The effects of agriculture on fish communities in the Upper Mississippi River System through archaeological and modern time periods

Background/Question/Methods

Throughout time, humans have impacted the environment. Scientists now recognize a new geologic epoch, the Anthropocene, defined as the period where human actions are the primary driver of climatic and environmental processes. One factor affecting the environment is agricultural production. Agriculture causes nonpoint source pollution, increasing phosphorus and nitrogen inputs, and sedimentation. More intensive agricultural practices developed during the Mississippian (900 and 1500 A.D.), and as such, Mississippian agricultural production may have affected the river and riverine fish communities in the past. We hypothesized that the development of intensive agriculture in the Mississippian period would cause fish communities to be more similar to fish communities in the modern era relative to fish communities in other archaeological time periods. To test our hypothesis, we compared fish communities represented among archaeological collections and modern fish monitoring programs. We specifically focused on those fish taxa sensitive to water quality.

Results/Conclusions

Modern samples differed significantly (P ≤ 0.0001) from all archaeological time periods. We found no significant differences (P ≥ 0.09) between fish communities in collections from the Mississippian period and the archaeological collections from other periods. The Emergent Mississippian differed significantly (P ≤ 0.0006) from the Middle and Late Woodland. While our hypothesis was not supported, we know sedimentation from agriculture has impacted fish communities over time. Additional research using modern data that is sensitive to sedimentation should be used to determine how fish communities have been impacted by agriculture. The difference in the Emergent Mississippian temporal period could be the result of an environmental anomaly and should be investigated.