Glyphosate , the con­tro­ver­sial main ingre­di­ent in Mon­san­to ​’s Roundup and oth­er her­bi­cides, is being con­nect­ed to Lake Erie’s trou­bling algae blooms, which has fouled drink­ing water and suf­fo­cat­ed and killed marine life in recent years.

Phos­pho­rus—attrib­uted to farm runoff car­ried by the Maumee Riv­er — has long been iden­ti­fied as a lead­ing cul­prit feed­ing the exces­sive blooms in the west­ern Lake Erie basin. Now, accord­ing to a new study from chem­istry pro­fes­sor Christo­pher Spiese, a sig­nif­i­cant cor­re­la­tion has been estab­lished between the increased use of glyphosate to the per­cent­age of dis­solved reac­tive phos­pho­rus (DRP) in the runoff.

As No-Till Farmer observed from the study, DRP loads in Lake Erie increased in the mid-1990s at the same time that farm­ers began the wide­spread cul­ti­va­tion of crops genet­i­cal­ly engi­neered to with­stand mul­ti­ple appli­ca­tions of Roundup.

“For every acre of Roundup Ready soy­beans and corn that you plant, it works out to be about one-third of a pound of P [phos­pho­rus] com­ing down the Maumee,” Spiese told the agri­cul­tur­al publication.

Here’s how the team came to the con­clu­sion, as No-Till Farmer reported:

Through his own and oth­ers’ research, Spiese found that depend­ing on the types of met­al in the soil, glyphosate does release P. For exam­ple, when glyphosate is applied to soil con­tain­ing iron oxide-hydrox­ide, P is imme­di­ate­ly released. But almost noth­ing is removed when it’s an iron oxide material.

Final­ly, Spiese took soil sam­ples all over the Maumee water­shed, applied P to them and then sprayed glyphosate to see how much P was released vs. soil that was­n’t sprayed with glyphosate after 24 hours. He saw des­orp­tion occurred all over the water­shed, but cer­tain areas were high­er than oth­ers, specif­i­cal­ly in the south­east­ern corner.

Based on the aver­age two glyphosate appli­ca­tions grow­ers make every year, Spiese esti­mates that over­all, 20 – 25 per­cent of the DRP runoff is caused by glyphosate. But depend­ing on the loca­tion with­in the water­shed, that per­cent­age could be much low­er or much greater.

“Some of those sites, it’s less than a per­cent. Oth­er sites it’s almost 100 per­cent,” he says.

Pre­vi­ous stud­ies have tied glyphosate to the phos­pho­rous fuel­ing Lake Erie’s blue-green algae. In 2009, Ohio Sea Grant researchers, Drs. R. Michael McK­ay and George Buller­jahn of Bowl­ing Green State Uni­ver­si­ty, found that glyphosate could only be detect­ed in the lake at cer­tain times of year — after crops are planted.

“Our research is find­ing that Roundup is get­ting into the water­shed at peak farm­ing appli­ca­tion times, par­tic­u­lar­ly in the spring,” McK­ay said.

Approx­i­mate­ly 1,000 met­ric tonnes (about 2.2 mil­lion pounds) of Roundup is applied in the Lake Erie water­shed per year, and it is being detect­ed in adja­cent water­ways par­tic­u­lar­ly in the spring, the Ohio Envi­ron­men­tal Pro­tec­tion Agency (EPA) not­ed from McK­ay and Buller­jah­n’s study.

The researchers also found that the blue-green algae (cyanobac­te­ria) in the lake are capa­ble of using phosophonates.

“It turns out that many cyanobac­te­ria present in Lake Erie have the genes allow­ing the uptake of phos­pho­nates, and these cyanobac­te­ria can grow using glyphosate and oth­er phos­pho­nates as a sole source of phos­pho­rus,” Buller­jahn said.

A satel­lite image of the 2015 Lake Erie algae bloom. (Pho­to: NOAA Great Lakes Envi­ron­men­tal Research Laboratory)

Harm­ful Lake Erie blooms have increased at record lev­els over the last decade, accord­ing to the U.S. EPA and are expect­ed to become more com­mon due to warmer tem­per­a­tures and heavy rain­fall that feed algae growth.

The tox­ic algae rob oxy­gen from the waters cre­at­ing dead zones where fish and oth­er marine life are unable to sur­vive. The algae is also a threat to humans — swal­low­ing it can cause health prob­lems such as rash­es, vom­it­ing, numb­ness and dif­fi­cul­ty breathing.

In Feb­ru­ary this year, the Unit­ed States and Cana­da announced a goal to reduce the amount of phos­pho­rus enter­ing affect­ed areas of Lake Erie by a total of 40 per­cent by 2025.

A dead fish sur­round­ed by algae in Lake Erie dur­ing a record-set­ting algae bloom in 2011. (Pho­to: Tom Archer / NOAA)

(This arti­cle was pub­lished on EcoW​atch​.com)