Effects of Vascular Plants on Seasonal Pore Water Carbon Dynamics in a Lotic Wetland

We examined pore water dissolved carbon pools among three wetland habitats defined by different plant species, and asked if temporal dynamics in C pools were related to temporal patterns of plant production. Concentrations of CH(4), DIC, and dissolved organic carbon (DOC) were measured monthly at 4 sediment depths over 1 year in Nymphaea odorata (NY), Proserpinaca palustris (PR), and Juncus effusus (JU) habitats. CH(4) and DIC differed among plant zones, depths, and month, while DOC averaged 1 mM regardless of depth, time, or zone. CH(4) and DIC increased linearly with depth in NY and PR, while both forms remained low (<0.25 mmole/L CH(4) and <1.5 mmole/L DIC), between 2 and 20 cm in JU in most months. Temporal patterns were also distinct among zones. CH(4) had limited seasonal fluctuations in NY and PR but had a distinct summer peak in JU. Conversely, DIC was highly seasonal in NY and PR, but not JU. Correlations between CH(4) or DIC and plant density or production were limited to 3 of 12 possible zone-depth combinations. Nonetheless, spatial and temporal patterns of CH(4) and DIC revealed significant differences among habitats, and suggest a species-specific influence on local C cycling within the wetland.