ZooScan system analysis and output.

<p>Using ZooScan to measure the size and composition of zooplankton at Lady Elliot Island: a) Scanned image of a zooplankton subsample, and b) examples of digitally-separated vignettes.</p

Critical prey density foraging threshold.

<p>Logistic regression of reef manta ray behaviour (feeding n = 17, non-feeding n = 12) in relation to zooplankton biomass (mg m^-3). The black dashed line represents the critical density threshold of zooplankton biomass required to trigger reef manta ray feeding from <i>in-situ</i> sampling (11.2 mg m^-3) and the red dashed line represents the theoretical calculation of the density threshold (25.24 mg m^-3).</p

Oceanographic drivers of zooplankton biomass and manta ray feeding.

<p>Final generalized additive models for: a) Zooplankton biomass as the response and <i>Trip</i>, <i>Time to low tide</i> and <i>Temperature</i> as predictors (r² = 42.8%, n = 70), and b) Manta ray behaviour (0 = non-feeding; 1 = feeding) as the response and <i>Month</i>, <i>Time to low tide</i> and <i>Temperature</i> as predictors (r² = 5.3%, n = 2973). For each plot, the y-axis is a relative scale, and its magnitude reflects the importance of each variable. Dashed lines and error bars represent 95% confidence intervals.</p

Sampling sites of Lady Elliot Island.

<p>Map of Lady Elliot Island (24°07’S, 152°43’E) in the southern Great Barrier Reef, Australia. Plus signs indicate the three <i>in-situ</i> sampling sites of Lighthouse Bommie, Sunset Drift and Encounters. High-resolution image obtained from the Quickbird satellite (Geoimage Pty Ltd., <a href="http://www.geoimage.com.au" target="_blank">www.geoimage.com.au</a>) and processed using ArcGIS 10.</p

Zooplankton size spectra analysis.

<p>Normalised Biovolume Size Spectra of the zooplankton community showing higher biovolume across all size classes (body volume intervals) when reef manta rays are feeding (n = 17) than when non-feeding (n = 12) or absent (n = 21). Dashed lines represent 95% confidence intervals.</p

Zooplankton composition and manta ray foraging behaviour.

<p>Zooplankton composition at Lady Elliot Island in relation to reef manta ray behaviour showing little differences in composition: a) Feeding (n = 17), b) Non-feeding (n = 12), and c) Absent (n = 21). Nonmetric multidimensional scaling analysis of the community: d) with no transformation, and e) after a presence-absence transformation (n = 50).</p