industrial activity has increased and more 

 metals have been discharged into the 

 environment, the levels of the metals in 

 marsh sediments have also increased. 



At the other extreme, Giblin et al . 

 (1980) found that cadmium forms soluble 

 complexes as well as sulfides in seawater. 

 If the application or supply of cadmium to 

 the marsh is stopped, it only takes about 

 2 years for the metal to disappear from 

 the marsh muds. Other metals occupy 

 intermediate positions between lead and 

 cadmium in their transit through the 

 marsh. Metals such as copper and chromium 

 are fairly well retained by marsh 

 sediments; metals such as zinc pass 

 through the system rapidly. Where salt 

 marsh retention of experimentally applied 

 heavy metals has been examined (e.g., the 

 Great Sippewissett Salt Marsh), retention 

 of the added metals is always less 

 complete than that of the "naturally 

 arriving metals in the control plots" 

 (Giblin 1982); perhaps this is because the 

 "naturally arriving" metals are more 

 effectively bound to particles. Giblin 

 (1982) also stated, "Although in a 

 geochemical sense wetlands are sinks for 

 some metals, . . . they may not function 

 as efficient traps for all metals." 



The marsh grasses stabilize sediments 

 so that they stay in place, become anoxic, 

 and are thereby able to interact with 

 heavy metals in seawater. In addition, 

 grasses take up metals, to a varying 

 extent, from the sediment. Metals are 

 concentrated in leaves and stems of the 

 grass. When the plant dies and becomes 

 detritus, these contained metals are 

 exported from the marsh to surrounding 

 waters. Giblin (1982) summarizes data 

 showing that there is little contamination 

 of tissues of salt marsh plants by 

 arsenic, manganese, mercury, or lead but 

 considerable contamination by cadmium, 

 zinc, copper, and chromium. In other 

 words, if salt marsh plants and sediments 

 are heavily contaminated with certain 

 metals, they can form a long-term source 

 for contamination of coastal areas. 



Plants can also mobilize heavy metals 

 by oxidizing sediments, a process which 

 turns insoluble sulfides into soluble 

 thiosulfates and sulfates. In 

 experimental plots at Sippewissett, where 



metals were added along with nutrients in 

 sewage sludge, mobilization of metals from 

 sulfides was accentuated. The nutrient 

 addition stimulated Spartina growth which 

 accentuated the tendency of Spartina roots 

 to oxidize sediments. This process both 

 stimulated mobilization of metals from 

 sulfides and enabled enhanced plant uptake 

 of metals applied to the marsh in the 

 sludge. The stimulation of production and 

 sediment oxidation after applications of 

 this type may be delayed for one or two 

 seasons so that it may initially appear 

 that marsh sediments are more efficient at 

 sequestering or holding heavy metals than 

 may eventually prove to be the case. 



There is additional accumulation of 

 heavy metals in dead leaves and fresh 

 detritus formed from marsh plants as they 

 begin to decompose (Breteler et al. 

 1981a). Detritus may be enriched to 

 potentially toxic levels by uptake of 

 metals in the more oxidized surface layers 

 of marsh sediments or by metals associated 

 with surface organic layers, just as the 

 detritus is about to enter the food chain. 

 If the amounts of metals are small, they 

 will have no effect, but in larger 

 concentrations, the marsh products may 

 reach toxic levels. 



There is little data on what levels 

 of heavy metals are damaging to the marsh 

 itself. The heavily polluted Berry Creek 

 portion of Hackensack Meadowlands contains 

 so much mercury that it could be 

 considered a mercury ore. Such extreme 

 cases are rare and considerably lower 

 levels are far more common. In the Great 

 Sippewissett Salt Marsh, there is no 

 indication that the marsh ecosystem has 

 been damaged by 12 years of experimental 

 application of sewage sludge containing 

 heavy metals at levels nine times higher 

 than those normally used in sludge 

 disposal in uplands (Giblin 1982). 



6.3.2. Organic Contaminants 



Though we have some knowledge of the 

 behavior of heavy metals in a salt marsh, 

 far less is known about the behavior of 

 organic pollutants. The added sewage 

 sludge in the Great Sippewissett Salt 

 Marsh studies contained aldrin during the 

 early years, at which time there was a 50% 

 reduction of fiddler crab populations in 



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