PREFACE 



The Nation's estuaries are 

 heterogeneous in size, physiography, 

 watershed interactions, chemistry, and 

 biota. In this Profile, we point out how 

 the various properties of Tijuana Estuary 

 compare to those of other estuaries within 

 the region as well as within the nation. 

 The designation of Tijuana Estuary as one 

 of the National Oceanic and Atmospheric 

 Administration's National Estuarine 

 Research Reserves shows that it is one of a 

 class of ecosystems worthy of research 

 and education, yet different enough to 

 warrant selection as a regional type. 



What makes Tijuana Estuary eligible 

 for national recognition? It functions as a 

 coastal water body that is influenced by 

 both marine and river waters. It supports 

 a range of natural plant and animal 

 communities that are especially adapted to 

 withstand the variable salinities that 

 occur when sea and fresh waters mix. It 

 has persisted through human history as an 

 ecosystem that retains many of its natural 

 qualities despite disturbance from urban 

 and agricultural land uses. Unique to 

 Tijuana Estuary is its international 

 setting, with three-fourths of its 

 watershed in Mexico; its diversity of 

 ecological communities, which provide 



habitat for a variety of rare and 

 endangered species; and its history of 

 ecological study, with extensive data from 

 years with and without catastrophic 

 disturbances. 



What sets California's estuaries apart 

 from others in the nation is the degree of 

 variability in the physical environment. 

 During most of the year, they are marine- 

 dominated systems, i.e., extensions of the 

 ocean. During the winter rainy season, 

 they may become completely fresh. In 

 addition, there is substantial annual 

 variation from years with no streamflow 

 to years with major floods. The extremely 

 variable nature of southern California's 

 coastal habitats is not evident from short- 

 term observation. Indeed, many visitors 

 enjoy weeks of warm, cloud-free days and 

 deny that we even have "weather." But 

 from over a decade of study, there have 

 been repeated opportunities to witness 

 extreme events within Tijuana Estuary, 

 ranging from catastrophic flooding to tidal 

 closure and drought. These events have in 

 turn allowed us to identify how physical 

 factors influence biotic communities, and 

 to quantify the dynamics of estuarine 

 organisms as they respond to 

 environmental extremes. 



