The lifespan of a zebra mussel is four to five years. In cases such as the zebra mussel, invasion of US waterways was unintentional. One invasive species, the zebra mussel, is also present. Recently, the introduction of the invasive zebra mussel has made the clear waters even clearer. The zebra mussel is an ecosystem engineer in North America. Infestations of the non-native zebra mussel also helped clear the water, as these are filter-feeders. The zebra mussel ("Dreissena polymorpha") is a small freshwater mussel. The zebra mussel causes problems because, among other things, it blocks water extraction pipes. The zebra mussel, an invasive species, is expanding upstream in the Ebro's waters. The quagga mussel resembles the zebra mussel, just as its namesake (quagga) resembles the zebra.