An estimated 2.4 tonnes of drifting sea lettuce is entering Tauranga's Waikareao Estuary on each cycle of the tide during the worst affected times of the year.
The impact of sea lettuce on the estuary was revealed in studies carried out by Intercoast PHD student Alex Port.
It follows revelations earlier this week that the fumes from rotting sea lettuce in Matua had made two boys vomit, with an expert warning the gas could even kill.
Mr Port was a guest speaker at yesterday's inaugural Tauranga Harbour symposium organised by Environment Bay of Plenty. It drew nearly 200 people including politicians and representatives of iwi and environmental organisations.
He based his estimate of drifting sea lettuce on the nets set at the entrance to the estuary. Each net was catching 15kg to 20kg of wet sea lettuce per tidal cycle.