Tag Archives: phosphorus pollution

The Fight Against Toxic Algae

Signs posted around the Grand Lake, Ohio read: “Danger: Avoid all contact with the water.”  When dangerously high levels of toxins from blue-green algae in Grand Lake, Ohiio were publicized in 2009, many residents and tourists stopped using the 13,000-acre lake in northwest Ohio. Hotel revenue and home values sank for several years as algae bloomed in the state’s largest inland lake.

Greenish water still laps at Grand Lake’s shores, but recent water samples show that the amount of algae-feeding nutrients entering the lake is down significantly. State, federal and private donations covered more than $10 million in projects aimed at improving water quality. More people are boating on the lake again. Grand Lake could now serve as an example for communities with algae problems across the nation, experts say.

Algal blooms are on the rise, from Lake Erie to the Florida Everglades. In August 2019, the Environmental Protection Agency listed algae-related beach closures or health advisories in 23 states, and it said other blooms may not have been reported. In 2010, the EPA found that 20% of 50,000 lakes surveyed had been affected by phosphorous and nitrogen pollution, which feeds algae.e  Cleaning up bodies of water choked with toxic algae has proved difficult. The project to repair Grand Lake, once one of the most polluted by algae in the nation, is one of the clearest successes. It shows cleanup is possible, but also expensive and time-consuming.

“It’s not restored yet, but it’s on the road to recovery,” said Stephen Jacquemin, an associate professor of biology at Wright State University-Lake Campus in Celina.  Beginning in 2012, wetlands areas were built around the lake, which was hand dug in the 1830s. The thick stands of bulrushes and other plants have reduced phosphorous and nitrogen levels in water entering the wetlands before reaching the lake by as much as 90%, Dr. Jacquemin said.  Three wetland areas, which cost a total of about $6 million to build, are constructed as a series of interconnected pools that allow particulates to settle out and plants and microbes to remove nutrients.

Areal View of Artificial Wetlands, Great Lake Ohio

 The state’s Department of Natural Resources has also dredged the lake bottom to remove nutrient-loaded sediment, and tried to clean up one of Grand Lake’s beaches near St. Marys by building a rock jetty and installing aerators and a curtain to filter water. Recent water tests there showed levels below 6 parts per billion of the toxin microcystin, under Ohio’s threshold of 20 parts per billion for avoiding contact with water.

As Green Algae Forces Beaches to Close, Ohio Lake Offers Hope, WSJ, Sept. 18, 2019

Forest Fires in Africa Feed the Amazon Rainforest

The world’s largest rainforest and a crucial store of carbon dioxide gets most of its phosphorous, an important nutrient, from an unexpected source: fires in Africa.  Strange as it may seem, we thought that the Amazon got much of its phosphorus from dust whipped up from the Sahara Desert and transported across the Atlantic on the wind.

Cassandra Gaston at the University of Miami, US, and her colleagues had set out to quantify the effect of the phosphorous in Saharan dust on the Amazon’s growth. To do this, they collected and analysed particles caught in filters from a hilltop in French Guiana, at the northern edge of the Amazon Basin. But at the same time, they used satellites to track smoke from fires in Africa — both people burning wood and natural forest fires — drifting Westwards across the ocean. It turned out that the arrival of patches of smoke coincided with high levels of phosphorous being detected in the filters.  Gaston and her team then estimated how much of the phosphorus deposited on the Amazon Basin comes from African biomass burning. They found that, in Spring, smoke from the fires was responsible for most of the nutrient entering the Amazon Basin. …The findings suggest that people burning wood and other materials in Africa might have an impact on how much the Amazon grows and therefore how much carbon it stores in future.

Excerpt from The Amazon rainforest depends on fires in Africa for a vital nutrient, New Scientist, July 29, 2019

Mining Rights on the Ocean Floor: phosphate

A persistent fear of diminishing phosphorus reserves has pushed mining companies to search far and wide for new sources. Companies identified phosphate deposits on the ocean floor and are fighting for mining rights around the world….

From April 2007 to August 2008, the price of phosphate, a necessary ingredient in fertilizer, increased nearly 950 percent, in part due to the idea that phosphate production had peaked and would begin diminishing. Before prices came back down, prospectors had already begun looking for deep sea phosphate reserves around the world.

Since then, the fledgling seabed phosphate industry has found minimal success. While several operations are proposed in the Pacific islands, New Zealand and Mexico rejected attempts at offshore phosphate mining in their territory.  This means southern African reserves – created in part by currents carrying phosphate-rich water from Antarctica – are the new center of debate.

Namibia owns identified seabed phosphate deposits, and the country has recently flip-flopped about whether to allow mining. A moratorium was in place since 2013, but in September 2016 the environmental minister made the controversial decision to grant the necessary licenses. Since then, public outcry forced him to set those aside…

Three companies, Green Flash Trading 251 (Pty) Ltd, Green Flash 257 (Pty) Ltd and Diamond Fields International Ltd., hold prospecting rights covering about 150,000 square kilometers, roughly 10 percent, of  South Africa’s marine exclusive economic zone…[G]reen Flash companies received drill samples, which showed current prices could not sustain seabed phosphate mining.

This leaves Diamond Fields as the only remaining player in South African waters. The company announced in a January 2014 press release that it received a 47,468 square kilometer prospecting right to search for phosphate.  According to information the company published summarising its environmental management plan, prospecting would use seismic testing to determine the benthic, or seafloor, geology. If mining commenced, it would take place on the seafloor between 180 and 500 meters below the surface.  “A vital and indisputable link exists between phosphate rock and world food supply,” the company stated, citing dwindling phosphate reserves…

Environmentalists argue that not only would phosphate mining destroy marine ecosystems, but it would also lead to continued overuse of fertilizers and associated pollution. They call for increased research into phosphate recapture technology instead of mining.“We could actually be solving the problem of too much phosphates in our water and recapturing it. Instead we’re going to destroy our ocean ecosystems,” John Duncan of WWF-SA said.

The act of offshore mining requires a vessel called a trailing suction hopper dredger, which takes up seafloor sediment and sends waste back into the water column.  “It amounts to a kind of bulldozer that operates on the seabed and excavates sediment down to a depth of two or three meters. Where it operates, it’s like opencast mining on land. It removes the entire substrate. That substrate become unavailable to fisheries for many years, if not forever,” Johann Augustyn, secretary of the South African Deep-Sea Trawling Industry Association, said….

Mining opponents also worry offshore mining would negatively impact food production and economic growth. Several thousand subsistence farmers live along South Africa’s coast, and the country’s large-scale fishing industry produces around 600,000 metric tonnes of catch per year.

“[Mining] may lead to large areas becoming deserts for the fish populations that were there. If they don’t die off, they won’t find food there, and they’ll probably migrate out of those areas,” Augustyn said.

South Africa is one of only three African nations – along with Namibia and Seychelles – implementing marine spatial planning. This growing movement toward organised marine economies balances competing uses such as oil exploration, marine protected areas and fisheries….[and mining.]

Excerpts from Mark Olalde, Phosphate Mining Firms Set Sights on Southern Africa’s Sea Floor, IPS, Nov. 17, 2016