Comparison of bacterial dynamics in tidal creeks of the lower Delmarva Peninsula, Virginia, USA

Abstract

Bacterial biomass, abundance, and productivity were greater in three tidal marsh creeks on the Chesapeake Bay side of the lower Delmarva Peninsula than in nearby creeks of the seaside coastal lagoon complex (biomass: 462 and 71 ng C ml-1; abundance: 21 × 106 and 3.8 × 106 cells ml-1; productivity: 46 and 7.3 ng C ml-1 h-1; bayside and seaside respectively). Bacterial cell-size distributions were also significantly different between the seaside and bayside creeks, with a larger proportion of smaller cells dominanting samples from the seaside creeks. Bayside and seaside concentrations of total suspended solids (TSS) and dissolved organic carbon (DOC) were similar (c 49 mg l-1 TSS and 3.5 mg l-1 DOC). Amount of organic matter (OM) and chlorophyll a was higher in the bayside creeks, while inorganic N and P concentrations were higher in the seaside creeks (OM: 9.0 and 3.4 mg l-11; chlorophyll a: 6.0 and 4.1 g l-1; PO43-: 0.2 and 1.2 μM; NH4+: 0.6 and 1.2 μM; bayside and seaside respectively). The high inorganic nutrient pools combined with the low levels of bacterial productivity suggest that bacterial production is not limited by N or P in the seaside creeks and that the amount of carbon moving through the bacterial loop is much less than on the bayside. In fact, DOC turnover times were much longer for the seaside (22 d) than for the bayside (6 d). Differences in bacterial dynamics for the bay and seasides may be related to differences in the source of the DOC (marsh grass vs phytoplankton), grazing on the bacterial cells, or bacterial community structure. -Authors