UCLA

Widespread overuse and large-scale production of antibiotics create antibiotic pollution, disrupting environmental microbiota and creating a public health risk. Highly urbanized coastal environments can be under high impact from antibiotic pollution from many trails of polluted effluents and runoff. The city of Long Beach is one such coastal area under high impact, since it is highly urban, industrialized, and experiences frequent sewage spills. We collected water samples from the LA River in a transect running southwest into the San Pedro Channel in order to investigate (1) how does strength of antibiotic resistance change as distance from shore increases, and (2) does antibiotic resistance correlate with composition of the bacterial community. There was no consistent relationship between strength of antibiotic resistance and distance from shore. Instead, we found that bacteria from the Pacific Ocean showed higher antibiotic resistance than bacteria from the LA River in five out of eleven antibiotic treatments. We also found that the alpha diversity of bacterial communities was lower in the LA River samples compared, and alpha diversity positively correlated with strength of antibiotic resistance in four antibiotic treatments. Our findings highlight how prevalence of antibiotic pollution does not always follow a distance dilution, as well as the need for understanding the strength behind antibiotic resistance in marine bacteria.