tion. Attention was confined to estimates of free amino acids in sea 

 water. 



Twelve genera of soft-bodied freshwater invertebrates were studied 

 in the author's laboratory, where it was observed that the rate of 

 uptake of amino acids was much less than that observed in marine 

 organisms. Further, none of the genera were capable of removing more 

 than that observed for marine organisms. The freshwater invertebrates 

 were incapable of removing more than a few percent of added labeled 

 glucose or amino acids over a period of 24 hours. Two species of 

 brackish-water nereids were studied with respect to their ability to 

 accumulate glycine at different salinities. Both Nereis succinea 

 and Nereis limnicola were capable of accumulating this compound at per- 

 missive chlorosities of the medium. It appears that the processes 

 that underlie osmotic regulation are incompatible with the rapid accumu- 

 lation of amino acids from the ambient medium, and essentially all 

 marine invertebrates examined exhibited such accumulation while none of 

 the freshwater invertebrates examined showed this tendency. 



The uptake of organic compounds of low molecular weight appears to be 

 a significant supplemental source of reduced carbon for several marine 

 animals. Comparison of the material available to the animals at concen- 

 trations characteristic of their environment and the amount of material 

 necessary to account for oxidative metabolism supports this position. 

 Finally, there is qualitative evidence that such material can enter 

 oxidative and synthetic pathways in the animals studied. (H.D.) 



Keywords: nutritional sources, invertebrates, detritus, biomass 



III-E-22 



Craven, T., and L.G. Williams. 1973. The role of Spartina detritus in the 



character of plankton assemblages of the Mobile Bay estuary. 



Association of Southeastern Biologists Bulletin 20:47. (Abstr.) 



Bacterial conglomerates of decomposing Spartina were associated 

 with a population density and structure of plankters having wide 

 variations among the salt marsh, Mississippi Sound, and the coastal 

 near-shore biota. High turbidities, high bacterial densities, and large 

 suspended organic particles were common in the Spartina marsh. Missis- 

 sippi Sound and the near-shore Gulf showed low densities of suspended 

 detrital particulates, but much higher densities of phyto- and zooplankton, 

 CA.A.) 



Keywords: detritus, Spartina , plankton, estuaries. Mobile Bay 



135 



