ENERGY FLOW 



Among all ecological systems throughout the world, rates of primary production 

 (primary productivity) are highest in estuaries (figure 5-28). The high rate 

 of primary productivity by estuarine phytoplankton, macroalgae, and rooted 

 macrophytes is supported by high nutrient levels from land runoff, influx from 

 deep nutrient-rich ocean water, and rapid regeneration from the bottom. 

 Research on energy flow in Maine estuaries has been limited to the study of 

 production by phytoplankton and emergent vegetation. No investigations have 

 addressed energy flows through or energy requirements of higher trophic level 

 organisms . 



Energy flow in the estuarine system is driven primarily by hydrologic and 

 climatic processes, as these forcing functions control primary production. 

 Hydrologic factors control the mixing of fresh water with sea water. This 

 mixing transports materials, such as nutrients essential for plant production, 

 into estuaries from adjacent marine and terrestrial systems. Climatic 



factors, such as temperature and insolation, influence 

 photosynthesis . 



the 



rate 



of 



A generalized schematic diagram of the functioning of the Maine estuarine 

 system is presented in figure 5-29. Growth of primary producers 

 (phytoplankton, macroalgae, rooted macrophytes, and benthic diatoms) is 

 influenced by nutrient supply, insolation, and temperature. 



COMPARATIVE PRODUCTION RATES OF THE GENERALIZED 

 ECOSYSTEM TYPES IN THE WORLD 



10 

 9 

 8 



7 

 6 

 5 

 4 

 3 

 2 

 1 

 



Tons Per Acre Per Year 



1/3 



,. lU-t- 



Desert 



1/3-1 V7 





Dry 

 Agriculture 





T'*""'**' 



5-10 



Moist 

 Agriculture 



1- 1 V2 , 



1/3 



Figure 5-28. 



A comparison of the primary productivity (tons of dry weight 

 produced per acre per year) for different types of terrestrial 

 and aquatic sy terns in the world. Shaded bars indicate 

 general ranges (Teal and Teal 1969). 



5-50 



