R 



o 

 O 



45- 

 40- 

 35- 

 30- 

 25- 

 20- 

 15- 

 10- 

 5- 

 0- 



-3.5 -3 



-2.5 -2 -1.5 -1 -.5 .5 1 1.5 



Difference Control- Weired Marsh PPT 



2.5 



10 15 20 



Control Marsh PPT 



Figure 2. Comparison of water salinity in control marshes and marshes with 

 weirs for the study sites listed in Table 1. Data are averages for those studies 

 with grouped control (natural marshes) and experimental (with weirs) 

 marshes. Data are for individual sites if samples were taken just inside and 

 outside of the weirs. 



frequency) leads to lower soil oxidation reduction potentials, which are measured by Eh. Although 

 soil scientists might measure soil Eh differently, or treat the field data differently now (for example, 

 normalize the data by adding +244 mV to the raw field readings that Hoar obtained), the relative 

 differences among or between marshes with and without weirs are seasonal and significant. 

 Summer values were lower than in any other season and values in marshes with weirs were much 

 lower (up to 150 mV lower) than in marshes without weirs. Low Eh values, such as those 



157 



