However, traditional methods, e.g., gut analysis and differential 

 growth studies, are unsuitable techniques to determine accurate rates 

 of detrital energy flow. Even isotope tracer techniques need careful 

 controls to account for errors due to carbon 14 leaching from the 

 labeled detritus. 



Rates of detrital utilization by different benthic species ( Rangia 

 cuneata , Macoma balthica . Nereis virens ) were investigated using 

 carbon 14-labeled detritus prepared from eel grass. The whole plants 

 were collected and then cultured in the laboratory. Carbon 14 was 

 introduced into the water and the cultures incubated for several days 

 to allow the incorporation of the isotope. This procedure minimized 

 leaching of carbon 14 during decomposition and also resulted in a 

 more confident measure of incorporation. The eel grass was then 

 dried and ground. At this point the detritus could be "aged" for 

 different time periods to study effects of decomposition on detrital 

 utilization. The labeled detritus was mixed with sediment and the 

 organisms introduced. In order to ascertain and correct for carbon 14 

 uptake due to isotope leached from the decomposing detritus, control 

 organisms placed in chambers with millipore filter sides were also 

 placed in the experimental cultures. After a short period of time, 

 e.g., 1 day, to minimize loss of activity through excretion and 

 respiration, the animals were removed, and placed in sea water to 



the gut. Techniques of tissue digestion and solubili- 

 and the activity measured by standard liquid scintil- 

 Corrections were made for activity due to the leached 

 respiration. 



allow voiding of 

 zation were used 

 lation methods, 

 carbon 14 and for 



Utilization rates were obtained for dominant organisms of a benthic 

 community. This information, along with biomass data, was used to 

 construct an energy budget for this detrital food chain of the benthic 

 community. (A. A.) 



Keywords: detritus, energy flow, estuarine organisms, biomass, food chain, 

 U.S. coastal regions 



F. Nutrient Turnover 



III-F-1 

 Pomeroy, L 

 waters. 



R. 1960. Residence time of dissolved phosphate in natural 

 Science 131 :1731 . 



The residence time 

 from approximately 

 dicative of depleted 

 The turnover rate of 

 per cubic meter, per 



of dissolved phosphate in natural waters varies 

 ,05 to 200 hours. Short residence times are in- 

 phosphate, active metabolic activity, or both, 

 phosphate is between 0.1 and 1.0 mg of phosphorus 

 hour, regardless of phosphate concentration. 



140 



