This study investigates how living benthic foraminifera react to variations in hydrography, periodic hypoxia and anoxia and variations in primary production.
Work was carried out in the Koljo¨ fjord (Fig. 1), which represented, as it were, a natural laboratory.
Conditions within the fjord allowed us to clarify how benthic foraminiferal populations evolve under natural conditions, in an environment that is subject to seasonal fluctuations in hydrography and food supply under oxic as well as hypoxic and anoxic
conditions. A uniquely long series of hydrographic measurements was taken, combined with sediment sampling.
Two periods of hypoxia to anoxia with an intervening period of oxic conditions, together with two autumn phytoplankton blooms and one spring phytoplankton bloom, made it possible to achieve the aims of this study. A depth transect was studied,
from a shallow, well-oxygenated environment down to periodically hypoxic or anoxic, stable deep-water conditions.
This kind of temporal and spatial study is essential to understand how and why foraminifera react to changes in the environment.
A knowledge of factors that control the development of foraminiferal
populations is essential, not only for biologists but also for palaeontologists, who use foraminifera as tools to reconstruct environments and environmental changes in the past.