Springtime phytoplankton dynamics in the Arctic Krossfjorden and Kongsfjorden (Spitsbergen) as a function of glacier proximity

Abstract

The hydrographic properties of the Kongsfjorden – Krossfjorden system (79° N, Spitsbergen) are affected by Atlantic water incursions as well as glacier meltwater runoff. This results in strong physical gradients (temperature, salinity and irradiance) within the fjords. Here, we tested the hypothesis that glaciers affect phytoplankton dynamics as early as the productive spring bloom period. During two campaigns in 2007 (late spring) and 2008 (early spring) we studied hydrographic characteristics and phytoplankton variability along 2 transects in both fjords, using HPLC-CHEMTAX pigment fingerprinting, molecular fingerprinting (DGGE) and sequencing of 18S rRNA genes. The sheltered inner fjord locations remained colder during spring as opposed to the outer locations. Vertical light attenuation coefficients increased from early spring onwards, at all locations, but in particular at the inner locations. During the end of spring, meltwater input had stratified surface waters throughout the fjords. The inner fjord locations were characterized by overall lower phytoplankton biomass. Furthermore HPLC-CHEMTAX data revealed that diatoms and <i>Phaeocystis</i> sp. were replaced by small nano- and picophytoplankton during late spring, coinciding with low nutrient availability. The innermost stations showed higher relative abundances of nano- and picophytoplankton throughout, notably of cyanophytes and cryptophytes. Molecular fingerprinting revealed a high similarity between inner fjord samples from early spring and late spring samples from all locations, while outer samples from early spring clustered separately. We conclude that glacier influence, mediated by early meltwater input, modifies phytoplankton biomass and composition already during the spring bloom period, in favor of low biomass and small cell size communities. This may affect higher trophic levels especially when regional warming further increases the period and volume of meltwater

Differences in free-living and particle-associated bacterial communities and their spatial variation in Kongsfjorden, Arctic

“…Many parameters, including particulate material, salinity, chlorophyll, dissolved nutrients and temperature, are known to vary along the length of Kongsfjorden and might impact bacterial community structure . In the present study, inner fjord (IF) station was located near to the Kongsbreen glacier thus experience heavy glacier meltwater influx loaded with dissolved nutrients (N and P), and organic matter of terrigenous origin during summer .…”

“…However, some studies reported their presence in both particle‐associated and free‐living fractions , as observed in our study with some differences in their relative abundance between both fractions. Firimicutes have been reported as a dominant phylum in Arctic permafrost , high Arctic snow , and meltwater streams . Therefore, higher incidence of Firmicutes in the IF_FL fraction could indicate enhanced terrestrial and glacier inputs.…”

“…Particle‐associated bacteria are an important functional component of the Arctic ecosystem and under a warmer climate, they are likely to play an increasing role in biogeochemistry and carbon fluxes as a result of increased particle transport to coastal waters . However, only a limited number of studies have examined particle‐associated (PA) and free‐living (FL) bacterial communities in Arctic coastal ecosystems . In addition, these studies were largely based upon the traditional DNA fingerprinting methods and/or Sanger sequencing of cloned 16S rRNA gene.…”

Diversity of retrievable heterotrophic bacteria in Kongsfjorden, an Arctic fjord

“…During June and September, the glacial melt water input could be higher as evident by the lower salinity values in the upper water column. High sediment concentrations derived from the input of melted glacial water can limit the light availability for phytoplankton growth near the glaciers 12 . The euphotic zone can be restricted to the upper 0.3 m close to the glaciers, 22 leading to highly unfavorable conditions for phytoplankton growth 23 …”

“…In the recent studies of Piquet et al11, 12 on the pelagic microbial communities of Kongsfjorden, the diversity of non-culturable communities of bacteria, phytoplankton, and protists was monitored. However, very few attempts have been made to understand the diversity of retrievable heterotrophic bacteria of this ecosystem 13, 14…”