Decay of leaves and macroalgae and their relation to detrital food webs

Background/Question/Methods

This project is addressing if decaying macroalgae and leaf detritus play a major role in the detrital pool of a 7^th-order karst riverine system. Decay rates and change in carbon and nitrogen isotopic ratios of Cladophora, Platanus occidentalis, and a mix of Acer negundo and A. saccharinum were tracked during summer and autumn in three consecutive years. Packs of air-dried Cladophora, P. occidentalis, and Acer were placed in mesh bags and put in groups (n=4) in wire baskets. Seven baskets were submerged in riffle (20-30 cm) and deeper run (2 m) habitats.

Results/Conclusions

Summer Cladophora and Acer decayed significantly faster than Platanus at both depths and across seasons. Platanus had similar decay rates between depths during each season. Seasonality had a strong influence on decay rates, leading to greater mass loss of all three species in the warm summer and fall months compared to the cooler winter months. The implication of rapid Cladophora decay during warm seasons, plus few colonizing macroinvertebrate taxa, is that the decaying macroalgae may pass through only a decomposer food web before being remineralized as CO₂