BALANCE BETWEEN LIVING AND DEAD MATTER 545 



In this connection tlie upper limit of total phytoplankton 

 abundance under one square meter may be of interest. In Burlew's 

 tank experiments, the maximal concentration may reach 3000 mg 

 of chlorophyll under a square meter, if we may assume chlorophyll 

 as representative of the total phytoplankton biomass. In a lake, 

 Gessner (1949) found a maximum of 2000 mg chlorophyll per 

 square meter. In a fjord in Kiel Bay, there was 280 mg/m- calcu- 

 lated only for the trophogenic layer. The latter yielded 62.5 g of dry 

 organic matter in a layer only 2.5 m thick. The development of 

 phytoplankton is actually a self-limiting process. Extreme con- 

 centrations only appear to be in a stable balance with their 

 environment. We must consider the oscillations and also the 

 possibility of rapid decomposition when zooplankton preys upon 

 it or when any other environmental factor stimulates the further 

 growth of the standing stock. 



The zooplankton has a relatively simple relationsh'p to our 

 problem of balance, because the reaction is one-sided. As long as 

 particulate nutrients are available, the zooplankton will feed on 

 it and grow as quickly as biological conditions allow\ Here only 

 one example will be considered, under conditions in which inert 

 material plays a role, namely, when the zooplankton feeds on 

 detritus. Detritus, also called "tripton," serves as an adsorbent 

 for organic matter in solution, but there are unfortunately no 

 investigations on its role in the cycle of organic substances in the 

 sea. From investigations, such as those of Alarshall and Orr (1955), 

 we may estimate its value. Jannasch (1954) has photographed the 

 bacterial population on the surface of detritus, thus suggesting its 

 nutritive value. 



Detritus is the only source of food for all filter-feeding animals 

 in the deep sea, including the sediment feeders. Over sufficiently 

 large areas and periods of times, we might expect a dynamic 

 equilibrium between the detritus and filter feeders in the deep sea. 

 This differs principally from that mentioned above between the 

 phytoplankton and its nutrients because in the former no cycle 

 exists. 



In the relationship between living and dead matter, respiration 

 in the zooplankton is much more intense than in the phytoplank- 



