The plant litter, which falls down from the vegetation growing on the marshes along the Schelde, is brought into the Schelde by the tide. This study contributed to the understanding and quantification of the ecological fate of this plant litter. Four aspects were considered:1. How much plant litter is accumulated at the boarders of the marsh by the tide? 2. How rapidly does the litter sink when it comes into the water? 3. How does the decomposition of the litter process? 4. How long time does the litter exist on the marsh or water? Four sampling stations have been selected on the Durme-marsh at Tielrode (Belgium). An area of 4*2 m² (4*4 m² in station 1) was sampled for plant litter at several dates during fall-winter 1999-2000. The double exponential model fitted the dry weight (D.W.) data of plant litter significantly (ANOVA p<0.05). The total amount of plant litter input into the Schelde estuary as POC by tide is between 9.20*10³ T/month (Max.) and 2.24*10³ T/month (Min.). Yearly amount is between 3.46* 104 T/year (Max.) and 8.98*10³ T/year (Min.). In a series of sinking rate experiments, it was determined that Salix (Willow) leaves sank within 1 to maximum 6 days, while Phragmites australis (Reed) stems floated for as long as 3 month. Also, willow leaves in the Schelde were rapidly decomposed (after 6 weeks) into small unrecognizable pieces. These findings help to explain why relatively low concentration of recognizable plant litter is found in the Schelde surface water, and why mainly litter of reed sterns is found on the marsh edges of the Schelde estuary.
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