Are outdoor laboratories for scientists and educators
Provide sediment traps and erosion control
Serve as nurseries for marine fishes
Provide homes for endangered species
Provide habitat for migrating, wintering and breeding birds
Serve as repositories for native plants and animals
Click on graphic to enlarge.
Bolsa Chica is an Ecosystem
is an ecosystem? An ecosystem is a unit of the environment in
which living and nonliving components interact. Bolsa Chica may
be called an ecosystem where saltwater from the ocean and
freshwater from land meet and mix. A clear understanding of the
nature of the interactions between living things and nonliving
things at Bolsa Chica would be very helpful in determining how
best to protect it and maintain it in the future.
The prominent nonliving parts of the Bolsa Chica are the sun,
saltwater, freshwater, air and mud. The mud is composed of
detritus, or decomposed organic matter, and soil carried into
the marsh by rainfall draining off the upland slopes.
The living parts of the marsh include birds, fish,
invertebrates, and plants (including plankton). Of these
components, the plants are the most important to the ecosystem.
They are called the primary producers because they can make
their own food from carbon dioxide and water, using the sun’s
energy. This process is called photosynthesis, and it is
essential to the continued existence of the marsh. One important
by-product of photosynthesis is oxygen.
Bolsa Chica: A Tidal Salt Marsh
Click on graphics to enlarge.
What is a tidal salt marsh? It is a community
of plants and animals that are tolerant of wet, saline conditions.
This community is a transition between land and ocean systems, and
thus contains aspects of both. The soil is saturated with water or
covered by shallow water, and this water has a salinity level
generally between that of freshwater and saltwater. The level of the
water in a tidal salt marsh fluctuates daily due to tidal action.
The tidal salt marsh has
a complex zonation of plants and animals. The lower and upper limits
of the marsh are set by the tide range: the high marsh is flooded
irregularly and the low marsh (including mudflats) is flooded at
least daily. Narrow subtidal channels serve as conduits between the
salt marsh and the adjacent ocean. Each of these zones is a distinct
habitat favored by different groups of plants and animals.
Chica is dominated by the high marsh, but it also has extensive
mudflats, with some channels and open water. Another habitat found
at the Bolsa Chica is the salt flat. The salt flats have no
vegetation, and contain water only after rains. These interim ponds
are quite salty and support many insect larvae. Shorebirds can feed
on these larvae without competition from fish.
depends on several factors: two important ones are salinity and
nutrient availability. Salinity changes depending on these
frequency of tidal inundation
c. tidal creeks and
d. soil texture
f. depth of water table
g. freshwater inflow
Nutrient availability varies considerably, especially the supply of
usable nitrogen and phosphorous. Often there is not enough oxygen
present in marsh soils to combine into useful nitrates and
Chica Wetlands Through the Changing Seasons
In Spring at the
Bolsa Chica Wetlands, the days and the water become warm and
tidal circulation is low. “Neap tides” are prevalent, with a
small tidal range between the high and low tides. Two kinds of
green algae grow and become dominant in the water during these
months: stringy Enteromorpha and flat Sea Lettuce. Marsh plants
such as Pickleweed, Saltgrass, Shoregrass and Jaumea begin
flowering, and the sand dune plants bloom from late March
Brown Sea Hares,
Horn Snails and Shore Crabs are easily seen grazing the algae in
the waters below and the walkbridge. Snakes and lizards come out
of hibernation. Side-blotched and Western Lizards sun themselves
on the trails.
decrease of winter ducks and shorebirds, with ducks leaving
earlier than the shorebirds for their northern breeding grounds.
Occasionally these birds show courtship behavior before they
leave, such as the Western Grebe which “runs” across the surface
of the water. The summer migrants (terns) begin arriving in
April from their southern wintering grounds. Throughout the
spring, the Elegant Terns perform aerial courtship displays and
male endangered Least Terns offer fish to prospective mates.
Male Red-wing Blackbirds cling to the cattails, and defend their
territory by calling and flashing their red wing patches.
In Summer, the warm dry days cause a decline in the green algae.
As the algae decomposes, it provides tiny particles of food
(“detritus”) for filter-feeding animals such as Clams, Sea
Squirts, and Sponges. Filamentous Blue-green Algae dominates in
summer, forming microscopic tufts or mats on the mudflats and
plant stems. Most of the marsh plants are flowering now,
including Sea Lavender which sends up tall stalks of tiny
“Spring tides” occur between May and June, with great ranges
between the high and low tides. The underwater life is easily
seen. Stingrays enter Bolsa Chica waters looking for clams and
crabs. In some years, large populations of Common Jellyfish are
pushed by the tides to the edges of the marsh.
Nesting Elegant and Caspian Terns cover Tern Island south of the
walkbridge and in late summer Black Skimmers join them.
Black-necked Stilts and Avocets loudly defend their chicks near
the parking lot and Rabbit Island. By late summer, these chicks
are grown and nearly identical in appearance to the adults.
In the Fall, dry wind,
high evaporation rates and a lack of “Spring tides” create
drought stress in the upper marsh habitats and saltflats. Trash
accumulates in the wetlands, blown over Pacific Coast Highway
from the summer beach-goers.
Most marsh plants cease flowering by late fall except for
Cordgrass and Sea Lavender. The Pickleweed begins to turn red or
pink; later the ends of the stems dry up and break off,
returning stored salt to the soil.
The terns and swallows which were present in summer depart the
Bolsa Chica, migrating south for the winter. The winter birds
begin arriving from the north in small numbers, with shorebirds
arriving earlier than the ducks. Some of the shorebirds may
still show portions of their summer “breeding” colors, such as
the Black-bellied Plover (pictured above) and other species of shorebirds.
In Winter, storms
provide freshwater which decreases the salinity (“saltiness”) of
the soil. Storm runoff from inland cities comes down the
Wintersburg Flood Control Channel, which empties near the
tidegates and carries unwanted trash into the wetlands along
with the freshwater. “Spring tides” occur again between December
and February, with saltwater reaching the upper portions of the
marsh. In some years, the high tides on the ocean side combine
with heavy rains to flood Pacific Coast Highway and cause its
The water is cool, and thus primary productivity of the plants
is low. However, the decreased salinity helps Pickleweed seeds
germinate, and large expanses of Pickleweed follow wet winters.
No marsh plants are in flower during these months, although
Heliotrope and Telegraph Weed bloom late into winter.
Winter brings the highest concentrations of ducks, grebes and
shorebirds which may be seen resting and feeding in the
wetlands. Flocks of “diving ducks” such as Surf Scoter, Lesser
Scaup, Bufflehead, Ruddy Duck float in the middle of the bays,
while Marbled Godwits, Willets, Dowitchers, Dunlin, and Western
Sandpipers congregate on the shores. “Dabbling ducks” include
Northern Pintail, American Wigeon, and Blue-winged Teal. Several
species of Loons and Western Grebes chase the abundant fish
The resident Belding’s Savannah Sparrow begins staking out
territories and is most visible as it perches on top of the
pickleweed. Spring approaches.