NATURE Will Clew Bay bloom this spring?

Will the ocean bloom this spring?


Marine Life
John paul Tiernan

The south shore of Clew Bay might have been tropical, driving west on the first weekend in  March, if one didn’t look up to the left and the cold, white-capped reek.
To the right, the underwater reefs and the sand-filled spaces between them were shimmering beneath a translucent green sea, remarkably clear and suggesting a temperature far greater than its actual nine or ten degrees.
An extraordinary three-month episode of east winds and hushed seas meant the water column, usually so clouded with sediment and nutrients stirred up from below by the hefty swells of winter, were settled and clear. Divers across the fjord at ScubaDiveWest in Little Killary were describing unusually sharp visibility in the month where one’s hand often murkily disappears at arm’s length underwater.
In the strict calendar of marine ecosystems, where everything has a function, such nutrients are hungrily awaited. The spring phytoplankton bloom is this month’s big event; an event where the tiniest of marine organisms hint at their importance in an surprisingly immense explosion of life.
Phytoplankton (microscopic algae) need light to grow, and when daylight levels reach a critical point at the end of March and beginning of April, the abundance of nutrients in the water causes a sudden, out-of-control growth in their population resulting in a discolouring ‘bloom’ stretching over hundreds or thousands of square kilometres in places.
Though tiny, phytoplankton’s contribution to the planet is not insignificant; it is now believed that they contribute as much, if not more, oxygen to the earth as the rainforests, and that they soak up carbon dioxide equally industriously.
The spring bloom is all over in a few weeks, as growth is so wild and uninhibited that the nutrient supply is rapidly used up.
But what will happen this year, when the daylight hours come and the nutrients still sit unroused on the sea floor? Such a run of inactivity as we have had is almost unprecedented so it’s hard to say, but a swell is promised for next week; the water column will likely become replenished in time.
Blooms occur from time to time in nutrient-loaded estuaries. These are sometimes obvious to coastal observers, but they can be dangerous to shellfish. The spring bloom, however, usually comes and goes unnoticed. Occurring offshore and covering large expanses of surface ocean it is best appreciated from above. Satellite images of Ireland are a good place to view it (check out www.eosnap.com). If one times it right, it may be possible to witness the phenomenon from the top of Croagh Patrick.

John Paul Teirnan, Louisburgh, runs www.irishmarinelife.com, a website dedicated to the creation of knowledge of our marine ecosystems. He is currently studying for an MSc in Marine Science.