Have you ever noticed that the sea has a unique smell? The sea smell is something like a weak mixture of fish and rotten eggs. The rotten egg smell comes from gaseous sulfur compounds that are produced from marine algae and bacteria. However, one of the biggest causes of this smell comes through the activity of viruses!

Marine algae, also known as phytoplankton, produce a compound known as dimethylsulfoniopropionate, or DMSP, for short. Usually, DMSP is kept inside of the phytoplankton cell; however, when a phytoplankton cell dies, it releases its DMSP into the water. Once the DMSP is released, bacteria quickly change the DMSP into dimethylsulfide, or DMS for short. DMS is a gas that rises out of the water and into the atmosphere. It is the sulfur in DMS that gives the sea its slight rotten egg smell. So how do viruses fit into the story, and what is the connection to rain?

We all know that in order to have rain, first there have to be clouds. But how are clouds made? As it turns out, the water vapor that makes up clouds comes from gaseous sulfur compounds like DMS. In the atmosphere, these compounds attract water, forming larger and larger drops, which eventually form clouds. As the drops continue to grow by adding more and more water, they eventually get so large that they fall to the Earth as rain. So DMS, the rotten egg smell of the sea, is actually involved in making rain clouds over the ocean. But where do viruses come in?

All living things are affected by viruses, including phytoplankton. Viruses which infect phytoplankton use the phytoplankton cells to make more viruses. Eventually, once enough virus particles are made, the phytoplankton cell ruptures to release the virus particles. Because the phytoplankton cell ruptures from the viral infection, DMSP is also released into the water. Bacteria quickly change the DMSP into DMS. Once this happens, the sea smell and rain are sure to follow. So go ahead and blame algal viruses the next time you have a rainy day at the beach!