AbstructA formal approach is presented of ordering the time scales of the dominant fluxes of material in an estuary and then accordingly choosing the spatial and temporal resolution of the sampling program. In this way bounds can be derived for the internal turnover times, boundary exchange rates, and import or export fluxes of a particular substance purely from measurements of the standing stock values in the estuary water. Application of this methodology to an experiment in the Duplin River, Georgia, showed that if the effects of the water motion and mixing are extracted from the variation of a biological component, then the variability of the residual can be successfully interpreted. For a typical summer condition it was shown that ammonium was cycled rapidly within the marsh water, its distribution was very patchy, and only its decomposition products left the marsh; that the refractory dissolved organic carbon (DOC) component was steadily exported by longitudinal mixing while labile DOC was rapidly recycled in the water; that silicate was produced in large amounts in the marsh and exported by longitudinal mixing; that particulate organic carbon (POC) concentrations were almost completely determined by the turbulence intensity in the water; and that compared to this internal cycling, export was of minor significance.bution 398 of the University of Georgia Marine Institute.

Spabal and temporal patterns of nutnent dlstnbutions m the Neuse h v e r Estuary, North Carol~na were assessed from a 4 yr study lnvolvlng 82 longitudinal transects of the estuary T h s major nver-dominated estuary receives water from a 16 000 km2 dralnage basin and 1s connected to the Atlantic Ocean by Pamhco Sound Concentratlons of nltrogen and phosphorus species and chlorophyll a were measured in assoclabon u l t h environmental factors Intrastahon d~s t r l b u t~o n s of variables were generally non-normal and interstat~on dlstrlbutlon patterns vaned considerably between specles measured Concentrations of d~ssolved species decreased down-estuary although lnternal sources of both ammonlum and filterable reachve phosphorus were apparent Particulate specles demonstrated maxlma in the upper estuary associated with autochthonous production The relat~ve isolation of the Neuse k v e r Estualy from ocean inputs and long flushlng tlmes of freshwater provide an environment whlch promotes nonconservahve m w n g of nutrient species The average flushlng time for the estuary was 51 d providing an extended period w t h l n the estuary for substantial recycling Thus I s t n b u t l o n patterns reflect the dominance of biolog~cal and chemical achvlty except when large freshets cause r a p~d movement of water to the lower estuary and out Into Pamhco Sound

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Phytoplankton primary productivity in the Neuse Rlver estuary (North Carolina. USA) was assessed for spatial and temporal patterns over 4 yr as a function of associated influential factors, especially biomass (chlorophyll a, chl a) and light. From I4CO2-uptake assays maximum photosynthetic rates (P,,,,,), photosynthesis versus irradiance relationships, daily pnmary productivity (Pd), and annual pnmary productivity (P,) for the system were calculated. Both physical and chemical characteristics of the estuary were profoundly influenced by river flow; this became especially apparent during the near record high flow events of spring 1987. Salinity was depressed throughout the estuary while average photic depth declined. A significant 'washout' of chl a occurred as a result of freshwater input upstream. The effects of this high flow persisted for months after the events and influenced the spatial pattern of primary productivity in the estuary. For the 4 yr period, dally primary productivity ranged from 0.002 to 4.84 g C d-' and unlike many estuaries, correlated poorly with chl a. However, the product of biomass (chl a), photic depth, and surface incident light, In(B Zp .I,), was found to explain 66 %of the variance in lnPd. Pooled data from estuarine stations had a sign~f~cantly lower slope of the regression line and higher y-intercept than riverine stations. This may have been due to the increased biomass specific production (PmB) of the phytoplankton in the mesohaline zone relative to the river species. No significant differences in the relationship of ln P, , to In (B Z, I,) were found between seasons or years. There was no better relationship between P, and any other measured parameters. The 1985 to 1988 annual primary productivity estimates for the Neuse River estuary were 395, 455, 491, and 493 g C m-2 yr-' with the mean being 456 g C m-2 yr-l

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