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I don't think the story is about caffeination, but rather caffeine as a marker of human waste. 45 nanograms per liter doesn't sound like a lot, especially when

I don't think the story is about caffeination, but rather caffeine as a marker of human waste. 45 nanograms per liter doesn't sound like a lot, especially when considering the short half life of caffeine.

natrius 14y ago
Can you give a value for the half-life of caffeine? I think you might be confusing its biological half-life with its half-life as it decomposes in water. From what I can gather, the latter isn't particularly short.
- dalke 14y ago
  According to the linked-to article: "Caffeine ... might persist for up to 30 days in marine waters, study co-author Granek noted."
  - natrius 14y ago
    Ah. Serves me right for skimming.
Florin_Andrei 14y ago
> considering the short half life of caffeine But the thing is - it's 45 ng/l in the whole environment around sea organisms. I don't know if that's a large dose or not, I'm just saying the half-life comment doesn't seem to apply in this case.
- bo1024 14y ago
  Right, we should presume that it's being replenished at the same rate it's decaying unless the measurement happened to be taken right after a big dump or something.
- frozenport 14y ago
  It is not unreasonable to claim that the fish actively pump the caffeine out of their system. In many ways fish are hermetically sealed.
miahi 14y ago
45 nanograms per liter means about 1 cup of coffee every 6000 liters of water. This doesn't sound like a lot, but 6000 liters fit in a cube of ~1.8m - and there is a lot of water out there. The biological half-life of caffeine (how long it takes the human body to eliminate it) is not important here; it's not about humans but the sea life; nobody knows what happens to marine life in a continuous exposure to traces of caffeine and other substances.
- switch007 14y ago
  Slight miscalculation: 6,000 litres fits in 6m3 not 1.8m3 (ref: http://www.wolframalpha.com/input/?i=6000+litres+in+meters+cubed http://www.wolframalpha.com/input/?i=6000+litres+in+meters+c...)
  - corin_ 14y ago
    He said a cube of 1.8m, not 1.8m3 - he means 1.8m x 1.8m x 1.8m, making it easier to visualise :)
  - computator 14y ago
    No, the grandparent was right. He's talking about how big a cube could contain 6000L, but you're calculating the volume of 6000L. Simple way to visualize this: Think about the difference between a 4-foot square and 4 square feet. The former is a much bigger area.
    - switch007 14y ago
      Of course! Thanks :)
- gshubert17 14y ago
  If 1 cup of coffee contains 150 milligrams of caffeine (http://www.wolframalpha.com/input/?i=how+much+caffeine+in+1+cup+of+coffee http://www.wolframalpha.com/input/?i=how+much+caffeine+in+1+...) that would take 3.3 million liters (not 6000).
- pfraze 14y ago
bcoates 14y ago
So is caffeine actually easier to measure than coliform bacteria detection? It'd be cool if this resulted in better ocean water safety reports.

natrius 14y ago

Can you give a value for the half-life of caffeine? I think you might be confusing its biological half-life with its half-life as it decomposes in water. From what I can gather, the latter isn't particularly short.

dalke 14y ago
According to the linked-to article: "Caffeine ... might persist for up to 30 days in marine waters, study co-author Granek noted."
- natrius 14y ago
  Ah. Serves me right for skimming.

Florin_Andrei 14y ago

> considering the short half life of caffeine But the thing is - it's 45 ng/l in the whole environment around sea organisms. I don't know if that's a large dose or not, I'm just saying the half-life comment doesn't seem to apply in this case.

bo1024 14y ago
Right, we should presume that it's being replenished at the same rate it's decaying unless the measurement happened to be taken right after a big dump or something.
frozenport 14y ago
It is not unreasonable to claim that the fish actively pump the caffeine out of their system. In many ways fish are hermetically sealed.

miahi 14y ago

45 nanograms per liter means about 1 cup of coffee every 6000 liters of water. This doesn't sound like a lot, but 6000 liters fit in a cube of ~1.8m - and there is a lot of water out there. The biological half-life of caffeine (how long it takes the human body to eliminate it) is not important here; it's not about humans but the sea life; nobody knows what happens to marine life in a continuous exposure to traces of caffeine and other substances.

switch007 14y ago
Slight miscalculation: 6,000 litres fits in 6m3 not 1.8m3 (ref: http://www.wolframalpha.com/input/?i=6000+litres+in+meters+cubed http://www.wolframalpha.com/input/?i=6000+litres+in+meters+c...)
- corin_ 14y ago
  He said a cube of 1.8m, not 1.8m3 - he means 1.8m x 1.8m x 1.8m, making it easier to visualise :)
- computator 14y ago
  No, the grandparent was right. He's talking about how big a cube could contain 6000L, but you're calculating the volume of 6000L. Simple way to visualize this: Think about the difference between a 4-foot square and 4 square feet. The former is a much bigger area.
  - switch007 14y ago
    Of course! Thanks :)
gshubert17 14y ago
If 1 cup of coffee contains 150 milligrams of caffeine (http://www.wolframalpha.com/input/?i=how+much+caffeine+in+1+cup+of+coffee http://www.wolframalpha.com/input/?i=how+much+caffeine+in+1+...) that would take 3.3 million liters (not 6000).
pfraze 14y ago

bcoates 14y ago

So is caffeine actually easier to measure than coliform bacteria detection? It'd be cool if this resulted in better ocean water safety reports.