Hi Dana,
I am suspect of your "visually judged" water velocity within a cylindrical chamber as provided by a magnetic stir bar. The background for my skepticism stems from the past 60 days I have spent straightening, quantifying and characterizing the flow in a sealed rectangular flow chamber. The only way I can think of visually judging water movement in your setup is timing the trajectory of a particle on the perimeter of your vessel in which case you would want to correct for tangential motion. But then, if your small coral is sitting in the center of the vessel in which rotational motion is the primary water movement provided, the velocity of the water decreases linearly with proximity to the center of the vessel. This effect is even worse if you are placing the probe in the center of the a coral sitting in the center of a vessel within which water is basically spinning. But then, I am uncertain of the effect of the eggcrate placed horizontally in your washing machine chamber.
Also, you say that your corals were exposed to a peak of 800mmol but that they showed reduced photosynthesis at 260mmol at "15cm/s". My trial corals (Pdam), are acclimated to a steady 400mmol (probably by the same lamp we wont mention), not including ripples, and they show no sign of photoinhibition at 400mmol at flowrates down to 3 cm/s. By this I mean that the P:R ratio is greater than 1. besides an integration curve, i dont know how you would compare the irradiation provided by a rising and setting sun and a steady metal halide lamp.
I am not disputing if photoinhibition occurs in aquaria, I am sure it does, but 260 mmol seems like a real low ball figure to me.
By the way, congrats on the Ocean Optics Photo prize. I showed the catalog to everyone in the lab. I use an S2000 and Foxy probe and i am hoping to get one of the prizes when i enter my photo this year.
Jake Adams
I am suspect of your "visually judged" water velocity within a cylindrical chamber as provided by a magnetic stir bar. The background for my skepticism stems from the past 60 days I have spent straightening, quantifying and characterizing the flow in a sealed rectangular flow chamber. The only way I can think of visually judging water movement in your setup is timing the trajectory of a particle on the perimeter of your vessel in which case you would want to correct for tangential motion. But then, if your small coral is sitting in the center of the vessel in which rotational motion is the primary water movement provided, the velocity of the water decreases linearly with proximity to the center of the vessel. This effect is even worse if you are placing the probe in the center of the a coral sitting in the center of a vessel within which water is basically spinning. But then, I am uncertain of the effect of the eggcrate placed horizontally in your washing machine chamber.
Also, you say that your corals were exposed to a peak of 800mmol but that they showed reduced photosynthesis at 260mmol at "15cm/s". My trial corals (Pdam), are acclimated to a steady 400mmol (probably by the same lamp we wont mention), not including ripples, and they show no sign of photoinhibition at 400mmol at flowrates down to 3 cm/s. By this I mean that the P:R ratio is greater than 1. besides an integration curve, i dont know how you would compare the irradiation provided by a rising and setting sun and a steady metal halide lamp.
I am not disputing if photoinhibition occurs in aquaria, I am sure it does, but 260 mmol seems like a real low ball figure to me.
By the way, congrats on the Ocean Optics Photo prize. I showed the catalog to everyone in the lab. I use an S2000 and Foxy probe and i am hoping to get one of the prizes when i enter my photo this year.
Jake Adams
