Diameter classes histograms of worm tubes measured in thin section with ImageJ© software. Density of tubes is shown. Maximum diameters are recorded in March 2014. In September 2013 and March 2014, many tubes with small diameters occur. Minimum and mean diameter of the worm tubes continuously increase from September 2013 to August 2014. The greatest/largest difference between maximum and minimum diameter is recorded in March 2014 while the least/lowest difference occurs in August 2014. The column showing the name of the season contains the list of the five sample areas for each seasonal sampling set with the abbreviations: AO1, AO2, etc.