12-degree dawn aside, spring really is here. The hopping sugar house at Harris Farm’s Maple Sunday was proof of that.
But spring is happening offshore too. In the coming weeks, something magical — and completely ordinary — will start happening. Spring phytoplankton blooms will begin all along the shallow coastal waters of the North Atlantic.
These two stock NASA images show blooms in the Atlantic, the first off Newfoundland, the second off of western Iceland.
Source for this and many more amazing satellite photos
Plankton blooms don’t just “happen.” They’re triggered. By the same forces of reawakening that start sending sweet sap up through sugar maples, and push the first crocuses and tulips through the still snowy soil.
As days lengthen and temperatures rise, the snowpack starts to melt. Hills and mountains shed their heavy loads, swelling streams and rivers over a period of weeks, or sometimes even months. These swollen rivers, laden with meltwater dump their burden into the ocean.
There’s of course nothing unusual about rivers emptying into the sea. But after a long winter, when frozen mountains constrict and restrict and slow a river’s flow, the sudden & growing torrent of new water does something magical to the ocean. It churns it up. It adds months’ worth of pent-up silt and soil and nutrients to coastal waters, and helps to bring all of those nutrients to the ocean’s surface.
Then that meltwater does something else sneaky & cheeky. It locks the nutrients at the surface. The ocean in winter is well-mixed by storms. Nutrients can float up, down, wherever they like. But when the spring melt freshens the surface of the ocean, that mixing stops. The ocean becomes “re-stratified.” The fresher water on the surface, warmed by the sun’s growing springtime energy, becomes very different from the cold, saltier water underneath. Nutrients become locked in place.
After that, the warming rays of springtime sun give their energy to small groups of phytoplankton that survived winter storms. That growing energy, plus all the nutrients in the surface water around them, cause an explosion of life. A phytoplankton bloom. Such blooms can be thousands of square miles across.
All of that new life feeds the rest of the ocean. Which feeds us. Moreover, plankton in the ocean are responsible for almost half of all the free oxygen in the atmosphere. Oxygen that we use with every breath.
Try this at home: take a breath, now take another breath. Every other breath you take is thanks to the ocean. And thanks to the ocean in springtime.
Happy spring, Maine. It really is here.