Effects of an Organic Arsenical Herbicide on a Salt Marsh Ecosystem1
- A. C. Edwards and
- D. E. Davis2
The effects of single and repeat applications of monosodium methanearsonate (MSMA) on the standing crops of smooth cordgrass (Spartina alterniflora L.), a periwinkle (Littorina irrorata Say), and a rib mussel (Modiolus demissus Dillwyn) were investigated. Treatments applied were as follows: (i) single foliar application 90,000 ppm; (ii) 30 foliar applications of either 10,000, 1,000, 100, 10, or 0 ppm; and (iii) 30 floodings of enclosed areas of the salt marsh with 100 or 0 ppm MSMA. Post-treatment sampling revealed: (i) no treatment altered the density of smooth cordgrass; (ii) 30 applications of 10,000 ppm decreased the dry weight living smooth cordgrass; (iii) flowering shoot production was reduced by 30 applications of 10,000 or 1,000 ppm; (iv) one application of 90,000 ppm and 30 applications of 10,000 or 1,000 ppm increased the percentages of dead and necrotic tissue on living shoots of smooth cordgrass and; (v) the periwinkle population was decreased by 30 applications of 10,000 ppm. None of the other treatments showed any significant effects on these parameters. Survival of the rib mussel was apparently not affected by flooding with 100 ppm in sea water. Arsenic levels in smooth cordgrass and soil samples were significantly increased by 30 foliar applications of 10,000 ppm or flooding 30 times with 100 ppm. Arsenic levels in periwinkles and rib mussels also increased immediately following these treatments with MSMA.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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