Effects of Atrazine on the Microbiome of the Eastern Oyster

AbstractThe Effects of Atrazine on the Microbiome of the Eastern Oyster: Crassostrea virginicaThe Chesapeake Bay has suffered a dramatic loss of its native mollusk species, the eastern oyster (Crassostrea virginica). It is believed that this loss is caused in part by contamination of the bay with atrazine, a herbicide that washes off of agricultural crop land and penetrates into surrounding surface and groundwaters. The long-term ecological effects of this herbicide on oyster-prokaryote interactions are unknown. There is long-standing evidence that microbiota are of vital importance for the survival, homeostasis, and overall development of marine mollusks, and that shifts in their microbial environment can dictate chances of survival into adulthood. Here, 16S rRNA gene amplicons were used to evaluate how microbial compositions shift in response to exposure of environmentally relevant concentrations of atrazine found within the Chesapeake Bay (30 µg/L, 20µg/L, 10µg/L and 3 µg/L respectively). The dominant bacterial genera found within all groups included those belonging to Pseudoalteromonas, Burkholderia, Bacteroides, Lactobacillis, Acetobacter, Allobaculum, Ruminococcus, and Nocardia. Although our results confirm that oysters maintain similar core microbial communities when compared to previously published studies, we also report a novel finding, namely, that oysters exposed to atrazine concentrations as low as 3µg/L saw a significant loss of microbial species from their microbiome. The runoff and persistence of atrazine in the Chesapeake Bay may be contributing to a significant shift in the microbiomes of juvenile oysters, leading to a decline in restoration efforts which target reseeding baby oysters instead of adults.