that microorganisms are the most important consumers of marine macro- 

 phytes and that detritus-feeding invertebrates derive their nourishment 

 mainly by stripping the microorganisms from the plant material as it 

 passes through their guts. The fecal pellets may be recolonized by 

 microorganisms and the process repeated until all the plant material 

 has been utilized. W. E. Odum's opinion is cited to the effect that 

 the important consumers of detritus in the estuary are the inverte- 

 brates and that fish production is sustained primarily by predation 

 on these detritus-feeding invertebrates. Also, the export of detritus 

 in suspension to the coastal waters makes a substantial contribution 

 to the planktonic food chains. (J.B.) 



Keywords: productivity, detritus, macrophytes, food chain, coastal waters 



III-A-3 



Saunders, G.W. 1972. Summary of the general conclusions of the symposium. 

 Pages 533-540 iji U. Melchiorri-Santolini and J.W. Hopton, eds., Detritus 

 and its role in aquatic ecosystems. Memorie dell 'Instituto italiano 

 di idrobiologia. 29 Suppl . 



The IBP UNESCO Symposium on detritus and its role in aquatic ecosystems 

 provided a general consensus in several areas. It was recognized 

 that detritus is quantitatively important in most aquatic ecosystems, 

 both freshwater and marine. Detritus tends to be present in greater 

 quantities than living organisms although this is not always true. One 

 major problem considered was that of isolating and quantitatively measur- 

 ing the amount of detritus. A method for isolating detritus from other 

 particles suspended in water has not yet been discovered. 



It was also shown that adsorption of nutrient substances, attachment 

 of bacteria, and assimilation of the nutrient substrate on the sur- 

 faces of particles proceeded in a yery complicated manner and could 

 be important in determining the distribution of bacteria in the water and 

 the rate at which bacterial metabolism might occur. Dead macrophytic 

 plant material provides an abundant nutrient source on which luxurious 

 growths of bacteria occur. 



Detrital particles in the deep-sea zone were shown to undergo only 

 yery slow decomposition and represent a very small percentage of partic- 

 ulate matter produced in the open ocean. The settling rate of 

 particulate matter, both dead and living, is a major process involved 

 in redistributing the potential energy produced initially by photo- 

 synthesis. If the detritus is slow in settling, more soluble 

 organic matter will be released in a unit volume of water than if 

 the detritus settles rapidly. 



It was shown that detritus has, in general, a relatively slow decom- 

 position rate, and if it is ingested by animal organisms it may not be 

 so easily assimilated as it is by microorganisms. One would expect, 



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