Norwegian Sensitivity Index (NSI) for marine macroinvertebrates, and an update of Indicator Species Index (ISI)

Abstract

This report describes the development of a new Norwegian species-sensitivity based index (NSI) for assessment of ecological quality status, and its comparison with the AMBI index. AMBI is an extensively used index in Europe, including Norway. Species sensitivity assignments of 516 taxa common to NSI and AMBI were compared. Significant discrepancies were revealed in the assignments. The performance of NSI and AMBI along different types of pressure gradients was compared. In most cases, NSI showed a better correlation with different pressures compared to AMBI. This was most pronounced in the fjords and coastal areas in Norway, less so at offshore sites in the North Sea. As a common set of taxa was used, differences in the correlations with pressures were entirely caused by different sensitivities assigned to the same taxa by NSI and AMBI. The results indicate that the Norwegian classification system will be improved by replacing AMBI with NSI as sensitivity component in assessing ecological status in coastal waters. The Indicator Species Index (ISI) from 2002 was updated for 591 taxa using data up to 2011.