Phytoplankton Ecology in the Fjords of the Vestfold and Larsemann Hills
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From the abstract of the referenced paper: Spring phytoplankton communities in the water column of Ellis Fjord are characterised by diatoms originating from the bottom sea-ice strand community. Upon ice break-out in early summer, these are replaced by blooms of the phytoflagellates, Phaeocystis puchetii, Cryptomonas cryophila, Pyramimonas gelidicola, silicoflagellates and dinoflagellates. The narrow entrance of the fjord and the development of summer stratification is probably limiting the availability of nutrients and containing the magnitude of the small bloom (maximum 2.8 million cells per litre).
Biology of Antarctic Algae
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Metadata record for data from ASAC Project 102 See the link below for public details on this project. From the abstracts of some of the referenced papers: Six species of marine microalgae, namely Phaeodactylum tricornutum Bohlin, Dunaliella tertiolecta Butcher, Isochrysis galbana Parke, Porphyridium purpureum (Bory) Ross, Chroomonas sp., and Oscillatoria woronichinii Anis., have been examined with respect to their gas exchange characteristics and the inorganic carbon species taken up by the cells from the bulk medium. All species showed a high affinity, in photosynthesis, for inorganic carbon and low CO2 compensation concentrations. Such data are suggestive of operation of a 'CO2-concentrating mechanism' in these microalgae. Direct measurements of internal organic carbon pools in four of the species studied confirm this (O. woronichinii and Chroomonas were not tested). By comparison of achieved photosynthetic rates with calculated rates of CO2 supply from the dehydration of bicarbonate, it was shown that Phaeodactylum, Porphyridium and Dunaliella could utilise the bicarbonate present in the medium. Data for the other species were inconclusive although the pH dependence of K 1/2CO2 for photosynthesis by Oscillatoria indicated that this species too could utilise bicarbonate. Such observations could, however, not be used as evidence that, at least in the eucaryotic algae examined, bicarbonate was the inorganic carbon species crossing the plasmalemma as Phaeodactylum, Porphyridium and Dunaliella, and Isochrysis all showed the presence of carbonic anhydrase activity in intact cells as well as in crude extracts. 'External' carbonic anhydrase activity represented from 1/4 to 1/2 of the total activity in the cells of these algae. It is concluded that, as a consequence of a CO2-concentrating mechanism, photorespiration was suppressed in the marine microalgae examined although the data obtained did not allow any firm conclusions to be drawn regarding the species of inorganic carbon transported into the cell. Analysis of the age composition of a given species within a community is fundamental to any study of population dynamics and to the subsequent analyses of community interactions such as competition, succession and productivity. A problem exists in that calendar age often provides little information on the role played by any given individual plant within a population. For many populations the most useful definition of population structure is obtained from an analysis of both the functional age and the vitality of the component plants. Data from such studies on populations of marine macroalgae are lacking mainly because of the lack of suitable methods. This paper provides a review of the methods which have ben applied to such analyses in both terrestrial and marine communities, discusses these methods in the context of marine algae and presents the results of a case study on the analysis of population structure in the large brown alga Durvillaea potatorum. Evidence is presented for the occurrence of sexual reproduction including plasmogamy and meiosis, events previously undescribed in the life history of Ascoseira mirabilis. Ascoseira is monoecious. Gametangia are formed in chains within conceptacles. Synaptonemal complexes, structures concerned with chromosome pairing in meiosis, have been observed in the nucleus of gametangial initials. Mature male and female gametes have the same size and appearance, and resemble typical brown algal zoids. Sexual interaction begins after the female gamete settles down, and both zygotes and unfused gametes develop into sporophytes. It is concluded that Ascoseira has the same basic pattern of life history that characterises the order Fucales, and it is argued that this is probably the result of convergent evolution rather than being indicative of close phylogenetic relationship. Life histories are of central importance in understanding evolution and phylogeny of brown algae. Like other hereditary
Phytoplankton Distribution in Surface Samples and Cores from Prydz Bay and Long Fjord and its Relationship to Sea Level and Climatic Change
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Metadata record for data from ASAC Project 492 See the link below for public details on this project. From the abstracts of the referenced papers: Diatom assemblages in two Holocene sediment cores (GC1 and GC2) from the Mac. Robertson Shelf, East Antarctica, are compared with modern sedimentary diatom assemblages from the same area. Open marine deposition commenced in Iceberg Alley (GC1), on the outer continental shelf, greater than 10.7 adj. 14C kyr BP. Chaetoceros resting spores, which may indicate water-column stabilsation from melting glacial and/or sea ice or the maximum summer sea-ice retreat, dominate the diatom assemblage. Approximately 7.5 adj. 14C kyr BP, a sea-ice diatom assemblage was deposited. This assemblage is similar to that being deposited in the surface sediments of the Mac. Robertson Shelf today and suggests that perennial sea ice has persisted in the vicinity of Iceberg Alley since that time. Interbedded within the sea-ice assemblage, however, are Corethron-rich sediment layers that suggest mid- to late-Holocene high-productivity events associated with a climatic optimum. The diatom record from Nielsen Basin (GC2), on the inner continental shelf, is relatively uniform compared to that in GC1. Glacial ice was present over the region c. greater than 5.6 adj. 14C kyr BP and a dissolution diatom assemblage was deposited beneath it. following ice retreat, an ice-edge diatom assemblage was deposited briefly before sea-ice conditions similar to that on the continental shelf today developed. There is no evidence in GC2 for the mid- to late-Holocene high-productivity events identified in GC1. Four diatom assemblages are identified from the surface sediments of Prydz Bay and the Mac. Robertson Shelf using multivariate analysis. A coastal assemblage is characterised by the sea-ice diatoms Fragilariopsis curta, F. angulata, F. cylindrus and Pseudonitzschia turgiduloides. A continental shelf assemblage is characterised by the open-water diatoms Fragilariopsis kerguelensis, Thalassiosira lenuginosa, T. gracilis var. expecta and Trichotoxin reinboldii. The Cape Darnley assemblage contains both sea-ice and open-water diatoms, but all are characteristically large and heavily silicified. Multiple regression has been used to identify the relationships between the diatom assemblages and known environmental variables. There are strong correlations between the coastal, shelf and oceanic assemblages and ecological conditions, including latitude, sea-ice distribution and ocean currents. The Cape Darnley assemblage is thought to represent an assemblage from which the smaller and more lightly silicified species have been removed by current winnowing. The palaeo-depositional environment of inner Prydz Bay, East Antarctica, has been reconstructed for the past 21,320 14C yr B.P., using diatom assemblages and sediment facies from a short, 352 cm long gravity core. Between 21,320 and 11,650 14C yr B.P., compact tillite and diamicton are present in the core, and diatom frustules are rare to absent. These data suggest that an ice sheet grounded over the site during the last glacial maximum. Following glacial retreat, siliceous muddy ooze was deposited, from 11,650 to 2600 14C yr B.P., in an open marine setting. During this stage, diatom frustules are abundant and well preserved, and Thalassiosira antarctica resting spores and Fragilariopsis curta dominate the assemblage. This assemblage suggests open marine deposition in an environment where the spatial and temporal distribution of sea ice is less than today. Since 2600 14C yr B.P., sea-ice and ice-edge diatom species have become more abundant, and neoglacial cooling is inferred. The assemblage is similar to that forming currently in Prydz Bay, where sea-ice is absent (less than 10% cover) for 2-3 months of the year and permanent ice edge and/or multiyear sea ice remains in close proximity to the site.
Casey marine sediment meiofauna 2005
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Marine sediment meiofauna community composition and sediment environmental data collected in 2005 and published in Stark, J. S., M. Mohammad, A. McMinn, and J. Ingels. 2020. Diversity, abundance, spatial variation and human impacts in marine meiobenthic nematode and copepod communities at Casey station, East Antarctica. Frontiers in Marine Science 7:480. From the abstract: The composition, spatial structure, diversity and abundance of Antarctic nematode and copepod meiobenthic communities was examined in shallow (5 – 25 m) marine coastal sediments at Casey Station, East Antarctica. The sampling design incorporated spatial scales ranging from 10 meters to kilometres and included testing for human impacts by comparing disturbed (metal and hydrocarbon contaminated sediments adjacent to old waste disposal sites) and control areas. A total of 38 nematode genera and 20 copepod families were recorded with nematodes being dominant, comprising up to 95% of the total abundance. Variation was greatest at the largest scale (km’s) but each location had distinct assemblages. At smaller scales there were different patterns of variation for nematodes and copepods. There were significant differences between communities at control and disturbed locations. Community patterns had strong correlations with concentrations of anthropogenic metals in sediments as well as sediment grain size and total organic content. Given the strong association with environmental patterns, particularly anthropogenic disturbance, meiofauna may be seen as very useful indicators of natural and anthropogenic environmental changes in Antarctica. Methods derived from: Stark, J. S., M. Mohammad, A. McMinn, and J. Ingels. 2020. Diversity, abundance, spatial variation and human impacts in marine meiobenthic nematode and copepod communities at Casey station, East Antarctica. Frontiers in Marine Science 7:480. Sampling design Sampling was undertaken using a hierarchical, nested design with three spatial scales, Locations (separated by kms); within each location there were two sites (~ 100 m apart) and at each site there were two plots (~10m apart). Within each plot (1m diameter), two replicate cores were taken for meiofauna and two for environmental analysis, making a total of 8 meiofauna and 8 environmental cores per location, except at O’Brien Bay-5 where one meiofauna core was lost during sampling. Six locations were sampled around Casey Station. There were three control locations, two of which were within O’Brien Bay to the south of Casey (O’Brien Bay-1 (OB-1) and O’Brien Bay-5 (OB-5)); and one within Newcomb Bay, in McGrady Cove (Fig. 1). There were three locations adjacent to waste disposal sites: two locations were situated along a gradient of pollution within Brown Bay (Inner and Middle)(Stark et al. 2004, Stark 2008); and a third location was at Wilkes, adjacent to the abandoned waste disposal site at the derelict Wilkes station (Stark et al. 2003a), all within Newcomb Bay (Fig. 1). These waste disposal sites were used historically to dispose of all waste and rubbish generated on station and included used oil, building materials, electronics and batteries, food, clothing and chemicals (Snape et al. 2001, Stark et al. 2006). Both waste disposal sites are contaminated with metals and hydrocarbons above background levels (Stark et al. 2008, Stark et al. 2014b, Fryirs et al. 2015). Sample collection, meiofauna preparation and identification Sediment samples were collected by divers using modified 60 ml syringes with their intake end cut off to form a small core tube (28mm internal diameter). Cores were pushed into the sediment to a depth of 10 cm, extracted, and the bottom end was capped. In a few cases samples were only taken down to 5-7 cm, where sediments were less than 10 cm deep due to underlying rock. No sediments less than 5 cm deep were sampled. Cores were transported to Casey Station laboratories where they were emptied into sample jars and 4% formalin was added