Southern California lagoons are complex environments that require informed management practices. In their natural states, many of these lagoons periodically open and close to the sea. However, watershed alterations and lagoon inlet modifications have reduced their capacity to open and close as they usually do. In response, coastal managers have begun to manage these lagoons to remain open for water quality purposes. However, scientists and managers have recently been reconsidering this one-size-fits-all approach to lagoon management, since managing a lagoon mouth to be continually open can be expensive and may compromise the lagoon's unique biodiversity and ecosystem services. A 2015 Science Transfer project led by the Tijuana River Reserve analyzed existing lagoon mouth literature and long-term monitoring data to provide managers with the information needed to improve the health of Southern California's coastal lagoons.

This is an updated version of the "(Don't) Shut Your Mouth" Estuaries 101 curriculum previously developed by reserve staff that includes lessons from this project. It focuses on conditions which can lead to mouth closure and emphasizes using extreme events as a preview of potential climate impacts. These teaching resources are also available and regularly updated here: NOAA Estuary Education Resources: Don't Shut Your Mouth.