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Plastic pollution has become ubiquitous even in remote polar ecosystems such as the Arctic. Previous research at HAUSGARTEN observatory with Fram infrastructure has shown that microplastic concentrations are particularly high in water and sediment samples taken close to the marginal ice zone and in sea ice cores and zooplankton grazers associated with sea ice. Here, we analysed samples of the ice algae Melosira arctica that attach to ice floes and often form long filaments, curtains, nets and other growth forms, which could capture microplastics released from melting sea ice. Samples and field and procedural blanks were taken opportunistically in Fram Strait during a helicopter-based ice sampling campaign in summer 2021 and analysed by µ-Raman. Microplastics were found in all samples in significant quantities across a variety of polymer types and particles sizes. Whilst more data are needed our results indicate that ice algae could be an important sink and also accelerate the transport of microplastics to the deep seafloor, since ice algae are known to form aggregates that accelerate their sinking rates. Ice algae could thus also be vectors for microplastics into benthic or zooplankton food webs. Also see: https://micro2022.sciencesconf.org/427180/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

We studied ice algae utilization by benthic fauna from the northern Bering and Chukchi Seas using highly branched isoprenoid (HBI) biomarkers. We assessed whether various food acquisition strategies influence the observed HBI signatures. The proportion of phytoplankton to ice algae-sourced HBIs was determined through the H-Print approach that is presumed to reflect the percentage of sea ice organic carbon (iPOC) incorporated into tissues, relative to phytoplankton organic carbon. Cluster analysis separated 3 groups based on location and feeding strategy that were significantly influenced by annual sea ice persistence. Ice algae utilization was most significant in the northeast Chukchi Sea, where seasonal sea ice was present the longest. General feeding strategy was determined to be a significant factor in the degree of ice algae utilization. Predominant deposit feeders (both surface and subsurface) used more ice algae relative to suspension feeders. Organic carbon incorporated by predominant suspension feeders was primarily phytoplankton-based. The vast majority of all organisms sampled (~90%) incorporated a measurable quantity of iPOC. Sipunculids and brittle stars had the highest relative dependence on ice algae, while other taxa displayed plastic dietary responses, including the suspension/surface deposit feeder Macoma calcarea. This study indicates that ice algae are widely utilized in Pacific Arctic benthic food webs, but most benthic organisms displayed flexibility in consuming the available food sources. The elevated utilization of ice algae by deposit feeders may prove to be a disadvantage for these organisms if they cannot adapt to the ongoing decline of iPOC as seasonal sea ice declines.

Ice algae are key contributors to primary production and carbon fixation in the Arctic, and light availability is assumed to limit their growth and productivity. We investigated photo-physiological responses in sea ice algae to increased irradiance during a spring bloom in West Greenland. During a 14 d field experiment, light transmittance through sea ice was manipulated to provide 3 under-ice irradiance regimes: low (0.04), medium (0.08), and high (0.16) transmittances. Chlorophyll a decreased with elevated light availability relative to the control. Maximum dark-adapted photosynthetic efficiency (ΦPSII_max) showed an initially healthy and productive ice algae community (ΦPSII_max > 0.6), with ΦPSII_max decreasing markedly under high-light treatments. This was accompanied by a decrease in the light utilization coefficient (α) and photosynthetic capacity (maximum relative electron transfer rate), and a decrease in the ratio of mono- to polyunsaturated fatty acids. This was partly explained by a corresponding increase of photoprotective pigments (diadinoxanthin and diatoxanthin), and a development of mycosporine-like amino acids as identified from a distinctive spectral absorption peak at 360 nm. After 14 d, in situ fluorescence imaging revealed significant differences in ΦPSII_max between treatments of dark-adapted cells (i.e. those sampled before sunrise and after sunset), during diel cycles, with clear chronic photoinhibition in high and medium treatments. Data demonstrate the high sensitivity of spring-blooming Arctic sea ice algae to elevated irradiance caused by loss of snow cover. The predicted loss of snow cover on landfast ice will negatively impact ice algae, their potential primary production, and nutritional quality for higher trophic levels.

On January 6, 2020, Lyudmila Vasilyevna Ilyash, an outstanding hydrobiologist, Doctor of Biological Sciences, professor of the Department of General Ecology and Hydrobiology of the Biological Faculty of Lomonosov Moscow State University. Research interests L.V. Ilyash covered a wide range of issues and topics related to the ecology of marine planktonic and ice algae, patterns of formation of the structure and functioning of phytocenoses in marine ecosystems

In the Bering Sea shelf, annual changes in the sea ice extent are large. In this study, we compare the viable diatom resting stages in sediments during the summer of 2017 when the sea ice retreat was late and 2018 when the sea ice retreat was early. South of St. Lawrence Island, the germinating cell number was 10-100 times greater in 2018 than it was in 2017. The taxonomic composition also showed large annual differences: Fragilariopsis/Fossula spp., which are ice algae species, were abundant in 2017, but Thalassiosira spp. dominated in 2018. Satellite observations confirmed that sea ice diminished before the ice-edge bloom in 2018, but sea ice remained until the ice-edge bloom in 2017. This study shows that the community composition of viable diatom resting stages is largely affected by the timing of the sea ice retreat.

The impact of the rapidly changing Arctic on zooplankton community structure and seasonal behaviour is not yet understood. Here we examine 6 months of under-ice zooplankton observations from the N-ICE2015 expedition (January to June 2015) in the Nansen Basin and on the Yermak Plateau north of Svalbard. Stratified sampling in the water column was done with MultiNet during the entire expedition, and sampling in the upper 5 m below sea ice was performed during April-May by divers using a hand-held net. Hydrographic conditions were dominated by northward-flowing warm and saline Atlantic Water at intermediate depth, and southward-flowing cold Polar Surface Water in the upper 100 m. The mesozooplankton was dominated by copepods. Most numerous were the small ubiquitous Oithona similis in the upper 200 m, with Microcalanus spp. and Triconia borealis further down the water column. Calanus finmarchicus dominated among the Calanus species while Metridia longa was also numerous. The most abundant deep-water copepods were Paraeuchaeta spp. and Spinocalanus spp. Arrow worms (Chaetognatha) and comb jellies (Ctenophora) were the most numerous non-copepods. The mesozooplankton community was more dependent on surrounding water mass characteristics, such as salinity and depth, than geographical location. Algal food availability, which was closely linked to seasonality, explained the community changes seen in surface waters in May and June due to seasonal ascent and recruitment. Seasonal changes from winter to spring mostly involved an increase in the herbivorous C. finmarchicus and its nauplii in the upper 200 m of the water column coinciding with the peak of the phytoplankton bloom in late May. The Yermak Plateau and adjacent Nansen Basin were characterised by oceanic North Atlantic and Arctic species, many of which are deep water specialists. Despite the late onset of the spring bloom due to consolidated sea ice, both North Atlantic and Arctic species successfully reproduced in the study area. This explains the species-rich mesozooplankton community in this region as opposed to the less productive central Arctic Ocean. Future prospects of less sea ice and earlier onset of the bloom will likely be positive for the overall secondary production by both Arctic and boreal zooplankton in this region.

The global cryosphere, Earth's frozen water, is in precipitous decline. The ongoing and predicted impacts of cryosphere loss are diverse, ranging from disappearance of entire biomes to crises of water availability. Covering approximately one-fifth of the planet, mass loss from the terrestrial cryosphere is driven primarily by a warming atmosphere but reductions in albedo (the proportion of reflected light) also contribute by increasing absorption of solar radiation. In addition to dust and other abiotic impurities, biological communities substantially reduce albedo worldwide. In this review, we provide a global synthesis of biological albedo reduction (BAR) in terrestrial snow and ice ecosystems. We first focus on known drivers—algal blooms and cryoconite (granular sediment on the ice that includes both mineral and biological material)—as they account for much of the biological albedo variability in snow and ice habitats. We then consider an array of potential drivers of BAR whose impacts may be overlooked, such as arthropod deposition, resident organisms (e.g., dark-bodied glacier ice worms), and larger vertebrates, including humans, that transiently visit the cryosphere. We consider both primary (e.g., BAR due to the presence of pigmented algal cells) and indirect (e.g., nutrient addition from arthropod deposition) effects, as well as interactions among biological groups (e.g., birds feeding on ice worms). Collectively, we highlight that in many cases, overlooked drivers and interactions among factors have considerable potential to alter BAR, perhaps rivaling the direct effects of algal blooms and cryoconite. We conclude by highlighting knowledge gaps for the field with an emphasis on the underrepresentation of genomic tools, understudied areas (particularly high-elevation glaciers at tropical latitudes), and a dearth of temporal sampling in current efforts. We detail a global framework for long-term BAR monitoring that, if implemented, would yield a tremendous amount of insight for BAR and would be particularly valuable in light of the rapid ecological and physical changes occurring in the contemporary cryosphere.

Phytoplankton communities in seasonally ice-covered areas are largely affected by ice algae. The Okhotsk Sea is the southernmost sea ice zone in the northern hemisphere with a sizeable seasonal ice cover, thus ice algae of the Okhotsk sea ice have a large potential to seed the early spring bloom. Little is known about the Okhotsk ice algal communities and their seeding effects. We investigated the dynamics of the composition and the photophysiological performances of an Okhotsk ice algal community in a 6-day laboratory incubation experiment that simulated the natural ice melt conditions. Centric diatoms, especially Thalassiosira spp., overwhelmingly dominated the ice algal community throughout incubation, whereas pennate diatoms, mostly Navicula and Nitzschia, showed little growth with much higher mortality. The maximum photochemical efficiency of Photosystem II (Fv/Fm) was the lowest at the beginning of the ice melt, suggesting a suppressed photosynthetic functioning by changes in salinity. The cellular pigment contents decreased by 30% due to physical damage of the cellular membrane, evidenced by deformed plastids under a microscope. The transcript level of the rbcL gene that encodes the large subunit of RubisCO was significantly higher during ice melt and decreased in the no-ice period, suggesting an urgent need for osmoprotectants under the melt condition. Full recovery of photosynthesis and growth was also made after complete ice melt. Our results indicated high seeding potential of Thalassiosira to spring blooms owing to their photophysiological plasticity to dynamic salinity changes.

Krill overwintering strategies vary with ontogeny and year; understanding this variability is essential to predicting how the species will respond to climate change in the future. Overwintering studies have focused on larval and adult krill, but we know little about how juvenile krill overwinter. The late winter diet of juvenile krill is important because it will determine their growth and development rates and consequently their reproductive potential the following spring. A diet rich in ice algae would promote growth and reproductive development. The Bransfield Strait (northern Antarctic Peninsula, AP) is an important overwintering ground for krill; it has been proposed this region offers a food-rich winter environment. We examined the contribution of ice algae to the energy budget of overwintering juvenile krill during 2 years with contrasting sea ice conditions. Grazing on ice algae contributed ∼146% to their winter energy budget in 2015, even though ice concentrations were ≤50% and consisted of newly formed pancake ice. However, when sea ice advanced late in the Bransfield Strait (2016), ice algae contributed significantly less (∼16%) to the winter energy budget of juvenile krill. Delayed sea ice advance may negatively affect growth and reproductive development of overwintering juvenile krill.

We would like to thank the officers and crew of CCGS ‘Amundsen’ and the ArcticNet scientific and technical personnel for support onboard. We would also like to thank C. Grant (ISMER) and G. Kazanidis (University of Aberdeen) for field assistance, ArcticNet 2013 cruise CTD operators and L. Treau de Coeli and L. de Montety (ISMER) for macrofauna identification help. Additional thanks go to V. Johnston (University of Aberdeen) for general lab assistance and K. Chalut (ISMER) for sample preparation help. Work was supported by University of Aberdeen The North theme funding for A.M., Natural Environment Research Council ArcDEEP project grant NE/J023094 awarded to U.W. and ArcticNet and Green Edge funding to P.A.

This chapter is a description of the field and laboratory methods that are generally applied in sea ice ecological research. The first section describes sampling techniques and handling of sea ice samples (6.1). Calculations of brine and gas volumes are dealt with in (6.2), and how to measure and calculate optical parameters (6.3). Sampling, handling, and calculation of ice bacterial production are described (6.4), and methods for ice algae biomass spatial distributions are dealt with in (6.5). Measuring photosynthesis and ice algae primary production are described (6.6), and the determination of Chl a content is explained (6.7). The recently developed fluorescence imaging of ice algae distributions and derived photosynthetic parameters are described (6.8). This is followed by a description of the IP25, a substance synthesized by ice algae and applied for mapping sea ice and food web studies (6.9).

When the air is very cold, water at the surface of the ocean freezes, forming sea ice. Parts of the Arctic Ocean are covered by sea ice during the entire year. Often, snow falls onto the sea ice. Despite the cold, many plants and animals can live in the Arctic Ocean, some in the water, and some even in the sea ice. Particularly, algae can live in small bubbles in the sea ice. Like other plants, algae need energy to grow. This energy comes from food and sunlight. But how can the sunlight reach these little algae living inside the sea ice? From the sun, the light must pass through the atmosphere, the snow, and finally the sea ice itself. In this article, we describe how ice algae can live in this special environment and we explain what influences how much light reaches the algae to make them grow.

The objective of this chapter is to establish communication between marine science and the arts by giving the ocean a voice. The first topic is the dynamics and thermodynamics of sea ice and related threats due to global warming. When seen from the geophysical scale, sea ice is a beautiful and fragile plastic–viscous material sensitive to changes in heat fluxes, snow, and wind. It protects the underlying water and serves as a medium for life for many marine species, from ice algae to polar bears. Should humans be fearful, their souls are frozen at the ultimately violent use of fossil fuels that has caused the melting of sea ice? The ocean responds by challenging us to cultivate our curiosity. The conclusion is that curiosity is a much better attitude towards the ocean than either fear or guilt.

Colonization by ice algae at the bottom of the sea ice is important ecologically as these algae are the major carbon source for zooplankton and the Polar food chains from early spring and until ice break-up several months later. At that time, ice algae can seed the water column promoting the pelagic production. We collected a time-series of ice growth, surface roughness, ice algae biomass (Chl-a), photosynthetic performance, primary production, irradiance, species composition, under ice ADCP data, nutrients, and ice algae spatial distribution in Kangerlussuaq, Greenland. A significant increase in biomass, primary production, and photosynthetic performance was observed at the bottom of the first-year sea ice. This colonization was not related to any change in light or nutrient availability, but instead occurred over a few days after which all parameters remained stable and constant. Colonization was concurrent with active ice growth associated with a period of very cold air temperatures as low as minus 35 °C. This new ice growth featured ice crystals and dendrites that significantly increased the surface roughness of the bottom, which facilitated the colonization. The dendrites are about 0.5 mm high and with a similar distance between the crests. The species composition of ice algae was similar in the water below and at the ice bottom, though biomass remained significantly lower in the water, and was dominated by Fragilariopsis oceanica and Navicula vanhoeefi. It is concluded that the colonization of the bottom of the sea ice is solely related to the increase in surface roughness initiated in the growing ice.

High concentrations of microplastics have been found in sea ice but the mechanisms by which they get captured into the ice and which role ice algae might play in this process remain unknown. Similarly, we do not know how the presence of microplastics might impact the colonization of sea ice by ice algae. To estimate the ecological impact of microplastics for Polar ecosystems, it is essential to understand their behaviour during ice formation and possible interactions with organisms inhabiting sea ice. In this study we tested the interaction between the ice algae Fragillariopsis cylindrus and microplastic beads with and without sea ice present and, in a third experiment, during the process of ice formation. With sea ice present, we found significantly less algae cells in the ice when incubated together with microplastics compared to the incubation without microplastics. However, during ice formation, the presence of microplastics did not impact the colonisation of the ice by F. cylindrus cells. Further, we observed a strong correlation between salinity and the relative amount of beads in the water and ice. With increasing salinity of the water, the relative amount of beads in the water decreased significantly. At the same time, the relative amount of beads in the ice increased significantly with increasing ice salinity. Both processes were not influenced by the presence of F. cylindrus. Also, we found indications that the presence of algae can affect the amount of microplastic beads sticking to the container walls. This could indicate that EPS produced by ice algae plays a significant role in surface binding properties of microplastics. Overall, our results highlight that the interactions between algae and microplastics have an influence on the uptake of microplastics into sea ice with possible implications for the sea ice food web.

In the Arctic Ocean, increased sea surface temperature and sea ice retreat have triggered shifts in phytoplankton communities. In Fram Strait, coccolithophorids have been occasionally observed to replace diatoms as the dominating taxon of spring blooms. Deep-sea benthic communities depend strongly on such blooms, but with a change in quality and quantity of primarily produced organic matter (OM) input, this may likely have implications for deep-sea life. We compared the in situ responses of Arctic deep-sea benthos to input of phytodetritus from a diatom (Thalassiosira sp.) and a coccolithophorid (Emiliania huxleyi) species. We traced the fate of 13C- and 15N-labelled phytodetritus into respiration, assimilation by bacteria and infauna in a 4-day and 14-day experiment. Bacteria were key assimilators in the Thalassiosira OM degradation, whereas Foraminifera and other infauna were at least as important as bacteria in the Emiliania OM assimilation. After 14 days, 5 times less carbon and 3.8 times less nitrogen of the Emiliania detritus was recycled compared to Thalassiosira detritus. This implies that the utilization of Emiliania OM may be less efficient than for Thalassiosira OM. Our results indicate that a shift from diatom-dominated input to a coccolithophorid-dominated pulse could entail a delay in OM cycling, which may affect benthopelagic coupling.

This chapter focuses on the chemical composition of ice algae is reviewed and discussed in relation to the physiological ecology and adaptive strategies of the organisms. Annual sea ice in the Arctic and Antarctic contains favorable microhabitats within the ice or on the bottom surface of the ice which are colonized by microalgae. Information on the chemical composition and biochemistry of ice algae is useful for field ecology investigations and for providing an insight into the adaptive strategies of species living in the habitat. Estimation of the physiological state of microalgae by measurement of the cellular ratios of several defined chemical components may provide an indirect measure of growth rate. Certain chemical markers in microalgae may also be useful for demonstrating the relationship between different trophic levels. The most commonly used chemical markers in microalgae are fatty acids which are highly conserved in the predator.

The Arctic is being disproportionally affected by climate change compared with other geographic locations, and is currently experiencing unprecedented melt rates. The Greenland Ice Sheet (GrIS) can be regarded as the largest supraglacial ecosystem on Earth, and ice algae are the dominant primary producers on bare ice surfaces throughout the course of a melt season. Ice-algal-derived pigments cause a darkening of the ice surface, which in turn decreases albedo and increases melt rates. The important role of ice algae in changing melt rates has only recently been recognized, and we currently know little about their community compositions and functions. Here, we present the first analysis of ice algal communities across a 100 km transect on the GrIS by high-throughput sequencing and subsequent oligotyping of the most abundant taxa. Our data reveal an extremely low algal diversity with Ancylonema nordenskiöldii and a Mesotaenium species being by far the dominant taxa at all sites. We employed an oligotyping approach and revealed a hidden diversity not detectable by conventional clustering of operational taxonomic units and taxonomic classification. Oligotypes of the dominant taxa exhibit a site-specific distribution, which may be linked to differences in temperatures and subsequently the extent of the melting. Our results help to better understand the distribution patterns of ice algal communities that play a crucial role in the GrIS ecosystem.

Sea-ice biophysical properties are characterized by high spatio-temporal variability ranging from the meso- to the millimeter scale. Ice coring is a common yet coarse point sampling technique that struggles to capture such variability in a non-invasive manner. This hinders quantification and understanding of ice algae biomass patchiness and its complex interaction with some of its sea ice physical drivers. In response to these limitations, a novel under-ice sled system was designed to capture proxies of biomass together with 3D models of bottom topography of land-fast sea-ice. This system couples a pushbroom hyperspectral imaging (HI) sensor with a standard digital RGB camera and was trialed at Cape Evans, Antarctica. HI aims to quantify per-pixel chlorophyll-a content and other ice algae biological properties at the ice-water interface based on light transmitted through the ice. RGB imagery processed with digital photogrammetry aims to capture under-ice structure and topography. Results from a 20 m transect capturing a 0.61 m wide swath at sub-mm spatial resolution are presented. We outline the technical and logistical approach taken and provide recommendations for future deployments and developments of similar systems. A preliminary transect subsample was processed using both established and novel under-ice bio-optical indices (e.g., normalized difference indexes and the area normalized by the maximal band depth) and explorative analyses (e.g., principal component analyses) to establish proxies of algal biomass. This first deployment of HI and digital photogrammetry under-ice provides a proof-of-concept of a novel methodology capable of delivering non-invasive and highly resolved estimates of ice algal biomass in-situ, together with some of its environmental drivers. Nonetheless, various challenges and limitations remain before our method can be adopted across a range of sea-ice conditions. Our work concludes with suggested solutions to these challenges and proposes further method and system developments for future research.

Assessing the role of sea ice algal biomass and primary production for polar ecosystems remains challenging due to the strong spatio-temporal variability of sea ice algae. Therefore, the spatial representativeness of sea ice algal biomass and primary production sampling remains a key issue in large-scale models and climate change predictions of polar ecosystems. To address this issue, we presented two novel approaches to up-scale ice algal chl a biomass and net primary production (NPP) estimates based on profiles covering distances of 100 to 1,000 s of meters. This was accomplished by combining ice core-based methods with horizontal under-ice spectral radiation profiling conducted in the central Arctic Ocean during summer 2012. We conducted a multi-scale comparison of ice-core based ice algal chl a biomass with two profiling platforms: a remotely operated vehicle and surface and under ice trawl (SUIT). NPP estimates were compared between ice cores and remotely operated vehicle surveys. Our results showed that ice core-based estimates of ice algal chl a biomass and NPP do not representatively capture the spatial variability compared to the remotely operated vehicle-based estimates, implying considerable uncertainties for pan-Arctic estimates based on ice core observations alone. Grouping sea ice cores based on region or ice type improved the representativeness. With only a small sample size, however, a high risk of obtaining non-representative estimates remains. Sea ice algal chl a biomass estimates based on the dominant ice class alone showed a better agreement between ice core and remotely operated vehicle estimates. Grouping ice core measurements yielded no improvement in NPP estimates, highlighting the importance of accounting for the spatial variability of both the chl a biomass and bottom-ice light in order to get representative estimates. Profile-based measurements of ice algae chl a biomass identified sea ice ridges as an underappreciated component of the Arctic ecosystem because chl a biomass was significantly greater in this unique habitat. Sea ice ridges are not easily captured with ice coring methods and thus require more attention in future studies. Based on our results, we provide recommendations for designing an efficient and effective sea ice algal sampling program for the summer season.

The retreat and thinning of Arctic sea ice associated with climate warming is resulting in ever-changing ecological processes and patterns. One example is our discovery of myriad new "marine aquaria" formed by melt holes in the perennial sea ice. In previous years, these features were closed, freshwater melt ponds on the surface of sea ice. Decreased ice thickness now allows these ponds to melt through to the underlying ocean, thus creating a new marine habitat and concentrating a food source for the ecosystem through accumulation of algae attached to refreezing ice in late summer. This article describes the formation of these late-season algal masses and comments on their overall contribution to Arctic ecosystems and the consequences of a continued decline in sea ice.

During the second Chinese National Arctic Research Expedition in summer 2003, sea ice cores and the underlying water were sampled from seven stations in the pack ice zone of the Canada Basin and were examined with a phase contrast microscope. A total of 102 and 78 algal species were identified for the ice cores and the underlying water, respectively, ranking in the middle range among the surveys of the Arctic Ocean up to the present despite seasonal variability. The Shannon-Wiener indices ranged from 1.40 to 4.88 with an average of 3.58 ± 0.68. Diatom species, especially pennate species, dominated in all the samples. A large number of algal spores were contained in every layer (abundance percentage > 1%). The microalgal abundances ranged from 1.4 × 104 to 8.73 × 105 cells L−1 and the biomass ranged from 0.56 to 89.49 μg L−1. They were correlated with the number of algal species (P < 0.05) but not with the diversity index (P > 0.05). Ice algal maxima were observed in various layers (bottom, interior and near the surface of the ice floes). The phytoplankton biomass in the ice-water interface was one order of magnitude lower than that in the bottom ice (P < 0.05). The species number and the diversity index in water samples, with much less biomass (P < 0.01), were comparative with the ice samples (P > 0.05). Spatial heterogeneity in both horizontal and vertical directions was the main characteristic of the algal community structure, which was demonstrated by the cluster analysis result and the distribution patterns.

Plankton and ice assemblages of antarctic algae were studied in 2006-2007. Diatoms prevailed in number of species and abundance in both ice and plankton samples. Three genera Chaetoceros, Thalassiosira and Fragilariopsis were the most diverse. Species of 10 genera (Chaetoceros, Thalassiosira, Coscinodiscus, Rhizosolenia, Proboscia, Eucampia, Corethron, Odontella, Fragilariopsis, Pseudo-nitzschia) dominated in plankton. Ice flora included mainly 6 diatom genera (Fragilariopsis, Berkeleya, Nitzschia, Entomoneis, Navicula, Cylindrotheca).

A mechanism connecting ice algal ecodynamics with the buildup of organic macromolecules in brine channels is tested offline in a reduced model of pack geochemistry. Driver physical quantities are extracted from the global sea ice dynamics code CICE, including snow height, column thickness and internal temperature. The variables are averaged at the regional scale over ten Arctic biogeographic zones and treated as input matrices at four vertical habitat levels. Nutrient-light-salt limited ice algal growth is computed along with the associated grazing plus mortality. Vertical transport is diffusive but responds to pore structure. Simulated bottom layer chlorophyll maxima are reasonable, though delayed by about a month relative to observations. This highlights major uncertainties deriving from snow thickness variability. Upper level biota are generated intermittently through flooding. Macromolecular injections are represented by the compound classes humics, proteins, polysaccharides and lipids. The fresh biopolymers behave in a successional manner and are removed by bacteria. In baseline runs, organics are introduced solely through cell disruption, and internal carbon is biased low. Continuous exudation is therefore appended, and agreement with dissolved organic or individual biopolymer measurements is achieved when strong release is coupled to light availability. Detrital carbon then reaches hundreds of micromolar, sufficient to support physical changes to the ice matrix. Through this optimized model version we address the question, are high molecular weight organics added to the brine network over and above background spillage? The mechanism is configured for ready extension to the Antarctic, so that global ice organic chemistry issues can be targeted., Comment: In preparation for submission to Biogeosciences (Copernicus, EGU)

The taxonomic characterization of two strains of Antarctic ice algae, Chlamydomonas sp. ICE-L and Chlamydomonas sp. ICE-W, were analyzed on the basis of morphological and molecular traits. The results indicate that they are the same species and belong to Chlamydomonas (Chlorophyta). According to I SS rDNA and ITS-I sequences they are very close relatives of Chlamydomonas sp. Antarctic 2E9, if not identified as such. They belong to the 'monadina clade', Cd. monadina and Cm. subdivisa as the sister group, on the basis of 18S rDNA sequence. They occur in 'Chlamydomonas clade' according to rbcL sequencing and are close relatives of Cd. kuwadae. The ITS sequences of ICE-L and ICE-W are 1302 base pairs and 1300 base pairs in length, the longest Volvocales ITS sequences ever reported.

The primary production and fluxes of organic matter to the seabed and their variations were estimated in the Greenland, Barents, Kara, Laptev, East Siberian, and Chukchi seas in 2003–2012 on the basis of satellite and in situ data. When counting the open water area with the assumptions made for the assessment of the primary production in the sea areas hidden under clouds, an increase in primary production was recorded in all these seas, the total production (phytoplankton and ice algae) has grown from 250 × 106 to 400 × 106 t of C per year over the last ten years. The calculation of the OM flux to the seabed showed growth for certain seas from 4 to 12% per year.

Получена коллекция чистых культур, изолированных из подледных альго-бактериальных сообществ, обитающих на нижней поверхности льда озера Байкал. Методами классической микробиологии показано различие в морфологии культивируемых бактерий и в их ферментативной активности. С помощью секвенирования гена 16S рРНК была определена таксономическая принадлежность нескольких чистых культур, которые были отнесены к Pseudomonas putida, P. psychrophila, Methylobacterium extorquens, Rhodococcus aerolatus, Brevundimonas aurantiaca, B. vesicularis, Sphingomonas subarctica, Roseomonas frigidaqua и Janthinobacterium lividum. Данные таксоны адаптированы к выживанию при низких температурах., A collection of pure cultures isolated from the sub-ice algae-bacterial communities inhabiting the lower ice surface of Lake Baikal was obtained. The differences in morphology of the cultured bacteria and their enzymatic activities were revealed by the methods of classical microbiology. The taxonomic affiliation of several cultures was determined by the 16S rRNA gene sequencing. They belong to the genera Pseudomonas putida, P. psychrophila, Methylobacterium extorquens, Rhodococcus aerolatus, Brevundimonas aurantiaca, B. vesicularis, Sphingomonas subarctica, Roseomonas frigidaqua, and Janthinobacterium lividum. These taxa are adapted to low-temperature environments.

A possible coupling between UV radiation (UVR; 280 to 400 nm) induced stress and the production of dimethylsulfoniopropionate (DMSP), the precursor of the climate-regulating gas dimethylsulfide (DMS), was investigated in the marine prymnesiophyte Emiliania huxleyi. To this end, axenic cultures of E. huxleyi were exposed to a range of UVR doses for 2 consecutive days. During and after these treatments, growth, photosynthetic activity, cell size, DNA damage, sugar accumulation and DMSP concentrations were followed, The vulnerability of E. huxleyi for relatively low UVR doses was demonstrated by the inhibition of growth and the simultaneous occurrence of DNA damage. Also, mean cell size increased and sugars accumulated as a result of the UVR treatments. In contrast, no effect was observed on the optimal quantum yield of Photosystem II (PSII), a measure of the efficiency of photosynthesis. With increasing UVR dose, cellular DMSP content increased, However, the intrdcellular DMSP concentrations remained constant at the level typical for the applied temperature and salinity conditions, due to accompanying increase in cell size. The increased cellular DMSP content did not compensate, therefore, for the decreased growth rates, resulting in an overall decrease in the total amount of DMSP produced in the cultures. The UVR effects as induced in this study are assumed to be severe as compared with natural solar conditions, especially because high in situ UVAR (315 to 400 nm) may ameliorate UVBR damage by activation of photorepair. Yet the presented results imply that when (increased) UV(B)R causes growth rate reduction of E. huxleyi in situ, DMSP fluxes are likely to be reduced too.

The response of ice algae to low salinity was determined at three levels of silicate enrichment during the winter of 1992 in Saroma-ko Lagoon, Hokkaido, Japan. Regardless of the silicate concentration, the chlorophyll a content decreased by 50% of its initial value within the first day of exposure to low salinity water (22 psu) and continued to decrease gradually thereafter. The degree of decrease after the first day was a function of silicate concentration. The size distribution of the ice algae at the beginning of the incubation was 52% in the size class > 10 μm, 39% in 10-2 μm and 9% in 2-0.2 μm. Within two weeks of silicate enrichment, the 2-0.2 μm fraction decreased to less than 1% while the > 10 μm fraction increased to more than 90%. Low salinity and low silicate concentrations reduced the chlorophyll a biomass and photosynthetic activity. Silicate enrichments, even at the low salinity, enhanced photosynthetic activity and the relative abundance of the > 10 μm cells. Our results suggest that ice algae may not survive if trapped in the low salinity lens that is present immediately below the ice during melting because of possible osmotic damage associated with silicate deficiency. However, ice algal cells may recover from the damage when they sink into the high salinity and silicate-rich underlying water in Saroma-ko Lagoon. The ecological role of low salinity water is discussed in relation to vertical flux of ice algae.

International audience; Heterotrophic microflagellates and ciliates (i.e., 20–200 μm size fraction) were examined for evidence of their response to the spring accumulation of algal biomass in the bottom of the annual sea ice in Resolute Passage (Canadian High Arctic, 74°N, 95°W). The most abundant heterotrophic microflagellates were dinoflagellates in the water column and cryothe-comonad-type cells in the ice. Ciliates were exclusively represented by typical planktonic species in the water column while the ice community was characterized by the occurrence of benthic-type species. This contrasts with observations in the Antarctic and at the southern limit of sea ice in the northern hemisphere, where annual sea ice seems to serve as a temporary habitat for planktonic communities. Protist biomasses in Resolute Passage were one to two orders of magnitude higher in the ice than in the plankton. In the ice, a seasonal increase in the biomass of phagotrophic microprotists as well as in the number of micrometazoa (from our microprotist samples) followed the spring algal bloom. These observations (1) support previous suggestions of the existence of a functional microbial food web within sea-ice communities and (2) indicate that micrograzers may represent one of the basic levels of the ice food web that responds to the seasonal accumulation of algal biomass. Heterotrophic microprotists growing in the ice accumulated about 4 mg C m−2 d−1, a net production rate that is two to four times higher than those reported for sea-ice bacteria (both Arctic and Antarctic), and represented 1–9% of the net production of ice algea in the early season at resolute. A carbon budget exercise indicated that the required energy for microprotozoan growth in the later season, when algal biomass was declining, corresponded to 1–8% of the net biomass loss from the ice algal populations. The specific growth rates of microprotozoan populations within the ice (0.04–0.18 d−1) appeared to increase significantly with decreasing algal productivity. This may be critical for the protracted heterotrophic food web in multi-year ice and to many consumers during the long polar winter.

The aim of the study was to investigate the capacity of microalgae from the extremely low light habitat of bottom ice to acclimate to different light conditions. During austral spring 1997 the bottom layer of land-fast ice in Terra Nova Bay displayed high values of microalgal biomass up to 2,400 μg Chla L−1 concentrated in a few centimetres ice layer. The algal assemblage was dominated by benthic pennate diatoms. Photoacclimation of the microalgae was addressed in terms of pigment spectra and photosynthetic parameters. Immediate and long term (minutes to days) changes in the photoprotective pigments (DD-cycle) were analysed. Severe photodamage occurred in microalgal assemblages exposed to high light. However, part of the bottom ice algal community showed a notable ability to acclimate to high irradiance levels. Changes in photosynthetic parameters preceded the sudden abrupt changes in pigment synthesis and the rapid increase in biomass and growth rates.

Uptake rates of NH4+, NO3? and dissolved organic nitrogen (urea) were measured in phytoplankton and in ice algae in the Barents Sea using a 15N-technique. NO3? was the most important nitrogen source for the ice algae (f-ratio = 0.92). The in situ irradiances in the subsurface chlorophyll maximum and in the ice algal communities were low. The in situ NO3? uptake rate in the ice algal communities was light-limited The in situ NO3? and NH4? uptake rates in the subsurface chlorophyll maximum were at times light-limited. It is hypothesised that NH4+ may accumulate in low light in the bottom of the euphotic zone and inhibit the in situ NO3? uptake rate.

Ice algal chlorophyll a, (Chl), an estimator of biomass, was measured throughout the growing season (March–May) near Chesterfield Inlet on the northwest coast of Hudson Bay (63°30′N). The log10 transformation of Chl per square metre was a negative linear function of snow depth at any given date and location. Maximum biomass reached about 170 mg Chl∙m−2 over deep water but only one tenth as much over shallow water. This smaller standing crop was correlated with lower concentrations of nitrate in shallow water, postulated to result from nitrogen uptake by kelp. Ice-associated amphipods were abundant but had little detectable effect on the development of ice algal biomass. Ice algal Chl over deep water was predicted closely by the model developed for Resolute at 75°N, relating Chl to overlying snow depth and cumulative surface light. It appears that, where nutrients are adequate, ice algal biomass below first-year sea ice can be predicted for much of the Arctic from two variables, cumulative surface light and snow depth.

A conceptual and numerical model adapted to the local plankton ecosystem (ECOHYDROMVG) has been developed on the basis of the information acquired during various oceanographic cruises in the Ross Sea. The construction of the biological/physical coupled 1-D model of the upper water column ecosystem is presented. The model takes into account the control of the plankton ecosystem by ice cover, ice edge dynamics, atmospheric forcing and surface circulation, nutrients being non-limiting factors. Ice-edge thickness, retreat and melting determine the initial conditions for the spring bloom (ice algae concentration, vertical structure of the water column) and allow the biological processes of primary production in the water column to start. The combined effects of wind and solar irradiance determine the depth of the upper mixed layer and quantitatively control photosynthetic levels.

Lipids are important to aquatic ecosystems, as essential dietary components for animals (including some of economic importance in both wild and cultured food production) (Olsen, this volume), as vectors for movement of hydrophobic materials (including many important contaminants), and as the proximate agents of toxicity in a variety of organisms (Landrum and Fisher, this volume). Microalgae, including phytoplankton and attached forms such as ice algae and periphyton, are major producers of aquatic lipids. A substantial body of measurements of lipid synthesis by natural populations of microalgae has developed, thanks largely to the relative ease with which 14C and simple chemical extraction protocols can be applied to measure the intracellular allocation of recent photosynthate (Morris et al., 1981,Morris et al., 1974; ). In practice, the term photosynthate here refers to carbon incorporated (and therefore labeled) within the span of typical primary production experiments (usually 4-24 hours). Such measurements have revealed substantial variation in the synthesis and relative allocation of photosynthate to lipids, which may be related to environmental and taxonomic factors (Madariaga, 1992; Wainman and Lean, 1992).

Volatile halogenated organic compounds are trace constituents of the oceans. The origin of these compounds is both anthropogenic and biogenic. With few exceptions, primarily chloroform and methylchloride, fluorinated and chlorinated compounds are regarded as exclusively man made (Class and Ballschmiter 1987). The brominated and iodinated substances are known as biogenic (Moore 1977, Fenical 1981), and marine macroalgae are believed to be the main source in sea water. Only a few investigations have dealt with the formation of volatile halocarbons by phytoplankton, but several distribution studies have indicated that these organisms have such an ability (Klick and Abrahamsson 1992, Moore and Tokarszcyk 1992, Reifenhauser and Heumann 1992, Abrahamsson and Ekdahl 1993). Sturges et al. 1992, have shown the formation of halocarbons from ice algae communities. Halogenated substances have been suggested to be formed either as intermediates in biosynthesis (Fenical 1975, Theiler et al. 1978) or through produced HOBr (Wever 1991).

As part of an extensive investigation of halocarbons (low molecular weight halogenated hydrocarbons) in the waters of the Weddell Sea, Antarctica, in January-February 1993, a set of four brominated and eight iodinated hydrocarbons were measured in sea ice containing algal colonies, and the results were compared with those of surrounding surface seawater. Samples were collected in two ways. On one occasion, brownish ice was taken underneath an ice floe, and the ice pore water analysed. On another occasion, samples were collected from colonies living in the interface between the snow and the sea-ice. Some of the latter samples were also analysed for their content of chlorophyll a.

Climate change could hurt the Arctic bottom fauna and the large creatures that live off it by wiping out ice and hence ice algae, lengthening growing seasons for zooplankton, and giving warm-water species a foothold. ([Read more][1].) [1]: http://www.sciencemag.org/cgi/content/full/315/5818/1527

M icrobiologist Brian Duval hates this part, so let's just deal with the snickering up front. Yes, he studies yellow snow. He also studies red, green, and orange snow and would love to examine other colors if he were lucky enough to discover them. His palette comes from springtime blooms of algae that live only in deep, persistent snowfields. And yes, even a professional sometimes gets fooled. "I was outside a penguin rookery in Antarctica, and I thought I was collecting this greenish-yellow algae," recalls the microbiologist now at the Massachusetts Department of Environmental Protection in Worcester. "I was saying, 'Yeah, yeah, this looks like the stuff."' When he checked his treasures under a microscope, however, he diagnosed the obvious nonalgal origin. "It gets embarrassing," he admits. Despite the yellow-snow raillery, Duval and his colleagues stay with their studies of snow algae because of the marvels of the chilly lifestyle. Somehow the 350 species of snow algae thrive in the near-freezing, nutrientpoor, acidic, sun-blasted slush of melting snowfields around the world. The algae support a food web in the snow-a world of tiny, wormy, crawly beings as odd as Spielberg-movie creatures. Algal life cycles combine the drama of salmon runs and the nightmare of icebound explorers. Snow-algae chemistry captivates biologists musing about life on other planets or prospecting for novelties on our own. These flashy algae are on their way to becoming glamour species in what Duval and like-minded specialists see as the dawning of a great era of snow ecology. Plus, snow algae can be gorgeous. In high Western snowfields, they blush red in footstep-size patches and meters-long streaks that hikers call watermelon snow. In northern New England, they give salmonorange sunset streaks to the last mounds of snow at the season's end. Fie on snickering. Such wonders deserve awe. "They're amazing," Duval sums up. He doesn't say that they're cool. That's another one that he's heard too often. S now algae aren't ice algae. Many of the ice species tolerate salt water and survive in solid ice packs at the poles. "They're completely different species," Duval says, sounding a little surprised that anyone would want to lump the groups together.

In situ measurements of the primary productivity of ice algae and phytoplankton were carried out in the fast ice area near Syowa Station (69°00′S, 39°35′E) during the austral spring and summer of 1983/84. Standing stock of ice algae reached a maximum of 45.1 mg chla m−2 in late October. Phytoplankton standing stock attained a value of 3.57 mg chla m−2 in mid-January. Primary production of ice algae in late October (7.64 mgC m−2 hr−1) was 14 times greater than that in mid-January (0.54 mgC m−2 hr−1). Production in the water column in mid-January (3.46 mgC m−2 hr−1) was 50 times greater than that in late October (0.07 mgC m−2 hr−1). These results indicate a substantial production by ice algae in the spring and by phytoplankton in the summer period.