A continuous culture apparatus was used to measure growth rates of Nitxschk cbsterium and T&w.seZmis sp. at different temperatures and light intensities and at two different levels of nitrate and phosphate cnrichmcnt of artificial senwntcr.A set of symmetrical relationships was found between light, temperature, and nutrient concentration in which the intcraction of any two of the factors was modified by varying the third. The optimum temperatures yielding maximum growth rates in a daily light-and-dark cycle were lower when a medium with nitrate and phosphate concentrations similar to those found in natural waters was used than when a medium having higher concentrations of these substances was used. The results of batch culture cxncriments with high nutrient concentrations may not bc applicable, thcrcfore, to natural situations.

Brine pollution from a sea-salt works occasionally flows into Bahia Fosforescente causing stagnation, severe anoxia and accumulation of hydrogen sulfide (88 ml/liter) with conscquent toxic effects on local flora and fauna. The bottom brine (salinity

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Knowledge of the microdistribution and of the microecology of plankton is an important aspect of biological oceanography. Work in this area has been hampered by observational inadequacies. Operational considerations are discussed and a specific technique is presented which offers an improved solution for some of the problems involved in this field of study. A device is described which can measure the number and sizes of individual particles such as zooplankton organisms in situ and record their spatial distribution as it is towed along transects through the sea.