Coastal “dead zones” are on the increase. Algae farms may be the solution


In May 2019, the Mississippi River released a daily average of over 5,000 metric tonnes of nitrate and 800 metric tonnes of phosphorus into the Gulf of Mexico, the highest levels of the past 40 years. These excess nutrients from Midwestern farm fertilizers and animal wastes rob Louisiana, Mississippi, and Texas waters of oxygen, fueling toxic algal blooms and causing what is known as a dead zone.

The size varies each year, but the five-year average for this particular patch hovers around 5,000 square miles. To date, a US government task force has made little or no progress toward the goal of reducing it to 2,000 square miles.

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For environmental experts, the problem seems insoluble. Known as eutrophication, dead zones are proliferating all over the world. There are currently over 700 coastal areas around the world that are either dead zones or negatively affected by runoff. While the United States primarily suffers from agricultural waste, urban wastewater is the main culprit in South America, Asia and Africa.

Each year they inflict $ 3.4 billion in economic damage Europe and the United States alone due to loss of tourism and fishing, declining property values, water treatment and adverse health effects. Over the past 10 years, 85 U.S. communities have spent more than $ 1 billion combined to prevent or treat algae blooms. Among the hardest hit is the mouth of the Mississippi, where the constant ejection of water-borne waste from the heart of the United States is decimating local seafood and tourism industries.

But there may be a solution on the horizon. A A new study shows that the Gulf of Mexico could swap its slimy algae for silky green algae, which, if planted in sufficient numbers, could absorb much of this damaging waste. The concept is in its infancy and further implementation, but given the lack of progress on other fronts, study co-author Phoebe Racine said, “there is no other option than to consider alternative practices. “

Algal blooms can inflict economic damage through loss of income from tourism and fishing, declining property values, water treatment costs, and adverse health effects.

Photographer: Joe Raedle / Getty Images

Growing several species of algae in less than 1% of the waters of the Gulf of Mexico could potentially help the United States meet pollution reduction targets that were out of reach, University researcher Racine said. from California to Santa Barbara. She and her colleagues have already mapped areas suitable for seaweed farms in the Gulf and have found more than 24,000 square miles of potentially available sites.

Algae aquaculture dates back 1700 years in China. Nowadays, countries like Indonesia and the Philippines, as well as China and South Korea, are leading the world in this area. In South Korea, where aquaculture has grown by 300% over the past 30 years, an intensive effort has proven its usefulness as a waste reduction tool. As one of the largest producers of algae in Asia (where 99% of all algae is cultivated), the country has at least 2,144 seaweed farms covering a total of 350 square miles, according to Jang Kim, a marine scientist based at Incheon National University. . It’s an area about the size of Dallas.

Farms of three main algae species and two crustacean species (all filter feeders not requiring additional feed) absorbed the equivalent of 5.7% of carbon dioxide and 8.6% of nitrogen releases of all sewage treatment plants in Korea, according to a study led by Kim.


Algae aquaculture dates back 1,700 years.

Photographer: Hector Retamal / AFP / Getty Images

The key to the success of seaweed cultivation is its growing commercial potential and the fact that these aquatic plants can take up excess nitrogen and phosphorus and transform them not only into human food, but also into a growing array of additional commercial uses. The most cultivated algae include the red or brown algae species or the kelps. Some are used to make culinary thickening agents or agar to grow bacteria in the laboratory. Others are dried in sheets called nori used to make sushi rolls. While sugar kelp can be used as a sweetener, kelps are also used in toothpastes, shampoos, and frozen foods. and even pharmaceuticals.

Making seaweed farms profitable will be a crucial consideration in promoting them as a solution to agricultural and urban waste. Asia has a high demand for seaweed. Human consumption, including everything from sushi rolls and broth to salad, is the biggest market for harvested seaweed, Kim said. But growing demand can also be seen in the cosmetics and fertilizer industries, as well as in farmed seafood feed. “We have over 50% of the kelp production going to abalone feed,” Kim said.

Harvesting seaweed on a seaweed farm

In Maine, kelp growers harvested 482,000 pounds of wet seaweed in 2020 for a value of just under $ 300,000.

Photographer: Gregory Rec / Portland Press Herald / Getty Images

Mass aquaculture faces significant obstacles, including its labor intensive nature. The cultivation of marine algae either relies on laboratory nurseries to cultivate and tie juvenile algae to the net or line, or on the transfer of cuttings from mature plants to a submerged line. Harvesting usually involves several people on boats cutting the algae out of the water.

Globally, demand for marine algae is expected to double to $ 30 billion by 2025. In the United States, however, the market for marine algae is relatively small. Gretchen Grebe, an aquaculture researcher based at the Marine Biological Laboratory in Woods Hole, Mass., Said seaweed cultivation in America “is still in the midst of R&D.” She is studying coastal seaweed aquaculture in Maine, where in 2020 kelp farmers harvested 482,000 wet pounds worth just under $ 300,000. (Also in Maine, a company received $ 11 million in seed funding to grow kelp, then plunge it into the deep ocean to get carbon credits.) Racine argues that carbon credit markets used to slow pollution. “could be used more fully ”to encourage the extraction by algae of pollutants – including nitrogen, carbon and even heavy metals – from coastal areas.

refers to the increasing coastal “dead zones”.  Algae can be a solution

In the Faroe Islands, seaweed is cultivated for use in food, cosmetic and research projects.

Source: Courtesy of Ocean Rainforest

“Using algae aquaculture to remedy substantial amounts of nutrient pollution will require massive expansion – the current scale of cultivation will not even make a dent,” said Grebe.

In the United States, states have widely differing aquaculture licensing regulations. While it’s relatively easy to get a seaweed farm license in Maine and Alaska, California, it requires negotiating a maze of overlapping regulations.

“Offshore operations are where the promise lies,” said Bailey Moritz, program director for the World Wildlife Fund. “Our goal is to see algae grow in a way that will have significant impacts [on nutrient depletion], and the scale is needed for that. WWF has invested in Ocean Rainforest in the Faroe Islands, an operation that has designed platforms to withstand weather conditions at sea.

But large-scale seaweed operations are still at least a decade away in the United States, she predicted, and probably only if biofuels, bioplastics and animal feed create enough demand.

And while the US Department of Energy has invested $ 35 million dollars in research into the development of algae-based biofuels, with pilot projects starting in Puerto Rico, to date the Army Corps of Engineers has granted only one permit for a project seaweed in the Gulf of Mexico, according to Nakeir Nobles, a spokesperson for the Corps of Engineers. Nobels said other hurdles include site selection, endangered species law consultations, design plans that prevent entanglement of marine animals, and public education.

Algae holds great promise, said Grebe, but scientists are quick to point out that it is imperative to reduce upstream waste inputs as well. “We ask a lot of algae aquaculture to take care of the nutrient waste that we dump into the gulf,” she said.

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