(Figure 1). Not surprisingly,
acetate mineralization was greatest in the spring and summer, and was
minimal during fall and winter. These results were presented at the last
VCR-LTER All-Scientists meeting.
We used a litter bag technique to measure decay of dead
S. alterniflora roots. Three clipped (no live roots) and 3 vegetated
(live roots) plots were established in both creekbank and interior sections
of Phillips Creek marsh. One month later, litter bags containing dead
Spartina alterniflora roots and rhizomes were buried in the marsh
plots. Every 2 months, a litter bag was removed from each treatment plot and
examined for decay and the presence of live roots. Samples were also
collected for bacterial abundance and activity (as acetate mineralization).
Over an 18-month period, little root decay was measured regardless of
the location or the presence of live roots. However, significantly
greater numbers of bacteria were evident in the vegetated plots of
both creekbank and interior marsh locations. Rates of acetate
mineralization were not correlated with bacterial abundance; rates were
greater in creekbank than in interior sediments regardless of the presence
or absence of live roots
(Figure 1). Not surprisingly,
acetate mineralization was greatest in the spring and summer, and was
minimal during fall and winter. These results were presented at the last
VCR-LTER All-Scientists meeting.
Because spring and summer differences in acetate mineralization between creekbank and interior sediments could be related to the concentration of acetate in sediment pore water, we have been measuring actetate mineralization and pore-water concentrations, and bacterial abundance during the past year in both vegetated and clipped plots at the creekbank and interior locations. Bacterial abundance and acetate mineralization rates were similar to those measured during the decay experiment. Pore-water acetate concentrations are currently being measured using an enzymatic assay which couples the synthesis of acetyl-CoA (from acetate) to AMP production. AMP concentrations are measured by HPLC. Once sediment acetate concentrations have been obtained, acetate turn-over rate constants will be calculate for plots with and without live roots. These data will yield evidence to indicate the potential for live roots to enhance microbial activity in the rhizosphere of intermediate (creekbank) and short-form (interior) S. alterniflora.