site formed a sandy shoal in the Inter- 

 coastal Waterway. The site was divided 

 into three replicate blocks covering the 

 three tidal zones (upper, middle, and 

 lower thirds). Within each block and 

 tidal zone the blocks were further sub- 

 divided into 90 plots which were either 

 planted with marsh plants, sprigs, or 

 seeds, or fertilized with various 

 amounts of organic or inorganic ferti- 

 lizers. Each plot was bordered by a 

 0.5-m (1.6-ft) wide pathway for access 

 to the plots (Figure 3). 



For practical reasons, the microbi- 

 ology was done on two planted areas, 

 sprigged with either Spartina alterni- 

 flora (SA) or Spartina patens (SP), and 

 a nonpl anted (NP) area within each rep- 

 licate-tidal block. The random location 

 of SA, SP, and NP plots within each 

 block is shown in Figure 4. 



MICROBIAL BIOMASS 



Adenosine triphosphate (ATP) stand- 

 ing stocks in planted and nonplanted 

 plots were measured over time and at 

 various depths (Bancroft et al. 1976). 

 In addition, bacterial biomass was esti- 

 mated by plate counts on Difco 2216 Ma- 

 rine Agar, and the plates were incubated 

 aerobically and anerobically. Yeast 

 biomass was estimated by planting on 

 Sabouraud Dextrose Agar (2% NaCl). Ben- 

 thic algae, diatoms, and protozoans were 

 followed qualitatively (microscopically) 

 by noting which genera were present. 



RESULTS AND DISCUSSION 



ATP BIOMASS 



Seasonal variation of ATP biomass 

 with depth in 27 plots (NP, SA, and SP) 

 is shown in Figures 5, 6, and 7. From 

 January to about July, the concentration 

 of ATP increased in the surface stratum 

 but ATP concentrations remained un- 

 changed in the 5- to 7-cm and 10- to 

 12-cm (2- to 2.8-inch and 4- to 4.7- 

 inch) strata. The decrease in ATP bio- 

 mass with depth suggests that the carbon 

 input is from the surface and the source 

 of carbon may be from the detrital and 

 algal carbon deposited on the surface. 



Unfortunately, data are not avail- 

 able on microbial development at other 



dredged material sites. However, for 

 comparison with other coastal systems, 

 the ATP biomass found at Buttermilk 

 Sound was 20 times lower than microbial 

 biomass reported by R.L. Ferguson and 

 M.B. Murdock working in subtidal estua- 

 rine sands in the Newport River estuary, 

 North Carolina. Christian et al. (1975) 

 working in the Spartina marshes contig- 

 uous to Sapelo Island, Georgia, reported 

 microbial ATP biomass 50 times higher 

 than the concentration measured at But- 

 termilk Sound. These differences are not 

 surprising because the habitat at But- 

 termilk Sound is in its early stages of 

 development. 



The biomass may have had an effect 

 on the initial establishment of marsh 

 plants in dredged materials, but that 

 hypothesis is unlikely when one consid- 

 ers the ATP biomass similarity in the 

 NP, SP, and SA plots. The opposite is 

 also possible, i.e., plant growth is not 

 influencing microbial ATP biomass in the 

 sediment, at least in the early stages 

 of development. 



Since there was no plant-microbial 

 biomass correlation, and biomass was 

 similar in planted and nonplanted plots, 

 detritus deposition may be one of the 

 most important factors in the carbon en- 

 richment of coastal systems. Detritus 

 is defined as silt and clay (abiogenic 

 origin) and organic matter (biogenic or- 

 igin). Thus, given suitable time, the 

 course sands at Buttermilk Sound will be 

 filled in with smaller particles which 

 will hold a larger microbial flora. In 

 addition, the detritus deposited on the 

 site probably contained attached micro- 

 organisms. In the estuary, 80%-90% of 

 the bacteria are attached to detrital 

 particles larger than 14 micron and few 

 are free in the water (Hanson and Wiebe 

 1977). Cammen (1976a), working with 

 dredged materials near Drum Inlet, North 

 Carolina, reported an accumulation of 

 organic matter at an annual rate of 80 

 to 100 gC/m 2 for the top 13 cm (5 

 inches). Therefore, microbial biomass 

 will be increasing with detrital build 

 up at BSHDS. 



BACTERIAL BIOMASS 



The bacterial populations (aerobic 

 and anaerobic) in dredged materials were 



39 



