Protocol Benthic Indicator Species Index (BISI): Protocol BISI for generic application (BISI v3). Version v170424.

Protocol Benthic Indicator Species Index (BISI) The Benthic Indicator Species Index (BISI) is a methodology developed to evaluate benthic habitat quality status or quality developments based on benthic community data. This page gives an overview of the methodology and applications and provides the available (background) information in the form of reportings, protocols and assessment tools. Developed BISI assessment tools and results of applications are made available here. BISI in short With the BISI indicator, the occurrence (either densities, biomass or presence/absence data) of combinations of specific indicator species are compared with predefined reference levels (BISI internal reference) for those species representing a good quality status. Basically, area-specific indices (indicator species with reference levels) are constructed with the BISI methodology. The most recent version is BISI v3, which comes with a protocol for application (see below). Additionally ‘Assessment tools’ for application including a manual in the assessment tools themselves are available. With BISI v3 the selection of indicator species and derivation of reference levels is part of the methodology and takes place at the level of (high aggregation) ecotopes (e.g. MSFD broad habitat types (EUSeaMap, 2021) or other ecotope classifications with clearly distinguishable benthic communities). Herewith, the BISI is equipped for generic application. BISIs at the level of ecotopes can be applied in other areas (within the same geographical region). BISIs for compiled (ecotope) areas can easily be constructed taking surface distribution into account. In case of sufficient and representative benthos monitoring data BISI-values (representative for the quality status) can be calculated and compared between assessment moments and/or between different areas. With the current methodology (BISI v3) indicator species are selected in a standardized way. Indicator species are selected at the level of ecotopes on basis of either being characteristic, being indicative for at least one of the (area specific) dominant disturbances, or being characterized by a combination of biological traits. Additionally, indicator species are preferably ‘smart species’ in such a way that potential differences in occurrences can be observed with realistic monitoring efforts and techniques (resulting in sufficient power of statistical tests). Selected indicator species should be present in the vicinity or have opportunities to return to the area of concern. Reference values are preferably obtained from suitable reference areas. When reliable reference data lack, (BISI) internal reference values are derived from current and maximum observed occurrences considering natural variation. Therefore a standardized decision scheme, taking recent historic data availability and current monitoring efforts, possible availability of reference (as indicated) or alternative areas, and suitability of monitoring techniques or possible alternative techniques, is used as guidance to retrieve area specific reference occurrences for BISI indicator species. The BISI provides an assessment of the general quality status of an ecotope (habitat) or compiled (aggregation of ecotopes) area and several specific assessments. Specific assessments should identify possible causes and effects of the observed quality status (and their importance), based on subsets of indicator species. Specifically developed for the benthic quality status in marine waters based on benthos; application in other systems and types of habitats and inclusion of other types of biota as indicators is however possible. At present applications and examples are available at (sub)regional scale, national scale, scale of Natura 2000 areas and Marine Protected Areas (MPAs) and for specific management areas (parts of MPAs with different protection status). BISI can be used to evaluate current quality status, trends in quality status and/or to determine the effect of management measures with specific monitoring designs (e.g. Before-After-Control-Impact designs). Threshold levels (management targets for desired sufficient good quality status) with regards to Marine Strategy Framework Directive (MSFD) or Habitat Directive (HD) application are suggested. BISI formula The BISI is calculated as the sum of observation to reference ratios for individual indicator species; optionally the relative importance of indicator species is distinguished in the specific assessments using indicator values (‘weights’); individual indicator species results are combined by calculating the geometric mean (logarithmic transformation). BISI = exp((1/S)*∑(IVi*ln(Oi/Ri))) BISI = Benthic Indicator Species Index; S = Number of indicator species included; IVi = Species specific Indicator Value calculated as species specific standard indicator value ivi (value between 0-1) divided by average indicator value ivavg; Oi = Observed occurrence species i (either presence/absence ratio, density or biomass); Ri = Reference occurrence species i (presence/absence ratio, density or biomass under reference conditions). (‘exp’ is similar to putting e to the power of the formula as indicated, which equals the inverse natural logarithm, as a back-transformation of the natural logarithm (ln) taken from the occurrence-to-reference ratios). Wijnhoven, S. (2023). Protocol Benthic Indicator Species Index (BISI): Protocol BISI for generic application (BISI v3). Version v170424. Ecoauthor Report Series 2023 - 01, Heinkenszand, the Netherlands.