Abstract: A major goal in the field of toxicology is to determine the effects of contaminants, like antimicrobials, that are increasingly becoming more abundant and thus more of a concern regarding biota and the environment. Despite the implications of elevated concentrations of antimicrobials in urban ecosystems, few studies have addressed the bioavailability and consequences of these contaminants on higher trophic levels. Triclocarban (TCC) and triclosan (TCS) are two of the most utilized antimicrobial compounds in the world and they can be introduced into ecosystems through a variety of sources including the application of biosolids to agricultural fields. I hypothesized that antimicrobials found in biosolids would be bioavailable and would negatively impact bird populations. To test these hypotheses, I compared the transfer of antimicrobials from land-applied biosolid to the eggs of two bird species between an Experimental (biosolid applied over a seven year period) and Control (no application of biosolid) agricultural site.
I also tested the impact of antimicrobials on egg morphometrics (egg length, egg mass, and egg shell thickness) and nesting success of birds. I used Liquid Chromatography-Mass Spectrometry to quantify the concentration of antimicrobials in biosolid, soil, earthworms, rodents, and eggs of the American kestrel (Falco sparverius) and the European starling (Sturnus vulgaris). Antimicrobials were significantly higher in soil, earthworms, rodent tissue, and eggs of starlings on the Control site compared to the Experimental site. Concentrations of antimicrobials in the eggs of kestrels did not differ between the Control and Experimental site. There was no correlation between antimicrobial concentrations and egg morphometrics for either bird species. Nesting success for kestrels was significantly lower on the Experimental site than the Control site, whereas nesting success of starlings did not differ between sites. This study demonstrated that antimicrobials from biosolids can be transferred to eggs of secondary and tertiary consumers and contaminants from biosolids and should be further investigated as a potential factor influencing the nesting success of birds.