As an unprecedented amount of floodwater makes its way down the Mississippi River, the U.S. Army Corps of Engineers opened the Bonnet Carre Spillway at New Orleans for the second time this year.
“The river is changing, that’s not news, and we should pay close attention to what that means for us,” said Mark Davis with the Tulane Bywater Institute.

Corps officials also try and limit spillway openings to minimize the impact of invasive freshwater species entering the Lake Pontchartrain basin. One of those impacts could be harming marine life. A number of dead dolphins have been showing up recently in coastal Louisiana and Mississippi.

St. Bernard Parish President Guy McInnis says they have documented 26 dolphin deaths in the past two months, and most of the animals had freshwater lesions. Though Louisiana Wildlife and Fisheries officials have not made a direct link to the influx of fresh river water, officials in coastal Mississippi have after conducting a number of dolphin necropsies.

For oystermen, the opening of the spillway is always a cause for concern because it leads to plummeting water salinity levels as the freshwater suddenly dilutes the estuary’s brackish waters, which can kill the oysters they harvest.