Ecosystem Kongsfjorden: new views after more than a decade of research

Impacts of Atlantic water intrusion on interannual variability of the phytoplankton community structure in the summer season of Kongsfjorden, Svalbard under rapid Arctic change

Atlantification, known as impacts of high-latitude Atlantic water inflows on the Arctic Ocean has strengthened owing to climate change, corresponding to the rapid ice retreat in the Arctic. The relationship between phytoplankton and environmental changes in the Arctic on the interannual scale is unclear because of the lack of long-time series data. In this study, we discuss the ecological response to Atlantic water intrusion in the Kongsfjorden,Svalbard. We measured chlorophyll a and photosynthesis pigments for the water column samples from a fixed section along the Kongsfjorden to study the response of phytoplankton biomass and communities to Atlantic water intrusion in the summer season from 2007 to 2018. The results showed that dinoflagellates, prasinophytes, cryptophytes, and chlorophytes consistently accounted for over 50% of the total biomass, with the distinct annual variation of chlorophyll a. Bioavailable nitrogen was the main limiting factor on phytoplankton growth in the study area, as inferred by its concentration and nutrients ratios. The relationship between phytoplankton and water mass analysis suggested that the intrusion of Atlantic water in Kongsfjorden may cause interannual variability of the phytoplankton biomass and community structure by influencing the nutrient supply and water stratification in the fjord region. Our study provides insights into the ongoing impact of Atlantification on the phytoplankton community in the Arctic fjord.

Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic

Primary biological aerosol particles (PBAP) play an important role in the climate system, facilitating the formation of ice within clouds, consequently PBAP may be important in understanding the rapidly changing Arctic. Within this work, we use single-particle fluorescence spectroscopy to identify and quantify PBAP at an Arctic mountain site, with transmission electronic microscopy analysis supporting the presence of PBAP. We find that PBAP concentrations range between 10-3-10-1 L-1 and peak in summer. Evidences suggest that the terrestrial Arctic biosphere is an important regional source of PBAP, given the high correlation to air temperature, surface albedo, surface vegetation and PBAP tracers. PBAP clearly correlate with high-temperature ice nucleating particles (INP) (>-15 °C), of which a high a fraction (>90%) are proteinaceous in summer, implying biological origin. These findings will contribute to an improved understanding of sources and characteristics of Arctic PBAP and their links to INP.

High Ecophysiological Plasticity of Desmarestia aculeata (Phaeophyceae) Present in an Arctic Fjord under Varying Salinity and Irradiance Conditions

The seaweed Desmarestia aculeata (Phaeophyceae) is distributed in the temperate zone of the North Atlantic up to the Arctic, where it is exposed to a high Arctic light regime and fluctuating salinity conditions resulting from glacial and terrestrial run-off. Information on how this species is able to thrive under current and future Arctic conditions is scarce. During the Arctic summer of 2019, D. aculeata was collected in Kongsfjorden, Svalbard (78.9° N, 11.9° E) to investigate its physiological and biochemical responses to variations in salinity (salinities: 34, 28 and 18) and daily cycles of irradiance (50-500 μmol photons m^-2s^-1) at 0 °C over 21 days. The species revealed effective short-term acclimation to both abiotic drivers. Maximal quantum yield of PSII (F_v/F_m) fluctuated with the light cycle at a salinity of 34, while the maximum relative electron transport rate (rETRmax) significantly differed between salinities of 28 and 18. Chlorophyll a and β-Carotene remained at high concentrations in all treatments showing pronounced acclimation during the experiment. High mannitol concentrations were measured throughout the experiment, while phlorotannins were high at low salinity. Hyposalinity and light are interacting drivers of the physiological and biochemical acclimation process for D. aculeata. Our experiment highlights the high ecophysiological plasticity of D. aculeata, suggesting that the species will likely be capable of withstanding future habitat changes in the Arctic.

Photosynthetic adaptation to polar life: Energy balance, photoprotection and genetic redundancy

The persistent low temperature that characterize polar habitats combined with the requirement for light for all photoautotrophs creates a conundrum. The absorption of too much light at low temperature can cause an energy imbalance that decreases photosynthetic performance that has a negative impact on growth and can affect long-term survival. The goal of this review is to survey the mechanism(s) by which polar photoautotrophs maintain cellular energy balance, that is, photostasis to overcome the potential for cellular energy imbalance in their low temperature environments. Photopsychrophiles are photosynthetic organisms that are obligately adapted to low temperature (0⁰- 15 °C) but usually die at higher temperatures (≥20 °C). In contrast, photopsychrotolerant species can usually tolerate and survive a broad range of temperatures (5⁰- 40 °C). First, we summarize the basic concepts of excess excitation energy, energy balance, photoprotection and photostasis and their importance to survival in polar habitats. Second, we compare the photoprotective mechanisms that underlie photostasis and survival in aquatic cyanobacteria and green algae as well as terrestrial Antarctic and Arctic plants. We show that polar photopsychrophilic and photopsychrotolerant organisms attain energy balance at low temperature either through a regulated reduction in the efficiency of light absorption or through enhanced capacity to consume photosynthetic electrons by the induction of O₂ as an alternative electron acceptor. Finally, we compare the published genomes of three photopsychrophilic and one photopsychrotolerant alga with five mesophilic green algae including the model green alga, Chlamydomonas reinhardtii. We relate our genomic analyses to photoprotective mechanisms that contribute to the potential attainment of photostasis. Finally, we discuss how the observed genomic redundancy in photopsychrophilic genomes may confer energy balance, photoprotection and resilience to their harsh polar environment. Primary production in aquatic, Antarctic and Arctic environments is dependent on diverse algal and cyanobacterial communities. Although mosses and lichens dominate the Antarctic terrestrial landscape, only two extant angiosperms exist in the Antarctic. The identification of a single 'molecular key' to unravel adaptation of photopsychrophily and photopsychrotolerance remains elusive. Since these photoautotrophs represent excellent biomarkers to assess the impact of global warming on polar ecosystems, increased study of these polar photoautotrophs remains essential.

Anthropogenic sound field and noise mapping in an Arctic fjord during summer

Sound Pressure Levels were recorded using an Automated Noise Measurement System, during July 2015 - April 2016 at the Kongsfjorden, Arctic. The fjord houses the NyAlesund port and has many vessels plying during summer, which contributes to anthropogenic noise. Spectral distribution and average sound level at 1/3-octave band from 63 Hz to 5000 Hz has been analyzed and correlated with Automatic Identification System marine traffic data. The radiated acoustic field from vessel transits has been predicted through source level modeling for different category vessels. Further, an acoustic propagation model MMPE based on Parabolic Equation method has been used to evaluate range dependent propagation along the fjord and Transmission Loss estimates have been calculated for upslope and down slope cases. Noise due to shipping has been estimated using Source-Path-Receiver Model using Propagation Loss model estimates, Sound Pressure Level, and Source Level predictions. Noise maps with level contours are generated for shipping, depicting the maximum sound levels for the Kongsfjorden.

Patterns of Benthic Communities in Arctic Fjords (Novaya Zemlya Archipelago, Kara Sea): Resilience vs. Fragility

Despite a large number of studies, a detailed overall picture of benthic communities zonation in the Arctic fjords is currently lacking. Our study aimed to find out whether there is a universal model for the distribution of benthic communities based on the structural features of the fjords. We examined benthic macrofaunal communities in fjords with various environmental settings on the eastern coast of Novaya Zemlya Archipelago, Kara Sea. The material was collected during five cruises undertaken from 2013 to 2016. A total of 50 stations located in the five fjords were taken. In all five fjords, macrofauna had a similar composition assembled from a regional species pool, with a predominance of species tolerant to glacial sedimentation and fluctuations in temperature and salinity. Benthic communities changed consistently along the axis of the bay from the outer slope to the inner parts. Biodiversity and quantitative characteristics of the macrofauna decreased along the environmental gradient related to terrigenous and glacial runoff, consistent with patterns reported in other studies of Arctic glacial fjords. The most impoverished communities were dominated by bivalve Portlandia arctica and isopod Saduria sabini. At the same time, fjord walls and sills, characterized by low sedimentation rates, strong currents and the presence of ice-rafted debris, were inhabited by patchy distributed benthic communities dominated by species confined to hard substrates. In general, the distribution of communities corresponded to five zones: depleted inner periglacial areas, the upper subtidal belt with stony substrates, deep inner semi-isolated basin, outer non-isolated basins and upper slope transitioning to lower slope. Our study can provide a reference point for monitoring changes in fjord ecosystems in response to climate change and the potential impact of human activities.

Microbial Abundance and Enzyme Activity Patterns: Response to Changing Environmental Characteristics along a Transect in Kongsfjorden (Svalbard Islands)

Svalbard archipelago is experiencing the effects of climate changes (i.e., glaciers’ thickness reduction and glacier front retreat), but how ice melting affects water biogeochemistry is still unknown. Microbial communities often act as environmental sentinels, modulating their distribution and activity in response to environmental variability. To assess microbial response to climate warming, within the ARctic: present Climatic change and pAst extreme events (ARCA) project, a survey was carried out along a transect in Konsfjorden from off-shore stations towards the Kronebreen glacier. Total bacterial abundance and the fraction of actively respiring cells (labelled by cyanotetrazolium chloride, CTC), cultivable heterotrophic bacterial abundance, and extracellular enzymatic activities (leucine aminopeptidase (LAP), beta-glucosidase (GLU), and alkaline phosphatase (AP)) were measured. In addition, water temperature, salinity, dissolved oxygen, turbidity, total suspended matter (TSM), particulate and chromophoric dissolved organic matter (CDOM), chlorophyll-a (Chl-a), and inorganic compounds were determined, in order to evaluate whether variations in microbial abundance and metabolism were related with changes in environmental variables. Colder waters at surface (3.5–5 m) depths and increased turbidity, TSM, and inorganic compounds found at some hydrological stations close to the glacier were signals of ice melting. CDOM absorption slope values (275–295 nm) varied from 0.0077 to 0.0109 nm−1, and total bacterial cell count and cultivable heterotrophic bacterial abundance were in the order of 106 cells/mL and 103 colony forming units/mL, respectively. Enzymatic rates <1.78, 1.25, and 0.25 nmol/L/h were recorded for AP, LAP, and GLU, respectively. Inorganic compounds, TSM, and turbidity correlated inversely with temperature; AP was significantly related with CDOM absorption spectra and heterotrophic bacteria (r = 0.59, 0.71, p < 0.05); and LAP with Chl-a, Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON) (0.97, 0.780, 0.734, p < 0.01), suggesting that fresh material from ice melting stimulated the metabolism of the cultivable fraction.

Habitats and movement patterns of white whales Delphinapterus leucas in Svalbard, Norway in a changing climate

BACKGROUND

The Arctic is experiencing rapid reductions in sea ice and in some areas tidal glaciers are melting and retracting onto land. These changes are occurring at extremely rapid rates in the Northeast Atlantic Arctic. The aim of this study was to investigate the impacts of these environmental changes on space use by white whales (Delphinapterus leucas) in Svalbard, Norway. Using a unique biotelemetry data set involving 34 animals, spanning two decades, habitat use and movement patterns were compared before (1995-2001) and after (2013-2016) a dramatic change in the regional sea ice regime that began in 2006.

RESULTS

White whales were extremely coastal in both study periods, remaining near the islands within the Svalbard Archipelago, even when winter sea ice formation pushed them offshore somewhat (later in the year in the recent period), into areas with drifting sea ice (concentrations up to 90%). In both periods, the whales followed the same basic patterns seasonally; they occupied the west coast in summer and shifted to the east coast as winter approached. However, space use did change between the two periods, with the whales spending less time close to tidal glacier fronts in the second period compared to the first (2nd-36% vs 1st-51%), a habitat characterized by low swimming speeds and high turning angles, and more time out in the fjords (2nd-26% vs1st-10%). Use of coastal transit corridors remained the same in both periods; the whales appear to minimize time spent moving between fjords.

CONCLUSIONS

Glacier fronts have previously been shown to be important foraging areas for white whales in Svalbard and the movement metrics documented in this study confirms that this is still the case. However, use of the Fjords habitat in summer and fall (frequency of occupancy and movement metrics) seen in the recent period suggests that the white whales might now also be feeding on Atlantic prey that is increasingly common in the fjords, concomitant with influxes of Atlantic Water along the west coast of Svalbard. Such behavioural flexibility, if confirmed by further diet studies, would likely be important for white whales in adapting to new conditions in Svalbard.