gregt
Premium Member
Thanks for the effort of doing the assay. I'm sure the wife is very happy that it is done. 
I'm having trouble with your conclusion that heavy metals are responsible for the survival results in your assay.
Perhaps I'm missing something but let me explain my confusion.
If I understand correctly, your conclusion is based on the fact that there is a correlation of survival rates to heavy metal concentrations. This would seem obvious when comparing NSW and the artifical mixes. There is significantly larger amounts of heavy metals in the mixes and likewise a significantly lower survival rate in the assay. Based on that it is logical to suggest that heavy metals are a likely causative agent.
However, if you use the same criteria in comparing the two commercially available artificial mixes (IO and coralife), you come to the inverse conclusion. IO, in fact is lower in all metals except Manganese, Potassium, Sodium, and Strontium, of which none are the commonly "worried about" metals. Despite this, the survival rates of IO are roughly half that of Coralife, which is not what I would have expected if heavy metal concentrations are causative. I would have expected them to be similar or IO to have a worse survival rate.
This suggests to me that there is more at work here than simply heavy metals.
Do I find the levels of heavy metals in our salt mixes acceptible? Absolutely not, but based on my own personal experience with one of the commercial salts involved, I'm not quite ready to change my salt brand yet.
Any comments are appreciated,

I'm having trouble with your conclusion that heavy metals are responsible for the survival results in your assay.
The two salts that made artificial seawater with the lowest survivorship of larvae consistently have heavy metals concentrations hundreds to hundreds of thousands times those found in natural seawater.
Perhaps I'm missing something but let me explain my confusion.
If I understand correctly, your conclusion is based on the fact that there is a correlation of survival rates to heavy metal concentrations. This would seem obvious when comparing NSW and the artifical mixes. There is significantly larger amounts of heavy metals in the mixes and likewise a significantly lower survival rate in the assay. Based on that it is logical to suggest that heavy metals are a likely causative agent.
However, if you use the same criteria in comparing the two commercially available artificial mixes (IO and coralife), you come to the inverse conclusion. IO, in fact is lower in all metals except Manganese, Potassium, Sodium, and Strontium, of which none are the commonly "worried about" metals. Despite this, the survival rates of IO are roughly half that of Coralife, which is not what I would have expected if heavy metal concentrations are causative. I would have expected them to be similar or IO to have a worse survival rate.
This suggests to me that there is more at work here than simply heavy metals.
Do I find the levels of heavy metals in our salt mixes acceptible? Absolutely not, but based on my own personal experience with one of the commercial salts involved, I'm not quite ready to change my salt brand yet.
Any comments are appreciated,