Uploaded June 2026 | Updated September 2026, 1 week ago
A bar-built estuary is a coastal lagoon separated from the ocean by a sandbar, which prevents a direct surface connection between fresh and salt water. These unique ecosystems are characterized by variable conditions, as water levels are maintained by inland runoff and subterranean filtration through the sand. During the summer, intense evaporation and solar radiation often cause these lagoons to become significantly hotter and saltier than the surrounding ocean. While these extreme environments are stressful for many organisms, they serve as a critical refuge for native species that can withstand the heat and salinity. These native populations, such as the endangered tidewater goby, thrive in these lagoons because the harsh conditions often exclude invasive predators. Eventually, powerful winter storms provide enough water volume to breach the sandbar, temporarily flushing the system and reconnecting it to the sea.
A bar-built estuary is a coastal lagoon separated from the ocean by a sandbar, which prevents a direct surface connection between fresh and salt water. These unique ecosystems are characterized by variable conditions, as water levels are maintained by inland runoff and subterranean filtration through the sand. During the summer, intense evaporation and solar radiation often cause these lagoons to become significantly hotter and saltier than the surrounding ocean. While these extreme environments are stressful for many organisms, they serve as a critical refuge for native species that can withstand the heat and salinity. These native populations, such as the endangered tidewater goby, thrive in these lagoons because the harsh conditions often exclude invasive predators. Eventually, powerful winter storms provide enough water volume to breach the sandbar, temporarily flushing the system and reconnecting it to the sea.
