The phylum Bryozoa contains the most abundant collection of freshwater invertebrates that live attached to submerged surfaces. These tiny, colonial organisms live in aquatic environments where they feed on diatoms, green algae, bacteria, rotifers, protozoa, and even the occasional tiny crustacean or nematode. Like corals, these sessile creatures were thought to be plants until the mid-1700s.

The majority of Bryozoans are marine (several thousand species), but one class, Phylactolaemata, is found exclusively in freshwater. Pectinatella magnifica is one species belonging to this class, and is commonly found in freshwater lakes and rivers in North America. Most people call them jelly blobs or just plain blobs given their appearance. Each colony is a collection of genetically identical organisms (zooids) that exude a protective matrix, a gelatin-like substance made mostly of water that is firm but slimy to the touch.

The surface appears divided into rosettes, each containing 12-18 zooids. Massive colonies may exceed two feet (60 centimeters) in diameter and contain upwards of two million zooids, although more typical sizes are one foot or less. Colonies form on submerged logs, twigs, and even wooden docks. Brought to the surface, the jelly blobs exude a pungent aroma; the aroma may be linked to chemicals released to inhibit fish predation or to reduce competition for growing space. Few other organisms are willing to grow next to the magnificent jelly blob.