Arctic fjords are sensitive to the enhanced climate warming-induced glacial meltwater
discharge that influences its hydrography and biology. The study showcased in this presentation explains the impacts of the
underwater light environment and nutrient limitation on the phytoplankton biomass,
composition, and light absorption in the sunlit zone of the Kongsfjorden (KG)-Krossfjorden
(KR) twin fjord ecosystem during summer when the meltwater discharge is at maximum.
Observations in two phases in each fjord revealed pronounced spatial hydrographic variations
between the phases and among the fjords. The intrusion of warm Atlantic water into fjords
and subsurface chlorophyll maxima was observed. Meltwater-induced higher concentrations
of optically active constituents in KG resulted in a shallower euphotic zone than KR. Nitrate
and silicate limitation was evident in both fjords. Higher phytoplankton light absorption
coefficient (aₚₕ , m⁻¹ ) and chlorophyll-a in KR implied its higher productivity potential.
However, the light-absorption efficiency of surface microplankton was affected by pigment-
package effect. Phytoplankton pigments analyses revealed an inter-fjord difference in surface
phytoplankton composition predominated by microphytoplankton followed by nano and
picoplankton. The average diversity index for the phytoplankton group (H') was higher in KR
(0.71) than KG (0.55), which was possibly controlled by microzooplankton grazing. This
study reveals that environmental settings in both fjords were quite different, which drives
their productivity potential and species diversity. Thus, increased warming climate can have
different impacts on fjord ecosystems despite their close geographical proximity.
