you're reading...


Measuring “Roundup” in the Great Barrier Reef

Mercurio, P., Flores, F., Mueller, J. F., Carter, S., & Negri, A. P. (2014). Glyphosate persistence in seawater. Marine pollution bulletinDOI: 10.1016/j.marpolbul.2014.01.021

"Roundup Ready technology" is a form of herbicide-resistant crop developed by Monsanto (MonsantoBlog.com)

“Roundup Ready technology” is a form of herbicide-resistant crop developed by Monsanto (MonsantoBlog.com)

What is glyphosate?

Glyphosate is a form of broad spectrum herbicide commonly found in “Roundup” which was brought into popularity in the U.S. during the 1970’s by Monsanto.  Glyphosate kills plants via contact with foliage or roots; in small doses, it can control growth.

Glyphosate reached greater popularity when Monsanto released glyphosate-resistant crops.  Farmers could now apply the herbicide broadly to their fields without harming crops.  Glyphosate is now an integral part of worldwide agriculture used in massive quantities annually.  With such a long history of use, it is no wonder that several glyphosate-resistant weeds have developed under agricultural selection pressure.  In 1996, the first resistant weed was reported in Australia followed by many others in Canada and the U.S.

The Environmental Protection Agency (EPA) states that glyphosate has relatively low dermal and oral toxicity.  Studies with rats indicate that it does not bioaccumulate in the food chain and there is insufficient evidence to suggest glyphosate causes cancer.  However, rats directly exposed to the herbicide did experience blood, liver, and pancreatic problems.  In high doses, glyphosate may also act as an endocrine disruptor.  Dietary studies used in the EPA assessment do not indicate significant risks from consuming plants exposed to glyphosate at current levels of usage.  A 2002 study commissioned by the European Union reached the same conclusions.

The half-life (time needed for the initial concentration to degrade by half) of glyphosate in soil or freshwater can vary from just a few days to nearly 200 days (Table 1).   Glyphosate is broken down fairly quickly to a major metabolite aminophosphonic acid (AMPA) through organic processes.  However, it is also applied in great quantities during the summer season when heavy precipitation washes much of the herbicide into coastal waters.  Water quality in near shore waters is of particular concern for sensitive corals and seagrass in the Great Barrier Reef (GBR) system.  Glyphosate is the mostly widely used herbicide in the Australia with about 15,000 tons of glyphosate applied annually.

Researchers from Australia set out to quantify how long it takes for glyphosate to biodegrade in the Great Barrier Reef (GBR) system.  This is the first study to measure the persistence of glyphosate in seawater.

Table 1. Glyphosate half-life time in various soil and freshwater studies (Mercurio et al. 2014, Table 2).

Table 1. Glyphosate half-life time in various soil and freshwater studies (Mercurio et al. 2014, Table 2).


Figure 1. Satellite image of the Great Barrier Reef off of Queensland (retrieved from Wikipedia, photo by NASA).

Figure 1. Satellite image of the Great Barrier Reef off of Queensland (retrieved from Wikipedia, photo by NASA).


Glyphosate degradation was measured in a flask “simulation tests” over the course of 330 days.  Tests used natural seawater containing native bacteria present in the Great Barrier Reef (GBR).  No nutients or food were added to the flasks.  Three treatments were used to mimic conditions in the GBR lagoon: (1) 25°C in the dark (mean annual seawater temperature in the GBR), (2) 25°C in low light, and (3) 31°C in dark (maximum summer temperature for near-shore waters in the GBR).

The half-lives of glyphosate in each treatment were calculated using the slope of the data for the natural log of glyphosate concentration over time.

Results and Significance

Half-lives were much greater for both dark treatments than the light treatment.  Although the light treatment was comparable to other freshwater studies (Figure 2; Table 1), the dark treatments at 25°C and 31°C (267 days and 315 days) persisted much longer than previous reports. These results suggest that glyphosate is highly persistent in dark conditions with a modest temperature effect between the two treatments.


Figure 2. Glyphosate concentrations (natural log) and half-life (t ½) for each treatment (Mercurio et al. 2014, Figure 2).

Figure 2. Glyphosate concentrations (natural log) and half-life (t ½) for each treatment (Mercurio et al. 2014, Figure 2).

Although the methods used in this study mimicked the natural environment, the authors state more work is needed to determine details of glyphosate’s fate in the marine environment.  For example, glyphosate is known to bind to organic material which suggest glyphosate would stay near to shore.  However, this binding potential also prevents degradation and may translate to very long distance transport.

Glyphosate is not incorporated in most marine monitoring programs.  This is surprising given that is one of the most widely used herbicides in the world.  Other recent work also suggests that the toxicity of glyphosate is tied to the surfactants it is often combined with in commercial products such as “Roundup”.  Further work is needed to examine glyphosate’s potential in the marine environment.


The authors also measured the metabolite product of glyphosate degradation aminophosphonic acid (AMPA) in the flasks.  As glyphosate was metabolized by bacteria, the concentrations of AMPA increased (Mercurio et al. 2014, Figure 1).

glyphosate 1






No comments yet.

Post a Comment


  • by oceanbites 6 days ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 2 weeks ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 3 weeks ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 1 month ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 3 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 3 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 4 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 4 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 5 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 5 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 6 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 6 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
  • by oceanbites 7 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
  • by oceanbites 7 months ago
    Have you seen a remote working setup like this? This is a photo from one of our Oceanbites team members Anne Hartwell. “A view from inside the control can of an underwater robot we used to explore the deep parts
  • by oceanbites 8 months ago
    Today is the day of  #shutdownacademia  and  #shutdownstem  and many of us at the Oceanbites team are taking the day to plan solid actions for how we can make our organization and the institutions we work at a better place
  • by oceanbites 8 months ago
    Black lives matter. The recent murders of Ahmaud Arbery, Breonna Taylor, and George Floyd have once again brought to light the racism in our country. All of us at Oceanbites stand with our Black colleagues, friends, readers, and family. The
WP2Social Auto Publish Powered By : XYZScripts.com