The commenters have it: all that yellow was pine pollen. And for those who haven’t seen it on a lake surface before, here’s a pulled-back view.
This was just one cove; the pollen was thick as pea soup in many other coves along the shoreline as well, and covered the entire lake to a lesser degree. Now consider that each one of those tiny pollen particles is actually a male gamete, and that there must have been billions upon billions of them to create great glopping soups like this one, and you’ll understand why a standard phrase among biologists is “sperm is cheap.” That stuff can be produced by the wagonload for very little cost in energy or resources, so it’s no big deal to fling clouds of it into the air in the hopes that a few gametes will find their targets.
Later that week, when we were hiking a hilltop trail in south central Oregon, I looked out across a valley and thought something was wrong with my eyes, because a section of trees on the opposite ridge looked blurry. When I looked back a few seconds later, they seemed perfectly normal. It wasn’t until a pine tree closer to me let loose with a giant poof of yellow pollen that I realized what I’d seen: an entire stand of trees releasing their gametes. From a distance, that cloud had made the trees seem out of focus.
Thank heavens I’m not allergic to that stuff.