Waterborne nutrients enter Great Sippewissett Marsh through groundwater, rain, and tidal flooding. The ebb of tidal water removes nutrients. During summer, uptake by marsh biota leads to net import of nutrients. The increased export of ammonium in August may be due to leaching from senescent marsh plants. There is a net annual export of ammonium, nitrate, nitrite, dissolved organic (DON) and particulate (PN) nitrogen, particulate carbon (PC), and phosphate. Ammonium, DON, and PN are the major forms of nitrogen exported. Nutrient concentrations in coastal and marsh water are correlated, and marsh exports could contribute substantially to nutrient supplies of coastal waters. Groundwater entering the marsh provides primarily NO3‐N and DON. Nutrient inputs through precipitation consist primarily of DON, NO3‐N, and NH4‐N. Particulate materials in rain have a high C:N ratio, contributing little to enrichment of the nitrogen‐limited salt marsh. Groundwater carries over 20 times the amount of nutrients brought in by rain. The nitrogen provided by both sources is more than enough to support annual plant growth. Inputs of nitrogen by groundwater arc therefore important to the nitrogen economy of a salt marsh. About half the dissolved inorganic nitrogen brought into the marsh by groundwater is converted to and exported as PN. The marsh thus transforms the nitrogen that would have been used by primary producers into a form suitable for consumers such as shellfish. Large amounts of apparently refractory DON enter the marsh in groundwater and similar amounts are exported by tides. PC exported to coastal water is equivalent to 40% of the net annual production of Spartina alterniflora, the dominant marsh plant.

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We tested the hypothesis that currents, waves, and sediment grain size affect the dispersal of seeds and seedlings of the submersed angiosperms Ruppia maritima, Potamogeton perfoliatus and Stuckenia pectinata. Seed settling velocities and initiation of motion of seeds and seedlings and distance transported were quantified on four sediment types under a range of currents and waves in a flume. The rapid settling velocities of R. maritima and S. pectinata seeds and the increased settling velocity of P. perfoliatus in currents above 8 cm/second suggest that primary dispersal of these species is localized to the general area colonized by their parents. Once settled within a bed, seeds are exposed to weak currents and waves, and are likely to be subject to sediment deposition which may further limit dispersal. In contrast, in restoration projects, the absence of vegetation is likely to make seeds more vulnerable to grazing and transport, and may contribute to the lack of plant establishment. If seeds germinate without being buried, they are susceptible to secondary dispersal at relatively low current velocities and small wave heights due to the drag exerted on the cotyledon. Sand grains tend to stick to the seed coat and rootlet of P. perfoliatus seedlings, perhaps a mechanism to reduce the chances of being displaced following germination. These data reveal the close links between sediment, water flow, and submersed angiosperm seedling establishment; these parameters should be considered when using seeds for restoration of submersed angiosperms.

Seagrasses are rooted flowering marine plants that provide a variety of ecosystem services to the coastal areas they colonize. Attenuation of currents and waves and sediment stabilization are often listed among these services. Although we have a reasonably good understanding of how currents affect seagrasses and vice-versa, less is known about interactions between waves and seagrasses, and standard methods for research on waves in seagrass systems have not yet been established. This report presents background information needed to inform and encourage further studies on waves in seagrass systems from both field and modeling perspectives. It reviews current knowledge of waves in seagrass systems, encompassing field and laboratory data as well as modeling efforts. It then describes various methods for measuring waves in seagrass colonized areas and modeling the dynamics of wave-seagrass interactions. Standardization of experimental designs, instrumentation, analyses, and modeling approaches to allow for ready comparison between studies is encouraged.

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