I mentioned it too Roger but I don\'t think anyone really wanted to think it just worms

Looking at it I\'m not sure they are encysted. I\'m willing to bet that that pipe normally has more water running through it which serves to keep them bouyant like in the photos. As the water level has gone down they\'ve just gone a bit limp like a sea anemone at low tide.
I read somewhere that the contractions could be caused by one worm in the colony responding to the light (or the heat from it) which then sets off all the surrounding worms causing the pulsing effect