Monitoring the tidal Delaware River for ambient toxicity.

This study assessed ambient waters in an urbanized area of the Delaware River, to determine whether river water samples exhibited chronic lethal or sublethal toxicity when measured in laboratory experiments. Toxicity was assessed at 16 fixed stations in the main-stem river and 29 stations in tributaries of the tidal Delaware River with salinities from 0 to 15 parts per 1000 (ppt) using Pimephales promelas, Americamysis bahia, Menidia beryllina, and Ceriodaphnia dubia in 7-d tests; Pseudokirchneriella subcapitata in a 96-h test; and Hyalella azteca in a 10-d water-only test. The toxicity tests measured organism survival, growth, and reproduction. Results from testing water samples collected in 4 different y indicated that the samples from sites tested in the main-stem of the Delaware River and from the majority of its tributaries did not produce chronic toxicity. The surveys identified tributaries that warrant further assessment for toxicity.