Common submerged aquatic vegetation includes eelgrass and widgeon grass. Juvenile crabs develop in eelgrass beds and estuaries where salinity levels tend to be low. Eelgrass, "Zostera marina", is sometimes affected by seagrass wasting disease. Zostera noltii is a species of seagrass known by the common name dwarf eelgrass. Eelgrass roots help stabilize muddy sediments and can trap moving sand, helping prevent erosion. Bottom dwelling rockfish have also seen a decline due to a lack of eelgrass. The green alga "Entocladia perforans", an endophyte, depends on this eelgrass. Beds of eelgrass occur on the more sheltered mud- and sandbanks. Invasive species have been shown to have a negative effect on eelgrass and associated ecosystems. Eelgrass ("Zostera") and algae may be swallowed incidentally. One meadow of cloned eelgrass was determined to be 3000 years old, genetically. It sometimes lives in eelgrass beds. Two species of eelgrass are found in the Fleet&colon; "Zostera marina" and "Zostera noltii". In 1930 most of the eelgrass in the Atlantic Ocean was killed by an epidemic. The Seri language has many words related to eelgrass and eelgrass-harvesting.