In the sunglint we can see the southward moving current moving past the archipelago. The current flow is visible in the Space Shuttle photography because of surface oils, both biological and man-introduced. The oils are carried by the currents and thus take the form of the flow.
Oils smooth out the surface capillary waves and create a smoother surface.
The smoother surfaces reflect more sunlight and appear brighter. The darker areas are due to winds ruffling the sea suface resulting in less sunlight being reflected.