Copepods in spring annual sea ice at Terra Nova Bay (Ross Sea,Antarctica)

The aim of this study was to investigate patterns of abundance, distribution, temporal changes and species composition of the dominant ice-associated copepods in the spring annual pack ice, platelet ice and water column at Terra Nova Bay, Ross Sea, during late spring 1997. Ice cores were drilled for temporal and spatial scales. Stephos longipes and Harpacticus furcifer dominated the sea ice meiofauna in terms of numbers in the lower few centimeters of the bottom ice associated with high chlorophyll a and phaeopigment levels. Nauplii dominated the S. longipes population (91.6%) and occurred in extremely high concentrations. In contrast, copepodids were the dominant stages in H. furcifer. How H. furcifer carries out its entire life cycle and how it differs from ecologically similar species such as Drescheriella glacialis should be examined in more detail.     

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.     

Spatio-temporal distribution and abundance of <Emphasis Type="Italic">Euphausia crystallorophias</Emphasis> in Terra Nova Bay (Ross Sea,Antarctica) during austral summer

Average abundance values for Euphausia crystallorophias in the shelf region of Terra Nova Bay were generally high. Mean number of adults and juveniles were 20 and 87 ind/m², respectively, while larval concentrations were much higher, reaching a mean of 14,764 ind/m². Euphausia crystallorophias were very patchy in their distribution during all stages of their life cycle. The distribution patterns of E. crystallorophias in TNB seem to be strictly correlated both to hydrological features such as the presence of polynyas, pack-ice zone and certain temperatures values. According to our data, E. crystallorophias spawned from early October to early January. For the two age groups (0+ and 1+) an average growth rate of 0.074 and 0.076 mm/day was found, respectively. The mean biomass of larval E. crystallorophias (from Metanauplius to Furcilia I) in January was estimated as 84 mg WW/m². This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.     

Microbial loop malfunctioning in the annual sea ice at Terra Nova Bay (Antarctica)

We investigated organic carbon quantity and biochemical composition, prokaryotic abundance, biomass and carbon production in the annual and platelet sea ice of Terra Nova Bay (Antarctica), as well as the downward fluxes of organic matter released by melting ice during early spring. Huge amounts of biopolymeric C accumulated in the bottom layer of the ice column concomitantly with the early spring increase in sympagic algal biomass. Such organic material, mostly accounted for by autotrophic biomass, was characterised by a high food quality and was rapidly exported to the sea bottom during sea ice melting. Prokaryote abundance (up to 1.3 × 10⁹ cells L⁻¹) and extracellular enzymatic activities (up to 24.3 μM h⁻¹ for amino-peptidase activity) were extremely high, indicating high rates of organic C degradation in the bottom sea ice. Despite this, prokaryote C production values were very low (range 5–30 ng C L⁻¹ h⁻¹), suggesting that most of the degraded organic C was not channelled into prokaryote biomass. In the platelet ice, we found similar organic C concentrations, prokaryote abundance and biomass values and even higher extracellular enzymatic activities, but values of prokaryote C production (range 800–4,200 ng C L⁻¹ h⁻¹) were up to three orders of magnitude higher than in the intact bottom sea ice. Additional field and laboratory experiments revealed that the dissolved organic material derived from algae accumulating in the bottom sea ice significantly reduced prokaryote C production, suggesting the presence of a potential allopathic control of sympagic algae on prokaryote growth. This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.     

Photoacclimation in Antarctic bottom ice algae: an experimental approach

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. This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.     

Organic-matter degradative potential of Halomonas glaciei isolated from frazil ice in the Ross Sea (Antarctica)

Halomonas glaciei isolated from frazil ice in the Ross Sea (Antarctica) during austral summer 2003 was phenotypically characterized and its capability of degrading organic matter was tested. We evaluated specific bacterial growth rates (mu) to understand at which temperatures bacterial growth shows a linear and direct relationship with the available substrate (4-22 degrees C) and afterwards we tested H. glaciei growth curves and degradative potential at 0, 10 and 37 degrees C using two different media (one enriched and one depleted in PO(4)). The strain grew exponentially only at 10 degrees C. The fastest hydrolysis rates were expressed by enzymes aimed at polysaccharide degradation (alpha-d-glucosidase, beta-d-glucosidase and beta-d-galactosidase) while alkaline phosphatase and aminopeptidase activities were rather low. Our data suggest a preferential demand for carbon derived from carbohydrates rather than from proteins: ectoenzyme activities transformed into carbon mobilization from organic polymers, showed that the total carbon potentially released from polysaccharides can be almost one order of magnitude higher than the protein carbon mobilization. Principal component analysis of the enzyme affinity separated the six experimental conditions, highlighting how different physical (temperature) and chemical (PO(4) enrichment or depletion) features actively lead to a differentiation in the efficiency of the ectoenzymes produced, resulting in preferential degradation of diverse kinds of organic substrates.     

A new Polygordius (Annelida: Polychaeta) from Terra Nova Bay, Ross Sea, Antarctica

Polygordius antarcticus sp. nov. is described from benthic material collected at depths ranging between 31 and 61 m in Terra Nova Bay, Ross Sea, during the 1987–1988 and 1988–1989 expeditions of the Italian National Research Program in Antarctica. This is the first named species of the genus from Antarctic waters. Although no fully mature specimens were available, the new species appears unique in combining the following features: a regular pygidium, inflated and with a single ring of round adhesive pads, a conical prostomium with short antennae (only half as long as the prostomium) and shallow head fold, and a well-developed circulatory apparatus, with circumoesophageal commissures entering the prostomium and long intersegmental commissures insinuating into the ventrolateral compartments of the trunk. These and other significant features were investigated by light and scanning electron microscopy. In the construction of the head and the scheme of the blood system, the new species resembles Polygordius triestinus Woltereck, described by Hempelmann in 1906, an aberrant species inhabiting muddy, anoxic sediments in the Adriatic Sea, but it differs significantly from it in the shape of the mouth (in P. triestinus the upper lip is hypertrophied and strongly protruding) and the pygidium (in P. triestinus this region is stump-like and non-adhesive). The pygidium of P. antarcticus sp. nov. is encircled by 28–30 small adhesive pads, each with 15–20 glandular openings. Preterminal cirri are lacking, as are perianal appendages. The anus is surrounded by six to seven lobes of which the midventral is largest and longest. A world distribution map of the genus is provided. Accepted: 27 August 1998     

Growth form analysis of epiphytic diatom communities of Terra Nova Bay (Ross Sea, Antarctica)

Diatoms have been long collected from the Southern Ocean but almost no data exist for epiphytic communities, despite their high ecological significance as an important food source in Antarctic coastal food chains. Here, we present a first growth form analysis of diatoms associated with rhodophyte hosts from Terra Nova Bay, Ross Sea, Antarctica. We performed this study to gather baseline information on the species composition of epiphytic diatom communities, determine the influence of some environmental variables on the diatom distribution patterns, and assess the caveats that must be taken into account in terms of sampling design. Macroalgal material was collected during the Italian Antarctic expeditions between 1990 and 2004. Epiphytic diatoms were studied by means of scanning electron microscopy. In terms of growth forms, there were no significant differences between the diatom communities on the different macroalgal host species. Motile (mainly small-celled Navicula perminuta and other Navicula spp.) and adnate (Cocconeis spp.) diatoms dominated the community throughout the study period. Many of the macroalgal blades examined were also covered by epiphytic animals (calcareous bryozoans, hydroids) over most of their surface, with a significant effect on the associated diatom community structure. Our findings suggest that the bio-physicochemical characteristics of each sampling site affected the epiphytic diatom communities more than the substrate type provided by the macroalgal host or the sampling depth.     

Structural and functional properties of sympagic communities in the annual sea ice at Terra Nova Bay (Ross Sea, Antarctica)

Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S, 164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition, microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to 35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations in the intact sea ice ranged from 0.5 to 2.3 mg l⁻¹ and 0.2 to 2.0 mg l⁻¹, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l⁻¹ h⁻¹ ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom layer was high, increasing during the sampling period from 680 to 2480 μg l⁻¹. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities. The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P ^B _max of 0.12 mgC mg Chl⁻¹ and low photoadaptation index (E _k=18 μE m⁻² s⁻¹, E _m=65 μE m⁻² s⁻¹). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m⁻² s⁻¹. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms. Accepted: 4 August 1999     

Biodiversity of cultivable psychrotrophic marine bacteria isolated from Terra Nova Bay (Ross Sea, Antarctica)

A set of 146 Antarctic marine isolates from the Ross Sea was characterized by a combination of molecular techniques in order to determine the degree of inter- and intraspecific variability. Isolates were analyzed by amplified rDNA restriction analysis (ARDRA) using the tetrameric enzyme AluI, resulting in 52 different groups, corresponding to at least 52 different bacterial species, indicating a high degree of interspecific variability. The phylogenetic position of bacteria belonging to some ARDRA groups was obtained by sequencing of 16S rDNA. Random amplified polymorphic DNA (RAPD) analysis, carried out on the largest ARDRA groups, revealed a high intraspecific genetic variability, too. The analysis of plasmid content revealed the existence of horizontal gene transfer between strains belonging to the same and to different species. A comparison of the whole body of morphological, physiological and biochemical data was finally carried out.     

Benthic isopods (Crustacea,Malacostraca) from the Ross Sea,Antarctica: species checklist and their zoogeography in the Southern Ocean

In this study isopod species of the Ross Sea were investigated. Literature until May 2008 was checked to provide an overview of all known and described species in the Ross Sea. This species checklist was then enlarged through material of the 19th Italica expedition in 2004. During this expedition for the first time a small mesh net (500 μm) was used. Nine thousand four hundred and eighty one isopod specimens were collected during this expedition. Through this material the number of isopod species in the Ross Sea increased from 42 to 117 species, which belong to 20 families and 49 genera. Fifty-six percentage of the isopods species collected during the Italica expedition are new to science. The zoogeography of the 117 species was investigated. A non-transformed binary presence-absence data matrix was constructed using the Bray–Curtis coefficient. The results were displayed in a cluster analysis and by nonmetric multidimensional scaling (MDS). This paper gives a first insight into the occurrence and distribution of the isopod species of the Ross Sea.     

Adaptive morphology of Capulus subcompressus Pelseneer, 1903 (Gastropoda: Capulidae) from Terra Nova Bay, Ross Sea (Antarctica)

Capulus subcompressus Pelseneer, 1903 (Gastropoda: Capulidae) is a small epibiont gastropod living at Terra Nova Bay (Ross Sea) down to 540 m on the calcareous tubes of its unique host, the serpulid Serpula narconensis Baird, 1865. This polychaete forms bush-like aggregates which host a rich microfauna of crustaceans, hydroids and molluscs. In contrast to all other capulids, C. subcompressus shows an evident oval shell aperture, which is due to an allometric growth that can be imputed to the Serpula tube morphology. Since the allometric growth is detectable in all size classes, it could be deduced that the compressed shape of the C. subcompressus shell is the stable result of a significant evolutionary history which binds tightly these two species in Antarctic waters. Accepted: 17 July 1999     

The trophic role and ecological implications of oval faecal pellets in Terra Nova Bay (Ross Sea)

We studied the role of oval faecal pellets in the carbon-cycle dynamics of the Antarctic coastal area in a laboratory experiment on pellet degradation over time. We observed a rapid increase in the bacterial biomass until 56 h (from 14.73 to 91.09 µgC/l), but a drop to 25.83 µgC/l at the end of the experiment. Dissolved proteins decreased rapidly (from 1,342.7 to 1,177.0 µg/l in the first 32 h) as did nitrate (from 1 to 0.43 µm in the first 56 h), confirming their consumption by microorganisms, but they were observed to increase in the second part of the experiment, up to 1,618.3 µg/l and 17.36 µm for the dissolved proteins and nitrate, respectively. The proteolytic activity increased throughout the incubation from 302.65 nmol/l per hour to 6,641.08 nmol/l per hour, especially in the second half of the experiment. Therefore, we concluded that the microbial community is able to produce, consume and remineralise the available organic substrates and to increase organic-pool quality and inorganic nutrient concentrations dissolved in the overlying water.     

Lipolytic activity of Antarctic cold-adapted marine bacteria (Terra Nova Bay, Ross Sea)

AIMS: The aim of this study was to investigate the lipolytic activity of cold-adapted Antarctic marine bacteria and, furthermore, the combined effect of some environmental factors on this enzymatic process. METHODS AND RESULTS: Strains were assayed for lipolytic activity on a basal medium amended with seven individual fatty acid esters. A significant activity was observed for 148 isolates (95.5% of the total screened). The interactive effect of pH, temperature and NaCl concentration on the substrates was tested for six representative isolates, identified as Pseudoalteromonas, Psychrobacter and Vibrio. Differences between strains according to NaCl and pH tolerances were observed. Only one strain degraded the substrate more efficiently at 4 degrees C than at 15 degrees C. CONCLUSIONS: Our findings demonstrate that the lipolytic activity of Antarctic marine bacteria is rather variable, depending on culture conditions, and occurs in a wide range of salt concentration and pH. SIGNIFICANCE AND IMPACT OF THE STUDY: Isolation and characterization of bacteria that are able to efficiently remove lipids at low temperatures will provide insight into the possibility to use cold-adapted bacteria as a source of exploitable enzymes. Moreover, research on the interactive effects of salt concentration, pH and temperature will be useful to understand the true enzyme potentialities for industrial applications.     

Polychaete populations of the shallow soft bottoms off Terra Nova Bay (Ross Sea, Antarctica): distribution, diversity and biomass

 Diversity, distribution and biomass patterns of polychaetes were studied in the shallow soft bottoms off Terra Nova Bay (Ross Sea, Antarctica). Benthic samples, collected in the austral summer 1989–1990, were sampled using a Van Veen grab at 14 stations distributed between 23- and 194-m depth. A total of 5,768 individuals of polychaetes belonging to 77 species were found. The species richness recorded was high, despite the few biotopes investigated at Terra Nova Bay in this study, especially when compared to that recorded from previous investigations in the same area and from the whole Ross Sea (146 species). Despite the high number of species found, only a few species accounted for 76% of the total abundance: Tharyx cincinnatus (27%), Spiophanes tcherniai (23%), Leitoscoloplos mawsoni (18%) and Laonice weddellia (5%) were mainly distributed in the deeper stations (below 100-m depth), while Aglaophamus ornatus (3%) was the only species abundant in the shallowest stations (above 50-m depth), characterized by gravels and coarse sands. Species richness, diversity and evenness showed an increase with depth. Abundances ranged between 40 to over 12,000 ind/m². Biomass values ranged between 0.9 to 176 g/m² (wet weight). A trophic-guild classification revealed the occurrence of various feeding categories that were, however, numerically dominated by deposit feeders with both discretely motile epiand endobenthic forms, and sessile ones. Both the Bray-Curtis similarity and Correspondence (C.A.) analyses showed stations ordered according to depth and to the local dominance of some species. Both poorly and well-structured polychaete assemblages occurred and they seemed related to depth-related factors, such as degree of environmental disturbance (shallowest bottoms vs deep ones), heterogeneity of the substrate and habitat complexity (gravel and coarse sands vs mixed sediment. The richest and most diverse assemblages of polychaetes were those occurring below 140-m depth, where the substrate was dominated by medium sands, often mixed with a mosaic of rocks and boulders. Received: 30 October 1995/Accepted: 1 May 1996     

Age and productivity of the Antarctic scallop, Adamussium colbecki, in Terra Nova Bay (Ross Sea, Antarctica)

Body size, geographical distribution, and biomass make Adamussium colbecki (Smith, 1902) one of the most conspicuous bivalve species in the Antarctic. Based on samples collected in austral summer 1999/2000 in Terra Nova Bay, the annual formation of shell growth bands visible on X-ray photographs was verified by stable isotope analysis. A general von Bertalanffy growth function was fitted to size-at-age data of 25 individuals (H_∞=108.86 mm, K=0.114 year⁻¹, t₀=−0.367, D=1.284). Somatic production calculated from mass-specific growth rates was 234.6 kJ m⁻² year⁻¹. Gonadal productivity amounted to 70.92 kJ m⁻² year⁻¹. Annual somatic and gonad production-to-biomass ratios (P/B) were 0.199 and 0.052, respectively. According to its consumption and production, A. colbecki is likely to play a significant role in the trophic web of Terra Nova Bay.     

Distribution and abundance of postlarval and juvenile Pleuragramma antarcticum (Pisces, Nototheniidae) off Terra Nova Bay (Ross Sea, Antarctica)

During the Italian Antarctic Expedition of 1987–1988 zooplankton was collected in Terra Nova Bay (Ross Sea) by a multinet BIONESS (250-μm or 500-μm net mesh size). The early life history of Pleuragramma antarcticum was described from 268 samples. More than 98% of a total of 34,436 fish larvae belonged to P. antarcticum. The mean relative abundance in the whole area for positive 0 to 150-m hauls was 434 ind./100 m³ (±720 SD). Postlarvae were most abundant and frequent in the samples (99.8%) while low concentrations of juveniles were found (n=67). Length of age group 0 ranged from 8 to 20 mm and age group 1+ were from 36 to 53 mm. Average growth rate over a period of 1 year was 0.08 mm per day. Based on modal values, the mean daily increment of P. antarcticum postlarvae in the period 5 January to 2 February (29 days) was about 0.21 mm. Highest abundances occurred near Cape Washington (mean: 2,108 ind./100 m³) while lower densities were recorded in the northern basin of the self (31 ind./100 m³). Horizontal and vertical distribution patterns in Terra Nova Bay seem to be strictly correlated to hydrographic features and different water masses with highest densities associated with the westward flowing current of the limb of the Antarctic coastal current and southern limb of the Ross Sea Gyre. These currents become part of the clockwise gyre in Terra Nova Bay. More than 62% of the postlarvae were collected in well-stratified warm surface water (0–50 m) near the summertime thermocline (20–70 m). The northern part of Terra Nova Bay seems to represent nursery ground of early stages of P. antarcticum and the presence of permanent polynya could provide favourable food conditions for development of the first stages of life. Differing distribution patterns probably reflect an interaction of various parameters including bathymetry, floating ice shelf, hydrographic features such as currents, local eddies and frontal systems, with P. antarcticum postlarval biology (spawning) and ecology (feeding, horizontal and vertical distribution patterns). Received: 10 June 1996 / Accepted: 19 July 1997