ALBERT

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 ice-free 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.

Description: In the present study, we report the results of comprehensive amino acid (AA) analyses of four Indian lakes from different climate regimes. We focus on the investigation of sediment cores retrieved from the lakes but data of modern sediment as well as vascular plant, soil, and suspended particulate matter samples from individual lakes are also presented. Commonly used degradation and organic matter source indices are tested for their applicability to the lake sediments, and we discuss potential reasons for possible limitations. A principal component analysis including the monomeric AA composition of organic matter of all analysed samples indicates that differences in organic matter sources and the environmental properties of the individual lakes are responsible for the major variability in monomeric AA distribution of the different samples. However, the PCA also gives a factor that most probably separates the samples according to their state of organic matter degradation. Using the factor loadings of the individual AA monomers, we calculate a lake sediment degradation index (LI) that might be applicable to other palaeo-lake investigations.

Description: Species distribution models (SDM) predict species occurrence based on statistical relationships with environmental conditions. The R-package biomod2 which includes 10 different SDM techniques and 10 different evaluation methods was used in this study. Macroalgae are the main biomass producers in Potter Cove, King George Island (Isla 25 de Mayo), Antarctica, and they are sensitive to climate change factors such as suspended particulate matter (SPM). Macroalgae presence and absence data were used to test SDMs suitability and, simultaneously, to assess the environmental response of macroalgae as well as to model four scenarios of distribution shifts by varying SPM conditions due to climate change. According to the averaged evaluation scores of Relative Operating Characteristics (ROC) and True scale statistics (TSS) by models, those methods based on a multitude of decision trees such as Random Forest and Classification Tree Analysis, reached the highest predictive power followed by generalized boosted models (GBM) and maximum-entropy approaches (Maxent). The final ensemble model used 135 of 200 calculated models (TSS 〉 0.7) and identified hard substrate and SPM as the most influencing parameters followed by distance to glacier, total organic carbon (TOC), bathymetry and slope. The climate change scenarios show an invasive reaction of the macroalgae in case of less SPM and a retreat of the macroalgae in case of higher assumed SPM values.

Description: FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION". 363322 values, 1037 CTD profiles (Conductivity, Temperature & Density), salinity, voltage and pressure data compiled at 123 stations, spatially distribute in entire Potter Cove. Variable available: Coordinates of stations, depth sampling [m], water temperature [°C], potential temperature [°C], salinity [psu], density [kg/m^3], conductivity [mS/cm], turbidity [NTU], voltage [V], press [dbar].The depth has been classified into three categories 0-5 m; 5-15 m and over 15 m. 5 stations were monthly sampled: E1, E2, E3 (18, 17, 6 years, respectively); Faro and Peñon de Pesca (all months except June & July for 2 and 3 years, respectively). The other 118 stations belong to summer season only covering 1 to 5 years sampling. Transects for summer 1996/1997, 2007 and 2008 have been georeferenced and newly available. Device used: CTD/Rosette (CTD-RO).

Description: FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION". A joined data set of CTD profiles (conductivity, temperature, density, salinity, voltage and pressure) with metereological variables (daily mean, maximum and minimum air temperature; daily range temperature ?max-min); atmospheric pressure; relative humidity; precipitation; visibility; mean and max wind speed of day; wind gut; direction and cloud cover ) in Potter Cove, Carlini Station, King George Island (Isla 25 de Mayo). Stations have been merged within a neighbourhood of 0-100 m and concerning their membership to a geochemical cluster analysis (https://doi.pangaea.de/10.1594/PANGAEA.856971). 85 stations are remaining from the original data set (doi parent). The depth has been classified into three categories: 0-5 m; 5-15 m and over 15 m. Comment: As soon as there are CTD sample without metereology abailable it exists empty rows. Device used: CTD/Rosette (CTD-RO).

Description: The sediment trap experiment started in 1986 and was expanded into the Bay of Bengal only one year later in 1987. The fieldwork ended at around 1998. In 2007 and 2008, we tried to reinitiate a sediment trap program in the Arabian Sea, although this could not be followed up due to piracy, which became an issue in the region at that time. The sediment trap sites in the northern and central Bay of Bengal were shifted slightly southward in some years, whereby the stations NBBT and CBBT were spilt into northern (NBBT-N, CBBT-N) and southern sites (NBBT-S, CBBT-S). Between 2001 and 2004 additional sediment trap experiments were carried out in the upwelling system off South Java.

Description: Scavenger guilds are composed of a variety of species, co-existing in the same habitat and sharing the same niche in the food web. Niche partitioning among them can manifest in different feeding strategies, e.g. during carcass feeding. In the bentho-pelagic realm of the Southern Ocean, scavenging amphipods (Lysianassoidea) are ubiquitous and occupy a central role in decomposition processes. Here we address the question whether scavenging lysianassoid amphipods employ different feeding strategies during carcass feeding, and whether synergistic feeding activities may influence carcass decomposition. To this end, we compared the relatively large species Waldeckia obesa with the small species Cheirimedon femoratus, Hippomedon kergueleni, and Orchomenella rotundifrons during fish carcass feeding (Notothenia spp.). The experimental approach combined ex situ feeding experiments, behavioural observations, and scanning electron microscopic analyses of mandibles. Furthermore, we aimed to detect ecological drivers for distribution patterns of scavenging amphipods in the Antarctic coastal ecosystems of Potter Cove. In Potter Cove, the climate-driven rapid retreat of the Fourcade Glacier is causing various environmental changes including the provision of new marine habitats to colonise. While in the newly ice-free areas fish are rare, macroalgae have already colonised hard substrates. Assuming that a temporal dietary switch may increase the colonisation success of the most abundant lysianassoids C. femoratus and H. kergueleni, we aimed to determine their consumption rates (g food x g amphipods -1 x day -1) and preferences of macroalgae and fish.

Description: ICP-OES and ICP-MS data of trace elements in sediment and pore waters of the DISCOL area, Peru Basin, SE Pacific

Description: Laminated sediments of the continental slope off the Makran coast in the northern Arabian Sea are well-known climate archives and record productivity as well as supply of material from land. Here we studied sediment core 275KL off Pakistan in concert with sediment trap, dust and river samples in order to characterise and quantify land-derived material deposited in varves and event layers. We analysed grain sizes, mineral assemblages, bulk components, and stable isotopes (δ13C, δ18O) of carbonates. In winter, enhanced river discharge is the main source of lithogenic matter contributing the major amounts to the total annual sedimentation of the northern Arabian Sea. During the late summer season, lithogenic matter accumulation is slightly enhanced, probably carried along with the southeastward blowing Levar winds from the Balochistan and the Sistan Basins and the summer monsoon discharge maximum of perennial streams. C/N ratios and stable carbon and oxygen isotopes could not be used to distinguish between organic matter produced on land and in the ocean, whereas stable carbon and oxygen isotope ratios of carbonates suggest that sedimentation of event layers is dominated by direct inputs from land. Catastrophic denudation and storm events occur on average once every 50 years and lead to sedimentation rates that exceed the mean annual sedimentations of 983 g m-2 yr-1 by 6 to 10 times. Nevertheless, due to their rare occurrence they contributed only 7% to the total sedimentation during the last ca 5,000 years. End-member modelling of grain sizes in accordance with lithogenic matter accumulation rates and event layer frequencies showed that arid conditions prevailed between 4,000 and 5,000 a BP while more humid conditions commenced around 2,000 ka BP in accordance with the Pacific ENSO record.

Description: At present the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 m and 1200 m. Active denitrification in this OMZ is recorded by enhanced d15N values in the sediments. Sediment cores show a d15N increase from early to late Holocene which is contrary to the trend in other regions of water column denitrification. We calculated composite sea surface temperature (SST) and d15N in time slices of 1000 years of the last 25 ka to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Pleistocene stadial d15N values of 4-6 per mil suggest that denitrification was inactive or weak. During interstadials (IS) and the entire Holocene, d15N values of 〉7 per mil indicate enhanced denitrification and a stronger OMZ. This coincides with active monsoonal upwelling along the western margins of the basin as indicated by low SST. Stronger ventilation of the OMZ in the early to mid-Holocene period during the most intense southwest monsoon and vigorous upwelling is reflected in lower d15N compared to the late Holocene. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position in the northeast was established during the last 4-5 ka. This was probably caused by (i) rising oxygen consumption due to enhanced northeast monsoon driven biological productivity, in combination with (ii) reduced ventilation due to a longer residence time of OMZ waters.