Decomposition in situ of the sublittoral Antarctic macroalgaDesmarestia anceps Montagne

 Large amounts of detached Antarctic macroalgae accumulate in hollows of the seabed, where decomposition rates of the detached macroalgae are expected to be low, caused by lack of contact of the major part of the macroalgae with the sediment. To determine decomposition rates in Antarctic waters, untreated and pre-killed Desmarestia anceps fronds contained in nylon net bags were studied for 10 months under natural conditions in Factory Cove, Signy Island. Physical decomposition was shown to be more important than microbial decomposition. A weight loss of 40% occurred in untreated material within 313 days, while pre-killed material almost all disappeared within 90 days. Despite the weight loss, changes in chlorophyll a content were negligible during the experiment. Changes in the C:N ratio and tissue N indicated low rates of microbial decomposition. Therefore, it was concluded that weight loss was mainly caused by fragmentation, and particles disappearing from the nets accounted for most of the loss of original tissue. It remains unknown as to how long nutrients stay in Antarctic macroalgal litter before they become available to the system. Received: 16 March 1995/Accepted: 18 June 1995     

Agarolytic culturable bacteria associated with three antarctic subtidal macroalgae

Bacterial communities of Antarctic marine macroalgae remain largely underexplored in terms of diversity and biotechnological applications. In this study, three Antarctic subtidal macroalgae (Himantothallus grandifolius, Pantoneura plocamioides and Plocamium cartilagineum), two of them endemic of Antarctica, were investigated as a source for isolation of agar-degrading bacteria. A total of 21 epiphytic isolates showed agarolytic activity at low temperature on agar plates containing agar as the sole carbon source. 16S rRNA identification showed that the agar-degrading bacteria belonged to the genera Cellulophaga, Colwellia, Lacinutrix, Olleya, Paraglaciecola, Pseudoalteromonas and Winogradskyella. The agarase enzyme from a potential new species of the genus Olleya was selected for further purification. The enzyme was purified from the culture supernatant of Olleya sp. HG G5.3 by ammonium sulfate precipitation and ion-exchange chromatography. Molecular weight of the agarase was estimated to be 38 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme exhibited activity at 4 °C, retaining >?50% of its maximum activity at this temperature. This is the first study reporting the phylogeny of agar-degrading bacteria isolated from Antarctic subtidal macroalgae and the results suggest the huge potential of Antarctic algae-associated bacteria as a source of cold-active hydrolytic enzymes of biotechnological interest.     

Die Wälder der Antarktis

Forests of Antarctica Antarctica is a continent of extremes, demanding a lot from the organisms living there. Antarctic macroalgae, as an important component of the coastal ecosystem of the Southern Ocean, have adapted their metabolism to permanent cold and to long periods of darkness. Due to the long cold‐water history and the isolation of the continent, a high number of endemic species developed in Antarctica. Antarctic macroalgae are important primary producers and serve as food for many organisms. Their more detailed investigation began relatively late and is far from complete. Climate change is visible in Antarctica as well, threatening the fragile ecosystem. Increased UV radiation e. g. can lead to changes in the depth zonation and increased temperature to changes in the geographical distribution of the individual macroalgal species.     

Predicting the cover and richness of intertidal macroalgae in remote areas: a case study in the Antarctic Peninsula

Antarctica is an iconic region for scientific explorations as it is remote and a critical component of the global climate system. Recent climate change causes a dramatic retreat of ice in Antarctica with associated impacts to its coastal ecosystem. These anthropogenic impacts have a potential to increase habitat availability for Antarctic intertidal assemblages. Assessing the extent and ecological consequences of these changes requires us to develop accurate biotic baselines and quantitative predictive tools. In this study, we demonstrated that satellite‐based remote sensing, when used jointly with in situ ground‐truthing and machine learning algorithms, provides a powerful tool to predict the cover and richness of intertidal macroalgae. The salient finding was that the Sentinel‐based remote sensing described a significant proportion of variability in the cover and richness of Antarctic macroalgae. The highest performing models were for macroalgal richness and the cover of green algae as opposed to the model of brown and red algal cover. When expanding the geographical range of the ground‐truthing, even involving only a few sample points, it becomes possible to potentially map other Antarctic intertidal macroalgal habitats and monitor their dynamics. This is a significant milestone as logistical constraints are an integral part of the Antarctic expeditions. The method has also a potential in other remote coastal areas where extensive in situ mapping is not feasible.     

Life strategy, ecophysiology and ecology of seaweeds in polar waters

Polar seaweeds are strongly adapted to the low temperatures of their environment, Antarctic species more strongly than Arctic species due to the longer cold water history of the Antarctic region. By reason of the strong isolation of the Southern Ocean the Antarctic marine flora is characterized by a high degree of endemism, whereas in the Arctic only few endemic species have been found so far. All polar species are strongly shade adapted and their phenology is finely tuned to the strong seasonal changes of the light conditions. The paper summarises the present knowledge of seaweeds from both polar regions with regard to the following topics: the history of seaweed research in polar regions; the environment of seaweeds in polar waters; biodiversity, biogeographical relationships and vertical distribution of Arctic and Antarctic seaweeds; life histories and physiological thallus anatomy; temperature demands and geographical distribution; light demands and depth zonation; the effect of salinity, temperature and desiccation on supra-and eulittoral seaweeds; seasonality of reproduction and the physiological characteristics of microscopic developmental stages; seasonal growth and photosynthesis; elemental and nutritional contents and chemical and physical defences against herbivory. We present evidence to show that specific characteristics and adaptations in polar seaweeds help to explain their ecological success under environmentally extreme conditions. In conclusion, as a perspective and guide for future research we draw attention to many remaining gaps in knowledge. Dedicated to Prof. Dr. Gunter O. Kirst and to Prof. Dr. Klaus Lüning on occasion of their retirement 28. Februar 2006 and 31. March 2006, respectively.     

Investigating essential and toxic elements in Antarctic macroalgae using a green analytical method

A systematic study for the determination of essential and toxic elements (such as As, Cd, Cu, Mn, Ni, Pb, V and Zn) in Antarctic macroalgae species (Desmarestia anceps, Iridaea cordata, Palmaria decipiens and Pyropia endiviifolia) was performed. For this purpose, a green sample preparation method combined with a high-sensitivity detection technique (inductively coupled plasma mass spectrometry) was used. By using the microwave-assisted digestion combined with ultraviolet radiation (MW-UV) method, 700 mg of macroalgae were digested using a diluted HNO₃ solution (2 mol L^?1). The accuracy was evaluated by analysis of certified reference materials of aquatic plant (BCR 060) and apple leaves (NIST 1515). Agreement with reference or informed values for all analytes ranged from 94 to 106%, except for As and Mo in BCR 060. The results were also compared with those obtained by the reference method, which did not present a significant difference (t test, 95% confidence level). Based on the results, analysed samples showed considerable variations in regards to the concentrations of Zn, Ni and Mn. Moreover, a relatively high concentration of As in Desmarestia anceps and Pyropia endiviifolia was observed. The results for most of the analytes in Antarctic macroalgae were in agreement with other studies that have been published in literature. In addition, the proposed method was suitable for determining toxic and essential elements in Antarctic macroalgae reducing reagent consumption and waste generation, which is in agreement with the green chemistry recommendation.     

Echiura from South Shetland Islands together with a review of its geographic distribution in the Antarctic Ocean

 Echiuran worms collected by the Spanish BENTART (=Bentos Antártico) cruises during years 1994 and 1995 to the South Shetland Islands from depths ranging from 24 to 1019 m are recorded. Three species are recognized: Alomasoma belyaevi, Echiurus antarcticus and Prashadus sp., with the presence of Prashadus sp. confirmed in the Antarctic. Distribution maps and a checklist of the echiuran species south of the Antarctic Convergence with depths and bibliographic references are included. Received: 10 July 1995/Accepted: 3 October 1995     

Diversity Patterns,Ecology and Biological Activities of Fungal Communities Associated with the Endemic Macroalgae Across the Antarctic Peninsula

We surveyed diversity patterns and engaged in bioprospecting for bioactive compounds of fungi associated with the endemic macroalgae, Monostroma hariotii and Pyropia endiviifolia, in Antarctica. A total of 239 fungal isolates were obtained, which were identified to represent 48 taxa and 18 genera using molecular methods. The fungal communities consisted of endemic, indigenous and cold-adapted cosmopolitan taxa, which displayed high diversity and richness, but low dominance indices. The extracts of endemic and cold-adapted fungi displayed biological activities and may represent sources of promising prototype molecules to develop drugs. Our results suggest that macroalgae along the marine Antarctic Peninsula provide additional niches where fungal taxa can survive and coexist with their host in the extreme conditions. We hypothesise that the dynamics of richness and dominance among endemic, indigenous and cold-adapted cosmopolitan fungal taxa might be used to understand and model the influence of climate change on the maritime Antarctic mycota.     

IMPACTS OF MESOGRAZERS ON EPIPHYTE AND ENDOPHYTE GROWTH ASSOCIATED WITH CHEMICALLY DEFENDED MACROALGE FROM THE WESTERN ANTARCTIC PENINSULA: A MESOCOSM EXPERIMENT1

It has been hypothesized that the extensive mesograzer community along the western Antarctic Peninsula regulates epiphytic algae as well as emergent filaments from endophytic species. Should grazing limit growth of fouling or potentially pathogenic microphytes, then Antarctic macrophytes may actually benefit from the remarkably high densities of mesograzer amphipods that occur in these waters. Although initially counterintuitive, the negative impacts of epi/endophyte fouling may outweigh stresses caused by limited amphipod grazing on chemically defended macrophytes by reducing stress from endo/epiphyte biomass. If so, then alleviating mesograzing stress should result in significant increases in endo/epiphytic biomass. To test this hypothesis, a mesocosm experiment was conducted. Individuals representing four common species of Antarctic macroalgae were placed in flow‐through seawater mesocosms. Amphipods were added to five mesocosms at simulated natural densities, while the other five remained herbivore free. At the end of 7 weeks, endo/epiphytic growth on individual macrophytes was quantified. Most species of macroalgae demonstrated noticeably higher instances of endophyte coverage, epiphytic diversity, and diatom colonization in consumer‐free mesocosms than in the presence of amphipods. These data suggest that macroalgae along the western Antarctic Peninsula rely on grazers to control populations of potentially harmful epiphytes. We hypothesize that the chemically defended macroalgal flora lives in mutualism with high densities of mesograzers, providing amphipods with shelter from predation while continually being cleaned of potentially harmful endo/epiphytes.     

Antarctic krill (Euphausia superba Dana) eat salps

 Feeding behaviour of Antarctic krill (Euphausia superba) on salps was observed in shipboard experiments during the 1994/1995 Kaiyo Maru Antarctic Ocean research cruise. The feeding rate was more than 0.5 salp/krill per day. When offered ethanol extracts of four prey types, salps, phytoplankton, krill and polychaetes, krill preferred the salp extracts. This evidence implies that the substances extracted from salps were most attractive to krill. These results might indicate a tight ecological relationship between krill and salps. Received: 24 May 1995/Accepted: 8 October 1995     

Discovery of ciliates reproducing in the gut of Antarctic krill

During a recent Antarctic research cruise (December 1994/February 1995), dissection of fresh Antarctic krill (Euphausia superba) on board ship revealed live motile ciliates in the gut of krill. Further observation of gut samples by scanning electron microscopy indicated that the ciliates were symbionts located within the gut. We inferred that the ciliates may have enabled the krill to digest a wider range of food items, and as a consequence, this had became an important strategy for Antarctic krill's survival in the Antarctic ecosystem. Received: 1 August 1996 / Accepted: 1 December 1996     

Phylogeny and bioactivity of epiphytic Gram-positive bacteria isolated from three co-occurring antarctic macroalgae

Marine macroalgae are emerging as an untapped source of novel microbial diversity and, therefore, of new bioactive secondary metabolites. This study was aimed at assessing the diversity and antimicrobial activity of the culturable Gram-positive bacteria associated with the surface of three co-occurring Antarctic macroalgae. Specimens of Adenocystis utricularis (brown alga), Iridaea cordata (red alga) and Monostroma hariotii (green alga) were collected from the intertidal zone of King George Island, Antarctica. Gram-positive bacteria were investigated by cultivation-based methods and 16S rRNA gene sequencing, and screened for antimicrobial activity against a panel of pathogenic microorganisms. Isolates were found to belong to 12 families, with a dominance of Microbacteriaceae and Micrococcaceae. Seventeen genera of Actinobacteria and 2 of Firmicutes were cultured from the three macroalgae, containing 29 phylotypes. Three phylotypes within Actinobacteria were regarded as potentially novel species. Sixteen isolates belonging to the genera Agrococcus, Arthrobacter, Micrococcus, Pseudarthrobacter, Pseudonocardia, Sanguibacter, Staphylococcus, Streptomyces and Tessaracoccus exhibited antibiotic activity against at least one of the indicator strains. The bacterial phylotype composition was distinct among the three macroalgae species, suggesting that these macroalgae host species-specific Gram-positive associates. The results highlight the importance of Antarctic macroalgae as a rich source of Gram-positive bacterial diversity and potentially novel species, and a reservoir of bacteria producing biologically active compounds with pharmacological potential.     

Towards the trophic structure of the Bouvet Island marine ecosystem

Although Bouvet Island is of considerable importance for Southern Ocean species conservation, information on the marine community species inventory and trophic functioning is scarce. Our combined study of stable isotopes and feeding relationships shows that (1) the marine system conforms to the trophic pattern described for other Antarctic systems within the Antarctic circumpolar current (ACC); (2) both the benthic and the pelagic subsystem are almost exclusively linked via suspended particulate organic matter (SPOM); and (3) there is no evidence of a subsystem driven by macroalgae. Bouvet Island can therefore be characterized as a benthic “oasis” within a self-sustaining open ocean pelagic system.     

THE BEGINNINGS OF ANTARCTIC MACROALGAL CHEMICAL ECOLOGY: DEFENSES AGAINST HERBIVORES IN A NITROGEN REPLETE,CARBON LIMITED OCEAN

Amsler, C. D.¹, Iken, K. B.¹, McClintock, J. B.¹, Furrow, F. B.², & Baker, B. J.^{2 1}Department of Biology, University of Alabama at Birmingham, Birmingham AL 35294-1170 USA; ²Department of Chemistry, Florida Institute of Technology, Melbourne, FL 32901 USA We examined palatability of Antarctic Peninsula macroalgae in feeding bioassays with three common, sympatric macroalgal-consuming omnivores (amphipod, fish, sea star). Antarctic macroalgae have low C:N ratios, high nitrogen contents, and are usually growth limited by carbon (light). The Carbon Nutrient Balance Hypothesis (CNBH) predicts that macroalgae would produce nitrogenous secondary metabolites for defense rather than high levels of non-nitrogenous defenses under these conditions. To date, feeding bioassays have been performed on fragments of thallus from 26 macroalgal species and 21 (81%) were rejected by at least one omnivore. Organic extracts from 13 macroalgal species rejected as thallus were used in feeding bioassays. At least one extract from 12 species (92%) was rejected by at least one omnivore, suggesting that chemical defenses against herbivores probably are present in at least some of the macroalgal species. We have identified a number of specific, non-nitrogenous secondary metabolites in these extracts and previous workers have also reported non-nitrogenous secondary metabolites from antarctic macroalgae. Additional extracts targeting nitrogenous metabolites from 25 species were subjected to thin layer chromatography and visualized by stains specific for nitrogenous compounds. No nitrogenous secondary metabolites were identified by this or other methods. Nitrogenous secondary metabolites are also extremely rare in macroalgae from other areas of the world. Consequently, although our bioassays suggest that chemical defenses probably do occur, our data cast doubt on the applicability of the CNBH for predicting the chemical composition of macroalgal defenses under carbon limited conditions. (NSF OPP9814538, OPP9901076)     

Patterns of gammaridean amphipod abundance and species composition associated with dominant subtidal macroalgae from the western Antarctic Peninsula

The communities of gammaridean amphipods associated with eight dominant macroalgal species were examined near Palmer Station, Western Antarctic Peninsula. A total of 78,415 individuals belonging to 32 amphipod taxa were identified with mean densities ranging up to 20 individuals/g algal wet wt. The most abundant amphipod taxon, Metaleptamphopus pectinatus, was found to associate predominately with the brown alga Desmarestia menziesii, while the second most common taxon, Jassa spp. occurred primarily on the red alga Gigartina skottsbergii. Non-metric multidimensional scaling analysis demonstrated that the population densities of each amphipod species and amphipod species composition were similar on the same algal species but dissimilar on different species of algae. Comparisons of amphipod communities associated with a given algal species but from different sampling sites indicated that although the structure of species-specific macroalgal-associated amphipod communities can vary across spatial scales of 3 km, 50% of the macroalgal species examined showed no significant inter-site differences in associated amphipod community structure. Spearman rank correlation analyses showed that higher abundances of amphipods occurred on the macroalgae with the highest number of branches. As many Antarctic amphipods are known consumers of macroalgae, their remarkable abundances are likely to play a significant role in mediating energy and nutrient transfer in nearshore Antarctic Peninsular macroalgal communities.     

Comparison of lipid content and fatty acid composition in muscle and liver of two notothenioid fishes from Admiralty Bay (Antarctica): an eco-physiological perspective

During Antarctic summer, total lipids (g/100 g dry matter) in Notothenia coriiceps (n=18) and Lepidonotothen nudifrons (n=10) were low (6.1 and 4.7 in muscle), which is typical of Antarctic benthic species. The liver of female N. coriiceps was heavier and contained more lipids per dry weight than the liver of males. The fatty acid composition of N. coriiceps and L. nudifrons was dominated by polyunsaturated fatty acids (PUFA, respectively, 44 and 49% of total fatty acids in muscle, 31 and 46% in liver), which included primarily C20:5n-3 (18 and 19% in muscle, 13 and 18% in liver) and C22:6n-3 (15 and 19% in muscle, 12 and 20% in liver). In L. nudifrons, the levels of some unsaturated fatty acids increased with age and size. The high percent unsaturation (PUFA+MUFA, 78 and 80% in muscle, 82 and 80% in liver) is a response to low water temperature (-0.4°C). Fish fatty acid profiles reflect fatty acid profiles of the diet (amphipods, macroalgae and fish).     

A winter sighting of killer whales (Orcinus orca ) in Antarctic sea ice

 A group of killer whales was sighted in open leads well inside Antarctic sea ice during August 1995. This was the first winter sighting of killer whales in Antarctic waters since 1955, and contradicts the view that all killer whales migrate north prior to the winter. A small calf was observed, providing the first evidence of a cetacean species breeding in Antarctic waters. Several potential prey species were also present. The sighting highlights the importance of lead and polynya systems to marine mammals, which probably use them to disperse within the winter sea-ice zone. Received: 23 April 1996 / Accepted: 25 August 1996     

Biomass and associations of benthic marine macroalgae from the inner Potter Cove (King George Island, Antarctica) related to depth and substrate

The biomass of the benthic marine macroalgae from the inner Potter Cove was studied along a depth profile across different substrates during Antarctic summer. Macroalgal associations were identified by means of cluster analysis. Twenty-two species were found in the study site, approximately half of the species present in the area. This paucity may be explained by the strong preponderance of the brown algae Desmarestia anceps and D. menziesii, which are able to exclude other species by competition for light. The mean biomass of all macroalgae was 1,390 g DW/m²ǃ,787 g DW/m². Nine macroalgal associations were identified with different preferences for depth, substrate and the degree of exposure. Overall, there was a tendency for macroalgae to grow on fine substrates with increasing depth. Species richness decreased at 20 m depth, probably due to limiting light conditions. The results are discussed with respect to previous studies in East and West Antarctica.     

Fish in the diet of the Antarctic shag Phalacrocorax bransfieldensis at Laurie Island, South Orkney Islands

The analysis of 29 stomach contents collected from a colony close to Pirie Peninsula, South Orkney Islands, from 2 January to 18 February 1995, showed that fish were by far the most important prey of the Antarctic shag Phalacrocorax bransfieldensis, followed by octopods, decapods and gammarids. The fish Notothenia coriiceps constituted the bulk of the diet; however, its importance decreased by the end of the study when Lepidonotothen nudifrons was the most important prey. The composition of the stomach contents varied throughout the breeding season according to changes in the chicks' energetic demands; as chicks grew older the adults increased the mass of the loads carried to the nests, preying on larger fish, a phenomenon also observed at the South Shetland Islands. Received: 3 July 1996 / Accepted: 9 March 1997     

Agar-degrading bacteria isolated from Antarctic macroalgae

This study describes the taxonomic diversity of pigmented, agar-degrading bacteria isolated from the surface of macroalgae collected in King George Island, Antarctica. A total of 30 pigmented, agarolytic bacteria were isolated from the surface of the Antarctic macroalgae Adenocystis utricularis, Monostroma hariotii, Iridaea cordata, and Pantoneura plocamioides. Based on the 16S rRNA data, the agarolytic isolates were affiliated to the genera Algibacter, Arthrobacter, Brachybacterium, Cellulophaga, Citricoccus, Labedella, Microbacterium, Micrococcus, Salinibacterium, Sanguibacter, and Zobellia. Isolates phylogenetically related to Cellulophaga algicola showed the highest agarase activity in culture supernatants when tested at 4 and 37 °C. This is the first investigation of pigmented agar-degrading bacteria, members of microbial communities associated with Antarctic macroalgae, and the results suggest that they represent a potential source of cold-adapted agarases of possible biotechnological interest.