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Unread 03/21/2014, 05:32 PM   #19
3D-Reef
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Join Date: Aug 2005
Location: Wichita,Ks
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Quote:
Originally Posted by Michael Hoaster View Post
Thanks, 3Dreef. I'll see if I can find that study.
Your welcome!

Quote:
Originally Posted by Michael Hoaster View Post
Basically, it sounds like you're suggesting I use less organic-rich substrate (my aged eco-complete), to avoid anoxic conditions (nearly zero oxygen) in the sand bed and eutrophic (nutrient-heavy) conditions too soon, rather than letting them build up naturally, correct?
Correct.

Quote:
Originally Posted by Michael Hoaster View Post
I would expect anoxic conditions at the bottom of my sand bed, that I estimate will be around 7 inches deep. But I wouldn't expect that to kill my seagrass. Can you elaborate? I would imagine that in nature anoxic conditions exist at similar depths without it doing harm to the grasses.
It's not so much that the lack of O2 causes harm to the plant,(the plants have a way of around that) but, it's more about what is happening in an anoxic environment that gets 'em.
Seagrass plants, more or less, depend on/need too interact with the bacteria there to release nutrients too them.They are kinda lazy in that aspect.They could do themselves,but at a cost.So,if there are more bacteria/nutrients than what the grass can support with O2/NO3 the bacteria then turn too SO4 (sulfate).
When the bacteria start using SO4 ...the end result is Hydrogen-sulfide,or bi-sulfide.This gas is highly toxic to everything alive including plants.
Basically it will suck out any oxygen from anything alive.This is what kills the plant.

Quote:
Originally Posted by Michael Hoaster View Post
That's a very good point about eutrophic conditions too quickly. Maybe I'm trying to give them too much of a good thing too soon? And I definitely don't want all that stuff seeping out into the water column right away and causing eutrophic water conditions! Algae-fest!
Tip of the day
"First,it has to be acknowledged that seagrasses seem to be adapted for growing in nutrient-poor environments.Not only the mechanisms described in the first sections of this chapter (nutrient resorption,use of poor water nutrients,storage,ect.) allow these plants to better use nutrients,but also it has to be considered that seagrasses require approximately 8-50 times less nitrogen and 1.5-100 times less phosphorus for daily growth than macroalgae or phytoplankton,respectively (Daurte,1995)."

Quote:
Originally Posted by Michael Hoaster View Post
I'm hoping that my 4 layer substrate plan allows a wide gradient of oxygen levels through its depth, while keeping the really nutrient-rich area at the very bottom, and not up in the water column.

And just in case, my fuge with chaeto and ulva should help in that regard.

Thanks for your insights! More please!



__________________
Seagrass,Mother nature's way of organic carbon dosing.

"Nitrification is controlled primarily by 02 and nitrogen as ammonium supply,
while denitrification is controlled by nitrate and organic carbon supply" Seagrasses 2006

Life on earth depends on plants-without plants,no life.Alf Jacob Nilsen

Current Tank Info: 125 DT,135 grass fuge/sump;75g seagrass/seahorse tank 70 fuge/sump

Last edited by 3D-Reef; 03/21/2014 at 05:47 PM.
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