Rapid and versatile routine measurements of plankton biovolumes with BACCHUS

A semi-automated biovolume measurement application called BACCHUS (Biovolume Analysis Cum Calculus and High Utility Statistics), based on an image-analysis program combined with a database, was developed. With this application, biovolumes of plankton taxa can be determined while counting routine samples. Statistical analyses of the ln-transformed results are performed on- line. The width of the 95% confidence interval is calculated and indicates the precision of the calcu- lated mean. By setting limits to the maximum allowed width of the interval, the extent of desired precision can be defined. For our laboratory, we decided that the limits of the confidence interval must be <0.2 ln units above or below the mean of the ln-transformed results. As soon as this criterion is reached, the user can stop measuring, thereby minimizing the number of measurements necessary to reach a mean biovolume which is sufficiently precise. Other advantages of the BACCHUS application are a very flexible input of master data, output of stored data and a user-friendly operation environ- ment. BACCHUS is very easy to customize because it does not require any expertise in database programming.