Update: What are those bright patches of water without ripples?

 I was walking on the bluffs along the Pacific this week...

A very clear region of lighter water. P/C Daniel M. Russell.
Taken at Black Point Beach, Sonoma county, CA looking north.

... and saw another of those long, meandering regions of lighter water... pieces of the sea surface that seem to have much fewer ripples than the surrounding water. 

You might recall that we discussed this a while ago (July 25, 2019--"A couple of questions about Polynesia").  In that post, I decided they're called Langmuir circulation lines, formed when wind blows across the surface of water.  

But as you might also recall, a couple of weeks later, I recanted that opinion in the post "Rethinking Langmuir Circulation lanes."  

Why did I change my mind?  Because on that very day I'd driven past some very clear Langmuir circulation lanes in a nearby lagoon... and they didn't look like the "long, meandering regions."  Langmuir circulation lanes, I learned, are absolutely straight.  

But in the image above (or the images below), you can see that the "regions of lighter water" don't really fall in straight lines.  

I've taken multiple photos over the years as I've thought about this Challenge.  You can see the variety of lighter water forms, all caused by a clear lack of wavelets in the water.  

Near Split, Croatia.

Cozumel, Mexico.

The Golden Gate, near San Francisco, CA.

Meandering lanes of brighter water. I've even kayaked through some of these, and there's nothing obviously different in the lanes.  So.. what's going on? 

The memory of that old post reminded me that I was still uncertain about what was causing these...things.  I wasn't even sure what they're called.  (And as I've said about a thousand times, having a name for something is incredibly useful when trying to learn about a topic.)  

Since we're living in a new era of multimodal AI abilities, I thought I'd ask the AIs what's going on in these images.   

Short answer: My searches with AI tools totally flopped.  I couldn't get any of the AI tools to tell me what these things are. I got a lot of very confident answers... that were completely and utterly wrong.  

BUT.. regular search has improved since 2019 as well, so I thought I'd try regular search again.  

This time I searched for [light patches on ocean] 

Which led me to a Reddit thread on this exact question: "What are the brighter parts in the ocean called?"

As you know, Reddit can be a mixed bag, but as I've also said a bunch, even low-quality results can give you a great lead. 

In that Reddit post I found a reference to something I hadn’t seen before – Redditor Smellzlikefish  (a SCUBA diver and at least part-time marine scientist) wrote that “These are called surface slicks, and they serve as important nursery habitats for developing fish. You can read more about them here" with a link to a NOAA article entitled “Surface slicks are pelagic nurseries for diverse ocean fauna” (the article is worth reading... it has a great time-lapse video of surface slick formation and movement over the course of a day).  

A quick trip to Google Scholar showed me that Smellzlikefish is right: this really IS what these lighter-colored regions are called.  

As that NOAA article points out, they are basically biofilms that are accumulated fatty alcohols and acids produced by animals and plants living in the water.  This causes a thin, near monomolecular, film on the sea surface. The thin film causes a suppression of the tiny wavelets (aka "capillary waves") in the area, making water surface seem brighter (and with far fewer wavelets). 

And now I know what they are… and why they make long, meandering lines of brightness in calm seas.  

Thought you'd like to know. 

Keep searching!