Coastal Habitats & Species—Salinity and Tides

Summary: Students learn about tides and salinity in estuaries. Based on observations of time-lapse models of tides and salinity distribution in an estuary, students make predictions about salinity changes, and use salinity data to generate graphs to explain salinity patterns in an estuary.

Concepts to teach: pH, temperature, dissolved oxygen, salinity, conductivity

Goals: Students identify several factors that determine why salinity changes are different depending on your location within the estuary.

H.2E.1, H.3 S.1, H.3S.2, H.3S.3

Specific Objectives: Students will be able to:

  1. Analyze different forms of data and synthesize information to develop a hypothesis.
  2. Explain how tides and the geology of the estuary affect water circulation in an estuary.
  3. Describe daily patterns of salinity changes in an estuary.

Activity Links and Resources:

  • Salinity and Tides in York River – from the NOAA Estuary Education website [pdf] 
    • Consider adapting this exercise to a local Oregon estuarine environment such as South Slough NERR.
    • Compare and contrast the conclusions made about salinity in the Chesapeake Bay with salinity patterns in an Oregon estuaries
  • Rhythms of Our Coastal Waters—This interactive NANOOS exhibit helps learners discover how salinity fluctuates in the Yaquina Bay estuary in Newport, OR.
    • Use real-time LOBO data to answer one or more of the four posed questions about salinity in Yaquina Bay.
  • Background information and activities dealing with salinity can be found in the middle school Life in the Waters topic guide.
  • Visit an estuary and measure salinity at a variety of points to generate that can be used to describe patterns and processes.
    • Measure salinity at several points along a transect perpendicular to the ocean and see to what degree the data show a gradient of inland fresh water to ocean salt water.
    • Measure salinity at the surface and at depth to determine whether a salt water wedge can be detected.
    • Measure salinity at different points in the tidal cycle.
    • If possible, compare student-collected data with existing data sets.


  • See the Check for Understanding section in the Salinity and Tides lesson for suggestions on how to assess student learning.
  • Level 5 of the Rhythms of Our Coastal Waters “tests” your LOBO abilities.