Temperature & biotic condition in urban streams

Biotic responses associated with increased temperatures in urban streams include (but are not limited to):

BENTHIC MACROINVERTEBRATES

• ↓ total abundance, richness or diversity
  [Sponseller et al. 2001]
• ↓ EPT abundance, richness or diversity
  [Sponseller et al. 2001, Wang & Kanehl 2003]
• ↓ quality of biotic indices
  [Wang & Kanehl 2003, Walters et al. 2009]

FISHES

• ↓ abundance, biomass, richness or diversity
  [Wang et al. 2003 (Fig 29), Stranko et al. 2008, Helms et al. 2009]
• ↓ quality of biotic indices
  [Wang et al. 2003]

Rainbow trout (Oncorhynchus mykiss)
Photo by Wayne Davis, courtesy of U.S. EPA

Coldwater fishes such as salmonids are among the taxa most affected by temperature increases. For example, Runge et al. (2008) found that the survival of stocked rainbow trout in the Chattahoochee River, Georgia, was negatively related to the amount of time water temperatures exceeded 20°C (Fig 30), and that fish dispersed from warmer downstream reaches to cooler upstream reaches.

It should be noted, however, that other studies have found little or no relationship between water temperature and biota in urban streams (Kemp & Spotila 1997, Walters et al. 2009)—and as with all urbanization-associated stressors, it often is difficult to determine which of these often correlated stressors are driving biotic responses.

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