\man/ 



MARSH PLANTS 

 & EPIPHYTES 



MIGRATORY 

 & RESIDENT 

 BIROS 



^anT 



OTHER 

 WILDLIFE 



LIGHT 



BENTHIC 

 ALGAE 



LIGHT 



DETRITUS 



-» BAY PROPER 



DECOMPOSERS 



CRUSTACEANS 

 SMALL FISHES 

 BENTHOS 

 (SMALL CONSUMERS) 



1 



> — * — S i 



•f ORGANIC > 1 



■»i ^ NP.&C J + 



\ DRAINAGE / 



■>■ BAY FISHES 



BAY PROPER 



BAY PROPER 



Figure 3. Conceptual model of wetlands. 



food web through the detrital pathway, and de- 

 composers are consumed by crabs and other ben- 

 thic crustaceans, bivalves, mollusks, and small 

 fishes. In any particular marsh, the small (in physi- 

 cal size) marsh consumer box will be dominated by 

 one particular species (R. Wetzel, pers. comm.), 

 e.g., fiddler crabs, insects, or small fishes. However, 

 the dominant consumer member of the compart- 

 ment will vary with the type of marsh and perhaps 

 with the time of year. Small consumers of marsh 

 detritus and benthic algae play a role in any marsh 

 food web. In turn, these small marsh consumers 

 support fishes which enter from the Bay during 

 high water, birds, and other wildlife. 



Material enters the Bay system with runoff 

 over lands which are not classified as wetlands. 

 This flow appears in figure 2 as drainage to the Bay 

 (organic and inorganic N, P, and C). Runoff intro- 

 duces a variety of substances into the Bay. Pollu- 



tants include herbicides and pesticides from agri- 

 cultural land, and toxic substances impregnating 

 wooden bulkheads, as well as natural (as opposed 

 to man-induced) nutrients and detrital material. 



River flow brings natural nutrients, trace 

 metals, and detritus, as well as chlorine and nutrient 

 loads from partially treated sewage, effluents from 

 power plants, and chemicals from industrial activi- 

 ties, into the Bay system. Trace metals and petrol- 

 eum hydrocarbons are introduced from shipping 

 traffic, Baltimore Harbor, and storm-sewer runoff. 



I found no estimates of the relative inputs of 

 natural and pollutant materials from rivers, land 

 runoff, pleasure and commercial boats, and Balti- 

 more Harbor. Some work along this line has been 

 done at Chesapeake Bay Institute at Johns Hopkins 

 University. Point sources such as sewage treatment 

 plants are monitored (A.J. Lippson, pers. comm., 

 Potomac River survey). Nonpoint sources such as 



