150 



Life 



DIATOMS-OFFSHORE-1938-41 



ZOOPLANKTON- OFFSHORE- 1952-55 

 BACTERIA-NEARSHORE 

 .■"■/ 1932-42 



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Figure 131. Average monthly 

 abundance of diatoms and 

 zooplankton. Diatom counts 

 (cells per cubic centimeter) for 

 the offshore area are averages 

 of concentrations measured by 

 Allen during 1938-1941 at 0, 

 20, 40, and 60 meters (Sverdrup 

 and Staff, 1942, 1943, 1944, 

 and 1947). Those for the shelf 

 area were measured by Resig 

 during 1947 and early 1958. 

 Zooplankton concentrations 

 (displacement volumes in cubic 

 centimeters per 1000 cubic 

 meters) were measured during 

 1952-1955 by the Staff, South 

 Pacific Fisheries Investigations 

 (1953, 1954, 1955, and 1956), 

 from oblique tow net hauls 

 between 140 meters and the surface. Bacterial concentrations (cells per cubic centimeter) are from plate counts reported 

 by ZoBell (1946f, p. 75) for collections at the pier end at Scripps Institution of Oceanography during 1932-1942. 

 Note the lag of greatest concentration of zooplankton and bacteria after the peak concentration of diatoms. Because 

 the bacteria were collected over quite shallow water (about 6 meters), their abundance may be controlled more by the 

 presence of bottom sediment stirred up by seasonal waves than by the presence of organic debris. 



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projecting spines to enlarge their surface 

 area compared with their volume. These 

 and other diatoms also increase their buoy- 

 ancy by secreting tiny droplets of oil. On 

 the death of the plant some of its oil may 

 be released to form surface slicks; the rest, 

 if not used as food, is carried inside the 

 frustule to the bottom, where it probably 

 serves as one of the source materials of 

 petroleum. The siliceous frustules them- 

 selves may become so concentrated on the 

 bottom, where not too much diluted by in- 

 organic or calcareous sediments, that they 

 form diatomaceous muds like those of the 

 Gulf of California, or the much purer 

 diatomites of the Middle Miocene strata at 

 the Palos Verdes Hills and near Santa Maria. 

 Most of the other important components 

 of phytoplankton have attributes of animals, 

 such as flagella and ability to catch and di- 

 gest solid particles, but they are generally 

 placed in the plant kingdom because of 

 their photosynthetic activity and the cellu- 

 lose body covering on some. Most abundant 

 of these animal-plants are dinoflagellates 

 (peridineans), unicellular organisms having 

 two flagella that permit a limited degree of 

 locomotion. Although there are many 



species of dinoflagellates (Butschli, 1883- 

 1887), the bulk of those off' southern Cali- 

 fornia consist of only four species belong- 

 ing to three genera (Allen, 1941), Procentrum, 

 Ceratium, and Goniaulax, in order of de- 

 creasing abundance. During the summer 

 Procentrum and Goniaulax sometimes form 

 blooms that are so intense that the water be- 

 comes red and soupy in texture (Allen, 1946). 

 Such blooms during July 1958 contained up 

 to 25 million Goniaulax per liter. This same 

 red color was observed during the early ex- 

 plorations of the Gulf of California, causing 

 Alarcon to give it the name Vermilion Sea. 

 Concurrently with the reddening, the water 

 becomes phosphorescent at night, especially 

 where agitated by the surf or by passage of 

 a moving body such as a fish. Indicative of 

 phosphorescent ability is a genus named 

 Noctiluca, but this is rare in southern Cali- 

 fornia. Summertime blooms of one species 

 of Goniaulax are considered the cause of 

 mussel poisoning when mussels and other 

 filter feeders ingest it in large quantities 

 (Sommer, Whedon, Kofoid, and Stohler, 

 1937). The poison causes paralysis and 

 even death to people who eat the mussels, 

 whether or not the flesh has been cooked. 



