no doubt play an important role. Their 

 consumption of foods in the marsh and on 

 the intertidal flats results in a rapid 

 recycling of nutrients. The excretions of 

 birds, fish and invertebrates can move 

 back to the marsh with the rising tides, 

 resulting in a net influx of nutrients, 

 seen as imported ammonia by Winfield 

 (1980). Rapid uptake by algal mats 

 completes the cycle. Overall, the salt 

 marsh is seen as an area of high 

 productivity; its high turnover rates are 

 driven by short food chains both in the 

 marsh and on adjacent intertidal flats. 

 Fertilization occurs frequently as 

 nutrients are brought by the tides from 

 feeding grounds to marsh "growing 

 grounds." 



While speculative, this conceptual 

 model may explain the dependence of many 



animals on their salt marsh habitat. At 

 the very least, it points out many 

 interactions among marsh organisms and 

 indicates the need for considering the 

 system in its entirety when attempting to 

 manage its wildlife. McCloy (1979) 

 provides a good example of the unexpected 

 results that manipulating one species can 

 have on another. When he crowded 

 hornsnails, adult mortality rose, dead 

 shells accumulated, and an anemone 

 (previously limited by substrate 

 availability) increased four-fold in 

 density. Such case studies make us aware 

 of subtle interactions among populations 

 and should cause us to be cautious about 

 managing for individual species. One 

 conclusion follows with 

 certainty: altering one population will 

 have impacts on others. 



85 



