Hi, we do have a bubbler actually two in the pond already. We just need to turn it on. Thank you very much.
I think your on the right track here, and do what you can to keep those roots cool. I don't know where you located, but it looks hot, so anything that keeps them cool and well oxygenated. If you've got a pump going to that area, and they are in a really wet area, you could even cover up the bases, (tarp or whatever) if enough oxygen is still getting into the area, and it would help keep them cooler.
Transpiration is the real driver of plant metabolism, so anything to that end is going to increase growth in a very big way. Plants are essentially natures "vacuum cleaners" and everything is moving with "negative pressure" like a straw, drawing water from the roots into the leaf mesophyll allowing photosynthesis, via evaporation of water though the leaf membrane. ie. cooler down below, warmer up above. (I encourage you to read the sticky about transpiration, it's a very good read).
Rain forest actually produce "rain" this way. A single column in a tree can create suctions of 16x atmosphere, that's a lot of energy dynamics. adhesion and cohesion are powerful chemical forces and water is a very amazing molecule,
Scientists uncover why it starts raining in the region several months before it should
www.sciencemag.org
Water is a molecule of fairly negligible mass: 18.01⋅g⋅mol−1. This is less than ammonia, or dioxygen, or dinitrogen, a little more than methane, but still less than ethane, and propane. (yet it's liquid at room tempature) And yet all these other molecules are GASES at room temperature, and have normal boiling points below that of water.
We know, or should know, that as atoms, and molecules get bigger, there should be a greater degree of dispersion forces that operate between particles, yet it seems that the boiling point of water is anomalously high. And so in fact it is.
The difference between water and these other molecules that another intermolecular force operates, and that is hydrogen bonding. Oxygen is electronegative with respect to hydrogen, and tends to polarize electron density towards itself. The result is that we may represent the water molecule as +δH−δ−O−Hδ+, i.e. as a dipole in which charge is strongly separated.
Given the strength of this dipole, and the small size of the water molecule, this interaction between the dipoles of adjacent molecules acts as a potent intermolecular force, it's the very life force of everything on the planet.