Factors affecting survival and recruitment of unionid mussels in small midwestern streams

Melody Lynn Myers-Kinzie, Purdue University

Abstract

The purpose of the present study was to investigate natural and anthropogenic factors affecting the survival and recruitment of unionid mussels in small midwestern streams. Unionid mussels have been undergoing a decline in many places, and it is thought that the juvenile is the most sensitive life stage. Because most studies have focused on larger rivers, the status of mussels in small streams is not well known. This study focused on the small streams of Tippecanoe County, Indiana, where a survey of 52 sites found streams having from 0 to 26 species. Mussel species richness was positively correlated with watershed area (r2 = 0.91) and fish species (r2 = 0.80) richness. Using presence/absence data on fish populations from these streams, a chi-square analysis indicated factors (p < 0.005) other than host fish availability limited mussel distributions. Shear stress is thought to be a factor in the failure of juveniles to survive the postparasitic period and a significant negative correlation (r2 = 0.74) was found between calculated shear stress at high flow at sites with mussels and number of mussel species present. A comparison of hydrologic variability of two streams, one with mussels and one without, for May, June and July showed that the stream with no mussels was significantly (p = 0.03) more variable. Substrate type was less important in determining adult mussel occurrence. A standardized habitat evaluation protocols designed for fish (QHEI) was of little utility in predicting mussel occurrence. Acute toxicity testing was done with artificially cultured Lampsilis siliquoidea juveniles, and 48 hour LC 50 results indicated that the agricultural pollutants ammonia (0.09 mg N/L), nitrite (0.19 mg N/L), and potassium (28 mg/L) may be significantly toxic to young mussels. Comparison of acute toxicity data of juvenile mussels to published reports of these same toxicants with other aquatic organisms indicates that juvenile mussels are more sensitive to pollutants than many other taxa. In addition, toxicity testing with agricultural stream water collected after storm events during peak planting season produced mortalities between 20% and 60%. Water quality standards based on other, less sensitive organisms therefore may not be protective of juvenile mussels.

Degree

Ph.D.

Advisors

Spacie, Purdue University.

Subject Area

Freshwater ecology|Ecology|Zoology

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