The Ecology of Tijuana Estuary, California: An Estuarine Profile

Figure 6. The 1904 map of Tijuana Estuary (from U.S. Coast and Geodetic Survey).
an isolated, land-locked lagoon in the northeastern were collected in 1976 and 1977; the average was
part of the estuary. Without a natural connection 41 1 calories/cm2/day, ranging from an average of
between the lagoon and the rest of the estuary, this 561 for June to 217 for December (Taylor 1978).
habitat must have been a highly variable wetland Griner and Pryde (1976) state that Sa'n Diegans
that filled in the rainy season and dried out in enjoy about 73% of the maximum possible
summer. Second, the mouth of the Tijuana River is sunshine. Daily temperatures average 17" C
represented as a minor bay, rather than a narrow (63" F), with monthly highs in July or August
channel. If this map does not represent an (26OC, 78" F) and lows in January (7OC, 45OF).
unusually high tide, then there was a much larger Frost is rare along the coast.
subtidal area than exists at present, and major
sedimentation occurred after 1904. Third, there The coastal climate of southern California is
are two river courses, one entering the center of
the estuary and one toward the southern end. The
reminiscent of the Mediterranean region (Barbour
and Major 1977), and the coastal vegetation is
latter no longer connects with the river.
similar to that of France, southern Africa, and
southwestern Australia, all of which have
2.2 MEDITERRANEAN-TYPE CLIMATE Mediterranean-type climates. For coastal wetland
vegetation, average rainfall on the coast is unlikely
Cool, wet winters and warm, dry summers to be the d~rect determining factor; rather, the
characterize the climate of southern California. timing and amounts of rainfall and river flows within
Most days are sunny, although morning fog is the entire watershed set limits on species
common along the coast. Solar radiation data for distribution and growth. For intertidal organisms,
Chuia Vista (the station nearest Tijuana Estuary) conditions that cause high evaporation rates are
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