40. HARRISON, P.G. , "Decomposition of Macrophyte Detritus in Seawater: 

 Effects of Grazing by Amphipods , " Oikos, Vol. 28, No. 23, Copenhagen, 

 Denmark, 1977, pp. 165-169. 



In the laboratory, amphipods collected from detritus in shallow water 

 grazed on eelgrass (Zosteva mavina) but did not consume leaves from which the 

 epibionts had been removed. The action of two adult amphipods increased the 

 rate of decomposition of Z. mavirux leaf particles by 32 percent (5° Celsius) 

 and 35 percent (21° Celsius) in 24 days. Experiments with homogeneously 

 ^'^C-labeled hay as the source of detritus gave similar results. The addition 

 of inorganic nitrogen and phosphorus also increased the rate of decomposition, 

 but the maximum daily rate was only 1.16 percent and was attained after 28 

 days. 



41. HARRISON, P.O., and MANN, K.H. , "Chemical Changes During the Seasonal 

 Cycle of Growth and Decay in Eelgrass (Zoetera marina) on the Atlantic 

 Coast of Canada," Journal of the Fisheries Research Board of Canada, Vol. 

 32, No. 5, May 1975, pp. 615-621. 



Newly formed leaves of eelgrass in winter and spring contained maximum 

 levels of total organic matter (90 percent of dry weight), soluble organic 

 fraction (45 percent), carbon (42 percent), and nitrogen (4.8 percent). These 

 decreased as the leaves matured, aged, and died. Soon after death, the leaf 

 contained only 70-percent total organic matter, 28-percent soluble organic 

 matter, 30-percent carbon, and 1.5-percent nitrogen. Intact dead leaves 

 showed little further change. The crude protein determination overestimated 

 true protein up to 180 percent. The carbon-to-nitrogen ratio (C:N) was an 

 unreliable index of the nutritional value of the plant. The two growth forms 

 were probably in response to wave action and substrate composition. Day 

 length, not temperature, probably controls the seasonal growth cycle. 



42. HARRISON, P.G., and MANN, K.H., "Detritus Formation from Eelgrass {Zostera 

 marina L. ) : The Relative Effects of Fragmentation, Leaching, and Decay," 

 Limnology and Oceanography, Vol. 20, No. 6, Nov. 1975, pp. 924-934. 



In the laboratory, dead eelgrass leaves lost a maximum of 35 percent of 

 the original (dry) weight in 100 days at 20° Celsius. Whole leaves lost 0.5 

 percent of their organic content per day whereas particles smaller than 

 1 millimeter lost 1 percent per day. Sterilization of leaves by dry heat or 

 potassium cyanide showed that leaching accounted for 82 percent of the total 

 loss of organic matter from predried material and 65 percent of the loss from 

 undried material. Bacteria alone increased the nitrogen content of the detri- 

 tus but only slowly degraded the leaf material. When protozoa were intro- 

 duced, they grazed on the bacteria, maintained the bacterial population in an 

 active metabolic state, and hastened the rate of decay. The C:N ratio of 

 incubated detritus decreased from more than 20:1 to as low as 11:1, indicating 

 an increase in its potential food value. 



43. HARTOG, CD., "A Key to the Species of Halophila (Hydrocaritaceae) , with 

 Descriptions of the American Species," ACTA Botaniaa Neerlandica, Vol. 8, 

 Amsterdam, The Netherlands, 1959, pp. 484-489. 



44. HARTOG, CD., Seagrasses of the World, North Holland Publishing Co., 

 Amsterdam, The Netherlands, 1970. 



A description and species key is given for the genera Zostera, Phyllo- 

 spadix, Heterozostera, Posidonia, Halodule, Cymodocea, Syringodium, Thal- 

 assodendron, Amphilobolis, Enhalus, Thalassia, and Halophila. The origin. 



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