Spillway’s fresh water destroys oyster beds, spurs algae blooms

22nd July 2019   ·   0 Comments

By Susan Buchanan
Contributing Writer

Fresh water from the Midwest floods has poured through the Bonnet Carre Spillway, 30 miles west of New Orleans, into southeast Louisiana and Mississippi this year. The spillway is a relief valve used to prevent local flooding.

River water running into Lake Pontchartrain and the Mississippi Sound has reduced salinity. And because of that, “we expect almost total devastation of oysters harvested east of the Mississippi River,” Ralph Pausina, president of the Louisiana Oyster Dealers and Growers Association, said last week. “Prime oyster areas are totally destroyed. They’ve been closed by the state as a precaution.”

According to the state’s Department of Wildlife and Fisheries, oysters can be harmed by a prolonged, fresh-water influx, depending on temperatures. In warm weather, extended exposure to fresh water increases oyster mortality.

On July 3, the state’s Department of Health closed harvest areas 1, 2 and part of 3 – in Lake Borgne, the Mississippi Sound and sections of St. Bernard Parish’s bays and bayous – after low salinity hurt oysters. Beds in areas 23 to 28 of Louisiana’s western Gulf were shut, starting on July 18, because of poor water quality following Tropical Storm Barry.

Before that, Governor John Bel Edwards on June 17 asked the Commerce Department in Washington to declare the state’s fisheries a federal disaster and sought funds from Congress to cover oyster, shrimp, crab and finfish losses. LDWF has been collecting data to support that request.

Louisiana is in its longest flood fight ever, according to state officials. Since its start in 1931, the Bonnet Carre Spillway has been open for the most days this year. Six trillion gallons of fresh water have killed oysters, fish and dolphins in Louisiana and Mississippi. Algae has flourished because of nutrients from farm and municipal runoff in the river water, closing beaches in both states.

“This year marks the first time the spillway structure has been opened twice in one year and the first time it has been opened in back-to-back years,” Rene Poche, U.S. Army Corps spokesman in New Orleans, said last week. The closing of the spillway, expected to start in mid-July, was delayed by Tropical Storm Barry.

“We’re waiting for the Mississippi River to drop to 21 feet at the spillway structure and to about 15.5 feet at the Carrollton Gage in New Orleans, before we can begin the closing process,” Poche said last week. Based on National Weather Service forecasts, closing could start in late July.

As of the middle of last week, “the structure has been opened 68 days and has 168 bays of the 350 bays open,” Poche said. “During the current opening’s peak, the structure passed 161,000 cubic feet of water per second.”

LDWF, in coordination with the National Oceanic and Atmospheric Administration, is monitoring an increase in dolphin strandings – most of which were animals found dead. Some of these stranded dolphins have had skin lesions consistent with freshwater exposure. As of July 11, NOAA declared an Unusual Mortality Event for common bottlenose dolphins in the northern Gulf. This event began in February, and strandings remain high, NOAA said. Ninety-two dolphins in Louisiana and 125 in Mississippi were stranded during the period.

In late June, Louisiana’s Department of Health issued an advisory about a developing, large algae bloom in Lake Pontchartrain and warned about swimming and plant contact.

Biologist Sibel Bargu Ates, Louisiana State University’s associate dean of the College of the Coast and Environment, explained that cyanobacteria, which are aquatic and photosynthetic, produce algae blooms. “Cyanobacteria is part of Lake Pontchartrain community,” she said last week. “When nutrients enter the lake, algae existing there take them up and grow. Cyanobacteria like warm, fresh water and a less turbid environment.”

Ates added, “Because the spillway is bringing lots of nutrients from the Mississippi River during summer’s high temperatures, cyanobacteria is in heaven and will continue to grow in optimum conditions.”

CyanoHABs, or Cyanobac-terial harmful algae blooms, and their toxins threaten human and animal health, aquatic ecosystems and drinking water supplies, according to the U.S. Environmental Protection Agency. They impact commercial and recreational fishing, swimmers and beach goers.

Because of harmful algae blooms, Mississippi’s Department of Environmental Quality as of July 7 closed all beaches to swimming, except those on barrier islands.

In a big nuisance, swarms of non-biting flies or midges have appeared this summer in New Orleans East, the city’s Lakefront near West End, Lakefront Airport and the Causeway Bridge. Their presence is attributed to the polluted, river water flowing into Lake Pontchartrain. These flies are smelly, and they end up in dead piles.

As for the oyster industry, “it will take two to three years for it to come back east of the Mississippi River,” Pausina predicted. “Even if the area’s oyster losses were 90 percent this year, the remaining 10 percent would be uneconomical to harvest, so it would be a 100-percent loss,” he said.

Benedict Posadas, associate extension-research economics professor at Mississippi State University, said that when Hurricane Katrina devastated the Mississippi Sound’s oysters in 2005, “it took more than two years for any significant landings to occur, and that was with intervention by state regulators.” In addition to oyster men, shuckers and processors were out of work then.

Louisiana supplies over 35 percent of oysters harvested in the nation, while Mississippi provides less than one percent. Local restaurants and merchants will turn to oysters from western Louisiana, Texas and Florida to fill their needs for now, Pausina said.

Louisiana has a voracious appetite for oysters, and the state supplies customers all along the nation’s coasts. But, last week, consultant Loren Scott, an LSU emeritus economics professor, said that oysters account for a modest share of local earnings. “For example in 2017, all fisheries and forestry activities generated $0.6 billion in Louisiana’s gross product of $238.1 billion,” he said. “The oyster part was particularly small.”

On the shore, however, “the effects of the disaster confronting the Mississippi Sound will linger for sometime, eroding quality of life for fishing households and communities and hurting businesses,” Posadas predicted.

This article originally published in the July 22, 2019 print edition of The Louisiana Weekly newspaper.