Photo 1. Carried by the bora wind, sea foam gathers on the rocky shore of Cres Island between Barnestrovica Cove and Toverašćica Cove at Punta Križa (Photo by M. Randić)
Sea foam on the shores of the Kvarner Bay islands
When the bora wind is blowing, coastal landscapes can take on many interesting and less common appearances which we may rarely get to see because that’s when weather conditions are not conducive to spending time on the shore. One such intriguing and picturesque but less known phenomenon is the formation of sea foam on shores. Sea foam occurs when particular conditions involving climate, wind and sea waves coincide with the rampant growth of microscopic planktonic marine organisms. It seems, however, that sea foam is not a particularly common phenomenon is our region because only twice on our field trips have we come across sea foam, once in early June on the east shore of the southern part of Cres Island (Photo 1) and once in late May on the north-western coast of Krk Island (Photo 2).
In explaining sea foam, scientists mostly agree that it forms when surface-active agents, or surfactants, are released into the sea with the decay of the cells of planktonic organisms. Brought to the surface by waves and sea currents, these surfactants behave in the same way as do detergents in a washing machine: they create a lot of white foam. In everyday life, the best known surfactants are detergents and soaps, while in a marine environment this role is taken over by proteins, fats and lignins that are the result of the decomposition and destruction of the cells of tiny planktonic organisms.