organics, petroleum hydrocarbons, and 

 just plain junk also may be brought 

 onto the high marsh each month with 

 the highest tides. Junk is often 

 evident along the drift line at the 

 upland edge of the marsh; when large 

 amounts accumulate the vegetation may 

 be smothered and the visual quality of 

 the area decreased. The accumulation 

 and effects of other anthropogenic 

 materials are usually more subtle. 



Petroleum Hydrocarbons 



Of the various oil spill 

 incidents in New England compiled by 

 Hyland (1977), few appear to have had 

 a major impact on salt marshes in 

 general or on the high marsh in 

 particular. Nevertheless, the poten- 

 tial is there. Because urban sewage 

 effluents are the major source of 

 petroleum hydrocarbons in coastal 

 waters (Van Vleet and Quinn 1S77), 

 many marshes in more developed 

 estuarine areas must be exposed to 

 tidal waters with elevated concentra- 

 tions of dissolved and particulate 

 petroleum compounds. The effects 

 of chronic, relatively low-level 

 (compared to spills) concentrations 

 of these materials on n.arshes have 

 never been assessed, however. The few 

 marsh-oil studies which are available 

 have been concerned with the impact of 

 single or repeated oil spills, and 

 most of this work has been carried out 

 in Europe or the Southern United 

 States (Cowell 1971; Bender et al. 

 1977; Baker 1979). The only major 

 study of the impact of an oil spill 

 on a New England salt marsh appears 

 to be the work of hampson and Moul 

 (1978), who documented the impact of 

 No. 2 fuel oil on a marsh in Buzzards 

 Bay, Massachusetts. Their observa- 

 tions indicated that, in general, 

 perennial plants such as Spartina and 

 Distich! is were more resistant than 

 annuals 1 ike Salicornia . But even for 

 S. alterniflora , the biomass, height, 

 and number of plants were markedly 

 reduced in oiled areas 3 years after 



the spill. As might be expected, they 

 also found that plants higher up in 

 the marsh recovered nore quickly 

 because their exposure to the oil was 

 less. However, petroleum compounds 

 vary widely in composition and 

 toxicity, and their impact must also 

 be a function of other factors 

 including temperature and season. At 

 this point, it is impossible to make 

 a very useful speculation about the 

 response of the New England high 

 miarsh community to oil spills or to 

 a large number of other possible 

 perturbations. 



He avy Metals 



Numerous researchers have 

 investigated the various aspects of 

 abundance, distribution, biological 

 uptake, and effects of heavy metals in 

 New England high marsh communities 

 (Nixon 1980). Because there are few 

 burrowing animals living under the 

 dense Spartina patens mat, there is 

 little bioturbation and the sediments 

 appear to provide a relatively 

 undisturbed record of metal input to 

 the marsh surface. The higher 

 concentrations usually found near the 

 surface may reflect an anthropogenic 

 influence (Figure 26) or m,ay be the 

 result of remobilization of the 

 material at depth. For example, in 

 the case of Mn it appears that manga- 

 nese oxide is reduced in the anoxic 

 sediments, and the soluble Mn is lost 

 from the solid phase by diffusing 

 through the pore waters and across the 

 sediment water interface (Figure 27, 

 McCaffrey 1977; Lord 1980). For 

 metals like Cu, Zn, and Pb, which are 

 relatively stable in the sediments, 

 it is possible to combine their 

 vertical distribution with measure- 

 ments of the sediment accretion rate 

 to gain an estimiate of the history 

 of anthropogenic inputs (Figure 28). 

 It is also possible to compare the 

 accumulation rates of different metals 

 with estimates of their input rates 

 to calculate the degree to which the 



55 



