DEVELOPMENT OF CONTINUOUS, LINEAR MODELS FOR MARINE BENTHIC MACROPHYTES DESCRIPTION

The European Water Framework Directive has fostered indicator development, pertinent to biological quality elements, for ecological status assessment of coastal waters. For seaweed communities, the CFR index considers composition, abundance and physiological status, through four constituents (Richness, Opportunistic species, Cover, physiological Status) with arithmetically added scores (integers), summing up in [0, 100] and yielding ecological quality ratio (EQR) values in [0, 1]. Quantities C, O and S are expressed as percentages; R as small integer values; each one’s range of values is subdivided into 5 intervals, each attributed a score (integer). Discontinuous (step-wise) score values cause CFR (integer) discontinuities in the ranges [0, 10] and [90, 100], affecting pertinent EQR values and precluding certain ones (e.g. 0.04, 0.93, 0.98). Based on the major contribution of quantities C and O to CFR, the present work transforms their combined, discontinuous variation into a continuous, linear model, employing recently used concepts (PRI approach), applied in developing a continuous, linear, composite model for another benthic macrophytic index. Application to CFR underlines the flexibility of the RPI approach.