Text Size: A  A  A

Sea Lettuce

Ulva lactuca

Sea lettuce grows in the Chesapeake Bay's shallow, brackish and salty waters. (N Sloth/Biopix)
Sea lettuce grows in the Chesapeake Bay's shallow, brackish and salty waters. (N Sloth/Biopix)

Sea lettuce is a type of algae that grows in thin, green, wavy-edged sheets. It can be found in shallow waters throughout most of the Chesapeake Bay.


Sea lettuce grows in thin, green sheets with wavy, ruffled edges. It looks similar to wilted lettuce. It grows to be 6 to 24 inches and usually grows in large masses.


Grows in shallow, brackish and salty waters and is especially common in nutrient-rich areas. Can be free-floating in the water or attached to rocks, pilings and other hard surfaces. Often found washed up on the shore.


Found throughout most of the Chesapeake Bay, except in the extreme upper Bay.

Reproduction and Life Cycle:

Sea lettuce goes through two reproductive phases. During the first phase, adults produce spores by meiosis. The spores settle and grow to form male and female plants. During the second phase, the male and female plants produce gametes by mitosis. The gametes unite and develop into adult plants. When sea lettuce dies, it sinks to the Bay’s bottom, where it is decomposed by bacteria. During this process, bacteria consume oxygen until there is little or none left in these bottom waters.

Other Facts:

  • Commonly referred to as seaweed
  • When abundant, sea lettuce can smother bay grasses growing in the shallows
  • Large masses of sea lettuce are often an indicator of nutrient pollution in the water
  • In some parts of the world, people eat sea lettuce in soups and salads

Sources and Additional Information:

  • Underwater Grasses in Chesapeake Bay & Mid-Atlantic Coastal Watersby Peter W. Bergstrom, Robert F. Murphy, Michael D. Naylor, Ryan C. Davis and Justin T. Reel
  • Chesapeake Bay: Nature of the Estuary, A Field Guideby Christopher P. White
  • Sea Lettuce (Ulva lactuca) – University of Rhode Island

Click tabs to swap between type and habitat.

410 Severn Avenue / Suite 112
Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
Directions to the Bay Program Office
Terms of Use | Privacy Policy
©2012 Chesapeake Bay Program | All Rights Reserved