Modeling of benthic reference values for species richness, Shannon and AMBI

In the Dutch national benthic monitoring program, two significant changes occurred in the period 2014-2016. In 2014, the sampling device used in the Delta waters in the South-West of the Netherlands was accidently changed in 2016 and 2017, from the analysis of two manual cores samples taken from a boxcore sample (combined area 0.015 m2 and pooled to 0.1 m2), to the analysis of the complete boxcore sample (0.078 m2). Note that the sample area decreased, and that pooling will add a beta-diversity component due to the sample coverage of a larger area. As a result of this change, the benthic reference values for the BEQI2 assessment of the benthic data (Van Loon et al. 2015) are not applicable to these unpooled boxcore samples. The aims of this study are (a) to develop correction factors for BEQI2 references values, calculated for small core samples pooled to 0.1 m2, to reference values calculated for unpooled box core samples; and (b) to model benthic reference values for water bodies with a small amount of benthic data using a habitat quality model.