Zostera marina

Distinct varieties of Zostera marina not recognized in Kartesz (1999).

Zostera marina is a perennial (or sometimes annual) seagrass occurring in the intertidal to sublittoral zones of marine habitats of North America, Greenland, Eurasia, and Africa. In North America, this species is found in cold waters of the North Atlantic and North Pacific, from British Columbia and the Northwest Territories (historic) east to Newfoundland Island, Canada, and Maine south through North Carolina in the eastern United States, and Alaska and Washington south to California in the western United States through western Mexico. There are over 1,000 estimated occurrences of this species worldwide, which are threatened by climate change, storm events such as cyclones, tsunamis, destructive fishing practices, invasive species, boat propellers, coastal development, disease outbreaks, and impacts to water quality as a result of nutrient addition and sedimentation. With a large range extent and large number of occurrences, abundant habitat, and broad habitat preferences, Zostera marina is considered secure. However, large-scale declines have been observed for seagrasses worldwide, and the status of this species should be monitored frequently. Existing populations should be protected from direct and indirect threats.

Zostera marina is a globally-widespread species, occurring in marine waters of North America, Greenland, Eurasia, and Africa (FNA 2000, POWO 2025). In North America, this species occurs in cold waters of the North Atlantic and North Pacific, from British Columbia and the Northwest Territories (historic) east to Newfoundland Island, Canada, and Maine south through North Carolina in the eastern United States, and Alaska and Washington south to California in the western United States through western Mexico (FNA 2000, Weakley and the Southeastern Flora Team 2025). Range extent was estimated to be 41 million square kilometers using herbarium specimens and photo-based observations documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).

By applying a 1 km separation distance to herbarium specimens and photo-based observations documented between 1994 and 2025, it is estimated that there are more than 1,000 occurrences rangewide (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).

Threats to Zostera marina and other marine seagrasses worldwide include climate change, storm events such as cyclones, tsunamis, destructive fishing practices, invasive species, boat propellers, coastal development, and impacts to water quality as a result of nutrient addition and sedimentation (Waycott et al. 2009). In addition, this species often occurs in single-species stands which can be vulnerable to disease outbreaks. In the 1930s, a "wasting disease" killed as much as 90% of Zostera marina populations occurring in the North Atlantic Ocean (Muehlstein 1989).