be 4,553.57 kg/ha x 10.87 ha or 49,497.31 

 kg/yr. 



Animal production of tall S. alterniflora marsh 

 has been estimated to be 5-7'7f of primary pro- 

 ductivity. Since mixed marsh is not as productive 

 of animals as tall S. alterniflora marsh, a figure 

 of 4% of the mixed marsh primary production 

 seems to be a reasonable estimate. Annual animal 

 production on the 10.87 ha of inundated mixed 

 marsh would then be 4% of 49,497.31 kg or 

 1,979.89 kg. 



Virtually the entire spoil areas have been 

 turned into homesites. If they had been left to 

 produce aPhragmites communis community, only 

 a relatively small proportion of the original 

 productivity would have been locally available 

 on a trophic level (Johnson, pers. comm.). 



Since approximately 45% of the net production 

 of a salt marsh (Teal, 1962) is exported outside 

 the area of its source, the loss of this productivity 

 will have repercussions beyond Goose Creek. 



The estimates given herein should be con- 

 sidered conservative, as E. P. Odum (1959) 

 estimated the primary productivity of tall S. 

 alterniflora in Georgia salt marshes at a high 

 of 14 tons/acre and Ryther (1959) gives a figure 

 for net organic production of Spartina marsh of 

 9.0 g/m2/day. 



H. T. Odum (1963) indicates that Thalassia 

 beds in Redfish Bay, Tex., recovered in the areas 

 not directly in the path of the dredge after one 

 year, but his data indicate that the dredged area 

 and an area 0.25 mile east of the channel had 

 no productivity due to removal of the substratum 

 to bedrock in one case and "beds covered with 

 30 cm of soft silt" in the other. Virtually all of 

 Goose Creek was within 0.25 mile of the dredge. 

 Studies of large embayments tend to deemphasize 

 dredging effects because of the dissipation of the 

 products of the dredging process and dilution 

 factors. Similarly, regions like Chesapeake and 

 Redfish Bays have relatively extensive bottom 

 areas and circumferences and dredge spoil is 

 either deposited back in the basin where it spreads 

 to form a relatively shallow homogeneous layer 

 often virtually indistinguishable from the bottom 

 (Biggs, 1968, 1970), or covers a relatively small 

 portion of the bay edge. 



The effects of dredging appear to be accentuated 

 as the size of the embayment decreases. 



FISHERY BULLETIN: VOL. 72, NO. 2 



DISCUSSION 



The Relationship of the Substratum to 

 the Distribution of Organisms 



Wilson (1938, 1953), Morgans (1956), Sanders 

 (1958), and Sasaki (1967) related larval or adult 

 infaunal population densities to sediment type. 

 McNulty, Work, and Moore (1962) and Harrison, 

 Lynch, and Altschaeffl (1964) fail to corroborate 

 either degree of sorting or median grain size as 

 definitive factors affecting the distribution of 

 deposit or filter feeders. It appears that animal- 

 sediment relationships are variable depending on 

 such factors as sediment type, life cycles of related 

 fauna, and location. 



In the Goose Creek study the analysis of 

 variance between biomass before and after 

 dredging as a function of sediment type revealed 

 no significant interaction between productivity of 

 animal biomass and sediment type in the bay as 

 a whole. In the channel, however, there was a 

 positive correlation between biomass and sta- 

 tions. Since the stations were arranged in linear 

 fashion virtually in descending order of particle 

 size and in the direction of lowered current 

 velocity, these factors appear to have had an 

 influence on productivity. 



The recovery rate of the macrobenthic popula- 

 tions varied in different substrata according to 

 a chi-square of the number of species found at 

 the stations representing different sediment 

 types. Similarly, the number of species was sig- 

 nificantly different before and after dredging, as a 

 function of sediment type. 



It appears, then, that productivity in terms of 

 animal tissue was not independently influenced 

 by substratum in the bay as a whole, but there 

 was a response to the specific conditions in the 

 channel. Recovery of species and specimen num- 

 bers appeared to be affected by sediment type in 

 both channel and bay. These data tend to sub- 

 stantiate those of Sasaki (1967). 



The Relationship of Current Velocity 



to the Characteristics of the Sediment 



and the Distribution of Organisms 



In a shallow bay with a narrow mouth like 

 Goose Creek, wind-driven currents probably have 

 a disproportionately large effect on the char- 

 acteristics of the sediment. Prevailing winds can 



470 



