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  • 1
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    Respiratory responses of three Antarctic ascidians and a sea pen to increased sediment concentrations (2012)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, 35(11), pp. 1743-1748, ISSN: 0722-4060
    Details
    Publication Date: 2019-07-16
    Description: Glacial retreat and subglacial bedrock erosion are consequences of rapid regional warming on the West Antarctic peninsula. Sedimentation of fine grained eroded particles can impact the physiology of filter feeding benthic organisms. We investigated the effect of increasing concentrations of sediment on the oxygen consumption of suspension feeding species, the ascidians Molgula pedunculata, Cnemidocarpa verrucosa, Ascidia challengeri, and the pennatulid Malacobelemnon daytoni in Potter Cove (South Shetland Islands, Antarctica). In A. challengeri and C. verrucosa oxygen consumption increased gradually up to a critical sediment concentration (Ccrit) where species oxygen consumption was maximal (Omax in mg O2 g-1 dm d-1) and further addition of sediments decreased respiration. Ccrit was 200 mg L-1 for A. challengeri (Omax of 0.651 ± 0.238) and between 100 and 200 mg L-1 for C. verrucosa (Omax of 0.898 ± 0.582). Oxygen consumption of M. pedunculata increased significantly even at low sediment concentrations (15-50 mg sediment L-1). Contrary to the ascidians, sediment exposure did not affect oxygen consumption of the sea pen. The tiered response to sedimentation in the four species corroborates recent field observations that detected a reduction in abundance of the sensitive ascidian Molgula pedunculata from areas strongly affected by glacial sediment discharge, whereas sea pens are increasing in abundance. Our investigation relates consequences (population shifts in filter feeder communities) to causes (glacial retreat) and is of importance for modelling of climate change effects in Antarctic shallow coastal areas.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Analysis of trends and sudden changes in long-term environmental data from King George Island (Antarctica): relationships between global climatic oscillations and local system response (2012)
    SPRINGER
    In:  EPIC3Climatic Change, SPRINGER, ISSN: 0165-0009
    Details
    Publication Date: 2019-07-16
    Description: The Western Antarctic Peninsula is one of the most rapidly warming regions on earth. It is therefore important to analyze long-term trends and inter-annual patterns of change in major environmental parameters to understand the process underlying climate change in Western Antarctica. Since many polar long-term data series are fragmented and cannot be analysed with common time series analysis tools, we present statistical approaches that can deal with missing values. We applied U-statistics after Pettit and Buishand to detect abrupt changes, dynamic factor analysis to detect functional relationships, and additive modelling to detect patterns in time related to climatic cycles such as the Southern Annular Mode and El Niño Southern Oscillation in a long-term environmental data set from King George Island (WAP), covering 20 years. Our results not only reveal sudden changes for sea surface temperature and salinity, but also clear patterns in all investigated variables (sea surface temperature, salinity, suspended particulate matter and Chlorophyll a) that can directly be related to climatic cycles. Our results complement previous findings on climate related changes in the King George Island Region and provide insight into the environmental conditions and climatic drivers of system change in the study area. Hence, our statistical analyses may prove valuable for other polar environmental data sets and contribute to a better understanding of the regional variability of climate change and its impact on coastal systems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 3
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    Succession of Antarctic benthic algae (Potter Cove, South Shetland Islands): structural patterns and glacial impact over a four year period (2017)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, ISSN: 0722-4060
    Details
    Publication Date: 2017-09-06
    Description: There is a general lack of information on the succession of marine benthic algae in Antarctica. We performed two colonization experiments in the upper subtidal (3 and 5 metres depth) using artificial substrates in Potter Cove (South Shetland Islands): in the outer cove, an area mainly unaffected by sedimentation, and in the inner cove, in close proximity to a retreating glacier, with high sediment inflow particularly during the melting season. Seasonal and interannual changes in total, diatom and macroalgal cover, species composition and ecological indexes were assessed over four years. Tiles were analysed in spring and summer in the laboratory and by year-round photographic monitoring. Irradiance (photosynthetically active radiation and ultraviolet radiation), salinity and temperature were monitored on a monthly basis. Benthic algae dominated the assemblages, with macroalgae reaching ~70% cover after two years. There were site and temporal differences in the contribution of diatom mats (mainly pennate forms) and macroalgal cover. Diatom cover was higher at the glacier-influenced site, particularly at the early stages, and decreased significantly with time. Between years, macroalgal assemblages changed significantly in a site-specific manner. Assemblages mainly comprised annual and pseudoperennial species at both sites, with absence of adult large Desmarestiales. Although a year separated the establishment of the two experiments, there were convergence patterns in the changes of cover over time - that seemed to be controlled by competitive interactions - and in the patterns of species replacement. However, the inner cove site exhibited lower number of macroalgal taxa and a tendency to decreased diversity over time that could be related to higher the level of stress and disturbance caused by glacial influence.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 4
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    Photosynthetic light requirements and vertical distribution of macroalgae in newly ice-free areas in Potter Cove, South Shetland Islands, Antarctica (2016)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, 39(1), pp. 153-166
    Details
    Publication Date: 2016-01-27
    Description: In Potter Cove, Antarctica, newly ice-free areas appeared due to glacial retreat. Simultaneously, the inflow of sediment increased, reducing underwater photosynthetically active radiation (PAR, 400–700 nm). The aim of this study was to determine the photosynthetic characteristics of two macroalgal species colonizing three newly icefree areas, A1, A2 and A3, with increasing degree of glacial influence from A1 to A3. Turbidity, salinity and temperature were measured, and light attenuation coefficients (Kd) calculated and considered as a proxy for glacial sediment input. The lower depth distribution of the red alga Palmaria decipiens and the brown alga Himantothallus grandifolius was 10 m in A3, 20 m in A2 and 30 m in A1. Both species were then collected, at 5 and 10 m at all areas. Photosynthetic parameters and the daily metabolic carbon balance (CB) were determined. Kd was significantly higher in A3 compared with A1 and A2. The CB of P. decipiens was significantly higher in A1 followed by A2 and A3, and significantly higher at shallower than at greater depth. For H. grandifolius CB was significantly lower in A3 and in A2 at deeper depths compared with the rest of areas and depths. The lower distribution limit of the algae was positively correlated to the light penetration. An increase in the sediment run-off due to global warming might lead to an elevation of the lower depth distribution limit but retreating glaciers can open new space for macroalgal colonization. These changes will probably affect macroalgal primary productivity in Potter Cove with consequences for the coastal ecosystem.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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