# Large-Scale Permanent Slide Imaging and Image Analysis for Diatom Morphometrics
## 3 Results  
Applying our automated approach, we analysed about 12,000 valves from 72 slides of samples taken from 21 different depths within sediment core PS1768-8 covering marine isotope stadiums (MIS) 1, 2, 5 and 6 (see Table 11). The according CSV file is supplied in the Supplementary Materials. Because this core originates from the central area of the opal belt it consists mainly of diatoms, which are generally well to moderately preserved and do not show significant effects of dissolution on the preserved diatom valves [8]. Our observations substantially expand the size ranges known for this taxon compared to previous reports (see Table 1 and Figure 6).  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Apical Axis Length (\(\mu\)m)**} & \multicolumn{6}{c}{**Transapical Axis Length (\(\mu\)m)**} \\ \hline
**MIS** & \(n\) & **min** & **max** & **mean** & **median** & **min** & **max** & **mean** & **median** \\ \hline
1 & 2853 & 11.3 & 101.1 & 36.8 & 34.1 & **3.7** & 13.5 & 9.0 & 9.1 \\
2 & 5691 & **11.1** & 95.5 & 35.2 & 33.1 & 4.6 & **14.2** & 9.2 & 9.2 \\
5 & 2610 & 12.8 & **118.9** & 37.0 & 33.6 & 4.1 & 14.1 & 9.0 & 9.1 \\
6 & 705 & 14.8 & 94.4 & 36.1 & 33.5 & 5.6 & 13.8 & 10.0 & 10.0 \\ all & 11859 & 11.1 & 118.9 & 36.0 & 33.4 & 3.7 & 14.2 & 9.2 & 9.2 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary on _F. kerguelensis_ valve sizes from our investigation. Extreme values are highlighted in bold type.  
Figure 6: _F. kerguelensis_ valves of extreme apical axis lengths (101.0 to 119.9 \(\mu\)m). Left: MIS 1, all others come from MIS 5.  
The values with the longest apical axis were found in the MIS 5 samples. To test whether the species shows a different distribution of apical axis lengths between this and the other MISs, Kolmogorov-Smirnov tests were used (see Tables A2 and A3). MIS 1 represents the most recent material we analysed and thus the best to be compared to the investigations of [16; 17; 18]. Between this and MIS 5 the two-sided test did not support a significant difference. This indicates that the occurrence of very large valves is not caused by a general shift in the valve length distribution of the species during MIS 5. The overall distribution of apical axis length is right-skewed (see Figure 7 top). To the contrary, distribution of the transapical axis length is symmetric (see Figure 7 bottom) but platykurtic (test for non-normality; see Appendix C). For individual analysis of each MIS see Figures A1 and A2 in Appendix D.  
Ca. 5.4% of all valves (505 in total) are sized outside the dimensions reported in the literature [16; 17; 18], depicted by the dashed rectangle in Figure 8.  
We modelled the relationship between transapical and apical axis length using linear models with an increasing order of polynomial terms (see Figure A3). A third-order polynomial gave a better fit (with a R\({}^{2}\) of 0.496) than a first- or second-order regression, and lowest values of the Akaike resp. Bayesian information criteria. Adding a term of order 4 did not significantly improve the model fit. This means that, in spite of what might be suggested by the symmetric distribution of transapical valve measurements (see Figure 7, bottom), the transapical tends to increase with apical length only up to about 50 \(\upmu\)m valve length. Above this value, the transapical length stays roughly constant or even decreases slightly with increasing apical length.  
Figure 7: Distribution of basic valve dimensions along the apical and transapical axes for all MISs. Red lines depict the mean, black lines the median values, and blue lines the estimated density curves. Dashed lines depict the valve size ranges reported in the literature. Whilst for the apical axis the distribution is right-skewed, the distribution of lengths of the transapical axis is symmetrical but not normal (platykurtic, i.e., has thinner tails than a normal distribution).