Bone Development in Creek Chub from a Stream Chronically Polluted with Heavy Metals

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Abstract
Creek chub Semotilus atromaculatus from Rocky Fork, a metal-contaminated stream in north-central Ohio [USA], and Clear Fork, a nearby uncontaminated stream, were studied to determine the effects of chronic heavy metal contamination from industrial and municipal sources on bone development. We examined bone development of fish from two contaminated sites in Rocky Fork and from four reference sites-three in Clear Fork and one in Rocky Fork-to evaluate variability among reference sites, and to determine if the clean-water headwater site on Rocky Fork was a suitable reference site for the two downstream contaminated sites. Collagen composition, density, strength, and energy-absorbing capacity of bone were significantly higher in fish from the headwater site on Clear Fork (upstream from an impoundment) than in fish at the other three reference sites. In bones of creek chub sites in Rocky Fork where the water contained high total concentrations of chromium, copper, iron, nickel, and zinc, the collagen content of bone was lower but density and strength were higher than in bone of fish from the reference site. Some fish also had deformed vertebrae in the caudal peduncle region of the spinal column, which is a condition characteristic of neuromuscular overload of vertebrae. The high concentrations of chromium and zinc in fish from the contaminated sites probably interfered with collagen metabolism and altered the density and mechanical properties of bone. Creek chub at the contaminated sites seem to be tolerant of heavy metal contamination and may be adapting physiologically to the chronic metal stress in their environment.