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Browsing by Subject "Decomposition"

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  • Bechtold, Cameron (2022)
    As the world urbanizes at a rapid rate, urban encroachment into coastal waters has the potential to reshape global carbon cycles by modifying organic matter decomposition processes. Litter decomposition is regulated by the litter quality, environmental conditions, and the decomposer community. This study aims to investigate if different coastline characteristics (urban/hardened versus natural/vegetated) have localized differences in decomposition rates and litter stabilization. To test this, the Tea Bag Index (TBI) has been applied to aquatic systems by including a “leaching factor” to initial masses. By using uniform litter in aquatic systems, the litter quality and moisture conditions are fixed so that other environmental conditions and the decomposer community can be considered for their impact on the rate of decomposition. Three pairs (urban and natural) of sites were selected around Helsinki, Finland in the brackish coastal water of the Baltic Sea in the summer of 2021. At each site, five green and rooibos tea bags were placed with a temperature logger, and on days 15, 29, 43, 60, and 84 a tea bag of each type was removed, dried, and weighed. Additionally, water quality measurements were collected using a YSI multiparameter sonde. There was no significant difference in the decomposition rate nor stabilization factor between urban and natural sites, although, the rate calculated according to the TBI-methodology differed from the rate determined by fitting a model to the observations. Despite no significant difference, the stabilization factors were higher than average in similar environments and are indicative of efficient litter decomposition in the waters around Helsinki. Water temperature was significantly higher, and turbidity was significantly lower at natural sites. Therefore, the cooler waters and inferred higher hydrodynamic forces at urban sites may have counteracted their individual effects on the rate of litter decomposition. In fact, since the decomposer community at natural sites is suggested to be more diverse, the rooibos tea at natural sites may have begun to stabilize, thus, implying that the study period was too long. Overall, this study found that coastlines currently have no clear localized effects on litter decomposition, but in the future, this may begin to change.