When a tear in the lining of a wastewater pool at a former phosphate plant threatened to unleash a 20-foot wave of contaminated water into neighborhoods in Piney Point, Florida, officials had no choice but to pump millions of gallons of the water into Port Manatee, a cargo port along the eastern shore of Tampa Bay.

The transfer of 165 million gallons into the bay averted catastrophe. But scientists and state officials are now urgently monitoring the bay’s water quality, fearful that nutrients in the wastewater could lead to harmful algal blooms and disrupt the bay’s marine ecosystem.

The 77-acre containment pond contains a mix of seawater, nitrogen, and phosphorus. Before the tear, first reported on March 25, it held