c 

 o 



Q. 



60 



:? 50 



> 40 



01 



^ 30 



20 



10 



♦ Detritus 





rate) 



Figure 5-48. 



Protein enrichment of Spartina detrital particles resulting 

 from microbial colonization (after Odum and de la Cruz 1967). 



Energy flow also may be traced through a system through the examination of a 

 food web (see chapter 1, "The Conceptual Framework of the Characterization" 

 for a discussion of food webs). The estuarine intertidal and subtidal food 

 web (figure 5-27) is dominated by the detrital food chain, in which dead 

 vegetation colonized with microbes is ingested as detritus. However, 

 zooplankton, barnacles, and bivalves, for example, may feed directly on 

 phytoplankton and diatoms. Consumers of primary production in the detrital 

 and grazing food chains include, for example, forage fish, such as the 

 mummichog, the shrimp ( Crangon sp.), the worms ( Nepthys incisa and 

 Scolecolepides viridis ) , the amphipods ( Gammarus spp. and Ampelisca spp . ) , the 

 molluscs (soft-shelled clam, Baltic clam, and Hydrobia spp.), and many 

 species of zooplankton and grazing fishes. The larvae of many of these 

 species and families also are primary consumers in the estuarine food web. 



Secondary and tertiary consumers, energy-intensive organisms, are dominated by 

 fish, waterfowl, and mammals. These species require high energy inputs from 

 the lower trophic levels to maintain themselves, grow, reproduce, and migrate. 

 Examples of high level consumers in Maine estuaries include the hakes, winter 

 flounder, harbor seal, and mergansers. People are high level consumers also. 



An important feature of the salt marsh habitat is the fact that the primary 

 producers (the green plants) are the primary energy sources. The energy fixed 

 through photosynthesis in the green plants is consumed directly (as leaves) or 

 indirectly (as detritus) by the higher consumers. Ultimately, the highest 



5-130 



