The annual cycle of phytoplankton primary production and hydrography in the Disko Bugt area, West Greenland

• Main Author: Andersen, Ole G. Norden
• Format: Article in Journal/Newspaper
• Language: English
• Published: Danish Polar Center/Museum Tusculanum Press 1981
• Subjects: Greenland; Kangikerdlak; Disko bugt; Godhavn
• Online Access: https://tidsskrift.dk/meddrgroenland_biosci/article/view/142187

The distribution and size of phytoplankton production and biomass in relation to physical and chemical parameters in the upper 50 m at Godhavn and in Kangikerdlak in the inner part of Disko Fjord was investigated through 2½ years (1973-75). Some data from other parts of Disko Bugt are presented. In both locations the hydrography alternates between an unstable winter situation with isothermal (-1.75°C) and isohaline (33.5-34.0‰) conditions throughout, and a highly stable summer situation when dilution and heating, especially of the upper 20- 30 m, raise the temperature at the surface to 9.9°C and at 50 m to 3.8°C at Godhavn, and to 12°C and 3.5°C respectively in Kangikerdlak. Salinities drop correspondingly to 30.6‰ in Kangikerdlak. The 1% depth for green light is greatly reduced beneath ice and snow. During the ice free period at Godhavn it varies from 12 m during the spring phytoplankton bloom to more than 60 m from Oct. through the winter. In Kangikerdlak the 1% depth reaches only 40 m in winter, and outflowing turbid fresh water creates I% depths of as little as 4-5 m in June-Aug. At Godhavn NO3-N reaches highs of 10.05 μgat /liter and 10.15 μgat /liter at 0 and 50 m respectively in winter, whereas during the summer, depletion to less than 0.01 μgat /liter occurs in the upper 40 m and to 1.0 μgat / liter at 50 m. PO4-P is similarly reduced from 0.8 μgat/liter and 1.1 μgat/liter to less than 0.01 μgat / liter in the upper 20 m and to 0.21 μgat /liter at 50 m. The N:P ratio drops from 13 to less than 0.01 in the upper 30 m and to 1.0 at 50 m. In Kangikerdlak depletion of NO3-N is similar to conditions at Godhavn, whereas PO4-P reaches a low of 0.1 μgat/liter only, while in mid summer it reaches 1.88 μgat /liter at the surface, giving an N:P ratio which is below 0.1 in the upper 5 m only. At Godhavn primary production is about 90 gC • m-2 • yr-1 (75-104 g) with a maximum of about 5 .5 gC • m-3 • yr-1 at 5- 10 m, whereas in Kangikerdlak production was concentrated near the surface with about 6.0 gC • m-3 • ...