Sea-ice Communities Research Articles

Process studies on the ecological coupling between sea ice algae and phytoplankton

The seasonal dynamics of pelagic and sea ice communities are closely related in ice-covered waters, however, modelling works that analyse such interactions are scarce. We use the Biogeochemical Flux Model in Sea Ice (BFM-SI) coupled to the pelagic Biogeochemical Flux Model (BFM) in a study area in Greenland to quantitatively investigate: (1) the significance of photoacclimation/photoadaptation strategies of autotrophs, (2) the fate of the sea ice biomass in case of algae seeding, algae aggregation and at different mixed layer depths and (3) the changes in community production under a climate change scenario. The results show that sea ice algae need to be both photoacclimated and photoadapted to the sea ice environment in order to grow, while phytoplankton may adopt different strategies for optimising their growth. The seeding of the phytoplankton bloom shows to be driven, both in timing and magnitude, by the viability of sea ice algae and by the degree of aggregation of algae released from the ice, which also affects the sinking rate to the sea floor. Under a mild climate change scenario (SRES B2, 2071–2090) the sea ice community is projected to be generally more productive, whereas phytoplankton growth will be reduced because the melt of sea ice will occur earlier in the season when light is less favourable to sustain the growth. While it is generally anticipated that the melting of multi-year ice in the Arctic Ocean will cause an increase in marine production, this study shows that seasonal ice-covered seas in the Northern hemisphere may actually be less productive and may shift to more oligotrophic conditions within the next 100 years.

Comparison of wintertime eukaryotic community from sea ice and open water in the Baltic Sea, based on sequencing of the 18S rRNA gene

The Baltic Sea is one of the world’s largest brackish water basins and is traditionally considered to be species poor. Here, we assessed the diversity of the nano-sized eukaryotic microbial wintertime community, using molecular ecological methods based on sequencing of small-subunit ribosomal RNA gene clone libraries. The results demonstrate that a rich community of small eukaryotes inhabits the Baltic Sea ice and water during winter. The community was dominated by alveolates and stramenopiles. Ciliates and cercozoans were the richest groups present, while in contrast to previous studies, diatoms showed a lower richness than expected. Furthermore, fungi and parasitic Syndiniales were present both in the water and in the sea ice. Some of the organisms in the sea-ice community were active, based on the RNA data, but a number of organisms were inactive or remnants from the freezing process. The results demonstrate that the sea-ice communities in the Baltic Sea are highly diverse and that water and ice of different ages include different protistan assemblages. Our study emphasizes the potential loss in biodiversity through diminishing ice cover as a result of climate change.

The analysis of dimethylsulfide and dimethylsulfoniopropionate in sea ice: Dry-crushing and melting using stable isotope additions

Sea ice is thought to be an important source of the climate-active gas dimethylsulfide (DMS), since extremely high concentrations of its precursor dimethylsulfoniopropionate (DMSP) have been found associated with high algal biomass. Accurate measurements of DMS and associated compounds in sea ice were until now not possible due to difficulties associated with the unavoidable melting process before analysis. Here we present and evaluate two methods to analyze DMS and DMSP in sea-ice cores accurately. The first, describes the dry-crushing method, which has its focus on the volatile compound DMS. A sub-sample of deeply frozen (<−30 °C) ice is crushed in a stainless steel vessel and the released gas phase is analyzed directly for DMS. The remaining ice is subsequently analyzed for its total DMSP content. With this method, DMS and DMSP profiles can be resolved even in ice cores stored deeply frozen for two years. The second method, involves a melting procedure, during which the conversion of compounds is monitored by adding differently deuterated isotopes of DMS and DMSP. Natural concentrations and stable isotopes of DMS and DMSP are simultaneously analyzed on a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS). Loss and conversion rates of the artificial isotopes are used to reconstruct the original concentrations of DMS and DMSP in ice and give important information on potential dynamical processes in sea-ice communities. It is concluded that in stored cores, the dry-crushing method provides the best results when the aim of the study is to differentiate between DMS and DMSP. When direct processing and analysis of the samples is possible, the isotope-addition method has the potential of providing concentrations of all S-compounds, including dissolved and particulate fractions. Moreover, it is suitable for the determination of process rates within the S-cycle.

Persistence of bacterial and archaeal communities in sea ice through an Arctic winter

The structure of bacterial communities in first-year spring and summer sea ice differs from that in source seawaters, suggesting selection during ice formation in autumn or taxon-specific mortality in the ice during winter. We tested these hypotheses by weekly sampling (January–March 2004) of first-year winter sea ice (Franklin Bay, Western Arctic) that experienced temperatures from −9°C to −26°C, generating community fingerprints and clone libraries for Bacteria and Archaea. Despite severe conditions and significant decreases in microbial abundance, no significant changes in richness or community structure were detected in the ice. Communities of Bacteria and Archaea in the ice, as in under-ice seawater, were dominated by SAR11 clade Alphaproteobacteria and Marine Group I Crenarchaeota, neither of which is known from later season sea ice. The bacterial ice library contained clones of Gammaproteobacteria from oligotrophic seawater clades (e.g. OM60, OM182) but no clones from gammaproteobacterial genera commonly detected in later season sea ice by similar methods (e.g. Colwellia, Psychrobacter). The only common sea ice bacterial genus detected in winter ice was Polaribacter. Overall, selection during ice formation and mortality during winter appear to play minor roles in the process of microbial succession that leads to distinctive spring and summer sea ice communities.

Photoadaptation of an ice algal community in thin sea ice, Saroma-Ko Lagoon, Hokkaido, Japan

We investigated the shade adaptation of a seasonally well-developed ice algal community in thin sea ice at Saroma-Ko Lagoon, Hokkaido, Japan on 3–4 March 2006 and 4–5 March 2007, by examining photosynthetic pigment concentrations, the chlorophyll a-specific light-absorption coefficient (aph*), and the light-saturation index (Ek). The high proportions of photosynthetic pigments, including chlorophyll a, fucoxanthin, and chlorophyll c, and the low values of aph*(440) and aph*(675) suggested that the lagoon’s ice algal community was shade-adapted. The high ratio of Ek to total photosynthetically active radiation (PAR) in the ice algal habitat suggested that the degree of shade adaptation is weak. Scaling of Ek to total PAR could be extended to studies of the degree of photoadaptive succession of ice algal communities in the Northern Hemisphere. The degree of shade adaptation of ice algal communities in the Northern Hemisphere might be related to ice thickness, regardless of latitude.

Microalgal composition and primary production in Arctic sea ice: a seasonal study from Kobbefjord (Kangerluarsunnguaq), West Greenland

We investigated the microalgal community in sea ice and in the water column of Kobbe- fjord, West Greenland, through an entire sea ice season. Temporal variation in physical (photosynthet- ically active radiation (PAR), temperature, brine volume) and chemical (salinity, nutrient concentra- tion) properties confirmed that sea ice is a very dynamic habitat. Nevertheless, a viable sea ice algal community was present throughout the year, with a species succession from flagellate dominance (di- noflagellates and cryptophytes) in December to February, followed by Chaetoceros simplex (a centric diatom) in March and pennate diatoms in May. Sea ice algal composition, biomass and productivity were influenced by PAR and brine volume, with colonization (enhanced by large brine volume) appar- ent during sea ice melt. Sea ice chlorophyll levels were generally low (<0.5 µg chl l -1 ), with 2 distinct blooms (maxima of 1.8 and 2.6 µg chl l -1 in March and May, respectively). Primary production mirrored biomass dynamic, which had 2 seasonal peaks of ca. 21 and 15 mg C m -2 d -1 . Integrated primary pro- duction over 7 mo was 0.8 g C m -2 in sea ice and 94.4 g C m -2 in the water column, with the vast major- ity of the pelagic production occurring just after sea ice melt (when primary production peaked at 4.2 g C m -2 d -1 ). There was no conclusive evidence of algal seeding. Sea ice algae contributed 30% of total (sympagic plus pelagic) primary production during the sea ice season, but less than 1% annually.

Internal melting in Antarctic sea ice: Development of “gap layers”

An internal “gap” layer of deteriorated sea ice is co‐located with a significant microbial biological community in late first year and second year Antarctic sea ice in summer. We modeled gap layer formation using a thermal flux model based on the summer reversal in thermal gradient and the thermal conductivity found in the upper ice column. The conductive model gives internal sea ice melt rates (gap layer formation rates) between 0.1 to 0.75cm/day. The cumulative melted layer thicknesses during summer computed from these rates agree with field observations. Since the processes for forming these structures act in the vertical direction only and over a significant range of expected conditions, they are commonly formed in the Antarctic sea ice zone during summer, supporting a significant contribution of gap layers to the ice mass balance and productivity on a circumpolar basis.

Embryo aberrations in sea ice amphipod Gammaruswilkitzkii exposed to water soluble fraction of oil

Offshore oil and gas activities have gained momentum in the European Arctic, raising concerns of the potential impact of oil-related chemicals on the polar marine ecosystem, notably on sea ice communities. Herein, malformations on embryos of the Arctic sea ice amphipod Gammarus wilkitzkii exposed to the water soluble fraction of oil were studied. The females ranged from development stage three to nine. No differences in reproductive stage were observed among the different treatments after 30 days of exposure. Frequency of embryo aberrations was significantly higher in the high-dose compared to controls, indicating that the embryos of G. wilkitzkiii were affected by oil.

Winter–spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean

An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom ( r values ≥ 0.74, p < 0.01). These relationships suggest that algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.

Responses of Microbial Communities in Arctic Sea Ice After Contamination by Crude Petroleum Oil

Microbial communities associated with Arctic fjord ice polluted with petroleum oils were investigated in this study. A winter field experiment was conducted in the Van Mijen Fjord (Svalbard) from February to June 2004, in which the ice was contaminated with a North Sea paraffinic oil. Holes were drilled in the ice and oil samples frozen into the ice at the start of the experiment. Samples, including cores of both oil-contaminated and clean ice, were collected from the field site 33, 74, and 112 days after oil application. The sampled cores were separated into three sections and processed for microbiological and chemical analyses. In the oil-contaminated cores, enumerations of total prokaryotic cells by fluorescence microscopy and colony-forming units (CFU) counts of heterotrophic prokaryotes both showed stimulation of microbial growth, while concentrations of oil-degrading prokaryotes remained at similar levels in contaminated and clean ice. Analysis of polymerase chain reaction (PCR)-amplified bacterial 16S rRNA gene fragments by denaturing gradient gel electrophoresis (DGGE) revealed that bacterial communities in oil-contaminated ice generated fewer bands than communities in clean ice, although banding patterns changed both in contaminated and clean ice during the experimental period. Microbial communities in unpolluted ice and in cores contaminated with the paraffinic oil were examined by cloning and sequence analysis. In the contaminated cores, the communities became predominated by Gammaproteobacteria related to the genera Colwellia, Marinomonas, and Glaciecola, while clean ice included more heterogeneous populations. Chemical analysis of the oil-contaminated ice cores with determinations of n-C17/Pristane and naphthalene/phenanthrene ratios indicated slow oil biodegradation in the ice, primarily in the deeper parts of the ice with low hydrocarbon concentrations.

Biomass, composition and activity of organism assemblages along a salinity gradient in sea ice subjected to river discharge in the Baltic Sea

A study was undertaken to examine the activity and composition of the seasonal Baltic Sea land-fast sea-ice biota along a salinity gradient in March 2003 in a coastal location in the SW coast of Finland. Using a multi-variable data set, the less well-known algal and protozoan communities, and algal and bacterial production in relation to the physical and chemical environment were investigated. Also, the first coincident measurements of bacterial production and dissolved organic matter (DOM) in a sea-ice system are reported. Communities in sea ice were clearly autotrophy-dominated with algal biomass representing 79% of the total biomass. Protozoa and rotifers made up 18% of biomass in the ice and bacteria only 3%. Highest biomasses were found in mid-transect bottom ice. Water column assemblages were clearly more heterotrophic: 39% algae, 12% bacteria and 49% for rotifers and protozoa. Few significant correlations existed between DOM and bacterial variables, reflecting the complex origin of ice DOM. Dynamics of dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) were also uncoupled. A functional microbial loop is likely to be present in the studied ice. Existence of an under-ice freshwater plume affects the ecosystem functioning: Under-ice water communities are influenced directly by river-water mixing, whereas the ice system seems to be more independent—the interaction mainly taking place through the formation of active bottom communities.

Bacterial incorporation of leucine into protein down to −20 °C with evidence for potential activity in sub-eutectic saline ice formations

Direct evidence for metabolism in a variety of frozen environments has pushed temperature limits for bacterial activity to increasingly lower temperatures, so far to −20 °C. To date, the metabolic activities of marine psychrophilic bacteria, important components of sea-ice communities, have not been studied in laboratory culture, not in ice and not below −12 °C. We measured [ 3H]-leucine incorporation into macromolecules (further fractionated biochemically) by the marine psychrophilic bacterium Colwellia psychrerythraea strain 34H over a range of anticipated activity-permissive temperatures, from +13 to −20 °C, including expected negative controls at −80 and −196 °C. For incubation temperatures below −1 °C, the cell suspensions [all in artificial seawater (ASW)] were first quick-frozen in liquid nitrogen. We also examined the effect of added extracellular polymeric substances (EPS) on [ 3H]-leucine incorporation. Results showed that live cells of strain 34H incorporated substantial amounts of [ 3H]-leucine into TCA-precipitable material (primarily protein) down to −20 °C. At temperatures from −1 to −20 °C, rates were enhanced by EPS. No activity was detected in the killed controls for strain 34H (or in Escherichia coli controls), which included TCA-killed, heat-killed, and sodium azide- and chloramphenicol-treated samples. Surprisingly, evidence for low but significant rates of intracellular incorporation of [3H]-leucine into protein was observed for both ASW-only and EPS-amended (and live only) samples incubated at −80 and −196 °C. Mechanisms that could explain the latter results require further study, but the process of vitrification promoted by rapid freezing and the presence of salts and organic polymers may be relevant. Overall, distinguishing between intracellular and extracellular aspects of bacterial activity appears important to understanding behavior at sub-freezing temperatures.

Changes in Phytoplankton Biomass and Nutrient Quantities in Sea Ice as Responses to Light/Dark Manipulations during different Phases of the Baltic Winter 2003

The response of Baltic Sea ice communities to changing light climate was studied in three subsequent 3 week in situ experiments on the SW coast of Finland. The investigation covered three different winter periods, short day with low solar angles leading to limited light in the ice, late winter with deep snow cover and early spring with melting snow and increasing light availability. The experimental setup consisted of transparent (no snow) and completely darkened (heavy snow cover) plexiglass tubes in which the ice cores were incubated in situ from 1 to 2 weeks. Changes in the concentrations of inorganic nutrients (NO 3 − -–N, PO4 3−-–P, SiO4 −-–Si) and chlorophyll-a concentration in the phytoplankton community composition were recorded as responses to different light manipulations. Changes in inner ice light intensity in untreated ice as well as the temperature both in air and ice were recorded over the entire study period. Increased irradiance in late winter/early spring and during meltdown affected the chlorophyll-a amount in the sea ice. During these periods the phytoplankton community in the top layers decreased possibly as a consequence of photo-acclimation. Closer to the bottom of the ice, however, the increased inner ice light intensity induced algal growth. Complete exclusion of light stopped the algal growth in the whole ice column. Darkening the ice cores also slowed down the ice melting opposite to accelerated melting caused by increased light. The significant differences found in nutrient concentrations between the light and dark treatments were mostly explicable by changes in algal biomass. No obvious changes were observed in the phytoplankton community composition due to light manipulation, diatoms and heterotrophic flagellates dominating throughout the study period.

Life history and population dynamics of the Arctic sympagic amphipods Onisimus nanseni Sars and O. glacialis Sars (Gammaridea: Lysianassidae)

The two sympagic amphipod species Onisimus nanseni Sars and O. glacialis Sars (Lysianassidae) are important constituents of the macrofaunal community in Arctic sea ice but little, as yet, is known about their autecology. In this paper we provide a description of the life cycles and population dynamics of these two species that were sampled beneath the ice pack surrounding Svalbard/Norway in September 2002 and May 2003. The distribution of Onisimus spp. was patchy and their numbers were low in sea ice throughout the year (∼0.8 ind. m−2 in spring, ∼1.0 ind. m−2 in autumn). In May the juveniles accounted for 37% and 22% of the population of O. nanseni and O. glacialis, respectively. The population structure of O. glacialis was relatively constant in spring and autumn, but of O. nanseni a shift towards a more mature structure was observed in September. Ovigerous females were virtually absent in both species during both sampling periods. Length–frequency distribution analysis on spring- and autumn-data showed three cohorts for O. nanseni and four cohorts for O. glacialis and suggests a temporal shift in the reproductive cycles of these two species. Both species appear to be univoltine (one generation per year) and probably iteroparous (several broods per female lifespan). The offspring of O. nanseni is presumably released in late spring and shows secondary sexual characters the first year allowing for reproduction in year 0+. In contrast, O. glacialis leaves the brood pouch in early spring and sexually matures in year 1+. The growth constants were comparable for the two species. The estimated life span was 3.5 years for O. glacialis and 2.5 years for O. nanseni.

Sea ice algae in the White and Barents seas: composition and origin

To examine algae populations, three expeditions (in March 2001, April 2002 and February 2003) were conducted in the Guba Chupa (Chupa Estuary; north-western White Sea), and one cruise was carried out in the open part of the White Sea in April 2003 and in the northern part of the Barents Sea in July 2001. Sea ice algae and phytoplankton composition and abundance and the content of sediment traps under the land-fast ice in the White Sea and annual and multi-year pack ice in the Barents Sea were investigated. The community in land-fast sea ice was dominated by pennate diatoms and its composition was more closely related to that of the underlying sediments than was the community of the pack ice, which was dominated by flagellates, dinoflagellates and centric diatoms. Algae were far more abundant in land-fast ice: motile benthic and ice-benthic species found favourable conditions in the ice. The pack ice community was more closely related to that of the surrounding water. It originated from plankton incorporation during sea ice formation and during seawater flood events. An additional source for ice colonization may be multi-year ice. Algae may be released from the ice during brine drainage or sea ice melting. Many sea ice algae developed spores before the ice melt. These algae were observed in the above-bottom sediment traps all year around. Three possible fates of ice algae can be distinguished: 1) suspension in the water column, 2) sinking to the bottom and 3) ingestion by herbivores in the ice, at the ice-water interface or in the water column.

Sea ice algae in the White and Barents seas: composition and origin

To examine algae populations, three expeditions (in March 2001, April 2002 and February 2003) were conducted in the Guba Chupa (Chupa Estuary; north-western White Sea), and one cruise was carried out in the open part of the White Sea in April 2003 and in the northern part of the Barents Sea in July 2001. Sea ice algae and phytoplankton composition and abundance and the content of sediment traps under the land-fast ice in the White Sea and annual and multi-year pack ice in the Barents Sea were investigated. The community in land-fast sea ice was dominated by pennate diatoms and its composition was more closely related to that of the underlying sediments than was the community of the pack ice, which was dominated by flagellates, dinoflagellates and centric diatoms. Algae were far more abundant in land-fast ice: motile benthic and ice-benthic species found favourable conditions in the ice. The pack ice community was more closely related to that of the surrounding water. It originated from plankton incorporation during sea ice formation and during seawater flood events. An additional source for ice colonization may be multi-year ice. Algae may be released from the ice during brine drainage or sea ice melting. Many sea ice algae developed spores before the ice melt. These algae were observed in the above-bottom sediment traps all year around. Three possible fates of ice algae can be distinguished: 1) suspension in the water column, 2) sinking to the bottom and 3) ingestion by herbivores in the ice, at the ice-water interface or in the water column.

Sea-ice microbial communities in the Ross Sea: autumn and summer biota

The composition of sea ice communities in the Ross Sea region was examined during the autumn to winter transition and during the summer. The biomass of autotrophs and heterotrophs in autumn reached maximum values of 709 and 167 mg C m -2 , and in summer maximum values of 3873 and 209 mg C m -2 , respectively. During the autumn-winter cruise, most of the biomass was found within ice floes as interior and bottom layer communities. During summer, surface-layer slush com- munities occurred throughout the ice-covered regions. The biomass was highly variable throughout the study regions during both cruises. Diatoms dominated the autotrophic biomass; however, autotrophic dinoflagellates and autotrophic flagellates contributed significantly to the community make-up. Among heterotrophs, ciliates predominated during both cruises, followed by heterotrophic flagellates and heterotrophic dinoflagellates. Similarity analysis, based on the biomass composition of major groups, showed consistency between and within cruises, with most samples >70% similar. The autumn to winter samples (all from within floes) showed higher similarity clusters that could be related to changing compositions of diatoms, ciliates, and autotrophic dinoflagellates. Most variable were some summer surface slush samples, where samples dominated by Phaeocystis, Pyramimonas, Gymnodinium, and the ciliate Gymnozoum formed outlying clusters. The dynamics of ice biota may be determined by relatively few taxa that are persistently found within the ice floes. Surface blooms may develop either from a biota within the ice or from opportunistic forms from the water column that are introduced during flooding events. Thus, these assemblages may show considerably more vari- ability in composition than those that develop within the underlying ice.

Influence of crude oil on changes of bacterial communities in Arctic sea-ice

The danger of a petroleum hydrocarbon spillage in the polar, ice-covered regions is increasing due to oil exploration in Arctic offshore areas and a growing interest in using the Northern Sea Route (NSR) as an alternative transportation route for Arctic oil and gas. However, little is known about the potential impact of accidental oil spills on this environment. We investigated the impact of crude oil on microbial community composition in six different Arctic sea-ice samples incubated with crude oil at 1 °C in microcosms for one year. Alterations in the composition of bacterial communities were analyzed with the culture-independent molecular methods DGGE (denaturing gradient gel electrophoresis) and FISH (fluorescence in situ hybridization). DGGE, FISH and cultivation methods revealed a strong shift in community composition toward the γ-proteobacteria in sea-ice and melt pool samples incubated with crude oil. Marinobacter spp., Shewanella spp. and Pseudomonas spp. were the predominant phylotypes in the oil-treated microcosms. The ability of indigenous sea-ice bacteria to degrade hydrocarbons at low temperature (1 °C) was tested using four representative strains cultivated from sea-ice enriched with crude oil. [ 14C]Hexadecane was degraded by the sea-ice isolates at 20–50% capacity of the mesophilic type strain Marinobacter hydrocarbonoclasticus, a known hydrocarbon degrader, incubated at 22 °C.

Preparation for the operational use of RADARSAT-2 for ice monitoring

Sea ice monitoring has been the most successful real-time operational application for RADARSAT-1 data. These data are used by several national ice services as a mainstay of their programs. Thus, the international sea ice community is looking forward to the future launch of RADARSAT-2. The RADARSAT-2 end-to-end system promises several technical enhancements beyond RADARSAT-1. These include multipolar/polarimetric data, improved data handling and processing and throughput, and a more streamlined ordering system. Ice versus water discrimination, sensitivity to surface topography and ridging, and enhanced iceberg detection capabilities are some of the improvements expected to result from the availability of like- and cross-polarized synthetic aperture radar (SAR) imagery. Beyond purely the information content, numerous challenges remain before the various improvements of the RADARSAT-2 system can be exploited operationally. Among these are handling the increased data volumes of multichannel data; developing new data display, visualization, and analysis techniques; operational scenarios and potential use of left- and right-looking to improve spatio-temporal coverage; improved order handling and satellite tasking; and acquisition planning and integration with other spaceborne SAR data (i.e., Envisat). In this paper we report on efforts underway at the Canadian, American, and Danish national ice services to address these elements necessary to be ready for the best operational use of RADARSAT-2 data.

Abundance, size distribution and bacterial colonization of exopolymer particles in Antarctic sea ice (Bellingshausen Sea)

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 35:283-296 (2004) - doi:10.3354/ame035283 Abundance, size distribution and bacterial colonization of exopolymer particles in Antarctic sea ice (Bellingshausen Sea) Klaus Meiners1,2,*, Robin Brinkmeyer3, Mats A. Granskog4,5, Antti Lindfors4 1Institute for Polar Ecology, University of Kiel, Wischhofstr. 1-3, Bld. 12, 24148 Kiel, Germany 2Dept. of Geology and Geophysics, Yale University, Box 208109, New Haven, Connecticut 06520-8109, USA 3Alfred Wegener Institute for Polar and Marine Research, Box 120161, 27515 Bremerhaven, Germany 4Division of Geophysics, Department of Physical Sciences, Box 64, 00014 University of Helsinki, Finland 5Arctic Centre, University of Lapland, Box 122, 96101 Rovaniemi, Finland *Email: klaus.meiners@yale.edu ABSTRACT: The abundance, size spectra and bacterial colonization of exopolymer particles were investigated in Antarctic sea ice and underlying water in the Bellingshausen Sea during April 2001. In addition to exopolymer particles (EP), different abiotic (temperature, salinity, ice texture, oxygen isotopic composition, inorganic nutrient concentrations) and biotic (particulate organic carbon/nitrogen, algal pigments, abundance and biomass of bacteria and diatoms) parameters were measured from the samples. The sea ice showed different communities occurring in physically distinct layers of the ice. Algal and bacterial biomass in the ice showed strong vertical gradients and ranged between 59.4 and 5140.4 μg C l-1 and 8.8 and 119.4 μg C l-1, respectively. EP concentrations in the sea ice were high, with EP abundance ranging between 10.2 and 260.1 × 106 particles l-1 and EP area between 3.4 and 92.1 cm2 l-1. Median EP concentrations in the ice exceeded under-ice values by 1 order of magnitude. Crude estimates of integrated sea ice EP carbon were equivalent to 14-32% of the integrated POC, and to 34-78% of the integrated diatom biomass. The estimated integrated EP carbon in sea ice exceeded the bacterial biomass by a factor of 10 to 20. The abundance of EP was inversely correlated with size of the particles. EP size spectra showed relatively flat slopes, indicating a relatively large contribution of larger particles. The bacterial colonization of individual EP in the ice and in the under-ice water was not significantly different. In contrast, due to the large difference of EP concentrations in the 2 habitats, the median proportion of attached bacteria was much higher in the ice (14.8% of the total bacterial number) than in the under-ice water (1.9% of the total bacterial number). The data suggest that EP are an integral component of Antarctic sea ice communities and that EP serve as important substrates for ice-associated bacteria. After the ice melts in spring, large amounts of EP are available to be released to the water, where they may significantly contribute to and alter the particle flux of the ice-covered Southern Ocean. KEY WORDS: Sea ice · Antarctica · Exopolymer particles · Extracellular polymeric substances · Particle colonization · Bacteria · Diatoms Full article in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 35, No. 3. Online publication date: May 19, 2004 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2004 Inter-Research.