First, a little history.  The Port of LA is one of the most important ports in the world, moving 190 metric tons annually.  The port was established 100 years ago, in 1907.  The harbor was visited by Portuguese explorer & the first European, Juan Rodriguez Cabrillo, to sail up the California coastline 1542.  At that time it was a marshland, and in 1771, the Spanish explorers established missions at San Juan Capistrano and San Gabriel.   

Cabrillo Beach is named for Cabrillo . Originally this area was a rocky beach and wetland area, but this began to change with the construction of the San Pedro Breakwater in 1899. Sand was added to the area after the completion of the breakwater. Local residents liked this new beach, and Cabrillo Beach officially opened to the public in 1928. Shortly thereafter, the first grunion run was spotted.

Image from: Los Angeles City Lifeguard Association

The new Cabrillo Beach consisted of three beaches, all in one location: an Inner Beach, located inside the breakwater; an Outer Beach, located outside the breakwater and facing the open ocean; and a Natural Beach, a remnant of what the area looked like prior to 1899.

Since then, development along the coast has destroyed nearly all of the coastal ecosystems in the area. According to the Southern California Coastal Water Research Project¹, the Southern California bight supported 19,591 hectares of estuarine habitats. Since 1850, about 48% of these areas have been lost, with the vegetated wetlands = aka salt marshes) suffering the most. Salt marshes are an important part of the coastal ecosystem. First, they are a filter for sediments entering the ocean. Lagoons, marshes, and other quiet water environments are also low energy environments, so sediments are deposited easily. This limits the amount of sediment entering into the coastal waters and keeps tidal and kelp ecosystems clear and sediment-free. The shallow, quiet waters are also the perfect location for the young of many fish and invertebrate species to spend their youth, protected from larger predators due to the reduced water depth, amount of silt in the water, and numerous plant species. Finally, estuarine habitats provide a place for birds to rest, and to find shelter, food, and water.

image source:  http://www.amigosdebolsachica.org/history.php

Sources:

1. Stein, Eric D., Kristen Cayce, Micha Salomon, Danielle Liza Bram, Danielle De Mello, Robin Grossinger, and Shawna Dark. Wetlands of the Southern California Coast: Historical Extent and Change Over Time. Tech. no. 826. Vol. 826. Costa Mesa: Southern California Coastal Water Research Project, 2014. Web = http://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/826_WetlandsHistory.pdf).

2. "The History of Bolsa Chica." The History of Bolsa Chica. Web. 15 May 2016. <http://www.amigosdebolsachica.org/history.php>.