98 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Many species are apparently restricted in tlieir seasonal appearance wliile 

 others inay be found at all seasons; for example, Lohmann (1908) records the 

 presence of Amphidininm crnssam and A. rotnndatum in the Baltic Sea near 

 Kiel, Germany, throughout the year. Other species have been recorded from 

 two or more places in the same latitude and general temperature conditions for 

 different months of the year, indicating a wide range of temperature relations. 



It has been found in the thecate dinoflagellates, and it is probable that it is 

 equally true here, that the period of greatest abundance, both specifically and 

 numerically, extends from June to October or November. During the latter 

 part of this period many tropical forms are found in the San Diego region, 

 brought northward by the currents in the Pacific. At other times of the year 

 drifters from the northern region are sometimes observed here. The occur- 

 rences of the latter species are influenced by the southbound California current 

 from more northern waters. 



One of the mysteries connected with the distribution of the dinoflagellates 

 is the sudden occurrence of vast quantities of a single species, so great in 

 amount as to give a distinct color to large areas of the sea. Such is the red 

 water frequently noted in patches in the Pacific off the coast of California 

 during the suimner months. This is caused by Gonyaulax polyJiedra, or in one 

 case of red water at La Jolla in 1916 by Prorocentrum micans. In other local- 

 ities species of Geratium and Peridininm have been known to cause a distinct 

 coloration of the water. 



Gymnodiniuni favum was the cause of an outbreak of yellow water at La 

 Jolla during the summer of 1914. This was not very great in extent or serious 

 in its results. This sudden appearance of vast numbers of a single s^Decies and 

 an almost complete disappearance a few days later has no apparent relation 

 to tides or currents. Its cause is probably a ph^^siological one, and may be the 

 response of a peculiarly susceptible organism to the stunulus of a sudden influx 

 of materials present in their normal habitat in only limited quantities. The 

 susceptibility of Dinoflagellata to extremely minute amounts of mineral sub- 

 stances is shown by the fact that one i^art in ten million by weight of copper 

 sulphate is sufficient to kill off utterly within a few days all Cerafium hinindi- 

 nella in California fresh-water reservoirs. The effect of this algicide is lasting, 

 for months at least. It is theoretically possible that these may be not only 

 growth depressants but excitants as well, the existence of which in minute quan- 

 tities woiild suffice to set in motion and to continue such massive changes in 

 production as api:»ear in the red water, where the tonnage per acre is enormous. 

 The possibility that such specific growth excitants exist among the organic sub- 

 stances accumulated by the processes of decay in the depths of the sea and near 

 the light floor of the high seas is suggested by the fact that red water areas lie 

 along our western coast where upwelling waters enrich the coastal region, and 

 that the greatest abundance of the dinoflagellates, both of individuals and of 

 species, in the ocean lies suggestively near the zone of initial decay of the 

 phytoplankton. 



