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

Abstract

Bacterial biornass, abundance, and product~vity were greater in 3 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' ; abundance: 12 X 10' and 3.8 X 106 cells ml-l ; productivity: 46 and 7.3 ng C rnl-' h-'; 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 dominating samples from the seaside creeks. Bayside and seaside concentrat~ons of total suspended solids (TSS) and dissolved organic carbon (DOC) were similar (approximately 49 mg 1.' TSS and 3.5 mg I ' DOC) The 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 1 l ; chlorophyll a. 6 0 and 4.1 g 1.'; PO, 0.2 and 1.2 FM; NH,' 0.6 and 1.2 ubI; bayside and seaside respectively). The high inorganic nutrient pools combined with the low levels of bacterial productivity suggest that bacterial production is not l~nli ted 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 ) . Reasons for the observed differences in bacterial dynamics for the bay and seasides are not known specifically, but may be related to differences in the source of the DOC (marsh grass vs phytoplankton), grazlng on the bacterial cells, or bacterial community structure