Actually, that may have been due to stormy weather, and the depth of the deepwater horizon well.
and the leftover oil dispersant
A lady is flying over that area every week looking for oil slicks that harm aquatic mammals, and she is seeing roiling seas of (assumed) methane streams EVERY time she flies over the area.
There is plenty of mixing, and in warm water like the gulf, there is enough heat to allow large blooms of methanotrophs, but in cooler waters, such as off the NW, and up in the arctic, that is a pretty big assumption, countered by the SWERUS team and the Sharakov studies, in every location they have looked.