pollution effect of the sewer line seemed negligible, as its outflow 

 was intermittent with prolonged intervening pauses and only a small 

 effluent volume. The presence of the garden eels is presumed to 

 have had a greater effect on plankton counts during the daytime. 



At night, some organisms seemed to pass by in aggregates, among them 

 cephalopod larvae, phyllosoma larvae, macrurans , calanoids, chaeto- 

 gnaths , and bipinnaria larvae. 



The results of the light experiment are difficult to evaluate, since a 

 number of factors introduced a probable bias of unknown magnitude. 

 Among these were the construction of the habitat, which caused an out- 

 flow of air resulting in some turbulence near one of the lights. The 

 periods allowable for each lighting arrangement were too short and 

 need to be repeated under more leisurely circumstances. Natural 

 fluctuations in plankton density almost certainly had an effect on 

 the sampling. Nevertheless, certain preferences were apparent. In 

 most instances, the blue light was favoured; this was the case with 

 calanoid copepods, macrurans, polychaetes, hyperiids, and the various 

 kinds of zoea. For all of these animals yellow was a strong second 

 choice. Yellow light was definitely preferred by chaetognaths and 

 mysids over other colors. Some groups, such as stomatopods, showed no 

 clear preference. Red light was the least attractive throughout. More 

 extensive studies of this kind are to be carried out from the under- 

 water laboratory at Helgoland. 



CONCLUSIONS 



In the vicinity of the coral reef the bottom plankton shows definite 

 distribution patterns in relation to substrate type. From the 

 frequency distribution found in all samples it appears, that the bulk 

 of the reef zooplankton is of local origin. It would be of interest, 

 to carry out this type of collection over longer periods of time and 

 with a simultaneous analysis of plankton in the upper strata, in 

 order to obtain estimates of standing crop, local production and 

 oceanic invasions of zooplankton. 



VI-284 



