IMR Benthic Biomass Density Observation

OGC Feature + SOSA observation profile for per-taxon benthic biomass density (kg m-2) sourced from the Institute of Marine Research (IMR / Havforskningsinstituttet) regional baseline series. Acts as the fallback D_{pre,i} binding when MAREANO has no taxon coverage at index i. Carries per-taxon density with explicit uncertainty_kg_m2, ICES area annotation, and mandatory provenance.