San Gabriel River Regional Monitoring Program

Aquatic Toxicity

Aquatic toxicity tests provide another measure of potential impact; however, unlike ecological monitoring, water column laboratory bioassay tests do not incorporate aggregate impacts associated with habitat condition and effects associated with sediment exposure. However, aquatic toxicity tests can furnish a more direct measure of potential impacts from chemical contaminants, particularly thosenot specifically measured.

From 2008 to 2014, 71 toxicity tests were conducted using the water flea, Ceriodaphnia dubia, survival and reproduction test. Seven day exposures to undiluted field collected stream water were conducted. The results of the reproduction endpoint (chronic toxicity as young per female) is presented here since it was far more sensitive compared to the survival endpoint.
On the map to the left you can explore the proportion of water samples that exceeded the toxicity categories presented below, for each region of the San Gabriel watershed. Significant toxicity was defined in three categories using a statistically significant reproduction response using the TST tool. These categories were as follows:
  1. Non-Toxic (TST not significant)
  2. < 50% Effect, TST significant
  3. > 50% Effect, TST significant