MEPS 223:157-165 (2001)  -  doi:10.3354/meps223157

ABSTRACT: The methods currently employed for seagrass production estimates include biomass, marking and metabolic techniques, the latter including the O₂ and ¹⁴C methods. Both are currently in general use and have generated a great deal of seagrass-production data. In this work, we measured carbon incorporation rates in Zostera marina L. using the stable carbon isotope ¹³C as a metabolic tracer. We tried this method in an attempt to overcome the 2 major methodological problems of the O₂ and ¹⁴C methods, i.e. the limitations when measuring low production rates and the hazardous and laborious handling of radioactive isotopes, respectively. To validate the ¹³C method we compared it with the classical O₂ and ¹⁴C methods in microcosm experiments. The 2 carbon-tracer techniques were in overall good agreement (¹³C = 0.12 + 1.03 x ¹⁴C; R² = 0.964, p < 0.001, n = 10). Production rates derived from the ¹³C method were on average 1.34 ± 0.03 (n = 42) times higher than those obtained with the O₂ method (¹³C = 0.99 + 1.15 x O₂; R² = 0.788, p < 0.001, n = 42), suggesting that for short incubation lengths (in this study between 0.5 and 4.0 h) the ¹³C method provides estimates very close to gross production. The pros and cons of all 3 methods are critically discussed.

KEY WORDS: Seagrass production · Zostera marina · Stable carbon isotopes · O₂ method · ¹⁴C method · ¹³C method