Examples of manually labeled rhodoliths (left) and the corresponding segmented rhodoliths (right).

White rectangles with a green dot mark “dead” calcareous algae labeled regions and rectangles with a yellow dot mark “stressed” calcareous algae labeled regions. The pixel regions of “live” or “stressed” calcareous algae are marked red.</p

Chamber configurations for the CCF design.

Chamber configurations for the CCF design.</p

The correlation loading plot obtained after PLS-regression.

<p>It was computed with light (), flow rate (), amount of sediment (, ), and time () as predictors (blue dots), and HSV-variables (), relative size (), photosynthetic efficiency (<i>P</i>) and sediment coverage (<i>SC</i>) as responses (red dots). The outer circle represents 100% explained variance and the inner circle 50% explained variance for the different variables.</p

A screenshot of the BIIGLE system in a web-browser.

<p>The images of the calcareous algae were examined and labeled using the BIIGLE system. Images can also be zoomed to examine more details. The experts were allowed to select single point label or customizable frame labels. The single point labels are represented as filled colored circles, the customizable frame labels are represented as white outlined rectangles with a filled colored circle in the upper left corner of the individual rectangle. The colors of the filled circles indicate the class of the individual label. Red is representing “live” calcareous algae, yellow “stressed” calcareous algae, green “dead” calcareous algae and Pink “bare substratum”.</p

The correlation loading plot obtained after PLS-regression.

It was computed with light (), flow rate (), amount of sediment (, ), and time () as predictors (blue dots), and HSV-variables (), relative size (), photosynthetic efficiency (P) and sediment coverage (SC) as responses (red dots). The outer circle represents 100% explained variance and the inner circle 50% explained variance for the different variables.</p

Example of an image recorded during the experiment completion and its different processing results of the pre-processing.

The original image (A), the result of the illumination correction (B), the result of the color correction (C) and the difference image (D) are displayed. In the original image (A) the color reference plate is located in the upper part, providing input for the pre-processing. The two calcareous algae samples are located below the reference plate. Comparing the result image from the illumination correction (see Illumination Correction section for details) with the original image a slight decrease in brightness can be noticed. Due to the stable illumination conditions during image recording only little differences between the images can be recognized visually. The color correction (see Reference Plate Detection, Color and Zoom Correction section for details) is changing the colors very little as only minor color shifts appear. Most of the visible differences in the difference image are caused by the illumination correction.</p

Illustration of color reference plate and camera setup.

<p>On the left the original color reference plate, used to obtain color constancy within the experiment, is displayed. Colors are referring to the RGB triplets (top-down): (0,0,255), (255,0,0), (255,0,255), (0,255,0), (0,255,255), (255,255,0). On the right a schematic layout of the underwater camera setup is presented, consisting of a water filled cylinder containing the sample, the color reference plate and the camera in the waterproof housing fixed on a tripod.</p

The correlation loading plot for the photosynthetic efficiency (<i>P</i>).

<p>It was obtained after PLS-regression with the HSV-variables () as predictors (blue dots), and photosynthetic efficiency (<i>P</i>) as response (red dot). The outer circle represents 100% explained variance and the inner circle 50% explained variance for the different variables. The plot showed that the predictor variables are highly correlated to the response variable. A prediction of the photosynthetic efficiency using the HSV-values is therefore possible for our experiment.</p

The relative position of the sample can have an effect on the segmentation result.

<p>Both images are displaying the same calcareous algae sample, but were recorded at different time points during the experiment. The calcareous algae sample was rotated around an axis not perpendicular to the image plane.</p