Multi-way exploration of regular environmental monitoring surveys

Offshore oil production is regularly monitored by environmental surveys of sediments close to the oil platforms. The type and abundance of benthic species at the different sampling sites are used as an indicator of possible pollution. Presently, the data for each survey are analysed independently of data from earlier surveys. Accordingly, it can be difficult to draw conclusions about trends and changes in the environmental state of the respective oil fields. In this work, it is suggested to organise the data from successive surveys in a three-way array, and use multi-way decomposition, here Tucker3, to identify possible changes in the benthic communities over the monitoring period. The feasibility of the approach is tested on two data sets from the Tordis and Embla oil fields, which both are located at the Norwegian Continental Shelf. The multi-way decomposition provides useful information about the changes over the monitoring period for both fields.