Onset of the spring phytoplankton bloom in the Barents Sea: influence of changing light regime and other environmental factors

摘要

The onset of the phytoplankton spring bloom in the Barents Sea usually takes place in April/May, at a time when the daily total irradiance and the `critical' depth increase fast. The onset of the spring bloom is normally assumed to be counteracted by water column vertical turbulence. During field investigations in the Barents Sea we observed that the blooms took place in vertically homogeneous water columns. By model simulations it is shown that entraiment of phytoplankton cells from the bottom sediments may be an important factor regulating the onset of spring blooms, and that if such processes exists, a vertically mixed water column may be beneficial for blooms. A new hypothesis is also presented where daylight is important, not through physiological processes enhancing photosynthesis, but by triggering the germination of phytoplankton spores.