282 Marine Microbiology 



species (Biddidphia weissflogii, Rliizosolenia chiinii and Actino- 

 cychis janus) in the close vicinity of iipwellings on the south 

 coast of New Soutli Wales. It is considered that these organisms 

 could only have come with antarctic water which passes under 

 the warmer water of the East Australian Current, i.e., below the 

 photic zone, and that they must therefore have remained for a 

 considerable time (years) in a spore or resting stage. 



Other instances are the occurrence of several diatoms char- 

 acteristic of the Arafura Sea (low salinity water) {Chaetoceros 

 messanense, Ch. laeve, Ceratium dens) in a patch of low salinity 

 water off New South Wales in 1958; and of cold water species 

 (Chaetoceros criophilum, Corethron criophilum, Chaetoceros 

 convohitiim) near the 17° isothenn north of New Zealand. If 

 we can fix the confidence limits of the salinity-temperature re- 

 lationsliips of a number of phytoplankters, any occurrence outside 

 the known regimen will demand an explanation, which must fit 

 known hydrological data. 



I would suggest that phytoplankton ecology may become an 

 important tool in oceanography, quite apart from its importance 

 in productivity studies. 



THE EFFECT OF ORGANIC SUBSTANCES 

 ON PHYTOPLANKTON 



The existence of extracellular organic substances in the sea 

 raises the question of the effect of such substances on the growth 

 and photosynthesis of phytoplankton. Although in vitro experi- 

 ments cannot be regarded as a true indication of in vivo activities, 

 tliey may give valuable clues, especially in instances such as this 

 where in vivo experiments are out of the question. 



Methods. Thalassiosira aestivalis, Skeletonema costatum, 

 Dunaliella marina and an Isochrysis were isolated from local 

 waters in bacteria-free culture, Dunaliella by plating on agar, 

 the others by dilution and washing after the method of Pring- 

 sheim (2). The cultures were made in large vessels, in Allen and 

 Nelson's seawater (1), and divided for test into a number of 

 aliquots. Counting was done using a Petroff Hausser bacterial 

 counting chamber and a fluorescence microscope, taking ad- 

 vantage of the auto-fluorescence of chlorophyll. Dark and light 



