Mississippi River runoff linked to declining health of Flower Garden Banks reef
New research shows rising nitrogen from the Mississippi River is harming the Flower Garden Banks coral reef, once considered a regional stronghold.
An international team examined coral skeleton cores from the Flower Garden Banks National Marine Sanctuary and a control site off northern Cuba, revealing a marked rise in nitrogen levels beginning around 1850 and accelerating after the 1960s. The nitrogen, primarily in the form of nitrate, is linked to agricultural fertilizer runoff from the Mississippi River. Researchers concluded that most of the nitrogen entering the reef originates from the Mississippi basin, despite other possible sources.
The sanctuary, historically resilient due to its cooler waters and distance from shore, suffered major disease outbreaks in 2016 and 2022 and bleaching events in 2022 and 2023. These stressors corresponded with the highest recorded nitrogen inputs and unusually warm temperatures, suggesting future increases in disease and bleaching if runoff continues.
Why it matters
The findings connect upstream farming practices to the degradation of a key Gulf of Mexico coral ecosystem.
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