FLUCTUATIONS IN THE ABUNDANCE OF PLANKTONIC DIATOMS IN THE PASSAMAQUODDY REGION, NEW BRUNSWICK, FROM 1924 TO 1931

• Published in: Contributions to Canadian Biology and Fisheries
• Main Author: DAVIDSON, VIOLA M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1933
• Subjects: General Earth and Planetary Sciences; General Engineering; General Environmental Science; Arctic; Phytoplankton
• Online Access: http://dx.doi.org/10.1139/f33-028; http://www.nrcresearchpress.com/doi/pdf/10.1139/f33-028

Collections made during a period of seven and a half years (1924–1931) weekly at a station of 30 m. depth in the St. Croix estuary and monthly at a station of 90 m. depth in the Outer bay show three dominant species. Thalassiosira Nordenskiöldi dominates during spring at both stations, being definitely stenothermic, finding somewhat under 6 °C. most favourable, and disappearing at that temperature, which is reached earlier in the estuarine station. Chaetoceros debilis dominates in June at that station. It is most abundant at 10–12 °C., but occurs at lower as well as at higher temperatures up to the summer maximum of 15 °C. Biddulphia aurita, an early spring littoral species, reaches its maximum at about 2 °C., and disappears when the spring freshet takes place. The forms were arctic-neritic in spring (beginning with the melting of the snow), arctic and boreal in June and July, and temperate and oceanic in late summer and autumn.There is no apparent lack of nutrient salts, nitrates, phosphates and silica being reduced but never depleted. Light is an important factor, but its effect is not clearly distinguishable, the peak of diatom production being reached usually in June at the outer station and in late June or early July at the inner station, while July had the most effective light. Marked reduction in surface salinity from river discharge with consequent stability of the water precedes the spring maximum of phytoplankton, and to a less degree local rainfall of summer has a corresponding effect.