Macrofaunal secondary production in a lagoon of the Po River Delta: an evaluation of estimation methods

The utility of calculating macrobenthic secondary production with estimation methods that have less rigorous data requirements than most classical techniques was investigated at three subtidal sites located in the Sacca di Goro, a brackish lagoon in the Po Delta area (Upper Adriatic Sea). Of the four estimation methods used, two that were based solely on biomass and individual body weight gave the lowest production estimates, while the two that also accounted for population or environmental parameters yielded higher values. Production estimates ranged from 16.6 to 107.4 g ash free dry weight (AFDW) m-2 yr-1 over the period studied. The secondary production of the few taxa for which growth and life-history had been formerly estimated in the Po Delta area, was calculated by means of a classical technique and compared with figures obtained with such empirical models. Average error varied from 13.5% to 75.6%, depending on the method used. Although they may be not preferable to classical techniques, empirical methods can provide a reliable and practical means of estimating secondary production in studies where logistical or economical constraints are operating