17 research outputs found
Higher sensitivity towards light stress and ocean acidification in an Arctic seaâiceâassociated diatom compared to a pelagic diatom
Thalassiosira hyalina and Nitzschia frigida are important members of Arctic pelagic and sympagic (seaâiceâassociated) diatom communities. We investigated the effects of light stress (shift from 20 to 380 ”mol photons mâ2 sâ1, resembling upwelling or ice breakâup) under contemporary and future pCO2 (400 vs 1000 ”atm). The responses in growth, elemental composition, pigmentation and photophysiology were followed over 120 h and are discussed together with underlying gene expression patterns. Stress response and subsequent re-acclimation were efficiently facilitated by T. hyalina, which showed only moderate changes in photophysiology and elemental composition, and thrived under high light after 120 h. In N. frigida, photochemical damage and oxidative stress appeared to outweigh cellular defenses, causing dysfunctional photophysiology and reduced growth. pCO2 alone did not specifically influence gene expression, but amplified the transcriptomic reactions to light stress, indicating that pCO2 affects metabolic equilibria rather than sensitive genes. Large differences in acclimation capacities towards high light and high pCO2 between T. hyalina and N. frigida indicate speciesâspecific mechanisms in coping with the two stressors, which may reflect their respective ecological niches. This could potentially alter the balance between sympagic and pelagic primary production in a future Arctic
Molecular diversity and temporal variation of picoeukaryotes in two Arctic fjords, Svalbard
Arctic spring awakening â Steering principles behind the phenology of vernal ice algal blooms
Marine ecosystems at high latitudes are characterized by extreme seasonal changes in light conditions, as
well as a limited period of high primary production during spring and early summer. As light returns at
the end of winter to Arctic ice-covered seas, a first algal bloom takes place in the bottom layer of the sea
ice. This bottom ice algae community develops through three distinct phases in the transition from winter
to spring, starting with phase I, a predominantly net heterotroph community that has limited interaction
with the pelagic or benthic realms. Phase II begins in the spring once light for photosynthesis
becomes available at the ice bottom, although interaction with the water column and benthos remains
limited. The transition to the final phase III is then mainly driven by a balance of atmospheric and oceanographic
forcing that induce structural changes in the sea ice and ultimately the removal of algal biomass
from the ice. Due to limited data availability an incomplete understanding exists of all the processes
determining ice algal bloom phenology and the considerable geographic differences in sympagic algal
standing stocks and primary production. We present here the first pan-Arctic compilation of available
time-series data on vernal sea ice algal bloom development and identify the most important factors controlling
its development and termination. Using data from the area surrounding Resolute Bay (Nunavut,
Canada) as an example, we support previous investigations that snow cover on top of the ice influences
sea ice algal phenology, with highest biomass development, but also earliest termination of blooms,
under low snow cover. We also provide a pan-Arctic overview of sea ice algae standing stocks and primary
production, and discuss the pertinent processes behind the geographic differences we observed.
Finally, we assess potential future changes in vernal algal bloom phenology as a consequence of climate
change, including their importance to different groups of grazers
State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic
The polar bear (Ursus maritimus) is among the Arctic species exposed to the highest concentrations of long-range transported bioaccumulative contaminants, such as halogenated organic compounds and mercury. Contaminant exposure is considered to be one of the largest threats to polar bears after the loss of their Arctic sea ice habitat due to climate change. The aim of this review is to provide a comprehensive summary of current exposure, fate, and potential health effects of contaminants in polar bears from the circumpolar Arctic required by the Circumpolar Action Plan for polar bear conservation. Overall results suggest that legacy persistent organic pollutants (POPs) including polychlorinated biphenyls, chlordanes and perfluorooctane sulfonic acid (PFOS), followed by other perfluoroalkyl compounds (e.g. carboxylic acids, PFCAs) and brominated flame retardants, are still the main compounds in polar bears. Concentrations of several legacy POPs that have been banned for decades in most parts of the world have generally declined in polar bears. Current spatial trends of contaminants vary widely between compounds and recent studies suggest increased concentrations of both POPs and PFCAs in certain subpopulations. Correlative field studies, supported by in vitro studies, suggest that contaminant exposure disrupts circulating levels of thyroid hormones and lipid metabolism, and alters neurochemistry in polar bears. Additionally, field and in vitro studies and risk a