Abundance and characteristics of Polychaeta taxa and associated sediment during POLARSTERN campaign ANT-XXII/3 (ANDEEP-IIII)

During the austral summer of 2005, the Weddell deep sea and adjacent basins were sampled in the course of the ANDEEP III project. In this study, 19 epibenthic-sledge stations are analyzed, with a focus on species diversity and distribution patterns of polychaetes. The polychaete fauna of the deep Southern Ocean has been found to be similarly speciose and diverse compared with deep-sea basins worldwide. Also, in depths below 2,000 m many polychaete species do not seem to be endemic for certain areas but are rather far spread within the Southern Ocean and beyond. Therefore, ongoing faunal exchanges between adjacent basins, even beyond the Antarctic convergence, are strongly suggested, ruling out a general isolation of the Southern Ocean deep-sea benthos. Driving forces behind species distribution patterns were investigated. The findings indicate that polychaete species' distribution in the Southern Ocean deep sea is rather dependent on local environment than depths.

Biodiversity context of selected samples from the Tara Oceans Expedition (2009-2013)

The present data set provides contextual data for samples from the Tara Oceans Expedition (2009-2013) that were selected for publication in a special issue of the SCIENCE journal (see related references below). Contextual data include various diversity indexes calculated for the sampling location using satellite and model climatologies (Darwin project, Physat) and results from the sequencing of Tara Oceans samples.

Pollen from 50 lake surface samples in Brandenburg, Germany, in 2009

Past changes in plant and landscape diversity can be evaluated through pollen analysis, however, pollen based diversity indexes are potentially biased by differential pollen production and deposition. Studies examining the relationship between pollen and landscape diversity are therefore needed. The aim of this study is to evaluate how different pollen based indexes capture aspects of landscape diversity. Pollen counts were obtained from surface samples of 50 small to medium sized lakes in Brandenburg (Northeast Germany) and compiled into two sets, with one containing all pollen counts from terrestrial plants and the second restricted to wind-pollinated taxa. Both sets were adjusted for the pollen production/dispersal bias using the REVEALS model. A high resolution biotope map was used to extract the density of total biotopes and different biotopes per area as parameters describing landscape diversity. In addition tree species diversity was obtained from forest inventory data. The Shannon index and the number of taxa in a sample of 10 pollen grains are highly correlated and provide a useful measure of pollen type diversity which corresponds best to landscape diversity within one km of the lake and the proportion of non-forested area within seven km. Adjustments of the pollen production/dispersal bias only slightly improve the relationships between pollen diversity and landscape diversity for the restricted dataset as well as for the forest inventory data and corresponding pollen types. Using rarefaction analysis, we propose the following convention: pollen type diversity is represented by the number of types in a small sample (low count e.g. 10), pollen type richness is the number of types in a large sample (high count e.g. 500) and pollen sample evenness is characterized by the ratio of the two. Synthesis. Pollen type diversity is a robust index that captures vegetation structure and landscape diversity. It is ideally suited for between site comparisons as it does not require high pollen counts. In concert with pollen type richness and evenness, it helps evaluating the effect of climate change and human land use on vegetation structure on long timescales.

Mega-epibenthos at Bouvet Island (South Atlantic)

Mega-epibenthic diversity was analysed using a seabed photography at four stations off Bouvet Island and one station at the Spiess Seamount in the South Atlantic. Surprisingly, the intermediate-scale diversity within the area of investigation was not lower compared to that on the Patagonian shelf and only moderately lower than that on the Antarctic continental shelf. This result is incompatible with Mac Arthur and Wilson's Island Biogeography Theory describing species richness as a function of immigration of new species into an area and its extension. The relatively high species number and the very small extension of the Bouvet shelf compared to the much larger continental shelves of the other two areas can be explained by long-range dispersal of marine benthic animals in the Antarctic Circumpolar Current and high habitat heterogeneity. The observed uncoupling of intermediate-scale from large-scale background species diversity on the Antarctic shelf raises the question whether in these benthic systems an upper capacity limit for diversity exists.

Collection of measurements on physical soil properties in plots of the Jena Experiment (time series since 2002)

This collection contains measurements on physical soil properties of the plots of the different sub-experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing

TABLE 2. - Number of Asellota isopods collected in the Beagle Channel

The shallow-water Asellota from the Beagle Channel were investigated, based on material collected at four localities in 2001-2002. A total of 3,124 asellotes were sorted, and three new species and 12 new records of distribution were reported. The Paramunnidae showed the highest species diversity and abundance (11 species and 1,463 specimens). The present research raises the number of species known from the Beagle Channel to 23; of these, 16 were previously reported from the Magellan Straits, representing 69% of similarity. Based on the present results and published data, the faunistic affinities for the shallow-water Asellota was 30% between the Magellan region and the Scotia Arc, and 26% between the Magellan region and the Antarctic Peninsula.

Ostracoda in surface sediments of the Arctic Ocean

Ostracodes were studied from deep Arctic Ocean cores obtained during the Arctic 91 expedition of the Polarstern to the Nansen, Amundsen and Makarov Basins, the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau, in order to investigate their distribution in Arctic Ocean deep water (AODW) and apply these data to paleoceanographic reconstruction of bottom water masses during the Quaternary. Analyses of coretop assemblages from Arctic 91 boxcores indicate the following: ostracodes are common at all depths between 1000 and 4500 m, and species distribution is strongly influenced by water mass characteristics and bathymetry; quantitative analyses comparing Eurasian and Canada Basin assemblages indicate that distinct assemblages inhabit regions east and west of the Lomonosov Ridge, a barrier especially important to species living in lower AODW; deep Eurasian Basin assemblages are more similar to those living in Greenland Sea deep water (GSDW) than those in Canada Basin deep water; two upper AODW assemblages were recognized throughout the Arctic Ocean, one living between 1000 and 1500 m, and the other, having high species diversity, at 1500-3000 m. Downcore quantitative analyses of species' abundances and the squared chord distance coefficient of similarity reveals a distinct series of abundance peaks in key indicator taxa interpreted to signify the following late Quaternary deep water history of the Eurasian Basin. During the Last Glacial Maximum (LGM), a GSDW/AODW assemblage, characteristic of cold, well oxygenated deep water > 3000 m today, inhabited the Lomonosov Ridge to depths as shallow as 1000 m, perhaps indicating the influence of GSDW at mid-depths in the central Arctic Ocean. During Termination 1, a period of high organic productivity associated with a strong inflowing warm North Atlantic layer occurred. During the mid-Holocene, several key faunal events indicate a period of warming and/or enhanced flow between the Canada and Eurasian Basins. A long-term record of ostracode assemblages from kastenlot core PS2200-5 (1073 m water depth) from the Morris Jesup Rise indicates a quasi-cyclic pattern of water mass changes during the last 300 kyr. Interglacial ostracode assemblages corresponding to oxygen isotope stages 1, 5, and 7 indicate rapid changes in dissolved oxygen and productivity during glacial-interglacial transitions.

(Table 1) Species richness and diversity of tundra plants in herbivore exclosure and control plots near Barrow, Alaska

To determine the role lemmings play in structuring plant communities and their contribution to the 'greening of the Arctic', we measured plant cover and biomass in 50 + year old lemming exclosures and control plots in the coastal tundra near Barrow, Alaska. The response of plant functional types to herbivore exclusion varied among land cover types. In general, the abundance of lichens and bryophytes increased with the exclusion of lemmings, whereas graminoids decreased, although the magnitude of these responses varied among land cover types. These results suggest that sustained lemming activity promotes a higher biomass of vascular plant functional types than would be expected without their presence and highlights the importance of considering herbivory when interpreting patterns of greening in the Arctic. In light of the rapid environmental change ongoing in the Arctic and the potential regional to global implications of this change, further exploration regarding the long-term influence of arvicoline rodents on ecosystem function (e.g. carbon and energy balance) should be considered a research priority.

Mean cover and frequencies of vascular plant species during three decades around Abisko Scientific Research Station

Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977-1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites.

Species occurrence and richness of lichen, bryophytes and vascular plants near Abisko, Sweden and Toolik lake, Alaska

Little is known about the impact of changing temperature regimes on composition and diversity of cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9-16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by cryptogams in high latitudes (e.g. carbon sequestration, N2-fixation, trophic interactions), these changes will have important feedback consequences for ecosystem functions and climate.