An investigation of the variability of concentrations of Giardia cysts
and Cryptosporidium oocysts in the Delaware River was conducted in 19
96 at Trenton, N.J. A goal of the study was to examine the relationshi
p between concentrations of Giardia and Cryptosporidium and a variety
of more easily measured microbial, water quality, and meteorological p
arameters. A positive correlation (Spearman rank; p < 0.05) was demons
trated between concentrations Giardia cysts or Cryptosporidium oocysts
and 15 other parameters. Increased concentrations of Giardia and Cryp
tosporidium as well as a variety of other microorganisms were associat
ed with rainfall. The effect of rain fall on parasite concentrations i
s due in part to increased particulate matter in the water column foll
owing surface runoff and resuspension of river bottom and storm drain
sediment.