Most of Hurricane Irene’s impacts — heavy rain, high winds, downed trees, coastal erosion, and storm-tide flooding — are all too familiar to the storm-weary residents of Chesapeake Bay and the Eastern seaboard. But based on post-storm queries to the Virginia Institute of Marine Science in Gloucester Point, Virginia, one impact remains a mystery — what are all those “gray blobs” floating atop waterways and strewn along beaches?