Assessing the effectiveness of surrogates for species over time: Evidence from decadal monitoring of a Mediterranean transitional water ecosystem

The use of higher taxa or alternative approach to species surrogacy, such as the BestAgg procedure, could represent cost-effective solutions to avoid expensive species-level identifications in monitoring activities, especially on the long term. However, whether a set of surrogates would be effective in subsequent reiteration of the same assessment remains largely unsolved. We used a long-term dataset on macro-benthic assemblages to test the hypothesis that family-level and BestAgg surrogates which are effective for a limited period of monitoring could be successfully applied to quantify community patterns also in subsequent monitoring programmes. The effectiveness of surrogates in detecting temporal variations in assemblage structure as at species level remained basically unaffected over a decade. Recognizing once and for all if species surrogacy may have a practical value for monitoring will strongly depend on future assessments of the potential of surrogates to reflect community changes and to retain this prerogative over time. •Species surrogacy is advocated as a cost-effective approach in long-term monitoring.•Effectiveness of species surrogates over time is often assumed but rarely documented.•Decadal data series on lagoon macroinvertebrate were used to test this assumption.•Surrogates for species from a limited period were effective in subsequent monitoring.•Species surrogacy as routine practice in long-term assessments needs further evidence.