Spatial and temporal variability in export fluxes of biogenic matter in Kongsfjorden
Résumé
The marine ecosystem of Kongsfjorden experiences large variations in primary productivity due to pronounced seasonal variations in sunlight, glacier melt, and ice cover. The objective of this study was to assess spatial and seasonal variability in the downward export of biogenic matter in Kongsfjorden. Short-term sediment traps were deployed for periods ranging from 21 to 52 h at three stations from the inner fjord to the outer fjord in May, August, and October 2012 and at one mid-fjord station in January 2013. Total particulate matter, particulate organic carbon, phytoplankton cells, chlorophyll a, biogenic particulate silica, and zooplankton fecal pellet fluxes were measured to determine the magnitude and composition of the material exported in the fjord. The amount and composition of export fluxes reflected a large phytoplankton bloom grazed upon by zooplankton in May, the melting of glaciers and the intrusion of Atlantic Water in August, the end of the glacier melt period in October, and the polar night in January. Overall, seasonal changes in the phytoplankton community impacted export efficiency in the fjord, directly through phytoplankton sinking and indirectly through zooplankton grazing. Results obtained in this study may reflect the magnitude and composition of export fluxes to expect in coming years in Kongsfjorden, especially under conditions of warmer Atlantic Water and longer glacier melt periods.