Growth rates and skeletal density of the scleractinian cold-water coral Desmophyllum dianthus at Isla Liliguapi (Fjord Comau, southern Chile)

It has been hypothesized that endolithic photo-autotrophs inside the skeleton of cold-water corals may have a mutualistic relationship with the coral host positively affecting coral calcification. This study investigated the effect of endolithic photo-autotrophs on the apical septal extension of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile (42.41° - 42.15°S, 72.5°W). The fluorescent staining agent calcein was used to document the linear apical extension of septae for a period of one and a half years between 2006 and 2007. The results showed a severe reduction in extension rates associated with the presence of endolithic photo-autotrophs. Infested individuals grew about half as fast as non-infested polyps with a median value of 1.18 µm/day compared to 2.76 µm/day. Contrary to the initial hypothesis, these results point toward a parasitic relationship between D. dianthus and its endolithic photo-autotrophs potentially impairing coral fitness. However, further data on physiological parameters and other aspects of the calcification process are necessary to confirm these findings.

Radiolarians in the Sea of Okhotsk

To assess the relationship of radiolarian production, species distribution in water and surface sediment to water-mass characteristics, biological productivity and export regimes in the Sea of Okhotsk (SOk) we accomplished a quantitative analysis of radiolarian assemblages obtained from 35 surface-sediment samples and 115 plankton samples recording the radiolarian depth distribution in the upper 1000 m of the water column at 23 locations. This study augments the knowledge on the autecological demands of radiolarians dwelling in a specific hydrographic and biological environment, and extracts new information on the significance of radiolarians for the assessment of past oceanographic and climatic development in high latitudes. Highest radiolarian accumulation rates and seasonal radiolarian standing stocks are encountered in the western part of the SOk close to Sakhalin, marking the environmental conditions in this area as most favorable for radiolarian production. Maximum standing stocks occur during summer, indicating that the radiolarian signal preserved in the sediment record is mainly produced during this season when the mesopelagic biomass is at highest activity. We identified seven radiolarian species and groups related to specific water-mass characteristics, depth habitats, and productivity regimes. Of those, Dictyophimus hirundo and Cycladophora davisiana are most prominent in the Sea of Okhotsk Intermediate Water (200-1000 m), the latter representing an indicator of the occurrence of cold and well ventilated intermediate/deep water and enhanced export of organic matter from a highly productive ocean surface. While Antarctissa (?) sp. 1 is typically related to the cold-water Sea of Okhotsk Dicothermal Layer (SODL), ranging between 50 and 150 m water depth, the surface waters above the SODL affected by strong seasonal variability are inhabited predominantly by taxa belonging to the Spongodiscidae, having a broad environmental tolerance. Taxa only found in the sediment record show that the plankton study did not cover all assemblages occurring in the modern SOk. This accounts for an assemblage restricted to the western Kurile Basin and apparently related to environmental conditions influenced by North Pacific and Japan Sea waters. Other important taxa include species of the Plagoniidae group, representing the most prominent contributors to the SOk plankton and surface sediments. These radiolarians show a more opportunistic occurrence and are indicative of high nutrient supply in a hydrographic environment characterized by pronounced stratification enhancing heterotrophic activity and phytodetritus export.

Miocene flora and paleoclimate estimations of Schrotzburg, South Germany

We present a detailed palaeoclimate analysis of the Middle Miocene (uppermost Badenian-lowermost Sarmatian) Schrotzburg locality in S Germany, based on the fossil macro- and micro-flora, using four different methods for the estimation of palaeoclimate parameters: the coexistence approach (CA), leaf margin analysis (LMA), the Climate-Leaf Analysis Multivariate Program (CLAMP), as well as a recently developed multivariate leaf physiognomic approach based on an European calibration dataset (ELPA). Considering results of all methods used, the following palaeoclimate estimates seem to be most likely: mean annual temperature ~15-16°C (MAT), coldest month mean temperature ~7°C (CMMT), warmest month mean temperature between 25 and 26°C, and mean annual precipiation ~1,300 mm, although CMMT values may have been colder as indicated by the disappearance of the crocodile Diplocynodon and the temperature thresholds derived from modern alligators. For most palaeoclimatic parameters, estimates derived by CLAMP significantly differ from those derived by most other methods. With respect to the consistency of the results obtained by CA, LMA and ELPA, it is suggested that for the Schrotzburg locality CLAMP is probably less reliable than most other methods. A possible explanation may be attributed to the correlation between leaf physiognomy and climate as represented by the CLAMP calibration data set which is largely based on extant floras from N America and E Asia and which may be not suitable for application to the European Neogene. All physiognomic methods used here were affected by taphonomic biasses. Especially the number of taxa had a great influence on the reliability of the palaeoclimate estimates. Both multivariate leaf physiognomic approaches are less influenced by such biasses than the univariate LMA. In combination with previously published results from the European and Asian Neogene, our data suggest that during the Neogene in Eurasia CLAMP may produce temperature estimates, which are systematically too cold as compared to other evidence. This pattern, however, has to be further investigated using additional palaeofloras.

Tab. 1+7: Hydrochemical analyses of firn and meltwater from different "cold" snow patches

In wide areas of Northern Siberia, glaciers have been absent since the Late Pleistocene. Therefore, ground ice and especially ice wedges are used as archives for paleoclimatic studies. In the present study, carried out on the Bykovsky Peninsula, eastern Lena Delta, we were able to distinguish ice wedges of different genetic units by means of oxygen and hydrogen isotopes. The results obtained by this study on the Ice Complex, a peculiar periglacial phenomenon, allowed the reconstruction of the climate history with a subdivision of a period of very cold winters (60-55 ka), followed by a long stable period of cold winter temperatures (50-24 ka), Between 20 ka and 11 ka, climate warming is indicated in stable isotope compositions, most probably after the Late Glacial Maximum. At that time, a change of the marine source of the precipitation from a more humid source to the present North AtIantic source region was assumed. For the Ice Complex, a continuous age-height relationship was established, indicating syngenetic vertical ice wedge growth and sediment accumulation rates of 0.7 m/ky. During the Holocene optimum, ice wedge growth was probably limited due to the extensive formation of lacustrine environments. Holocene ice wedges in thermokarst depressions (alases) and thermoerosional valleys (logs) were formed after climate deterioration from about 4.5 ka until the present. Winter temperatures were warmer at this time as compared to the cooler Pleistocene. Migration of bound water between ice wedges and segregated ice may have altered the isotopic composition of old ice wedges. The presence of ice wedges as diagnostic features for permafrost conditions since 60 ka, implies that a large glacier extending over the Laptev Sea shelf did not exist. For the remote non-glaciated areas of Northern Siberia, ice wedges were established as a powerful climate archive.

Impacts of passive warming chambers on soil parameters in Antarctica

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss the microclimate impacts of passive warming chambers (closed, ventilated and Open Top Chamber-OTC) commonly used in Antarctic terrestrial habitats, paying special attention to seasonal warming, during the growing season and outside, extreme temperatures and freeze-thaw events. Both temperature increases and decreases were recorded throughout the year. Closed chambers caused earlier spring soil thaw (8-28 days) while OTCs delayed soil thaw (3-13 days). Smaller closed chamber types recorded the largest temperature extremes (up to 20°C higher than ambient) and longest periods (up to 11 h) of above ambient extreme temperatures, and even OTCs had above ambient temperature extremes over up to 5 consecutive hours. The frequency of freeze-thaw events was reduced by ~25%. All chamber types experienced extreme temperature ranges that could negatively affect biological responses, while warming during winter could result in depletion of limited metabolic resources. The effects outside the growing season could be as important in driving biological responses as the mean summer warming. We make suggestions for improving season-specific warming simulations and propose that seasonal and changed temperature patterns achieved under climate manipulations should be recognised explicitly in descriptions of treatment effects.

Pteropod sedimentation at AWI HAUSGARTEN central station HGIV from 2000 to 2012

Pteropods are an important component of the zooplankton community and hence of the food web in the Fram Strait. They have a calcareous (aragonite) shell and are thus sensitive in particular to the effects of the increasing CO2 concentration in the atmosphere and the associated changes of pH and temperature in the ocean. In the eastern Fram Strait, two species of thecosome pteropods occur, the cold water-adapted Limacina helicina and the subarctic boreal species Limacina retroversa. Both species were regularly observed in year-round moored sediment traps at ~ 200-300 m depth in the deep-sea long-term observatory HAUSGARTEN (79°N, 4°E). The flux of all pteropods found in the trap samples varied from < 20 to ~ 870 specimen/m**2/d in the years 2000-2009, being lower during the period 2000-2006. At the beginning of the time series, pteropods were dominated by the cold-water-adapted L. helicina, whereas the subarctic boreal L. retroversa was only occasionally found in large quantities (> 50/m**2/d). This picture completely changed after 2005/6 when L. retroversa became dominant and total pteropod numbers in the trap samples increased significantly. Concomitant to this shift in species composition, a warming event occurred in 2005/6 and persisted until the end of the study in 2009, despite a slight cooling in the upper water layer after 2007/8. Sedimentation of pteropods showed a strong seasonality, with elevated fluxes of L. helicina from August to November. Numbers of L. retroversa usually increased later, during September/October, with a maximum at the end of the season during December/January. In terms of carbonate export, aragonite shells of pteropods contributed with 11-77% to the annual total CaCO3 flux in Fram Strait. The highest share was found in the period 2007 to 2009, predominantly during sedimentation events at the end of the year. Results obtained by sediment traps occasionally installed on a benthic lander revealed that pteropods also arrive at the seafloor (~ 2550 m) almost simultaneous with their occurrence in the shallower traps. This indicates a rapid downward transport of calcareous shells, which provides food particles for the deep-sea benthos during winter when other production in the upper water column is shut down. The results of our study highlight the great importance of pteropods for the biological carbon pump as well as for the carbonate system in Fram Strait at present, and indicate modifications within the zooplankton community. The results further emphasize the importance of long-term investigation to disclose such changes.

Counts of harpacticoid copepods associated with cold-water coral substrates obtained from several Belgica cruises, Porcupine Seabight (North-East Atlantic)

The influence of microhabitat type on the diversity and community structure of the harpacticoid copepod fauna associated with a cold-water coral degradation zone was investigated in the Porcupine Seabight (North-East Atlantic). Three substrate types were distinguished: dead fragments of the cold-water coral Lophelia pertusa, skeletons of the glass sponge Aphrocallistes bocagei and the underlying sediment. At the family level, it appears that coral fragments and underlying sediment do not harbour distinctly diVerent assemblages, with Ectinosomatidae, Ameiridae, Pseudotachidiidae, Argestidae and Miraciidae as most abundant. Conclusions on assemblage structure and diversity of the sponge skeletons are limited as only two samples were available. Similarity analysis at species level showed a strong variation in the sediment samples, which did not harbour a distinctly different assemblage in opposition to the coral and sponge samples. Several factors (sediment infill on the hard substrates, mobility of the copepods, limited sample sizes) are proposed to explain this apparent lack of a distinct difference between the microhabitats. Coral fragments and sediment were both characterised by high species diversity and low species dominance, which might indicate that copepod diversity is not substantially influenced by hydrodynamic stress. The additive partitioning of species diversity showed that by adding locations species richness was greatly enhanced. The harpacticoid community in the cold-water coral degradation zone is highly diverse and includes 157 species, 62 genera and 19 families. Information from neighbouring soft-bottom regions is necessary to assess whether total species diversity is increased by the presence of these complex habitatproviding substrates.