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Message in a Bottle? Caffeine Pollution Says 'Man Was Here'

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Who knew? Pacific fish might be kick-starting their day with a java jolt.

Another Sign of the Anthropocene

For some earth and environmental scientists the Industrial Revolution corresponded to a major transition in the Earth's history with the rise of a new geologic age -- the Anthropocene or Age of Man.

The distinctive characteristic of the Anthropocene relative to all other ages is that now a single species -- Homo sapiens -- is the major force for global environmental change. And with soot deposits showing up in remote Arctic regions, huge gyres of plastic debris swirling about in the middle of the Pacific Ocean, and atmospheric carbon dioxide concentrations at their highest level in at least 800,000 years, you've got to admit the concept has merit.

Caffeine With Those Factoids?

Now you can add another data point supporting the notion of the Anthropocene -- caffeine in near shore ocean and estuarine waters.

If you're like me, caffeine is an intimate friend. I start my day with a cup of joe -- fresh-brewed in my espresso machine, no less -- and then follow up with a cup or two or three as the day progresses. (I've even been known to frequent a certain java joint with Melvillian connections.)

But I learned a lot more about the stimulant by reading a paper by Zoe Rodriguez del Rey of Portland State University and co-authors published in the July edition of Marine Pollution Bulletin. For example, did you know that caffeine, one of the most widely consumed drugs in the world, is produced by more than 60 plant species, found primarily in the tropics, and has even been found in a few coral species? Most surprising for me is that that caffeine has been found at or above detectable levels in seas, bays, estuaries, and coastal ocean waters. (See here, here and here.) How does it get there? Is the caffeine from human sources or is it natural?

Observations reported by Rodriguez del Rey et al. in the coastal waters of Oregon shed some light on these questions. The data showed that caffeine in these waters varied considerably from below the detection limit (8.5 nanograms per liter) to as much as 44.7 nanograms per liter in coastal ocean water and 152 nanograms per liter in adjacent river estuaries. The locations with the highest concentrations did not correspond to the places closest to known water pollution sites. Instead, the peak concentrations were observed during a major storm event.

The authors conjecture that peak caffeine concentrations from storms may be linked to combined sewer overflow when heavy rainfall overwhelms metropolitan water treatment plants, forcing a release of untreated or partially treated sewage. They also note the possibility that increased surface runoff may be liberating caffeine from septic tanks and water treatment plants that do not remove caffeine.

There's Caffeine in Our Food, Should We Care It's in What the Fishes Eat?

What is the impact of caffeine on marine and estuarine ecosystems? It's a fair question. Caffeine is a biologically active drug, and, as co-author Elise Granek put it: "We humans drink caffeinated beverages because caffeine has a biological effect on us -- so it isn't too surprising that caffeine affects other animals, too."  And while the effect of caffeine on humans is more or less benign, that's not always the case for other species as illustrated in this cautionary information about caffeine effects on some of our favorite household critters.

But even the highest concentrations of caffeine observed by Rodriguez del Rey et al. are much, much smaller than the concentrations in a typical cup of coffee (500,000,000 nanograms per liter). Is that too low to have an effect? We'll have to await further study to know for sure. In the meantime, chalk another one up to the the growing list of environmental fingerprints attributable to humans in the Anthropocene.

Crossposted with TheGreenGrok. | Like us on Facebook.

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