Significance of advective transport of Ulva lactuca for a biomass budget on a shallow water location

Ulva lactuca biomass, growth and grazing rates and drifting biomass was measured in the early summer period at a 1 m deep near-shore station in a sheltered bay in Roskilde Fjord, Zealand, Denmark. The expected biomass was calculated for each sampling date and compared with the measured. Regression analyses were performed between drifting biomass and the relative difference between measured and calculated biomass (R2 = 0.65, P < 0.054) and between wind velocities and drifting biomass (R2 = 0.42, P < 0.057). Although not significant at the 5% level, the results indicated that advective transport was significant for balancing the biomass budget of U. lactuca. It is therefore proposed that dynamic modelling of U. lactuca should be based on a transport/dispersion model.