Portions of Lake Pontchartrain turn green as algae bloom

Effects from the Bonnet Carre linger weeks after the spillway closed

Portions of Lake Pontchartrain turn green as algae bloom
A plastic cup of algae from a site near the Causeway Bridge (Source: John Snell)

NEW ORLEANS, La. (WVUE) -- Motorists traveling the Causeway Bridge about four miles from the north shore of the lake might notice a green tint to the water.

An algae bloom under the Lake Pontchartrain Causeway
An algae bloom under the Lake Pontchartrain Causeway (Source: John Snell)

An algae bloom, which appears to be one of the larger ones to form this summer in the lake, runs under the bridge for three or four miles and stretches a couple miles to the east and west.

It shows the lingering effects of this year’s unprecedented back-to-back openings of the Bonnet Carre Spillway, which sent several trillion gallons of nutrient-laden river water into the lake.

The algae feast on fertilizer runoff, primarily from farms in the midwest.

“Everything has been pretty clear on the south shore,” said Dr. Brady Skaggs, Water Quality Program Director for the Lake Pontchartrain Basin Foundation, which has been collecting water samples in the lake.

“The algae has been mostly toward the north shore.”

Skaggs said the samples they have taken have not exceeded EPA guidelines for algae toxins.

However, the Louisiana Department of Health has advised against swimming in the lake.

A boat wake churns up green water from an algae bloom in Lake Pontchartrain
A boat wake churns up green water from an algae bloom in Lake Pontchartrain (Source: John Snell)
Algae in Lake Pontchartrain
Algae in Lake Pontchartrain (Source: John Snell)
Algae near pilings of the Lake Pontchartrain Causeway
Algae near pilings of the Lake Pontchartrain Causeway (Source: John Snell)
Algae near pilings of the Lake Pontchartrain Causeway
Algae near pilings of the Lake Pontchartrain Causeway (Source: John Snell)
The shoreline in Fontainebleau State Park shows no sign of the algae bloom in Lake Pontchartrain
The shoreline in Fontainebleau State Park shows no sign of the algae bloom in Lake Pontchartrain (Source: John Snell)

In many spots, the lake seems relatively normal. It’s even possible to see the lake bottom in a few feet of water about 300 yards from the shoreline.

However, a few miles to the west, algae mats pile onto the shoreline just east of the Causeway along the Mandeville lakefront.

Scientists say it will take time for the lake to return to normal, but gauging when exactly that might happen is difficult as the algae thrive in the heat of a Louisiana summer.

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