Episodic Acidification and Changes in Fish Diversity in Pennsylvania Headwater Streams By Matthew T. Moran
Why? • Concern for loss of species diversity in fish.
Objectives • Compare the diversity of the fish species in 70 streams in Pennsylvania’s Appalachian Plateaus and Valley and Ridge provinces during 1961-1971 with the diversity of fish species in these same streams during 1994-1995. • Relate any changes in fish diversity to changes in water chemistry and the occurrence of acidic runoff episodes.
Methods • 50 streams in the Appalachian Plateaus • 20 streams in the Valley and Ridge province • 1st, 2nd, or 3rd order streams • Predominately forested watershed • Uninfluenced by mining or gas wells
Tests • Measured colorimetric and laboratory pH • Conductivity-test for metals • Alkalinity-mainly composed of bicarbonates, carbonates, and hydroxides. • Streamflow-flowmeter • Total dissolved aluminum-amount of dissolved is strongly influenced by acidity. • Electrofished
Conclusion • In the past 24 years, a reduction on fish diversity has occurred in a large number of low alkalinity streams in PA. • Changes in stream pH and alkalinity during this period and the presence of near toxic to toxic concentrations of aluminum provide strong evidence that loss of diversity is linked to acidification of poorly buffered streams.