A synthesis of a comprehensive annual study of material processing in the Bly Creek marsh-estuarine basln is described. The project design provides statistical estimates of material fluxes for the water column, salt marsh, and oyster reef subsystems. Fluxes from a freshwater stream, groundwater, and rain are also presented Material processing by the Bly Creek marsh-estuarine basin is constituent-and subsystem-specific Inflows of material via rain, streamwater. and groundwater are small and relatively unin~portant compared to tidal fluxes. The salt marsh dominates the basin in aerial extent and in terms of net material fluxes. Most constituents exhibit significant net annual import to the salt marsh. Only DON is exported from the marsh and from the basin at significant levels. The salt marsh appears to recycle most of the nitrogen and phosphorus needed for marsh grass primary production. Sufficient inorganic particulate material is imported to allow the salt marsh to maintain its elevation with respect to ongoing sea-level rise. As a result of metabolic processes, the oyster reef imports particulate materials and releases dissolved nutrients. The reef is a significant consumer of chl a and produces enough dissolved inorganic nitrogen and phosphorus to support water column primary production The N:P ratio of Bly Creek dissolved inorganic nutrients is lower than that of North Inlet or ocean waters and implies nitrogen conservation or mobilization of particulate phosphorus into orthophosphate. In contrast to human-impacted coastal systems, this prist~ne basin reduces the N : P rat10 as water passes through it Differences in the N:P ratio are probably the result of DON export, denitnfication, and phosphorus import by the basin

Tidal fluctuations and transports of particulate organlc carbon (POC) were investigated at 3 marsh creeks (near Georgetown, South Carolina, USA) comprising the major transfer points between the North Inlet Marsh and the adjoining aquatic ecosystems. Two creeks, Town and North Jones, form the inlet mouth and are the only marsh-ocean exchange points. The third creek, South Jones, connects to a brackish water embayment. The creeks were simultaneously sampled every 1.5 h for 50 consecutive hours during neap tides (4 tldal cycles) and 50 consecutive hours during corresponding spring tides of each season. At the inlet. POC concentrations fluctuated in-phase with the tide during the winter and out-of-phase with the tide during the summer Combinations of in-phase and out-of-phase patterns occurred in spring and fall. The fluctuations at the brackish water location were irregular POC concentrations were similar in each season with values averaging about 1.4 g mP3. Net transports varied from tidal cycle to tidal cycle with regard to direction of transport (import or export) and magnitude, ranging from a net import of 240 g POC S-' to a net export of 228 g POC S-'. Annual budgets revealed Town Creek to export POC at a rate of 2.6 ? 0.5 X log g yr-'; North Jones Creek imported POC at a rate of 3.8 ? 0.7 X 10a g yr-l; and South Jones Creek exported POC at a rate of 5.5 k 0.8 X 108 g yr-' The 3222 ha North Inlet marsh serves as a source of POC to the ocean at a rate of 87 2 16 g of POC per m2 yr-l.

Intertidal reef communities dominated by filter feeding organisms (such as the American oyster Crassostrea mrginjca) are a prominent feature of some marsh-estuarine systems of the southeaste m United States. Such reef communities may be considered as major components in the coupling of aquatic and benthic systems within the marsh. The ability of the reef community to remove suspended microbial biomass (as ATP) was investigated through the use of a 10 m long plexiglas tunnel that covered 7.9 m2 of reef surface. Generally, there was a net loss of suspended microbial biomass as water flowed over the reef. Microbial biomass levels were lower at the output from the tunnel than at the input to the tunnel for 61 % of flood tides and 76 '10 of ebb tides. Determinations of net transport revealed that total microbial biomass was imported to the reef on 26 of 33 flood-tide phases and 27 of 33 ebb-tide phases. Import rates ranged between 0.1 1 and 5.39 pg ATP S-' during flood tides and between 0.46 and 18.20 pg ATP S -' during ebb tides. Annually 55 g ATP were imported to the reef community. T h s import rate corresponded to an equivalent carbon flow of 1750 g C m-' yr.' The net flow of microbial carbon into the reef community was 20 times greater than reported estimates of particulate organic carbon flow from the entire marsh system to the ocean.

Tidal fluctuations and transports of dissolved organic carbon (DOC) were investigated at a major creek draining 1800 ha within the North Inlet Ecosystem (South Carolina, USA). Samples were collected every 1.5 h for 50 consecutive hours during neap tides (4 tidal cycles) and 50 consecutive hours during corresponding spring tides of each season. DOC concentrations were vanable, ranging from 0.9 to 13.0 g m-3 of water with as much as 2.5 g m-3 of water variation during a 1.5 h period. DOC was exported from the marsh during each sampling period. Net transports ranged from approximately 5 to 480 g DOC S-'. Annual budgets revealed a DOC export rate as high as 7.5 + 1.8 X log g C yr-I corresponding to 416 g DOC m-' yr-'