Thursday, October 7, 2010

Sea foam – and why it can be bad for birds

The word “sea-foam” has a feminine mystique to it. I picture it used for frilly prom dresses and girly princess rooms. In the real world, sea foam is never the pretty light aqua colour of paint chips, instead it looks like dirty cappuccino foam – a yellowed off-white often with chunks of stuff in it. As the sea sloshes, salts, chemicals, dead plants, decomposing fish and sea weeds are churned into sea foam. Individual bubbles link together, and when a surface wave passes these bubbles they mass together as they swirl upwards to make foam on the sea surface.

Sea foam on the water's surface changes how wind energy is transferred into the water. This transfer of energy is a type of friction, called the wind stress, and it can play a part in important oceanographic processes such as currents and upwelling. What sea foam does is add another layer between the wind and ocean, so instead of the wind pushing the water, the wind has to push the foam and then the foam pushes the water, which is a much less efficient process. Sea foam can do much worse things.

In the coastal ocean red tides occur, which is a dangerous form of algal bloom. A red tide is better described as a Harmful Algal Bloom or HABs, because HABs aren't all red and not all red tides are HABs. Specific phytoplankton (little water plants) full of toxins are the culprit and are bad news for shell fish and anything that eats them, like us. Recently, migrating birds along the Washington State coast were found dead in large numbers at the same time as an HAB occurred. The birds weren't poisoned; instead they were freezing to death. Why? One or more of the HABs causing phytoplankton were getting churned up into the sea foam. Birds would rummage around in this foam getting themselves covered in it, because normally sea foam isn't a danger to them. But in this case, the phytoplankton-laced foam coated the bird's feathers is such a way that they lost waterproofing and insulation, so that the poor birds froze.

No comments:

Post a Comment