Here is what DT's website says about the smell.
DT?s Live Marine Phytoplankton does have a noticeable odor and it is normal that the odor is sulfurous. This is due to the fact that a type of sulfide, dimethylsulfide is produced by some phytoplankton and is associated with cryoprotection.
Sulfides produced by living phytoplankton: A small amount of sulfides are produced by phytoplankton that is always in the product. Sulfides are very volatile and they come out of solution and build up in the air within the bottle even at low temperatures. If the phytoplankton is kept at a temperature in the 40?s instead of the 30?s it will have more odor. If it warms up for even a short time, say during shipping, it will have more odor.
We had our product tested throughout its shelf life and beyond. The levels found were very low ranging from 17 to 20 ppm (ppm = parts per million). These levels are very low and were also very consistent from just packaged phytoplankton through phytoplankton that was more than 5 months old (beyond the shelf life). People are extremely sensitive to sulfides, which are detected at the very low levels of 0.5 ppb (parts per billion).
A bottle of DT?s Live Marine Phytoplankton may have a strong odor because dimethylsulfide builds up in the air that has been trapped in the bottle.
The odor from the phytoplankton is most noticeable in the air that is trapped in the bottle, and it builds up over time. That is why a half empty bottle smells more than a full bottle, and a large bottle smells more than a small bottle. While odor intensity is almost impossible to describe; it is normal for the odor of sulfides to be strong, particularly in DT?s that has been in storage for a while.