Studies on R-phycoerythrins from two Antarctic marine red algae and a mesophilic red alga

R-phycoerythrin was purified from two benthic red algae, Iridaea cordata and Phyllophora antarctica, obtained growing at ?2°C under thick sea ice off the coast of Antarctica. For the I. cordata protein, the molecular mass was 245,000 Da, and its secondary structure was 60% α helix, 17% β sheet, 16% turn, and 7% other. The light-harvesting faculties of the I. cordata protein resembled those of R-phycoerythrins from mesophilic red algae and were distinctive from the novel R-phycoerythrin from P. antarctica. Deconvolution of the visible absorption spectrum of R-phycoerythrin from I. cordata indicated a minimum of five component bands having maxima at 568, 558, 534, 496, and 481?nm. R-phycoerythrins from the mesophilic Porphyra tenera and psychrophilic Phyllophora antarctica had the same five bands. The protein from Phyllophora antarctica obtained its unique spectrum from a more intense component at 482?nm, and a less intense band at 533?nm. This change was probably produced by a replacement of phycoerythrobilin by phycourobilin. A temperature study of the circular dichroism CD was obtained for R-phycoerythrin from I. cordata from 4 to 80°C. Laser time-resolved fluorescence studies on R-phycoerythrin showed bilin to bilin energy transfer with a 60.2-ps lifetime, which should occur by the Förster resonance. The similarities in spectra between the proteins from I. cordata and Porphyra tenera and the different spectrum for the protein from Phyllophora antarctica show that only particular antarctic habitats require unique R-phycoerythrins.     

Vertical migration and diel activity patterns of hydromedusae: studies in a large tank

Vertical distributions and swimming behaviors of 7 species ofhydromedusae (Aequorea victoria, Bougainvillia principis, Gonionemusvertens, Mitrocoma cellularia, Phialidium gregarium, Polyorchispenicillatus, and Stomotoca atra) were observed over 24-h periodsin a 2 m high, 1500 1 transparent tank. In this tank, most speciesperformed well-marked diel vertical migrations that were mediatedby swimming. Manipulation of the light regime showed the didswimming behaviors to be light-dependent rather than intrinsic,even in species that do not possess recognized photoreceptors.Correlations between vertical migration and spawning times forseveral species of medusae suggest that in cases when verticalmigration reduces the distances between individuals (e.g., inmass movements to the surface) just prior to spawning, enhancedfertilization success may result from such movements. ¹Present address: Friday Harbor Laboratories, Friday Harbor,WA 98250, USA.     

Composition and abundance of zooplankton under the spring sea-ice of McMurdo Sound,Antarctica

Summary Zooplankton was sampled through holes in the sea-ice of McMurdo Sound from 8 November to 10 December, 1985. Replicated vertical hauls were made to 100 and 300 m off Pram Point in the inner Sound, near the edge of the permanent McMurdo Ice Shelf. The zooplankton was sparse, averaging 2.5 mg/m³ wet weight. The numbers of individual species varied between catches, depths, and occasions. Generally, small copepods, particularly Oithona similis, Ctenocalanus citer and Oncaea curvata, numerically dominated the catches, and higher densities of these were present in the shallower 100 m layer. Deeper hauls contained higher numbers of larger crustaceans, particularly copepods Metridia gerlachei, Calanoides acutus and Euchaeta spp., ostracod Conchoecia belgicae and euphausiid Euphausia crystallorophias. Pteropods Limacina helicina and Clione limacina were also consistently caught, but in equal densities in 100 m and 300 m hauls. Numerous other plankters were caught in low numbers, including amphipods, chaetognaths, medusae, radiolarians, and larval nemerteans, barnacles, shrimps, polychaetes and echinoderms. Comparative samples from 40 km further north, off Cape Royds and near the sea edge of the fast sea-ice in Wohlschlag Bay, and to 100 m deep, contained a similar species diversity to those near the McMurdo Ice Shelf, but always with higher densities of L. helicina. On the last sampling occasions, when microalgae were conspicuous under the ice off Cape Royds, there were increased densities of microcopepods and Paralabidocera antarcticus, indicating different ecosystem processes from the inner Sound location.     

SOME OBSERVATIONS ON THE DIET AND DISTRIBUTION OF NUDIBRANCHS AT SIGNY ISLAND, ANTARCTICA

Observations were made on the diet and distribution of eightspecies of nudibranchs found in Borge Bay, Signy Island, Antarctica.Specimens from seven sites were examined in situ on four separateoccasions during 1992 and 1993 using SCUBA. A small collectionfor identification was also made Six of the eight species presentwere identified, and the first ecological data for at leastone species (Charcotia granulosa) were recorded. Notaeolidiagigas was feeding principally on hydroids of the genus Tubulariaover the entire depth range surveyed (3–36 m), and wasmost abundant in shallow water, whereas Truomella belli wasonly found at deeper sites, mostly on an octocoral of the genusAscolepis. Charcoaa granulosa and Pseudotritoma gracilidensappeared to be specialist bryozoan feeders and, as has beenfound at other locations, Austrodoris kerguelenesis specialisedon the demosponge Dendnlla antarcnca. Two unidentified aeolidspecies occurred almost entirely on particular hydroids andthe prey of Tritonia antarctica was not apparent. The physicalsize of Antarctic nudibranchs may have important implicationsto the type of prey and feeding strategy used by different species. (Received 11 May 1995; accepted 3 December 1995)     

Observations on the relationship between the Antarctic coastal diatoms Thalassiosira antarctica Comber and Porosira glacialis (Grunow) Jørgensen and sea ice concentrations during the late Quaternary

The available ecological and palaeoecological information for two sea ice-related marine diatoms (Bacillariophyceae), Thalassiosira antarctica Comber and Porosira glacialis (Grunow) Jørgensen, suggests that these two species have similar sea surface temperature (SST), sea surface salinity (SSS) and sea ice proximity preferences. From phytoplankton observations, both are described as summer or autumn bloom species, commonly found in low SST waters associated with sea ice, although rarely within the ice. Both species form resting spores (RS) as irradiance decreases, SST falls and SSS increases in response to freezing ice in autumn. Recent work analysing late Quaternary seasonally laminated diatom ooze from coastal Antarctic sites has revealed that sub-laminae dominated either by T. antarctica RS, or by P. glacialis RS, are nearly always deposited as the last sediment increment of the year, interpreted as representing autumn flux. In this study, we focus on sites from the East Antarctic margin and show that there is a spatial and temporal separation in whether T. antarctica RS or P. glacialis RS form the autumnal sub-laminae. For instance, in deglacial sediments from the Mertz Ninnis Trough (George V Coast) P. glacialis RS form the sub-laminae whereas in similar age sediments from Iceberg Alley (Mac.Robertson Shelf) T. antarctica RS dominate the autumn sub-lamina. In the Dumont d'Urville Trough (Adélie Land), mid-Holocene (Hypsithermal warm period) autumnal sub-laminae are dominated by T. antarctica RS whereas late Holocene (Neoglacial cool period) sub-laminae are dominated by P. glacialis RS. These observations from late Quaternary seasonally laminated sediments would appear to indicate that P. glacialis prefers slightly cooler ocean–climate conditions than T. antarctica. We test this relationship against two down-core Holocene quantitative diatom abundance records from Dumont d'Urville Trough and Svenner Channel (Princess Elizabeth Land) and compare the results with SST and sea ice concentration results of an Antarctic and Southern Ocean Holocene climate simulation that used a coupled atmosphere–sea ice–vegation model forced with orbital parameters and greenhouse gas concentrations. We find that abundance of P. glacialis RS is favoured by higher winter and spring sea ice concentrations and that a climatically-sensitive threshold exists between the abundance of P. glacialis RS and T. antarctica RS in the sediments. An increase to > 0.1 for the ratio of P. glacialis RS:T. antarctica RS indicates a change to increased winter sea ice concentration (to >80% concentration), cooler spring seasons with increased sea ice, slightly warmer autumn seasons with less sea ice and a change from ~ 7.5 months annual sea ice cover at a site to much greater than 7.5 months. In the East Antarctic sediment record, an increase in the ratio from <0.1 to above 0.1 occurs at the transition from the warmer Hypsithermal climate into the cooler Neoglacial climate (~ 4 cal kyr) indicating that the ratio between these two diatoms has the potential to be used as a semi-quantitative climate proxy.     

Prolonged nitrate exhaustion and diatom mortality: a comparison of polar and temperate Thalassiosira species

The survival of two diatom species. Thalassiosira antarcticaComber isolated from the Southern Ocean and Thalassiosira rotulaMeunier isolated from the North Sea. was investigated duringa 21 day nitrate-exhaustion period, both in the light and indarkness. Both species endured 3 weeks of nitrate exhaustionin the light by forming a physiological resting state, characterizedby the development of shrunken, chlorotic protoplasts, a decreasein photosynthetic capacity and the accumulation of particulateorganic carbon (POC). These resting cells of both species stillresumed growth after 21 days of nitrate exhaustion, althoughthe viability of the cells decreased with time of nitrate exhaustion.Growth rates during subsequent growth experiments decreasedwith lengthening pre-incubation time in nitrate exhaustion.The viability of T.antarctica resting cells was lower than thatof T.rotula. After 21 days in nitrate exhaustion, T.antarcticagrew at 31% of the initial division rate, whereas the growthrate of T.rotula was 61%. When growth was resumed, accumulatedPOC decreased and paniculate organic nitrogen (PON), chlorophylla and photosynthetic carbon assimilation increased during thesubsequent 5 day growth periods, but never reached initial values.Darkness had no effect on cellular POC. PON and chlorophylla content of both species. In T.rotula, the capacity for photosyntheticcarbon assimilation decreased to almost zero during the 21 daydark period, although survival capacity was not affected. Aftera lag phase of 1–5 days, growth was resumed at initialgrowth rates, indicating that the bulk of cells of both diatomspecies were still viable. Thus, in the dark, both Thalassiosiraspecies survived nutrient exhaustion without physiological impairment.     

FEEDING AND GROWTH OF THE AEOLID NUDIBRANCH CUTHONA NANA (ALDER AND HANCOCK, 1842)

Feeding and growth of the aeolid nudibranch Cuthona nana wasdocumented. Cuthona nana feeds specifically on the colonialhydroid Hydractinia echinata. Nudi-branchs were observed onhermit crab shells in Gos-port Harbor at the Isles of Shoals,Maine and on old bridge pilings near Gerrish Island, Maine. Grazing rates of nudibranchs (3–25 mm) were quantifiedover 24 hour periods in the laboratory. Larger nudibranchs consumedmore hydroid tissue feeding mostly on polyps, whereas smallerindividuals consumed less and fed on mat tissue. Grazing intensityin the field at Gosport Harbor was determined by estimatingthe area of grazed patches of hydroid colonies attached to hermitcrab shells. The average patch size was 5.75% of the total colonyarea. Growth rates for nudibranchs were determined in the laboratory.Growth rates were greatest prior to maturation and oviposition.Animals from Gerrish Island and Gosport Harbor decreased insize after oviposition due to senescence. Nudibranchs from GerrishIsland reached a maximum size of 12 mm, compared to 23 mm foranimals at Gosport Harbor. ^*Present address: Division of Science and Mathematics. Universityof Minnesota, Morris. Minnesota 56267, USA     

林氏果蝇线粒体DNA分析

本文对Tamura(1988)提纯mtDNA的方法进行改进,建立了林氏果蝇Drosophila lini 线粒体DNA大量制备的方法;对采自原产地台湾省的单雌晶系TAW3146.1的线粒体DNA用10种限制性内切酶进行了酶切,得出了林氏果蝇mtDNA的分子量大小为16.3kb;用双酶切法制作了林氏果蝇线粒体DNA酶切图谱,并与属于同一复合种组的D.Kikkawai的酶切图谱进行比较。所用的内切酶有XbaI、AvaI、EcoRV、ScaI、SacI、EcoR I、HindIII、PvuⅡ、BamHI、PstⅡ。     

Molluscan Community Recovery in a New England Back‐Barrier Salt Marsh Lagoon 10 Years after Partial Restoration

Like many Eastern U.S. salt marshes, East Harbor salt marsh lagoon on Cape Cod was isolated from tidal flow in the 1800s, resulting in near‐freshwater conditions and loss of native salt marsh species. After its partial restoration in 2002, a variety of marine and estuarine fauna recolonized East Harbor, and soft shell clam (Mya arenaria) recolonization was particularly prolific. The goal of our study was to evaluate molluscan community composition, density, and distribution at regular intervals for 10 years following restoration, and to relate molluscan community recovery to various physical properties at the site. In 2007, 2008, and 2011, we sampled mollusks at several points across East Harbor, and we also recorded water salinity and temperature, particle size distribution, and submerged aquatic vegetation density. In 2007 and 2008, we encountered 12 and 11 mollusk species, respectively; M. arenaria was the most abundant species in 2007 and the second most abundant species in 2008. In 2011, we encountered eight mollusk species and M. arenaria was the most abundant species. Mollusk species richness declined from 12 to 8 species between 2008 and 2011. Our results show that mollusk species richness and density have declined significantly since the first few years following restoration; related studies attribute this to high summer water temperatures in the Main Lagoon and severe macroalgal blooms during 2005–2006. This suggests that East Harbor is still equilibrating to baseline conditions and that full tidal restoration may be necessary to sustain a diverse mollusk community at East Harbor.     

Animal associations with the dominant species of shallow water macrophytes along the coastline of the Vestfold Hills,Antarctica

Benthic grab samples, taken through core holes in sea-ice 1983, returned eight species of marine macrophytes which had associated fauna on at least one sample. A total of 24 animal taxa were found on these eight macrophytes. Phyllophora antarctica had a significantly greater biomass of attached fauna per unit of macrophyte biomass than any of the other seven species. It also had the greatest variety of epiphytic fauna (21 taxa). Phyllophora antarctica was the only macrophyte collected from comparatively protected Ellis Fjord, apart from filamentous algae, including Cladophora subsimplex and Geminocarpus austrogeorgiae, which were found in the most landward basin. It therefore played an important role in the ecology of the fjord. Palmaria decipiens was commonly collected at more exposed coastal sites and was dominant in Long Fjord, characterized here as intermediate in terms of water movement. Sixteen animal taxa were collected from this macrophyte with the greatest numbers being found in July and August. Only four animal taxa were collected from Iridaea cordata. The other five macrophyte species from which epiphytic animals were collected (Porphyra endiviifolium, Plocamium cartilagineum, Desmarestia menziesii, Himantothallus grandifolius and Cladophora subsimplex had animals associated with them on less than half the occasions when they were found.     

Abiotic versus Biotic Drivers of Ocean pH Variation under Fast Sea Ice in McMurdo Sound,Antarctica

Ocean acidification is expected to have a major effect on the marine carbonate system over the next century, particularly in high latitude seas. Less appreciated is natural environmental variation within these systems, particularly in terms of pH, and how this natural variation may inform laboratory experiments. In this study, we deployed sensor-equipped moorings at 20 m depths at three locations in McMurdo Sound, comprising deep (bottom depth>200 m: Hut Point Peninsula) and shallow environments (bottom depth ∼25 m: Cape Evans and New Harbor). Our sensors recorded high-frequency variation in pH (Hut Point and Cape Evans only), tide (Cape Evans and New Harbor), and water mass properties (temperature and salinity) during spring and early summer 2011. These collective observations showed that (1) pH differed spatially both in terms of mean pH (Cape Evans: 8.009±0.015; Hut Point: 8.020±0.007) and range of pH (Cape Evans: 0.090; Hut Point: 0.036), and (2) pH was not related to the mixing of two water masses, suggesting that the observed pH variation is likely not driven by this abiotic process. Given the large daily fluctuation in pH at Cape Evans, we developed a simple mechanistic model to explore the potential for biotic processes – in this case algal photosynthesis – to increase pH by fixing carbon from the water column. For this model, we incorporated published photosynthetic parameters for the three dominant algal functional groups found at Cape Evans (benthic fleshy red macroalgae, crustose coralline algae, and sea ice algal communities) to estimate oxygen produced/carbon fixed from the water column underneath fast sea ice and the resulting pH change. These results suggest that biotic processes may be a primary driver of pH variation observed under fast sea ice at Cape Evans and potentially at other shallow sites in McMurdo Sound.     

The macrophytobenthos of Terra Nova Bay (Ross Sea,Antarctica): results of three Italian scientific expeditions

Abstract

The results of a study on the benthic macroalgal flora and vegetation of Terra Nova Bay (Ross Sea) carried out during the Italian expeditions to Antarctica made in the years 1987/88, 1989/90 and 1993/94, are presented. The flora is rather poor (9 Rhodophyceae, 4 Fucophyceae, 4 Chlorophyceae), but richer than that known from adjacent areas. The vegetation is on the whole characterized by a prevalence of sciaphilous species among which Iridaea cordata, Phyllophora antarctica and Clathromorphum lemoineanum dominating in the upper infralittoral, lower infralittoral and circalittoral zones, respectively. Moreover, the results of a study on biomass of a population of I. cordata as well as of a population of P. antarctica, carried out in the austral summer 1993/94, are reported too. The values of the biomass of the population of I. cordata resulted to vary inversely with respect to those of the population of P. antarctica.     

Concentration of trace metals in excrements of two species of penguins from different locations of the Antarctic Peninsula

The presence of metals in Antarctica is becoming an issue that needs to be more investigated as human presence is increasing in the region, especially in the Antarctic Peninsula, where most of the polar animals, scientific bases and tourists are concentrated. Penguins are endemic species of Antarctica situated at the top of food web and are useful sentinels of pollution. To improve data of trace metal contamination in the Antarctic Peninsula region, concentrations of Cd, Pb, As, Cu and Zn in fresh excrement of penguins were determined by atomic absorption. Samples were collected in several locations during the 2011/2012 austral summer: eight sites (O’Higgins Station, Yankee Harbour, Mikkelsen Harbor, Danco Island, Gonzalez Videla Base, Yelcho Station and Brown Station) from gentoo penguin (Pygoscelis papua) colonies and four locations (Hydrurga Rocks, Cape Shirreff, Narebski Point and Kopaitic Island) from chinstrap penguin (Pygoscelis antarctica) colonies. Data showed that gentoo penguin colonies had higher levels of metals (μg g^?1 dw) like Pb, Cu and Zn at locations such as O’Higgins (2.89 for Pb, 199.95 for Cu and 379.99 for Zn) and Gonzalez Videla (2.74 for Pb and 222.51 for Cu). Levels of Cd in excreta of chinstrap penguins were higher at Narebski Point (3.13 μg g^?1). The levels of Pb, As, Cd, Cu and Zn were similar or even higher to those reported in excreta of the same species by previous studies at Antarctica. Data suggest that metals ingested by these two penguin species feeding in the sea end up in terrestrial ecosystems.     

High ice nucleating ability in plant leaves

A high ice nucleating ability in leaves of Veronica persicaand Buxus microphylla was observed on analyzing the frequencydistribution of their freezing temperatures. The most efficientice nucleators in Veronica leaves exist in structures withinthe leaf blades (mesophyll), and those of Buxus in structureswithin the midrib (vascular tissue). Dissolved or suspendedleaf structures were much less effective. (Received March 16, 1973; )     

Short-term changes in the mesozooplanktonic community in theSeine ROFI (Region of Freshwater Influence)(eastern English Channel)

Discrete-depth, hourly mesozooplankton samples were collectedover a 92 h period in May 1992 at an anchor station within theSeine Region of Freshwater Influence (ROFI) (English Channel).The mesozooplankton community defined as a euryhaline marineassemblage was dominated by the calanoid copepods Acartia spp.,Temora longicornis and Centropages hamatus, the cladoceran Evadnenordmanni and the appendicularian Oikopleura dioica. The semi-diurnaltidal current was the dominant factor in determining the short-termtemporal changes in the community in terms of density and speciescomposition so that zooplankton patches displayed oscillatingmotion in relation to tidal advection. Although a few species(e.g. Pleurobrachia pileus) exhibited higher densities aroundlow tide, maximum densities were observed for most species (e.g.T.longicornis and E.nordmanni) around high tide, according tosalinity variations. Diurnal changes were only reported forcyclopoid copepods (i.e. Halicyclops sp. and Cyclopina sp.)which wer$$$ mainly endobenthic during the day and moved intothe water column at night. Besides temporal changes in depth-averageddensities, most species exhibited vertical migrations at dieland/or tidal periods. Tidal vertical migrations were reportedonly for a few taxa and could be the result of passive mechanisms(e.g. vertical mixing) rather than of active behaviour. Dielvertical migrations were observed in most of the abundant taxa.While this migration pattern did not appear to be an adaptationto predator avoidance within the Seine ROFI, it could regulatehorizontal transport of organisms and promote their retention.The consequences of the short-term mesozooplankton fluctuationsfor sampling designs are discussed.     

Root Cell Ultrastructure in Developing Aerenchyma Tissue of Three Wetland Species

Patterns of root cortex cell development and ultrastructurewere analysed in Sagittaria lancifolia L., Thalia geniculataL. and Pontederia cordata L. using scanning and transmissionelectron microscopy (SEM, TEM). In all three species, cortexcells were arranged in radial columns extending from the endodermisto the hypodermis/epidermis. During gas space formation, thecortex cells elongated parallel to the root radius and shrankin the plane perpendicular to the radius leaving long and thinrows of cortex cells extending from the endodermis to the epidermis.Although the cortex cells appeared collapsed in tissue withwell-developed gas spaces, TEM revealed that the cortical cellsas well as the epidermal cells maintained intact membranes andmany normal organelles. Formation of root cortex tissue withwell-developed gas spaces does not require cell death in thesespecies. Living cortex cells in root tissue with mature gasspaces could provide a symplastic pathway for transport betweenthe root stele and the living epidermal cells. Copyright 2000Annals of Botany Company Sagittaria lancifolia, Thalia geniculata, Pontederia cordata, aerenchyma, root, wetland, development     

Microheterogeneity of N-glycosylation on a stylar self-incompatibility glycoprotein of Nicotiana alata

Gametophytic self-incompatibility, a mechanism that preventsinbreeding in some families of flowering plants, is mediatedby the products of a single genetic locus, the S-locus. Theproducts of the S-gene in the female sexual tissues of Nicotianaalata are an allelic series of glycoproteins with RNase activity.In this study, we report on the microheterogeneity of N-linkedglycosylation at the four potential N-glycosylation sites ofthe S²-glycoprotein. The S-glycoproteins from N.alata containfrom one to five potential N-glycosylation sites based on theconsensus sequence Asn-Xaa-Ser/Thr. The S²-glycoprotein containsfour potential N-glycosylation sites at Asn²⁷, Asn³⁷, Asn¹³⁸and Asn¹⁵⁰, designated sites I, n, IV and V, respectively. SiteIII is absent from the S₂-glycoprotein. Analysis of glycopeptidesgenerated from the S₂-glycoprotein by trypsin and chymotrypsindigestions revealed the types of glycans and the degree of microheterogeneitypresent at each site. Sites I (Asn²⁷) and IV (Asn¹³⁸) displaymicroheterogeneity, site II (Asn³⁷) contains only a single typeof N-glycan, and site V (Asn¹⁵⁰) is not glycosylated. The microheterogeneityobserved at site I on the S₂-glycoprotein is the same as thatobserved at the only site, site I, on the Srglycoprotein (Woodwardet al., Glycobiology, 2, 241-250, 1992). Since the N-glycosylationconsensus sequence at site I is conserved in all S-glycoproteinsfrom other species of self-incompatible solanaceous plants,glycosylation at this site may be important to their function.No other post-translational modifications (e.g. O-glycosylation,phosphorylation) were detected on the S₂-glycoprotein. fertilization microheterogeneity N-glycans plants RNase     

Dynamics of antarctic penguin populations in relation to inter-annual variability in sea ice distribution

To investigate the role of sea ice cover on penguin populations we used principal component analysis to compare population variables of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins breeding on Signy Island, South Orkney Islands with local (from direct observations) and regional (from remote sensing data) sea ice variables. Throughout the study period, the Adélie penguin population size remained stable, whereas that of chinstrap penguins decreased slightly. For neither species were there significant relationships between population size and breeding success, except for an apparent inverse density-dependent relationship between the number of Adélie breeding pairs and the number of eggs hatching. For both species, no general relationship was found between either population size or breeding success and the local sea ice conditions. However, the regional sea ice extent at a particular time prior to the start of the breeding season was related to the number of birds that arrived to breed. For both species, this period occurred before the sea ice reached its maximum extent and was slightly earlier for Adélie than for chinstrap penguins. These results suggest that sea ice conditions outside the breeding season may play an important role in penguin population processes.     

Epiphytic ferns and bryophytes of Tasmanian tree‐ferns: A comparison of diversity and composition between two host species

Abstract Ferns, bryophytes and lichens are the most diverse groups of plants in wet forests in south‐eastern Australia. However, management of this diversity is limited by a lack of ecological knowledge of these groups and the difficulty in identifying species for non‐experts. These problems may be alleviated by the identification and characterization of suitable proxies for this diversity. Epiphytic substrates are potential proxies. To evaluate the significance of some epiphytic substrates, fern and bryophyte assemblages on a common tree‐fern species, Dicksonia antarctica (soft tree‐fern), were compared with those on a rare species, Cyathea cunninghamii (slender tree‐fern), in eastern Tasmania, Australia. A total of 97 fern and bryophyte species were recorded on D. antarctica from 120 trunks at 10 sites, and 64 species on C. cunninghamii from 39 trunks at four of these sites. The trunks of C. cunninghamii generally supported fewer species than D. antarctica, but two mosses (particularly Hymenodon pilifer) and one liverwort showed significant associations with this host. Several other bryophytes and epiphytic ferns showed an affinity for the trunks of D. antarctica. Species assemblages differed significantly between both sites and hosts, and the differences between hosts varied significantly among sites. The exceptionally high epiphytic diversity associated with D. antarctica suggests that it plays an important ecological role in Tasmanian forests. Evidently C. cunninghamii also supports a diverse suite of epiphytes, including at least one specialist species.     

Intertidal benthic communities associated with the macroalgae <Emphasis Type="Italic">Iridaea cordata</Emphasis> and <Emphasis Type="Italic">Adenocystis utricularis</Emphasis> in King George Island,Antarctica

Antarctic benthos has been a main target in Antarctic research, but very few quantitative studies have been carried out in the littoral zone, which may be seasonally covered by macroalgae. In this work, we studied (1) cover and biomass of the macroalgae Iridaea cordata and Adenocystis utricularis, and (2) composition of macrobenthic assemblage associated with these macroalgal species at three locations at King George Island: Mareograph Beach (1 M), Tank’s Bay (2R) and Ardley Bay (3R). Iridaea cordata was collected by completely detaching the algae from the substrate, while A. utricularis was scraped. Adenocystis utricularis covered more than 80 % of the substrate at all locations, while coverage of Iridaea cordata was below 53 % or absent (3R). Fresh biomass of I. cordata was 0.8–61.4 g/individual and 4.7–93.0 g/100 cm² for A. utricularis. The assemblage associated with both macroalgae differed significantly between sites. The studied fauna was composed mainly of amphipods, gastropods and bivalves. Species diversity was higher in the community associated with A. utricularis. A total of ~27 ind/g DW were found associated with I. cordata, while ~112 ind/g DW were found associated with A. utricularis. The most abundant groups associated with I. cordata were amphipods at 1 M (57 %) and gastropods at 2R (46 %). Both groups were responsible for the dissimilarity between localities (62.50 %). The most abundant groups associated with A. utricularis were the gastropods at all localities reaching up to 82 % at 1 M. This study provides a first baseline on the diversity and abundance of benthic assemblages associated with intertidal macroalgae in the southwest of King George Island.