Phosphorus concentrations that 

 we observed are similar to those en- 

 countered by Heinle and Flemer (1976) 

 in the Patuxent Estuary, but were 

 somewhat higher than those measured 

 by Pomeroy et al. (1962) in Doboy 

 Sound, Georgia. The overall impor- 

 tation of phosphorus into the Nueces 

 marsh leads us to suspect that per- 

 haps the marsh is somewhat phosphorus 

 limited. This appears to contradict 

 the findings of Armstrong and Gordon 

 (1977) who found phosphorus to be 

 passively exported by flood and tidal 

 waters in a similar marsh environ- 

 ment. They concluded that net ex- 

 portation of phosphorus indicated 

 that an excess of this nutrient was 

 present and therefore was not a li- 

 miting factor to plant production. 

 Our data suggest that had we moni- 

 tored the transport of phosphorus in 

 July, August, and September of 1979, 

 we may have indeed seen a net export 

 of phosphorus since the June concen- 

 tration showed a net flux of and 

 0.4 kg/hr of total and ortho-phos- 

 phorus, respectively, out of the 

 marsh. However, the definite impor- 

 tation of both total and ortho-phos- 

 phorus during the spring months and 

 the fact that ortho-phosphorus con- 

 stituted 80 percent of the net phos- 

 phorus flux, indicates that phos- 

 phorus is not in excess in this sys- 

 tem. Similar findings that support 

 this hypothesis were reported by Es- 

 pey, Huston, and Associates (1977). 



data tend to agree with these stud- 

 ies, because we observed that there 

 was a net flux into the marsh of both 

 organic and inorganic nitrogen. The 

 fact that most of this importation 

 occurred during the spring growing 

 season reinforces the nutrient-limit- 

 ing concept. 



The higher organic nitrogen val- 

 ues (0.5 to 1.5 g/m observed on 

 flood and ebb tides during the fall 

 and winter coincide with the vegeta- 

 tional dieback and decomposition oc- 

 curring at this time. Inorganic ni- 

 trogen (NO and NQ ) concentrations 

 were low CO. 07 g/m ) throughout the 

 study period. In fact, the net flux 

 for each form was close to zero sug- 

 gesting that perhaps inorganic nitro- 

 gen demands within the marsh are just 

 barely being met by allocthonous in- 

 puts of inorganic nitrogen. This 

 supposition would seem logical if 

 the system was not impacted by other 

 sources of nitrogen, such as river 

 spills, agricultural runoff, and sew- 

 age contamination. Since the report- 

 ed concentrations of inorganic nitro- 

 gen are at or near their detecta- 

 bility limits and no other sources 

 of nitrogen were considered in the 

 estimation of inorganic nitrogen 

 transport, little credence can be 

 given to our estimates of direction 

 and magnitude of net fluxes of in- 

 organic nitrogen. 



Several investigators (Valiela 

 et al. 1973, Van Raalte et al. 1974, 

 and Valiela and Teal 1974) have sug- 

 gested that free nitrogenous nu- 

 trients are readily utilized in marsh 

 ecosystems. Valiela and Teal (1974) 

 observed increases in the standing 

 crop of Spartina sp. following the 

 application of a high nitrogen fer- 

 tilizer (without phosphorus) , thus 

 suggesting that higher salinity 

 marshes are nitrogen limited. Our 



CONCLUSION 



Nutrient transport in the Nue- 

 ces marsh appears to be rather atypi- 

 cal when compared to other high sali- 

 nity riverine marsh systems. It is 

 characterized by infrequent and in- 

 complete inundation by both flood 

 and tidal waters and tends to serve 

 as a nutrient sink. It appears to 



485 



