High profile disasters like the Gulf oil spill and realities like the Great Pacific Garbage Patch are reminders that while the ocean may look refreshing, it’d kind of like taking a dip in a slightly poisoned bathtub. Between industrial pollution and something scientists call “fecal indicator bacteria,” it’s no wonder popular beaches are often shut down because contamination levels put swimmers at risk.
In most cases, beach shut-downs come after a hard rain, which washes sewage and other contaminants into the shallow water, causing pathogen levels to spike. After a day or so, the levels return to “safe” levels, and authorities reopen the waterfront for public use.
You might think enjoying the ocean from the safety of your beach blanket will protect you from coming into contact with any nasty sewage-borne pathogens that might still be hanging around, but you’d be wrong.
Up until recently, beach monitoring programs only took samples from the water, because it was assumed that fecal bacteria couldn’t survive on land. But recent research shows that this assumption was incorrect. It turns out ”sands and sediments provide habitat where fecal bacteria may persist, and in some cases grow.”
This means that even though the fine, dry sands might seem completely devoid of life, it’s actually a breeding ground for bacteria that could make you very sick. This would also explain why high contamination levels are sometimes detected even when there’s been no rain.
Still, researchers are reluctant to say that monitoring programs should start to consider beach sand samples in their analysis. Graduate student Elizabeth Halliday and microbial ecologist Rebecca Gast, who published a 2011 study on this topic, say it’s not yet clear for how long fecal bacteria can remain alive in the sand.
“Put it this way: I go to the beach and walk on the beach all the time. I love the beach. But, I wouldn’t eat something that dropped on the sand,” Halliday said, noting that her research hasn’t scared her away from the beach, nor should it overly alarm the general public.
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