The field studies serve as a data base for the interpretation of 

 laboratory results and help to identify system components (fig. 

 1 1), which will be given detailed consideration in the labora- 

 tory. 



The objectives of the field program are to determine the 

 concentrations of Cd, Hg, and Pb in various compartments of 

 the system (fig. 12), and where possible, to determine the form 

 of the metal in each of the compartments (primarily methylmer- 

 cury in fishes and water). Another objective is to establish 

 budgets of the metals entering and leaving by determining the 

 input rate of the metals from river runoff and atmospheric 

 fallout and the rates of loss from the system by sedimentation 

 and seaward transport. From the difference an estimate can be 

 obtained of the quantity of metals that must migrate through the 

 system via various pathways to the open ocean. 



To establish those pathways important in the migration of 

 metals through the system, a relatively detailed understanding of 

 the dominant tropic interrelationships must be obtained. An- 

 other objective of the field studies, therefore, is to ascertain 

 which species represent most of the biota at each trophic level. 

 Also needed is a study of the feeding relationships between 

 organisms. 



Figure 12 shows the locations of the major rivers emptying 

 into the study area and locations of stations where data are 

 being obtained on rates of metal input from river runoff and 

 atmospheric fallout. Figure 12 also shows locations where cores 

 of marsh sediment are taken. Analysis of these cores will yield 

 data on the loss of the metals from the system due to sedimenta- 

 tion. Samples of the dominant marsh grass, Spartina alterniflora, 

 growing at the core locations, are also being analyzed for the 

 various metals. 



The first half year of work on this project was dominated 

 by the study of food chains supporting the quantitatively domi- 

 nant fishes in the southeastern inner Continental Shelf and 

 collection and dissection of organisms used in the determination 

 of levels of background trace metals. Cruises were made at 

 bimonthly intervals in the coastal areas from Georgetown, S.C., 

 to Jacksonville, Fla. Figure 13 shows the sampling areas for 

 obtaining biological samples for analyses of heavy metals and 

 stomach contents. Plankton samples were obtained from most of 

 the sampling stations at night. These samples were frozen and 

 will be analyzed for heavy metal content. 



Significant progress has been made in identifying the feed- 

 ing habits of many of the common estuarine fishes of the study 

 region. Collections will continue so that seasonal patterns can 

 be examined. 



Laboratory studies have been designed to investigate the 

 specifics of the transfer processes from compartment to com- 

 partment, with initial transfer studies involving the primary pro- 

 ducers. Data have been obtained on mercury uptake by phyto- 

 plankton, Spartina alterniflora, and S. alterniflora detritus. 



The following tables and raw data sheets are available 

 from NODC. They are cataloged under NODC accession 

 number 73-0575. 



1. Tables of tentative account of occurrence of food or- 

 ganisms in the diets of 29 common estuarine fish. 



2. Raw data sheets of 25 core analyses of marsh sedi- 

 ment for Eh, moisture, ph and total organic carbon as well as 

 Cd, Cu, Fe, Hg, Mn, Pb, S, and Zn; and analyses of marsh grass 

 for Cd, Cu, Fe, Hg, Mn, Pb, and Zn. 



Figure 12. — The major rivers emptying into the 

 Skidanay Institution of Oceanography study area, 

 as well as locations of atmospheric sampling 

 stations (•) and marsh sediment coring stations 

 (A). 



SOUTH CAROLINA 



O 



^WINYAH 

 U BAY 



-33°N 



NORTH 

 SANTEE. 



O CHARLESTON 

 HARBOR 



•32° 



<?« 



GEORGIA 



I SAVANNAH RIVER 

 WILMINGTON RIVER 

 OOSSABAW SOUND 



O ALTAMAHA SOUND 



— 31° O ST. ANDREWS SOUND 



FLORIDA 



O SISTER'S CREEK 



81°W 



80° 



Figure 13. — Skidaway Institution of Ocean- 

 ography sampling areas utilized for obtaining 

 biological samples for heavy metal analysis and 

 stomach content analysis. 



524-802 O - 73 • 



11 



