Did you find any explanation for the differences of the light penetration in coastal areas vs open water? (image diagram3_520_859 you posted above)

Why would the 550ish nm penetrate so much farther. I'd have to wonder if the measurements are skewed a bit. Coastal waters = high nutrients = higher concentrations of phytoplankton, algaes, etc = maybe they are seeing green/yellows at those depths since everything above would be filtering out the rest of the spectrum ? Or am I not holding my head right to see something different?