Sunday, October 27, 2013

Strangers In The Night

One of the advantages of shorter daylight hours in autumn is that I get to go for my morning swim in the dark. Now, while that may sound a little strange and scary, there are a couple of mitigating factors that make night swimming particularly beautiful. The first, particularly if the sky is clear, is having a little moonlight to guide you on the way.  At this time of year the moon is always overhead in the early morning hours and there's nothing more beautiful than a pathway of silver light over the ocean, even if you only have a seal to share the experience with.

Moon over English Bay - photo by Junie Quiroga
The other, perhaps even more interesting occurrence is the sparkling light that suddenly appears in the ocean itself as soon as you dip your hand in the water and a milky way of microscopic stars suddenly appears. What I'm referring to of course is a phenomena known as bio-luminescence, something made famous in the movie "Life of Pi".  Bioluminescence is a brief blue flash emitted by a type of marine plankton, known as dinoflagellates, when they are disturbed.

Microscopic photos of dinoflagellates
These dinoflagellates bloom in concentrations by the millions and, for the most part are quite harmless. However, at certain times of the year, particularly in the summer when nutrients are especially abundant, they reproduce in such a rapid fashion they become toxic and the ocean turns a reddish brown colour which is known as "red tide". The toxins they produce accumulate in shellfish and can be fatal to humans who eat them which is the reason there are often shellfish closures on the coast.

Red tide at midnight

In spite of being responsible for "red tide" most dinoflagellates are quietly nibbling on smaller algae and photosynthesizing during the day and only turn on their lights at night as a protective mechanism. The theory is similar to that of deterring a burglar when one enters your home and the lights go on to scare him/her off. In the case of the "dinos" the light not only exposes the predator, it makes them visible to other fish who might be looking for a meal. Very clever when you haven't got much else to defend yourself with, and it's all thanks to an enzyme called "luciferin".

Fortunately for the "dinos" I'm not interested in eating any of them, and fortunately for me there isn't anything out there interested in eating me either when the lights go on.  Occasionally I see a fish or a seal swim by bathed in blue/green light and it just makes me realize how magical the ocean really is. Photographs others have managed to take also demonstrate the beautiful effect such a small creature can have on such a vast area. So between the moon and stars above and the bioluminescence below I've got all the light I need and I'm quite happy to be swimming with these strangers in the night.

1 comment:

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