STUDIES ON THE MASS CULTURE OF PHAEODACTYLUM. II. THE GROWTH OF PHAEODACTYLUM AND OTHER SPECIES IN OUTDOOR TANKS

Abstract

Characteristics of the growth of Phaeodactylum in culture in fertilized sea water in 1,000‐L concrete tanks are described. Successful experiments showed a constant pattern of events as follows: 1) active growth of Phaeodactylum, 2) reduction in growth rate of Phaeodactylum, 3) period of constant cell density, or rapid decline, 4) regeneration period, and, 5) second period of active growth.Growth of Phaeodactylum shows seasonal variation, but final population density reached is more or less constant. N and P utilization follow parallel courses, the mean ratio of N:P uptake during the 1st growth period being 6.5 ± 0.44:1. During growth, inorganic P is incorporated in the cells as particulate organic P. Following decline of Phaeodactylum dissolved organic P increases, and later, inorganic P is regenerated and may be reutilized during the 2nd growth phase. Decline of Phaeodactylum is normally associated with increase of the heterotroph Monas. There was a close relationship between peak numbers of Monas and the number of Phaeodactylum in the previous peak. The second growth phase consisted either of one or more chlorophycean flagellates, or of Phaeodactylum.Estimates of production based on O2 bottle exposures, change in inorganic P, change in pH, and change in packed cell volume agree closely, although initial uptake of P may be excessive. Estimates from change in inorganic P indicate a seasonal variation in the rate of organic production of up to 2.2 gC/m2/24 hr in March, 4.9 gC/m2/24 hr in May–August, and 2.0 gC/m2/24 hr in October, November. For Tetraselmis production rates up to 5.2 gC/m2/24 hr were recorded.The efficiency of utilization of solar energy for Phaeodactylum culture ranged from 3.0 to 4.4% with a mean for 5 estimates of 3.7%. For Tetraselmis values of 1.0–1.3% were obtained.