CHAPTER 9, PART 1 



M 



M J J 



MONTH 



SON 



FIGURE 9.1-16. — Temporal variations in the proportion of water column POC accounted for by phytoplanklon in the Apex, September 1973 to 



March 1976. 



which the bloom occurred indicates that it did not develop 

 in response to local nutrient enrichment of the coastal 

 zone during the actual period of the bloom. This is sup- 

 ported by the observation that C tripos cell densities were 

 lowest in the Apex where local nutrient enrichment is 

 greatest. The causes of the bloom, whether related to 

 increased growth or decreased mortality rates, must have 

 involved processes operative on spatial scales on the order 

 of the continental shelf and time scales on the order of 

 months to years. 



The temporal and spatial development of the bloom 

 during April and May suggest an onshore transport of cells 

 once the population began to aggregate below the ther- 

 mocline. By mid-June a large population of cells was pre- 

 sent below the thermocline in a relatively flat region of 

 the New Jersey shelf between the 20- and 40-m isobaths. 

 Much of this population was below the euphotic zone in 



a subthermocline layer about 10 m thick. This is in marked 

 contrast to the population off the Long Island coast where 

 the layer of maximum concentration was well off the bot- 

 tom in a subthermocline layer about 30 m thick. (See 

 chapters 2 and 8.) Maximum population size was probably 

 achieved after March and before July; and population size 

 declined rapidly during July. 



There is no evidence that the C. tripos bloom influenced 

 the growth of netplankton diatoms or nannopiankton pop- 

 ulations. The distribution and abundance of these groups 

 were similar to previous years" observations. 



The role of C. tripos in the development of the oxygen 

 minimum layer off New Jersey is difficult to evaluate in 

 the absence of data on the time and space distribution of 

 D.O. in the bottom layer and more complete information 

 of the time and space distributions of POC, chlorophyll 

 a. and C. tripos. The Bight Apex has been subjected to 



213 



