of Syringodium onto the blowout floor over a period of 1 year confirm this. It 

 is estimated that in the region of blowouts any one point will be recurrently 

 eroded and restabilized at intervals of 5 to 15 years. Such processes limit 

 successional development of the seagrass beds, disrupt sedimentary structures, 

 and may result in deposits much coarser than those characteristic of the sandy 

 seagrass carpet. 



96. PENHALE, P.A. , "Primary Productivity, Dissolved Organic Carbon Excretion, 

 and Nutrient Transport in an Epiphyte-Eelgrass {ZosteiKi marina) System," 

 Ph.D. Dissertation, North Carolina State University, Raleigh, N.C., 1977. 



The biomass, productivity (^"^C), and photosynthetic response to light and 

 temperature of eelgrass {Zosteva rnavina) and its epiphytes were measured in a 

 shallow estuarine system near Beaufort, North Carolina, during 1974. The peak 

 of the biomass (aboveground) was measured in March. Eelgrass and epiphyte 

 productivity was low during the spring and early summer, peaked during late 

 summer and fall, and declined during the winter. 



The release and cycling of dissolved organic carbon by eelgrass and its 

 epiphytic community were examined by measuring the excretion of dissolved 

 organic carbon by eelgra'ss heavily colonized by epiphytes, the excretion by 

 relatively uncolonized eelgrass, and the excretion by an epiphytic community 

 attached to an artificial substrate. The excretion rates by eelgrass and 

 epiphytes were low compared to total carbon fixation. The annual primary 

 production and dissolved organic carbon excretion by phytoplankton, smooth 

 cordgrass (Spavtina altermiflora) , eelgrass and its epiphytes were esti- 

 mated. Eelgrass and its epiphytes contributed 47 percent of the total annual 

 primary production and 14 percent of the total excreted material. Thus, the 

 eelgrass and epiphytes play an important role in the primary productivity and 

 the dissolved organic carbon cycles in this estuarine system. 



97. PENHALE, P.A., and THAYER, G.W., "Uptake and Transfer of Carbon and Phos- 

 phorus by Eelgrass {Zosteva navina L. ) and its Epiphytes," Journal of 

 Experimental Marine Biology and Ecology, Vol. 42, No. 2, Jan. 1980, 

 pp. 113-123. 



The uptake of carbon and phosphorus by eelgrass (Zostera marina) and its 

 epiphytes under laboratory conditions was examined using ^ C and ^^P in par- 

 titioned chamber experiments. Both the carbon and phosphorus were taken up by 

 eelgrass roots and subsequently transferred through the plants to epiphytes on 

 the grass blades. The data suggested that only a small part of the carbon 

 fixed in photosyntheses is supplied through the roots and rhizomes. There was 

 very little net transfer of phosphorus through the plants during the 12-hour 

 experiments; the most active movement of phosphorus was from the water into 

 the roots where most of the material remained. Phosphorus uptake depended on 

 the concentration of dissolved inorganic phosphorus in the medium. An in- 

 crease in phosphorus concentration of the medium resulted in increased uptake 

 rates; however, the proportion of accumulation of ^^P in the roots, leaves, 

 and epiphytes remained similar. Experimental design should be carefully con- 

 sidered when comparing the results of various phosphorus uptake studies. The 

 data indicated that a close relationship exists between eelgrass and its epi- 

 phytic community; 15 to 100 percent of the phosphorus released by the leaves 

 was taken up by the epiphytes . 



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