Tuesday, 3 May 2011

Is the May bloom delayed this year?

Angling reports from the coast state their surprise that the water has remained so clear so late into the spring.

The most likely factor for this is that the exceptionally dry weather has prevented the usual spring run-off of fertilizer from agricultural land.  The increased run-off into the sea of the nitrates used in farming is one of the principal causes of oceanic algal bloom, a process known as eutrophication.

The presence of increased levels of nitrogen in salt water is more serious than it is in freshwater where the ecosystem is better adapted to cope.  In sea water, the naturally low level of nitrogen is the limiting factor preventing algal bloom from occurring.  Introduce more nitrogen into that environment, and watch the bloom boom...

Which begs the question, is the algal bloom inevitable but just delayed?  Are we likely to see the familiar green gloom come back into the waters after the first rains of May?  Quite likely.  Indeed, the fact that the two previous months' worth of fertilizer run-off could all come at once could make the bloom worse this year than normal, especially if it's followed by another warm spell of calm weather.  

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