Looks like a fuzzy cover on seaweed especially on the Bladder Kelp (Macrocystis pyrifera). It consists of colonies of individuals (called polyps) on a stem. Under the microscope they can look a bit like sea anemones, to which they are related. Otherwise they look like knotted threads.

This species normally grows on kelp fronds, especially on Macrocystis pyrifera in conditions of moderate wave exposure. It can also be found on other seaweeds, especially those with a flat blade (leaf).

A predator on small zooplankton.

Populations of the colonial hydroid Obelia geniculata in the White Sea reproduce asexually by frustule (bud) formation. The frustules detach from the stems of the hydroids and are found in plankton where they resemble small jellyfish (called a medusa). Production of frustules on branches occurs continuously during colony growth until water temperatures climb above 0 °C. They can also reproduce sexually while in the medusa stage, forming a small planktonic larva called a planula, this is the dispersal phase and the larvae drift with the plankton until they find a place to settle down.

Photo Credit : Jean McKinnon