The territorial battle of the Mute Swans continues on the Long Water. This time the male at the Lido turned up before the rest of his large family and confronted the lone resident male at the line of posts that is the current frontier of their territories. He then crossed the line and made efforts to push the other swan back to the next line, which is marked by a fallen horse chestnut tree sticking into the water.

These are both big birds, about equal in strength. Normally an intruder on to another swan's territory would lose, but this one has a family, which gives him considerable status in these confrontations. King David got this right:

Like as the arrows in the hand of the giant,
Even so are the young children.
Happy is the man that hath his quiver full of them;
They shall not be ashamed when they speak with their enemies in the gate.

(Psalm 127:4-5)

Nearby, a female Tufted Duck was foraging among the algae.

You can see that the Long Water is still fairly clear, though there are mats of dead green algae which, if the weather remains warm for the next few days as forecast, will be overgrown with toxic blue-green algae. However, the Serpentine is as murky as oxtail soup. The algae are nourishing a good growth of young fish -- these are mostly roach with a few bream. (Thank you, Gino, for telling me this when I was taking the picture.)

But the water is really in a pretty bad state. The murkiness is due largely to the work on the Olympic jetty, and careless use of motor boats, stirring up mud from the bottom. The top two feet of the heavy growth of algae has been cut back with a curious machine looking like a cross between a combine harvester and a tank -- it actually has tracks, which propel it on both water and land. This has also churned up a lot of mud. Once it comes up, it takes days to subside.

But even before this, the lake had been badly disturbed. Last year, when a triathlon was held in the lake as a trial run for the Olympics, the lake was also weedy, though not nearly as bad as it is now. So they poured thousands of gallons of hydrogen peroxide into it, which killed the algae but seems to have knocked the ecosystem badly out of kilter. This spring, many tonnes of mineral sludge were dumped in the lake in an effort to absorb the nitrates and phosphates that nourish algae -- it consisted mainly of fine clay with some compound of lanthanum (a radioactive element). Soon after this, although the weather was cold and no algae would normally have been expected, there was a strong growth of three kinds of green algae, which has not abated.

At the same time, all the Little Grebes left the lake and have not been seen since. In Regent's Park, where the water has not been mucked about with, there are plenty of Little Grebes and they have bred.

I would not want to swim in this water, and feel sorry for the athletes who will have to.

To return to more cheerful matters, here is a white dove that has managed to avoid involvement in the opening ceremony.

And here a purple loosestrife plant has escaped from the planting in the Italian Garden and is decorating a nearby fence, to the delight of a young photographer.