Yes. This is what I was going to say. Blue green algae isn’t always harmful but it’s impossible to know without thorough testing so “when in doubt, stay out!!”. It should be gone after the next rain storm or even a particularly windy day. Your state may have a place to report this, but best to just stay out. Pets too!!
The best way to tell if it's oil vs iron platelets from bacteria/algae is to drop a small rock through it.
If the sheen immediately reforms after the rock passes through it's likely some type of petroleum. If the rock passing through causes it to break apart and scatter without reforming it's likely an iron sheen from bacteria/algae.
Just going off the picture, this looks more like an oil or diesel slick to me. Do the rock test. If you determine it's oil please report it
If you upload your photo to [Bloomwatch](https://cyanos.org/bloomwatch/#bloomwatch_data)
EPA scientists will review it and let you know (and also your state).
To me it looks like pollen on the top possibly cyanobacteria below.
If so, it's dangerous and you and your pets should stay away from the water.
But sometimes there are other causes for scum in the water that are more benign.
Petroleum sheen are more localized, however because of the full coverage of the water system pictured, this is a growth of some sort that may be accompanied and exacerbated by urban runoff that contains petroleum or some other pollutant. Warm weather and nutrients would trigger algal growth. Some can be toxic to the respiratory system noticeable by nose and or eye irritation. If this is your pond, there are solutions.
Looks like blue-green algae. [Blue-green algae](https://aquaplant.tamu.edu/blue-green-algae/)
Yes. This is what I was going to say. Blue green algae isn’t always harmful but it’s impossible to know without thorough testing so “when in doubt, stay out!!”. It should be gone after the next rain storm or even a particularly windy day. Your state may have a place to report this, but best to just stay out. Pets too!!
https://www.pca.state.mn.us/air-water-land-climate/blue-green-algae-and-harmful-algal-blooms When in doubt, stay out! Pets too!
The best way to tell if it's oil vs iron platelets from bacteria/algae is to drop a small rock through it. If the sheen immediately reforms after the rock passes through it's likely some type of petroleum. If the rock passing through causes it to break apart and scatter without reforming it's likely an iron sheen from bacteria/algae. Just going off the picture, this looks more like an oil or diesel slick to me. Do the rock test. If you determine it's oil please report it
I do this with a stick, the old stick test!
Yep works the same! Either way this lake looks like hell lol
Thank you for this knowledge!
If you upload your photo to [Bloomwatch](https://cyanos.org/bloomwatch/#bloomwatch_data) EPA scientists will review it and let you know (and also your state). To me it looks like pollen on the top possibly cyanobacteria below. If so, it's dangerous and you and your pets should stay away from the water. But sometimes there are other causes for scum in the water that are more benign.
Fish semen
Petroleum sheen are more localized, however because of the full coverage of the water system pictured, this is a growth of some sort that may be accompanied and exacerbated by urban runoff that contains petroleum or some other pollutant. Warm weather and nutrients would trigger algal growth. Some can be toxic to the respiratory system noticeable by nose and or eye irritation. If this is your pond, there are solutions.
Pollen