Trojan Horse Herbicides

08 Sep

Red Mangrove (Rhizophora mangle) (CLICK for nice Gigapan Red Mangrove by John Bradford added subsequent to posting this blog)

Black Mangrove (Avicennia germinans)

White Mangrove (Laguncularia racemosa)

Toxic “Algae” (Microcystis aeruginosa)

John and George today worked on our tans portaging camera gear around the Kiplinger Natural Area on the St. Lucie River by Stuart.  John seized the day to capture Gigapan photos of the river shore.

Gigapan photos allow viewers to pan around and to zoom in on details.  Try it after CLICKING HERE to cyber-visit the river.

We had Mangroves on our mind, and they did not look healthy.  The shore is lined with a species jumble, including Brazilian Peppers, and many mangroves (especially red mangroves) are dead or visibly unhealthy.    (As pointed out in the commentary below,  the dead trees in the gigapan seem to be entirely or mostly Brazilian Pepper, although in the vicinity there are miserable mangroves too.  The mangroves at this site look decidedly less healthy than those directly on the Intracoastal where I spend a lot of time.  I have re-edited this post post-publication to reflect the fact that most of the dead trees are not mangroves.  The main point is the water contamination, so read on.)

Now you might say, justifiably, that 10 boat-miles upstream from the St. Lucie Inlet might be marginal mangrove habitat to begin with.  (What killed the Brazilian Peppers is interesting too.)  A possible reason mangroves to be so far upstream is increased salinity due to reduced freshwater flow from upstream thanks to some mix of water-control activities, dams and spillways,  diversion, droughty times, and altered land use patterns. (Or maybe not.)  Maybe that pulls the mangrove yo-yo upstream.

Now, if increased salinity crept up the St. Lucie River over some years, or even if it didn’t, the massive summer releases from Lake Okeechobee push the other way.  The lakewater this summer reduced salinity to almost zero even near the Inlet.  The usually brackish lower river was freshwater.

And that would be freshwater overloaded with nutrients, with nutrient-fed “Algae” (mostly Cyanobacteria), toxins from those Cyanobacteria, sediments, and whatever else enters the Lake and the River from agriculture and suburbia.

Yesterday the river water was dark, opaque, stinky, and lifeless.   A boat went by and you could smell its wake splashing on the marly shore where we saw no Fiddler Crabs, despite John photographing their abundance at exactly the same site not long ago in this very blog.  CLICK to see missing crabs.

I wonder if the missing crabs used to benefit the mangroves by churning and  aerating that watery soil?

(Come to think of it, there weren’t even any mosquitoes.)

Most local readers probably know about the Lake Okeechobee flush disaster this summer and other years.     No need to re-beat that dead horse in general terms.  But specifically, what about the dominant riverbank woody vegetation—those red, black, and white mangroves?

Known or suspected causes of mangrove decline, in addition to storms and freezes, include salinity changes,  excess sediments, excess nutrients, and herbicide contamination.  These all arrive in water from Lake O, on top of everyday watershed abuses.

The last culprit in the list is subtle.  Herbicides?  Studies of mangrove dieback in Australia pinpointed herbicide river contamination as a mangrove-killer, especially the herbicide Diuron, which has an extra- special vengeance for the genus Avicennia (Black Mangroves).

Diuron is toxic false-fertilizer.  It kills mangroves, and yep, we have it in local waters.

Diuron is toxic false-fertilizer. It kills mangroves, and yep, we have it in local waters.

So then, what about Diuron in the St. Lucie River?  Yes, in the notes below is a link to a dated but still-relevant USGS study of pesticides in the St. Lucie River.  The top five pesticides detected were all herbicides, including Diuron, as well as our traditional favorite lawn-weedkiller Atrazine and others.  Diuron is a Sneaky Pete herbicide.  Plants take up natural urea (or the ammonia soil microbes degrade it into).  Diuron is a urea mimic, water soluble, a Trojan Horse false-fertilizer similar to urea but with chlorinated timebombs built into the molecule.

The concentrations were “low,” but how low is low enough, especially in light of the gang-attack of several different herbicides, the probability that concentrations are higher in sediments than in the tested water,  that there is more development now than in the 90’s, and especially that those pulses of agricultural/suburban-lawn  contaminated lake water may have higher pesticide loads than “nice” water on a good day.

Can I say that Diuron killed the mangroves?  No.  Can I say that the Lake O water did it?  No.  But there’s something rotten in the State of Denmark.  Salinity volatility, crud,  N and P in gobs,  natural bacterial toxins,  and the fruits of modern chemistry all attacking a trio of mangrove species, each with specialized and delicate physiology with respect to salt, nutrients,  water transport and the soil ecosystem.

Some time ago in this blog we discussed the reproduction of Black Mangroves.  They drop their bare embryos directly from the fruit into the water.  CLICK

Yep, right into the Diuron-laced stinkwater sloshing around their snorkel roots jutting up to sustain life through the toxic sediment mud where the crabs ain’t no more.



USGS report on pesticides in St. Lucie River

Used the same item for both my blogs this week.  Don’t tell anyone.


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16 responses to “Trojan Horse Herbicides


    September 8, 2013 at 3:40 pm

    New post on Treasure Coast Natives Topic: My hopeful humble opinion:
    John and George-
    I really liked the Gigapan photo. Am I seeing a healthy treetop bloom of mangrove rubber vine? My main thought is this: You didn’t mention seeing huge numbers of Brazilian Pepper, so I’m going to make a wild guess that the primary healthy looking foliage might be buttonwood, which I and several of my colleagues include in the mangrove group, and which will flourish far away from a saline or brackish environment, whereas red mangrove will not. I’m not able to tell from the pictures whether the leaves are simple or compound, but they look like they have pointed tips, as would buttonwood. Let me know what you think.
    Best wishes, and keep up the good work
    Jay Barnhart Jr

    • George Rogers

      September 8, 2013 at 5:11 pm

      Lots of Mangrove Rubbervine around, including the distant flowers in the treetops no doubt. There is plenty of Brazilian Pepper around too and right up to the water in places, and it is plausible that Buttonwood is in the mix on the far shore, it is around, although plant inventory was not really on the agenda, and we did not cross the river. Fun to guess, no actual ground-truthing.

  2. Mary Hart

    September 9, 2013 at 3:24 am

    UK of course has no mangroves, but suffers exactly the same problems of herbicide (and fertilizer) run-off from farmland etc. which has caused drastic harm to both river and coastal waters.

  3. George Rogers

    September 9, 2013 at 6:35 am

    Mary, The worst case I’ve seen is in Barbados, where the top aquifer was to contaminated to use for tapwater, and contaminated groundwater leaked out after rains down the hillside on the “Gold Coast,” at times reaching the wet sand on beaches at the resorts, with extreme instances causing skin lesions on sunbathing tourists.

  4. Diane Goldberg

    September 9, 2013 at 7:57 am

    At the Aug. 22nd lagoon meeting, it was said that the state & local governments can not make any requirements of the farms & ranches as long as they follow ‘Best Management Practices’. These ‘practices’ should require & not just include the reuse or cleaning of their runoff or they should be required to pay a per acre charge for the government agencies to clean & dispose of the water for them. There are lots of things our government could require us to do, like use only iron instead of N & P fertilizer to green up grass during the rainy season (June, July & Aug.). Until septic tanks can be changed over to city sewer systems, the gov. can also require that septic tanks be emptied when more than half full before hurricane season, so they won’t overflow. It’s a shame that people don’t know to do these things, & some who do won’t do them.

  5. Mike Y

    September 9, 2013 at 8:37 am

    Hey George,

    I think that a lot of the dead vegetation that is visible on the far shoreline is Brazilian pepper. Did you see other areas of dead vegetation out there? Most of that far shoreline is dominated by Brazilian pepper and the mangroves grow closer to the center of the island. Also, I do not believe that there are green buttonwoods on that portion of the river. The only areas that I have found it are adjacent to the IRL and along the Hutchinson/ Jupiter Island.

    • George Rogers

      September 9, 2013 at 10:33 am

      Thanks mike for the detail. I’m sure you are correct, although I spied with my own little eye miserable mangroves on the side of the river where we stood, even in the water. That of course does not take an ounce away from your observation that those skeletons across the water could be BP. I’ve never been across there and the distance is longer than the gigapan makes it seem. I really don’t know about Buttonwoods at that site, so glad you cleared that up. If BP across the water, what killed them? (You?)

      • George Rogers

        September 9, 2013 at 10:39 am

        Mike, I went back and took a harder look at the gigapan and do see what you mean. Far more BP than mangrove, although one of the skeletons has stilt roots. going to re-edit the blog accordingly. So what did kill hte BP?

  6. ehopec

    September 9, 2013 at 9:09 am

    What a timely topic! Tomorrow, September 10, at 8:30 AM at Southwest Florida Water Management District Headquarters in Brooksville (2379 Broad Street, Brooksville, FL 34604
    ) there will be a hearing where the Public will protest SWFWMD’s ignoring of Florida’s Outstanding Waterway Laws, and demand that the State, DEP, and Water Management District uphold Clean Water Act and Florida Outstanding Waterway Laws by reducing consumptive use withdrawals, and restricting activities which further degrade Florida’s Outstanding Waterways, springs, and fresh water aquifer.

    SWFWMD has set consumptive withdraw targets of 3% (Reduction in Flow) to the Chassahowitzka and Homosassa Springs, which are both Outstanding Waterways, already suffering from pollution and degradation. Both of these world-famous spring-fed rivers are desperately in need of restoration, not further reduction in flow!

    Sadly, our state seems to be run by the “best Governor and Legislature that Money Can Buy,” our laws and municipal codes drafted by the likes of Scott, Syngenta, Monsanto, water bottlers, phosphate mining interests, big oil, big gas, big frac, the manufacturers and distributors of fertilizers, herbicides, pesticides; and of course, developers. It is past time for We the People to stand together and demand Laws and Legislators that work for US, and that protect Florida’s Native Habitats and Natural Resources, that sustain us all.

    Coast to Coast, and Panhandle to Keys, we should attend Public hearings, in the largest numbers possible, and remind our Elected Officials that they are in OUR Employ; that is not only Our natural resources and health in Their hands, it is Their Future (and Fortunes) in OURS.

    A coalition of Citizens, Environmental groups, and Save the Manatee Club, have joined together and organized as “Save Our Springs Now” and welcome your attendance and support as they attend Public Hearings, like the one at Water Management District Headquarters (2379 Broad Street, Brooksville, FL 34604) tomorrow (Sept. 10 at 8:30 AM), demanding that the Water Management District and State of Florida uphold Clean Water Act and Florida Outstanding Waterway laws, reduce pollution to Florida’s waterways and aquifer, and restrict activities that further degrade Florida’s Springs and Outstanding Waterways.

    Those unable to attend the Public Hearing tomorrow may submit written comments to

    For more information about Save the Manatee Club’s work with Save Our Springs NOW initiatives, see

  7. George Rogers

    September 9, 2013 at 10:29 am

    Thank you for all this input. I must confess part of my motive for selecting this topic this week, in addition to standing on the shore of the SLR in dismay, was to toss a tiny green grenade from the botanical corner.

  8. SmallHouseBigGarden

    September 9, 2013 at 10:41 am

    Very informant post and equally educational comments/remarks. Thank you to all! I’m new-ish to FL (here 4yrs this December) and appreciate all you do to enlighten us

  9. George Rogers

    September 9, 2013 at 10:44 am

    Whew—this mini-project has been “challenging” from the get-go, humping 100 pounds of gigapan gear to the river with John. I’m getting an education from this one. Now the questions is, who killed the Brazilian Pepper?

  10. Mike Y

    September 9, 2013 at 5:59 pm

    It looks like the peppers have been dead for some time and I don’t think anyone herbicided them. If anyone would have herbicided them it would have probably been me and I am pretty sure that I am not responsible. Perhaps the answer to the dead Brazilian peppers is the opposite of what you are saying about too much fresh water. We have had some pretty pronounced droughts over the last few years. Maybe the salinity levels got to high? Also we have seen crazy high tides over the last few years so maybe the culprit is sea level rise? I know what you mean with some of the mangroves looking unhappy, but that is something I have seen in many other shoreline areas. My guess on that would be waves/ boat wakes energy. Of course all of this is conjecture. It could be something entirely different or maybe its all just in our heads.

    • George Rogers

      September 9, 2013 at 6:07 pm

      Thank you Mike.

      • Keith Rossin

        February 13, 2014 at 11:19 am

        The white mangroves are very similar in a appearance to the buttonwoods have domatia along the central vein while whit mangroves have them in a row along the leaf margins. The buttonwoods have a creamy covered stem compared to the white mangrove. This is how you tell the difference between a buttonwood and white mangrove.

  11. George Rogers

    February 13, 2014 at 11:46 am

    True, and what those domatia are all abuut is mighty curious. Would take very fancy microscope work!


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