Obelia dichotoma is a broadly distributed, mainly marine but sometimes freshwater, colonial hydrozoan in the order Leptothecata that forms regular branching stems and a distinctive hydrotheca. O. dichotoma can be found in climates from the arctic to the tropics in protected waters such as marches and creeks but not near open coasts like beaches in depths up to 250m. O. dichotoma uses asexual and sexual reproduction and feeds on mainly zooplankton and fecal pellets. Obelia dichotoma has a complex relationship with the ecosystem and many economic systems.