An apparatus is described for exposing phytoplankton cultures to 64 different combinations of light and temperature. The light was of a known spectral energy resembling sunlight after passage through a few metres of clear coastal sea water and was measured in the energy units of cals/cm2/min (langlies/min or ly/min). The temperature range used varied in each experiment, the range of illumination was from about 0.005 to 0.4 ly/min, the latter being equivalent to bright summer sunlight at a depth of only a few metres in the sea.The growth of five bacteria-free cultures, Dunaliella tertiolecta, Amphidinium carteri, Monochrysis lutheri, Skeletonema costatum and Thalassiosira nordenskiöldii was followed for a period of 3–5 days using a cycle of 16 hr illumination and 8 hr of darkness every 24 hr. Growth was measured by counting cell numbers and the rate constants for cell division were evaluated at standard times.The resulting growth-response curves are reported and discussed in relation to their ecological significance. Except for T. nordenskiöldii cell division was relatively insensitive to temperature over a range exceeding 10 °C. Cell division showed a "stress" response, the growth rate being more susceptible to extremes of illumination when the cells were near to the extremes of temperature for a given species and to extremes of both temperature and light if the chemical nature of the medium was unsatisfactory. At optimum temperatures there was no inhibition of cell division at intensities of 0.4 ly/min of photosynthetically active light.

Primary production was measured at 14 stations covering a wide range of oceanic waters. Measurements were made by both the in situ method (Pi) and the simulated in situ method (Ps) Production v. constant irradiance (P v. I) was also measured. Available photosynthetic irradiance [Eq(350-700) in quanta m-2 s-1] was calculated from continuous records of total irradiance and measurements of the percentage submarine transmission of irradiance were made with a quantum meter. Using the P v. I curves and Eq(350-700), primary production at several depths at each station was calculated (P,). Pc was shown to be a precise estimate of Ps at all depths. Pc was also highly correlated with Pi, but both Pc and Pi overestimated Pi at the surface by 40 %. Some experiments at three stations showed that a 2-mm thickness of clear glass placed over surface samples in the measurement of Ps could increase Ps by about 50%. This suggested that U.V. irradiance in surface ocean waters decreased Pi and could explain the overestimates by Pc and Ps. The results showed the need for precise information of spectrai composition of irradiance in studies of primary production but demonstrated the kalidity of Eq(350-700) as an estimate of available photosynthetic irradiance. They also showed that Pc could estimate Pi with a high degree of precision, and that such a calculative method could provide a useful way of continuously monitoring the primary production of large bodies of water for extended periods.

Experiments were made on the effects of pH, phosphate concentration, particle size, iron, and organic matter on the adsorption of phosphate by estuarine bottom deposits in as natural a state as possible. Measurements of the ability of the silt to adsorb phosphate were made by isotope dilution, using 32P. The silt was separated into four fractions by sedimentation. The ability of silts to adsorb phosphate was directly related to the ratio of their contents of iron to organic matter. Organic matter depressed phosphate adsorption. Suspensions of silts (2.99g/1250ml) adsorbed 80-90 per cent. of the phosphate in solutions containing 0.55 to 2.55 mg of phosphate P. This suggested that adsorption caused estuarine silts to trap phosphates during run-off periods.

An analysis of productivity data from 150 stations in the area, carried out in the period January-March from 1958 to 1962, showed that the area could be divided into five homogeneous regions, each with characteristic magnitudes, vertical profiles, and diurnal variations. A comparison of these regions with the hydrological structure showed a close parallel to a system of three external water masses which mix to form all the major characteristics of the area. In the northern Coral Sea is a region of moderately productive waters (25 mgC/hr/m²) mainly of equatorial origin, with sharp vertical stratification at 50 m, and a high productivity index (3.7 mg C/ hr/mg chl.a) in the upper 50 m. The central part of the area is dominated by waters of the west central South Pacific Ocean with a low productivity (11 mg C/ hr/ m², no vertical stratification, and a low productivity index (1 -2). The southern Tasman Sea is dominated by waters of subantarctic origin with a very high productivity (49 mgC/ hr/ m²), a large subsurface maximum at 50 m, a sharp stratification below 50 m, and a high productivity index (3.9). Between these three regions are two others formed by mixing, and these have intermediate characteristics. In all five regions there are subsurface maxima of chlorophyll a below the layers of maximum productivity, and these sink even deeper as the productivity decreases. This suggests that the phytoplankton sink and lose their ability to photosynthesize as the waters become poorer. Diurnal variations of productivity in the five regions show an inverse relationship with latitude, the ratio of maximum to minimum productivity decreasing from 3.1 at 15� S. to 2.1 at 45� S, but this decrease is less than would be expected from other values published.

Simultaneous measurements with two types of incubators were made on replicate samples both in the incubators and in situ in the ocean. Both incubators used sunlight and blue glass filters to simulate light conditions at depths in the ocean. The first gave measurements of column production 1.58 times those in situ. This was due to the fact that at depths greater than 20 m the incubator gave much higher results with no significant relation to those measured in situ. In the second incubator the accuracy of reproduction of oceanic light conditions was improved by reducing reflected light and using a balance-by-depth twin photometer system for determining the depths of sampling. The measurements of column production in the second incubator were 1.03 times the in situ values.