Why, my friends, do we head to the beach? Is it for the sun, the surf, the sand, the salt? Seashells, seagulls, sandpipers, swimming, snorkeling? (oh god somebody stop me). No! Obviously, we pile ourselves in a hot, sandy car for hours and burn ourselves to a crisp for the smells.
Yes, you heard me correctly. What’s better than that bracing, briny, ever so slightly sulfurous smell of the sea slapping you in the face as you scrub sandy sunscreen into your face? Puts hair on your chest, it does. To put icing on that hairy cake, it turns out that a component of this smell is created by none other than my favorite marine creatures–phytoplankton! Phytoplankton are capable of some truly wonderous and terrible things, but this is just beyond the pale. You may not be able to see them with the naked eye, yet phytoplankton will not let you forget that they’re there, always watching…

The good: phytoplankton provide 50% of the oxygen in our air. The bad: In return, they want your crabbie patties.
It’s a compound called dimethylsulfiopropionate (ain’t nobody got time for words that long–call it DMSP) that gets this stinky ball rolling. Researchers aren’t quite sure why phytoplankton make DMSP, but think that perhaps it’s being used as a kind of sunscreen or as protection from the sea’s nasty saltiness. Bacteria then eat dying phytoplankton (circle of life and all that jazz), and in doing so convert DMSP into dimethylsulfide (DMS), the gas that stinks up the beach even at very low concentrations.
It’s not just about the phytoplankton, though. Birds have been found to use that sulfurous DMS stank as a kind of homing beacon in order to locate areas rich in phytoplankton and the larger organisms like fish that prey upon them. DMS, once in the atmosphere, breaks down into a number of chemical components. It’s thought that some of these components can act as cloud condensation nuclei–meaning that their presence helps clouds to form more readily, potentially affecting our climate on global scales. Bow down, phytoplankton would say if they had but the mouths to speak. Bow down.
For further reading, a bit heavier on the science: http://www.uea.ac.uk/mac/comm/media/press/2007/feb/Cloning+the+smell+of+the+seaside and http://www.telegraph.co.uk/science/6044238/The-science-behind-that-fresh-seaside-smell.html