Factors and Criteria to Quantify the Bioproduction Potential of Coastal Areas and Presentation of a Simple Operational Index of Biological Value (IBV) for Coastal Management

There are major differences in the bioproduction potential of different coastal areas. The aim of this work is to review and discuss simple, operational criteria related to the bioproduction potential of coastal areas and to present and motivate an Index of Biological Value (IBV) for coastal management. This index is based on two key variables, which can be determined easily from bathymetric maps and data from standard monitoring programs: (1) the bottom area of the coast above the Secchi depth and (2) the topographical openness (or exposure) of the coastal area. The exposure is defined by the ratio between the section area of the coast and the enclosed coastal area. The boundaries of the coastal area should not be defined in an arbitrary manner but according to the topographical bottleneck method so that the exposure attains a minimum value. IBV is meant to be used to identify coastal areas with a high production potential so that preservation plans and remedial actions can be directed to such areas in a cost-efficient manner. Applying the index using a dataset including 478 coastal areas from the Baltic Sea, there were 5 (1%) extremely productive coastal areas (IBV>50), 43 (9%) very productive coastal areas (25<IBV<50), 209 (43.7%) productive coastal areas (10<IBV<25), 214 (63.0%) moderately productive coastal areas (1<IBV<10) and 7 (1.5%) low-productive coastal areas (IBV<1).