the colony deprived of its pigmented living tissue (<1 day post-predation), <b>3</b>) recently killed portion of the colony covered by early colonizing algae and cyanobacteria (∼10 days post-predation), <b>4</b>) dead portion of the colony killed long ago and covered by turf algae (>3 weeks post-predation). © Photos Mohsen Kayal.</p