GEOG/ES&P 330

California Ecosystems

Wetlands

Wetland definition: a land area that is saturated by water

• Water may soak soil or even cover it to a shallow depth permenently or seasonally
• The water may be fresh (<0.05% dissolved salts), brackish or briny (0.05-3%), or saline (3-5%)

Globally, there are three basic types of wetland

• Mires or peatlands, visually dominated by heath shrubs on top of sphagnum moss, with undecayed dead organic matter going down dozens to hundreds of feet (and capable of long burning fires underground!): Vandenberg Peat Bog in Barka Slough up the coast.
  • Here is an intriguing story about peat bogs in Los Angeles (the cienegas) and a huge underground peat fire back in 1927: Peat bog madness in LA
  • And here's one about a peat bog fire at Vandenberg: Burning bogs and exploding pancakes
• Swamps are wetlands that are forested: Only one I know of in California is Lanphere Dunes up in Humboldt County, with "skeleton trees" and a spooky swamp "look"
  • Here's a classic swamp in North Carolina to get the idea: Cypress gum swamp
  • The Lanpher dunes swamp: Songbirds & Parasites blog
• Marshes are wetlands visually dominated by herbaceous species, and these are what dominate California
  • Bolsa Chica coastal wetlands
  • Hahamongna Basin freshwater marsh in Pasadena at mouth of the Arroyo Seco
  • vernal pond in the Great Central Valley

In Southern California, we have three types of marshland:

• Coastal wetlands, with varying mixes of brackish and salty water
• Freshwater wetlands, in areas of persistent wetness along streams and springs
• Vernal ponds, which intermittently appear in the winter and spring and then dry out completely in summer

Coastal wetlands: estuaries and salt marshes

• Types:
  • Bay estuarine marshes
    • largest ones in Southern California
      • Morro Bay
      • Bolsa Chica
      • Upper Newport Bay
      • Mission Bay
      • San Diego Bay
      • Tijuana Slough (pictured above)
    • places where gentle topography allows open access to the ocean during higher tides, often with extensive mudflats
    • not common along the Santa Monicas and the mountainous coasts of Santa Barbara, Ventura, and Orange counties, because their fault-block topography doesn't allow tidal flushing across a wide horizontal area; the few that exist are small
  • River mouth estuaries
    • permanent stream flows create a brackish mix of sea and fresh water
    • relatively little mudflat development compared to bay estuaries
    • examples:
      • Ventura River (pictured above)
      • Santa Clara River
  • Lagoons are variants on river mouth estuaries
    • they form at the mouths of rivers
    • the streamflow, however, varies drastically, enough to cause water to deposit its sediment load
    • this creates sandbars to develop in summer
    • these block off stream flow enough to create lagoons behind them
    • example: Malibu Lagoon (pictured above)
  • Structural basin marshes
    • structural depressions occur where faulting creates down- dropped basins that allow estuaries to develop
    • examples:
      • Goleta Slough
      • Carpinteria Salt Marsh (pictured above)
• Estuarine wetland systems are generally markedly zoned
  • this basically reflects the degree and duration of wetness
    • shallow water coverage most of the day
    • alternating submerged and dry spells each day
    • mostly dry but occasionally submerged
  • this also reflects the varying mix of exposure to ocean and stream water and associated salt levels
  • common zones:
    • subtidal or lower littoral zone, in Southern California, dominated by:
      • eelgrass or Zostera marina
      • surfgrass Phylospadix torreyi
    • intertidal zone with exposed mud flats alternating with sea water, in California:
      • cordgrass or Spartina foliosa
    • supratidal zone with salt marshes that develop where mud and sand deposits have built up above the mean high tide line: Plants here have their roots constantly in salt water but their stems are mostly out in the air. In California:
      • lower end of the supratidal zone, merging into the intertidal mudflats. Plants here have to be able to tolerate soaking from higher spring tides.
        • cordgrass or Spartina foliosa can be found on the lower end, merging into the intertidal mudflats
        • saltwort or Batis maritima
        • arrowgrass or Triglochin maritima
        • a group of similar species, called pickleweeds or glassworts, are commonly found in the lower supratidal zone
          • common pickleweed (aka Virginia glasswort) or Salicornia pacifica is a perennial subshrub
          • another closely related species in the lower supratidal zone is called common glasswort or Salicornia depressa and is an annual herb
          • dwarf glasswort or Salicornia bigelovii is another annual herb
      • the higher end of the supratidal zone, abutting/shading into the upland. Plants here rarely experience submersion, except during the occasional high spring tide or due to high storm seas:
        • a close relative of the Salicornia pickleweeds, Parish's glasswort or Arthrocnemum subterminale, tends to dominate areas higher up in the supratidal than the other pickleweeds, as it is quite tolerant of the saltier conditions that build up in the dryer parts of the supratidal zone
        • California seablite or Suaeda californica, a shrub in the same family as the pickleweeds and Parish's glasswort (Chenopodiaceae) is also found in the upper supratidal, often associated with eelgrass wrack, that is, deposits of dead eelgrass washed up from the subtidal zone
        • alkali heath or is found in the upper supratidal area. It is capable of facultative drought deciduousness.
        • saltgrass or Distichlis spicata is associated with seablite in the upper supratidal
        • another resident of the upper supratidal is sea lavender or Limonium californicum
        • marsh jaumea or Jaumea carnosa is common in the middle and upper parts of the supratidal zone
    • upland areas that are out of the reach of all but the most exceptional seas (CSS is a common dominant in the uplands surrounding Southern California wetlands, as here at Ballona Creek)
• Adaptations for dealing with salt
  • isolating it within one's tissues
    • vacuoles to keep it out of the cytoplasm
    • succulence as the vacuoles keep growing
    • eventually the plant dumps the salt-engorged leaves
    • examples, all common in the middle salt marshes:
      • pickleweed or Salicornia depressa
      • marsh jaumea or Jaumea carnosa, a composite
      • saltwort (Batis maritima)
  • tolerating it at fairly high levels in cytoplasm but secreting it out through salt glands, which you can see with a hand lens or microscope (and taste)
    • examples:
      • salt grass (Distichlis spicata, trailing mat, upper salt marsh)
      • alkali heath (Frankenia salina, upper salt marsh, mixed in with saltgrass
      • cord grass (Spartina foliosa, lowermost mudflats, seeming to float when flats covered in water, showy lavender flowers)
      • sea lavender (Limonium californicum, subshrub, in salt marshes mixed with pickleweed, tiny purple flowers on stems)

Freshwater wetlands

These would have been far less common in Southern California than coastal wetlands.

• They would have formed on river bottomlands inland, places with deep clay soil that wouldn't drain too well. The Spanish commented on marshes in the southern San Fernando Valley and the area on the Westside where the L.A. River used to flow out at Ballona Creek was named "la cienega." Such spots have long since been filled in, plowed, developed, and channelized out of existence. You can infer where a lot of these may have been by looking for liquefaction-prone areas in the Official Seismic Hazard Zone Maps. Here is an ambitious attempt to construct a map of various wetland types by the Ballona Creek Watershed Historical Ecology Project.
• Another place you'd find freshwater marshes is along the coastal plain behind dune belts or in hollows among dunes. They were quite extensive in the Oxnard Plain in Ventura County, the area south of Santa Monica down to Palos Verdes, as shown here. and a few places in Orange County. You have to drive a ways to get to anything like this nowadays: Vandenberg Air Force Base and points north.
• There are small occurrences here and there, including behind the Sepulveda Dam up in the Valley.
• Characteristic vegetation:
  • cattails in shallow water near lake or stream edges: Typha latifolia, with their distinctive brown, fuzzy flower spikes
  • bulrushes, Scirpus microcarpus, which look like huge grasses (2-4 m high!) but are actually sedges, again favoring the shallow waters right on the verge of a stream or lake
  • in among these thickets along the water's edge will be a number of more aquatic species, some with floating parts (such as water smartweed or Persicaria amphibi)
  • saturated soils nearby may support all kinds of herbaceous species, such as yerba mansa (Anemopsis californica (which has traditional medicinal uses as teas and poultices).
  • water ferns (Azolla filiculoides), which are tiny, mosslike plants that can float in water and, indeed, coat the surface of a small pond.

Vernal ponds

• Small ponds that form in landscape depressions during winter and spring in places where rain can pool or where groundwater can rise up. Unlike most freshwater marshes, these are wet only seasonally and completely dry out in summer.
• Here is a nice set of photos illustrating the wet, the flowering, and the bone dry phases of a vernal pool.
• This cycle has repeated for thousands, maybe millions of years, and it transforms the ephemeral pool's soils and chemistry profoundly, and has drawn unique and often endemic plant and animal species that can adapt to and thrive in the temporary wet conditions ... and somehow get through complete drying out in summer.
• Many species are annual and very short-lived annuals at that, getting through the summer as seeds the way desert annuals do.
• These species include very specialized plants that may be found only ina few nearby vernal ponds. There is a high rate of endemism among vernal pond species: They are found nowhere else on Earth.
• The biodiversity of vernal ponds considered all together is quite high, with perhaps a hundred endemic specialists. The particular subset of species found in one pond or related group of ponds will be smaller and highly variable from one area to the next.
• Given the high endemism and the rapid destruction of this particular kind of wetland, many of them are threatened or endangered.
• Probably more than 95% of them have been obliterated, particularly in Southern California. There are quite a few surviving, barely, in the North State and down in San Diego County. The former are associated with Cascades lava flows and the latter with coastal mesas.

Summary

Wetlands in general are among the most threatened ecoystems in California, probably worse off than CSS. They have been subjected to development, whether agricultural or real-estate development and, decades ago, it was popular to "drain the swamps." They are often kind of stinky, due to their unique soil conditions, and that made them repulsive to many people. During the nineteenth century, people thought that disease was caused, not by microörganisms, but by "miasma" or bad air wafting off a swamp, hence the desire to drain wetlands. Coastal wetlands have lost about 90% of their former extent, and vernal ponds are down to maybe 3-5%, carrying many of their endemic species close to the prospect of extinction.

Document maintained by Dr. Rodrigue
First placed on web: 03/07/16
Last revision: 10/11/17