100% toll 5. a/ tern i : flora 



• fertilized 



75 g/m 2 /week, 

 sewage sludge 



o control 



100% short 

 S alterniflora 



100%, Solicornio 

 europaea 



Figure 32. Distribution of percent cover 

 between the three major plant types in 

 Great Sippewissett Salt Marsh regularly 

 flooded areas between 1976 and 1981. 

 Dashed line shows presumed trend of 

 fertilized plot based on other observa- 

 tions. There has been little change in 

 the control area but great changes in 

 vegetation cover in plots highly enriched 

 in nitrogen. 



Sippewissett Salt Marsh, no clearly 

 detrimental effects of sewage sludge on 

 marsh plants were demonstrated, in spite 

 of the heavy metals in the sludge. The 

 observed changes in the marsh ecosystem 

 were mainly the results of changes in 

 nitrogen relations within the marsh 



system. Nitrogen first affected plant 

 production and structure, with consequent 

 changes in animal feeding and plant 

 decomposition. The marsh ecosystem itself 

 seems not to have suffered any 

 degradation. 



On the other hand, some of the marsh 

 products we are interested in (such as 

 shellfish), may show elevated levels of 

 heavy metals in polluted New England salt 

 marshes. This certainly affects their 

 value to human society and reduces it to 

 zero if the shellfish grounds must be 

 closed. If the marsh pollution includes 

 pathogens, shellfish may become 

 contaminated with the pathogens and have 

 to be depurated in cleaner waters to make 

 them safe for human consumption. However, 

 marshes may, in fact, reduce pathogens. 

 Many details about the function of these 

 systems and of their reactions to abuse 

 are still not well understood. Marshes 

 are remarkably resistant and the fact that 

 a salt marsh is polluted is not a reason 

 to write it off as lost or even as without 

 considerable value. 



As our knowledge of the functioning 

 of these rich intertidal grasslands has 

 grown, we have learned better how to 

 appreciate them. If we have been 

 overenthusiastic about some aspects of 

 their role in coastal ecology, we have 

 surely been less appreciative of some of 

 their other characteristics. On balance, 

 salt marshes remain of considerable value 

 to us and are well worthy of both our 

 concern and our protection. 



51 



