30 years of synoptic observations from Neumayer Station with links to datasets

The analysis of research data plays a key role in data-driven areas of science. Varieties of mixed research data sets exist and scientists aim to derive or validate hypotheses to find undiscovered knowledge. Many analysis techniques identify relations of an entire dataset only. This may level the characteristic behavior of different subgroups in the data. Like automatic subspace clustering, we aim at identifying interesting subgroups and attribute sets. We present a visual-interactive system that supports scientists to explore interesting relations between aggregated bins of multivariate attributes in mixed data sets. The abstraction of data to bins enables the application of statistical dependency tests as the measure of interestingness. An overview matrix view shows all attributes, ranked with respect to the interestingness of bins. Complementary, a node-link view reveals multivariate bin relations by positioning dependent bins close to each other. The system supports information drill-down based on both expert knowledge and algorithmic support. Finally, visual-interactive subset clustering assigns multivariate bin relations to groups. A list-based cluster result representation enables the scientist to communicate multivariate findings at a glance. We demonstrate the applicability of the system with two case studies from the earth observation domain and the prostate cancer research domain. In both cases, the system enabled us to identify the most interesting multivariate bin relations, to validate already published results, and, moreover, to discover unexpected relations.

Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates - Collection of source datasets - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types

The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedented global data set for ecological and biochemical analysis and modeling as well as a clear mandate for compiling additional existing data and for focusing future data gathering efforts on key groups in key areas of the ocean. The present collection presents the original data sets used to compile Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates

Gene sequences of the lichen Cetraria aculeata

Lichens are symbioses between fungi (mycobionts) and photoautotrophic green algae or cyanobacteria (photobionts). Many lichens occupy large distributional ranges covering several climatic zones. So far, little is known about the large-scale phylogeography of lichen photobionts and their role in shaping the distributional ranges of lichens. We studied south polar, temperate and north polar populations of the widely distributed fruticose lichen Cetraria aculeata. Based on the DNA sequences from three loci for each symbiont, we compared the genetic structure of mycobionts and photobionts. Phylogenetic reconstructions and Bayesian clustering methods divided the mycobiont and photobiont data sets into three groups. An AMOVA shows that the genetic variance of the photobiont is best explained by differentiation between temperate and polar regions and that of the mycobiont by an interaction of climatic and geographical factors. By partialling out the relative contribution of climate, geography and codispersal, we found that the most relevant factors shaping the genetic structure of the photobiont are climate and a history of codispersal. Mycobionts in the temperate region are consistently associated with a specific photobiont lineage. We therefore conclude that a photobiont switch in the past enabled C. aculeata to colonize temperate as well as polar habitats. Rare photobiont switches may increase the geographical range and ecological niche of lichen mycobionts by associating them with locally adapted photobionts in climatically different regions and, together with isolation by distance, may lead to genetic isolation between populations and thus drive the evolution of lichens.

Nitrogen isotope gradients off Peru and Ecuador related to upwelling, productivity, nutrient uptake and oxygen deficiency

We present new nitrogen isotope data from the water column and surface sediments for paleo-proxy validation collected along the Peruvian and Ecuadorian margins between 1°N and 18°S. Productivity proxies in the bulk sediment (organic carbon, total nitrogen, biogenic opal, C37 alkenone concentrations) and 15N/14N ratios were measured at more than 80 locations within and outside the present-day Peruvian oxygen minimum zone (OMZ). Microbial N-loss to N2 in subsurface waters under O2 deficient conditions leaves a characteristic 15N-enriched signal in underlying sediments. We find that phytoplankton nutrient uptake in surface waters within the high nutrient, low chlorophyll (HNLC) regions of the Peruvian upwelling system influences the sedimentary signal as well. How the d15Nsed signal is linked to these processes is studied by comparing core-top values to the 15N/14N of nitrate and nitrite (d15N[NOx]) in the upper 200 m of the water column. Between 1°N and 10°S, subsurface O2 is still high enough to suppress N-loss keeping d15NNOx values relatively low in the subsurface waters. However d15N[NOx] values increase toward the surface due to partial nitrate utilization in the photic zone in this HNLC portion of the system. d15N[sed] is consistently lower than the isotopic signature of upwelled [NO3]-, likely due to the corresponding production of 15N depleted organic matter. Between 10°S and 15°S, the current position of perennial upwelling cells, HNLC conditions are relaxed and biological production and near-surface phytoplankton uptake of upwelled [NO3]- are most intense. In addition, subsurface O2 concentration decreases to levels sufficient for N-loss by denitrification and/or anammox, resulting in elevated subsurface d15N[NOx] values in the source waters for coastal upwelling. Increasingly higher production southward is reflected by various productivity proxies in the sediments, while the north-south gradient towards stronger surface [NO3]- utilization and subsurface N-loss is reflected in the surface sediment 15N/14N ratios. South of 10°S, d15N[sed] is lower than maximum water column d15N[NOx] values most likely because only a portion of the upwelled water originates from the depths where highest d15N[NOx] values prevail. Though the enrichment of d15N[NOx] in the subsurface waters is unambiguously reflected in d15N[sed] values, the magnitude of d15N[sed] enrichment depends on both the depth of upwelled waters and high subsurface d15N[NOx] values produce by N-loss. Overall, the degree of N-loss influencing subsurface d15N[NOx] values, the depth origin of upwelled waters, and the degree of near-surface nitrate utilization under HNLC conditions should be considered for the interpretation of paleo d15N[sed] records from the Peruvian oxygen minimum zone.

Benthic cover map of Heron Reef derived from a high-spatial-resolution multi-spectral satellite image using object based image analysis

Providing accurate maps of coral reefs where the spatial scale and labels of the mapped features correspond to map units appropriate for examining biological and geomorphic structures and processes is a major challenge for remote sensing. The objective of this work is to assess the accuracy and relevance of the process used to derive geomorphic zone and benthic community zone maps for three western Pacific coral reefs produced from multi-scale, object-based image analysis (OBIA) of high-spatial-resolution multi-spectral images, guided by field survey data. Three Quickbird-2 multi-spectral data sets from reefs in Australia, Palau and Fiji and georeferenced field photographs were used in a multi-scale segmentation and object-based image classification to map geomorphic zones and benthic community zones. A per-pixel approach was also tested for mapping benthic community zones. Validation of the maps and comparison to past approaches indicated the multi-scale OBIA process enabled field data, operator field experience and a conceptual hierarchical model of the coral reef environment to be linked to provide output maps at geomorphic zone and benthic community scales on coral reefs. The OBIA mapping accuracies were comparable with previously published work using other methods; however, the classes mapped were matched to a predetermined set of features on the reef.

Investigations on seven sediment cores from the New Ireland Basin, east of Papua New Guinea

Sediment cores were recovered from the New Ireland Basin, east of Papua New Guinea, in order to investigate the late Quaternary eruptive history of the Tabar-Lihir-Tanga-Feni (TLTF) volcanic chain. Foraminifera d18O profiles were matched to the low-latitude oxygen isotope record to date the cores, which extend back to the early part of d18O Stage 9 (333 ka). Sedimentation rates decrease from >10 cm/1000 yr in cores near New Ireland to ~2 cm/1000 yr further offshore. The cores contain 36 discrete ash beds, mostly 1-8 cm thick and interpreted as either fallout or distal turbidite deposits. Most beds have compositionally homogeneous glass shard populations, indicating that they represent single volcanic events. Shards from all ash beds have the subduction-related pattern of strong enrichment in the large-ion lithophile elements relative to MORB, but three distinct compositional groups are apparent: Group A beds are shoshonitic and characterised by >1300 ppm Sr, high Ce/Yb and high Nb/Yb relative to MORB, Group B beds form a high-K series with MORB-like Nb/Yb but high Ce/Yb and well-developed negative Eu anomalies, whereas Group C beds are transitional between the low-K and medium-K series and characterised by flat chondrite-normalised REE patterns with low Nb/Yb relative to MORB. A comparison with published data from the TLTF chain, the New Britain volcanic arc and backarc including Rabaul, and Bagana on Bougainville demonstrates that only Group A beds share the distinctive phenocryst assemblage and shoshonitic geochemistry of the TLTF lavas. The crystal- and lithic-rich character of the Group A beds point to a nearby source, and their high Sr, Ce/Yb and Nb/Yb match those of Tanga and Feni lavas. A youthful stratocone on the eastern side of Babase Island in the Feni group is the most probable source. Group A beds younger than 20 ka are more fractionated than the older Group A beds, and record the progressive development of a shallow level magma chamber beneath the cone. In contrast, Group B beds represent glass-rich fallout from voluminous eruptions at Rabaul, whereas Group C beds represent distal glass-rich fallout from elsewhere along the volcanic front of the New Britain arc.

Adaptation to enemy shifts: rapid resistance evolution to local Vibrio spp. in invasive Pacific oysters

One hypothesis for the success of invasive species is reduced pathogen burden, resulting from a release from infections or high immunological fitness (low immunopathology) of invaders. Despite of strong selection exerted on the host, the evolutionary response of invaders to newly acquired pathogens has rarely been considered. The two independent and genetically distinct invasions of the Pacific oyster Crassostrea gigas into the North Sea represent an ideal model system to study fast evolutionary responses of invasive populations. By exposing both invasion sources to ubiquitous and phylogenetically diverse pathogens (Vibrio spp.) we demonstrate that within a few generations hosts adapted to sympatric pathogen communities. However, this local adaptation only became apparent in selective environments, i.e. at elevated temperatures reflecting patterns of disease outbreaks in natural populations. Resistance against sympatric and allopatric Vibrio spp. strains was dominantly inherited in crosses between both invasion sources, resulting in an overall higher resistance of admixed individuals than pure lines. Therefore we suggest that a simple genetic resistance mechanism of the host is matched to a common virulence mechanism shared by local Vibrio strains. This combination might have facilitated a fast evolutionary response that can explain another dimension of why invasive species can be so successful in newly invaded ranges.