Abundance, Biomass, C- and N- Content of Flaccisagitta enflata and Mesosagitta minima (Chaetognatha)

Abstract The annual variability in abundance and biomass of Flaccisagitta enflata (Grassi, 1881) and Mesosagitta minima (Grassi, 1881), along with the C‐ and N‐content of their different maturity stages, were investigated in the South Adriatic Sea on a weekly basis throughout 1996. Increases in abundance and biomass of F. enflata [maximum 554 indiv. · (10 m³)^–1 and 16.3 mg C · (10 m³)^–1] and M. minima [maximum 336 indiv. · (10 m³)^–1 and 3.1 mg C · (10 m³)^–1] were found in summer and autumn, a time of intense reproduction for these species. Mean carbon content (as a percentage of dry weight) varied from 30.41 to 40.39 % among maturity stages for F. enflata, and from 27.73 to 39.31 % for M. minima. Nitrogen contents of both species were ～ 3 to 3.5 times less than carbon contents and varied less. Accurate estimates of chaetognath biomass as carbon should be based on the separate contribution of each maturity stage present in the total population.