The official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve
Elkhorn Slough Plants: Sea Lettuce

Scientific Name:
Ulva intestinalis &
Ulva lactuca

Family:
Ulvaceae
(division: Chlorophyta)

Found at the Slough:
Intertidal mudflats, subtidal soft-bottom, rocky intertidal and subtidal, detached floating mat, and saltmarsh deposited on pickleweed

Did you know...
Sea lettuce is short-lived - only surviving for up to three months.

Sea Lettuce are among the most conspicuous species in the Slough because of the bright green color it gives to mudflats. This native aquatic algae is widespread throughout the salt water habitats of the Slough, especially the main channel. Erosion of marsh habitat into mudflats and high nutrient loading enables competitively inferior species, such as Ulva spp., to become a dominant species in Elkhorn Slough.

While there are many Ulva species found at the slough, two are most commonly found:

Ulva intestinalis has a thin tubular structure only one cell layer thick or (monostromatic).

Ulva lactuca has a distromatic (two cell layers) morphology, and is characterized by sheets that resemble lettuce.

Both species are ephemeral green alga with an opportunistic life history characterized by a short life span (0-3 months).

Ulva spp. is generally considered an early successional species, which is capable of occupying free space very rapidly by either recruitment or growth on attached algae (Sousa 1980). It is also very tolerant to varying levels of salinity (15-35 ppt) (Fong et al. 1996), which makes it an excellent inhabitant of estuaries. Although it is described as having an ephemeral life history it can recruit any time of the year in Elkhorn Slough. It can also have negative consequences for eelgrass (Zostera marina) communities because of its sensitivity to light and the shading capabilities of Ulva spp. mats.

Certain locations in Elkhorn Slough that have noticeable deposits of senescent or decaying Ulva spp. have decreased benthic invertebrate diversity, as well as shift in community assemblages from invertebrate to bacterial dominated (Oliver et al. 2009). Ulva spp.has an estimated annual biomass in the main channel of Elkhorn Slough (4,000 Mg dry weight) that is equal to or greater than that of the main salt marsh plant Sarcocornia pacifica (1,600 to 3,200 Mg dry weight) (Onuf et al. 1978, Schaadt 2005). Ulva spp. reaches a “critical threshold” for this biomass where local water quality shifts from productive to lethal anoxic conditions (Viaroli et al. 1996). This may be due to Ulva’s ability to facilitate the abundance of invertebrates and bacteria within floating and benthic mats, whose oxygen demand surpasses the oxygen production of Ulva (McGlathery et al. 2007, Nezlin et al. 2006). This becomes evident at night when invertebrate and/or microbial communities deplete oxygen supplies due to decreased photosynthetic activity and increased respiration rates of Ulva. These communities are also be facilitated by live or decomposing Ulva populations whose biomass can sink to the bottom creating an organic layer, if it is not transported out to Monterey Bay by tidal currents.

Slough specific research / studies:

  • Hughes, B. 2009. Synthesis for management of eutrophication issues in Elkhorn Slough.
    Elkhorn Slough Technical Report Series 2009:1.Download here.
  • Schaadt, T.J. 2005. Patterns and causes of variability in the cover, biomass, and totalabundance of Ulva spp. In Elkhorn Slough, California. M.S. Thesis. California State University Monterey Bay. 84 pp Download here.
  • Oliver, J.S., K.K. Hammerstrom, I.W. Aiello, J.A. Oakden, P.N. Slattery, and S.L. Kim. 2009.Benthic invertebrate communities in the peripheral wetlands of Elkhorn Slough ranging fromvery restricted to well flushed by tides. Monterey Bay National Marine Sanctuary Report.
  • Zimmerman, R.C. and J.M. Caffery. 2002. Primary Producers. Pages 117-133. J. M.
    Caffrey, M. Brown, W. B. Tyler, and M. Silberstein, editors. In: Changes in a California
    Estuary: A Profile of Elkhorn Slough. Elkhorn Slough Foundation. Moss Landing,
    California.



Photos:


All sources / citations:

  • Abbott, I.A and G.J. Hollenberg. 1976. Marine Algae of California. Stanford University
    Press. Stanford, California. 884 pp.
  • Fong P., R.M. Donohoe, and J.B. Zedler. 1994. Nutrient concentration in tissue of the
    macroalga Enteromorpha spp. as an indicator of nutrient history: an experimental
    evaluation using field microcosms. Marine Ecology Progress Series 106:273–281.
  • Fong, P., K. E. Boyer, J. S. Desmond, and J. B. Zedler. 1996. Salinity stress, nitrogen
    competition, and facilitation: what controls seasonal succession of two opportunistic green macroalgae? Journal of Experimental Marine Biology and Ecology 206:203-221.
  • Hughes, B. 2009. Synthesis for management of eutrophication issues in Elkhorn Slough.
    Elkhorn Slough Technical Report Series 2009:1.
  • McGlathery, K.J., K. Sundback, and I.C. Anderson. 2007. Eutrophication in shallow
    coastal bays and lagoons: the role of plants in the coastal filter. Marine Ecology Progress
    Series 348:1-18.
  • Nezlin, N., K. Kamer, E.D. Stein, A. Carr, and J. Hyde 2006. Relationships between
    dissolved oxygen and macroalgal distribution in upper Newport Bay. Southern California
    Coastal Water Research Project. Technical Report #494.
  • Oliver, J.S., K.K. Hammerstrom, I.W. Aiello, J.A. Oakden, P.N. Slattery, and S.L. Kim. 2009.Benthic invertebrate communities in the peripheral wetlands of Elkhorn Slough ranging fromvery restricted to well flushed by tides. Monterey Bay National Marine Sanctuary Report.
  • Onuf, C. P., M. L. Quammen, G. P. Shaffer, C. H. Peterson, J. W. Chapman, J. Cermak,
    and R. W. Holmes. 1978. An analysis of the values of central and southern California
    wetlands. P. 189-199 in P. W. Greeson, J. R. Clark, and J. E. Clark, eds. Wetland
    Functions and Values: the State of our Understanding. American Water Resources
    Association, Minneapolis, MN, USA.
  • Schaadt, T.J. 2005. Patterns and causes of variability in the cover, biomass, and total
    abundance of Ulva spp. In Elkhorn Slough, California. M.S. Thesis. California State
    University Monterey Bay. 84 pp
  • Sousa, W.P. 1980. The responses of a community to disturbance: The importance of
    successional age and species' life histories. Oecologia 45:72-81.
  • Viaroli, P., N. Mariachiara, C. Bondavalli, and S. Bencivelli. 1996. Growth of the
    seaweed Ulva rigida C. Agardh in relation to biomass densities, internal nutrient pools
    and external nutrient supply in the Sacca di Goro lagoon (Northern Italy). Hydrobiologia
    329:93-103.
  • Zimmerman, R.C. and J.M. Caffery. 2002. Primary Producers. Pages 117-133. J. M.
    Caffrey, M. Brown, W. B. Tyler, and M. Silberstein, editors. In: Changes in a California
    Estuary: A Profile of Elkhorn Slough. Elkhorn Slough Foundation. Moss Landing,
    California.

 

 

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