Dissolved organic carbon in sediments of the central Arctic Ocean collected during POLARSTERN cruise ARK-XXVII/3 from August-September 2012

Marine organic matter (OM) sinks from surface waters to the seafloor via the biological pump. Benthic communities, which use this sedimented OM as energy and carbon source, produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. We hypothesized that in the oligotrophic deep Arctic basin the molecular signal of freshly deposited primary produced OM is restricted to the surface sediment pore waters which should differ from bottom water and deeper sediment pore water in DOM composition. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether the signal of marine vs. terrigenous DOM is represented by different compounds preserved in the sediment pore waters and 3) whether there is any relation between Arctic Ocean ice cover and DOM composition. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometer, were correlated with environmental parameters by partial least square analysis. The fresher marine detrital OM signal from surface waters was limited to pore waters from < 5 cm sediment depth. The productive ice margin stations showed higher abundances of peptides, unsaturated aliphatics and saturated fatty acids formulae, indicative of fresh OM/pigments deposition, compared to northernmost stations which had stronger aromatic signals. This study contributes to the understanding of the coupling between the Arctic Ocean productivity and its depositional regime, and how it will be altered in response to sea ice retreat and increasing river runoff.

Distribution of clay minerals in surface sediments of the Eurasian Arctic Ocean

Clay-mineral distributions in the Arctic Ocean and the adjacent Eurasian shelf areas are discussed to identify source areas and transport pathways of terrigenous material in the Arctic Ocean. The main clay minerals in Eurasian Arctic Ocean sediments are illite and chlorite. Smectite and kaolinite occur in minor amounts in these sediments, but show strong variations in the shelf areas. These two minerals are therefore reliable in reconstructions of source areas of sediments from the Eurasian Arctic. The Kara Sea and the western part of the Laptev Sea are enriched in smectite, with highest values of up to 70% in the deltas of the Ob and Yenisey rivers. Illite is the dominant clay mineral in all the investigated sediments except for parts of the Kara Sea. The highest concentrations with more than 70% illite occur in the East Siberian Sea and around Svalbard. Chlorite represents the clay mineral with lowest concentration changes in the Eastern Arctic, ranging between 10 and 25%. The main source areas for kaolinite in the Eurasian Arctic are Mesozoic sedimentary rocks on Franz-Josef Land islands. Based on clay-mineral data, transport of the clay fraction via sea ice is of minor importance for the modern sedimentary budget in the Arctic basins.

Sedimentology and stable carbon and oxygen isotope record of the Central Arctic

Stable oxygen and carbon isotope and sedimentological-paleontological investigations supported by accelerator mass spectrometry 14C datings were carried out on cores from north of 85°N in the eastern central Arctic Ocean. Significant changes in accumulation rates, provenance of ice-rafted debris (IRD), and planktic productivity over the past 80,000 years are documented. During peak glacials, i.e., oxygen isotope stages 4 and 2, the Arctic Ocean was covered by sea ice with decreased seasonal variation, limiting planktic productivity and bulk sedimentation rates. In early stage 3 and during Termination I, major deglaciations of the circum-Arctic regions caused lowered salinities and poor oxygenation of central Arctic surface waters. A meltwater spike and an associated IRD peak dated to ~14-12 14C ka can be traced over the southern Eurasian Basin of the Arctic Ocean. This event was associated with the early and rapid deglaciation of the marine-based Barents Sea Ice Sheet. A separate Termination Ib meltwater event is most conspicuous in the central Arctic and is associated with characteristic dolomitic carbonate IRD. This lithology suggests an origin of glacial ice from northern Canada and northern Greenland where lower Paleozoic platform carbonates crop extensively out.

Analysis of minerals from Arctic Ocean sediments

The Arctic Ocean System is a key player regarding the climatic changes of Earth. Its highly sensitive ice Cover, the exchange of surface and deep water masses with the global ocean and the coupling with the atmosphere interact directly with global climatic changes. The output of cold, polar water and sea ice influences the production of deep water in the North Atlantic and controls the global ocean circulation ("the conveyor belt"). The Arctic Ocean is surrounded by the large Northern Hemisphere ice sheets which not only affect the sedimentation in the Arctic Ocean but also are supposed to induce the Course of glacials and interglacials. Terrigenous sediment delivered from the ice sheets by icebergs and meltwater as well as through sea ice are major components of Arctic Ocean sediments. Hence, the terrigenous content of Arctic Ocean sediments is an outstanding archive to investigate changes in the paleoenvironment. Glazigenic sediments of the Canadian Arctic Archipelago and surface samples of the Arctic Ocean and the Siberian shelf regions were investigated by means of x-ray diffraction of the bulk fraction. The source regions of distinct mineral compositions were to be deciphered. Regarding the complex circumpolar geology stable christalline shield rocks, active and ancient fold belts including magmatic and metamorphic rocks, sedimentary rocks and wide periglacial lowlands with permafrost provide a complete range of possible mineral combinations. Non- glaciated shelf regions mix the local input from a possible point source of a particular mineral combination with the whole shelf material and function as a sampler of the entire region draining to the shelf. To take this into account, a literature research was performed. Descriptions of outcropping lithologies and Arctic Ocean sediments were scanned for their mineral association. The analyses of glazigenic and shelf sediments yielded a close relationship between their mineral composition and the adjacent source region. The most striking difference between the circumpolar source regions is the extensive outcrop of carbonate rocks in the vicinity of the Canadian Arctic Archipelago and in N Greenland while siliciclastic sediments dominate the Siberian shelves. In the Siberian shelf region the eastern Kara Sea and the western Laptev Sea form a destinct region defined by high smectite, (clino-) pyroxene and plagioclase input. The source of this signal are the extensive outcrops of the Siberian trap basalt in the Putorana Plateau which is drained by the tributaries of the Yenissei and Khatanga. The eastern Laptev Sea and the East Siberian Sea can also be treated as one source region containing a feldspar, quartz, illite, mica, and chlorite asscciation combined with the trace minerals hornblende and epidote. Franz Josef Land provides a mineral composition rich in quartz and kaolinite. The diverse rock suite of the Svalbard archipelago distributes specific mineral compositions of highly metamorphic christalline rocks, dolomite-rich carbonate rocks and sedimentary rocks with a higher diagenetic potential manifested in stable newly built diagenetic minerals and high organic maturity. To reconstruct the last 30,000 years as an example of the transition between glacial and interglacial conditions a profile of sediment cores, recovered during the RV Polarstern" expedition ARK-VIIIl3 (ARCTIC '91), and additional sediment cores around Svalbard were investigated. Besides the mineralogy of different grain size fractions several additional sedimentological and organo-geochemical Parameterswere used. A detailed stratigraphic framework was achieved. By exploiting this data set changes in the mineral composition of the Eurasian Basin sediments can be related to climatic changes. Certain mineral compositions can even be associated with particular transport processes, e.g. the smectitel pyroxene association with sea ice transport from the eastern Kara Sea and the western Laptev Sea. Hence, it is possible to decipher the complex interplay between the influx of warm Atlantic waters into the Southwest of the Eurasian Basin, the waxing and waning of the Svalbard1Barents- Sea- and Kara-Sea-Ice-Sheets, the flooding of the Siberian shelf regions and the surface and deep water circulation. Until now the Arctic Ocean was assumed to be a rather stable System during the last 30,000 years which only switched from a completely ice covered situation during the glacial to seasonally Open waters during the interglacial. But this work using mineral assemblages of sediment cores in the vicinity of Svalbard revealed fast changes in the inflow of warm Atlantic water with the Westspitsbergen Current (< 1000 years), short periods of advances and retreats of the marine based Eurasian ice sheets (1000-3000 years), and short melting phases (400 years?). Deglaciation of the marine-based Eurasian and the land-based north American and Greenland ice sheets are not simultaneous. This thesis postulates that the Kara Sea Ice Sheet released an early meltwater signal prior to 15,000 14C years leading the Barents Sea Ice Sheet while the western land-based ice sheets are following later than 13,500 14C years. The northern Eurasian Basin records the shift between iceberg and sea-ice material derived from the Canadian Arctic Archipelago and N-Greenland and material transported by sea-ice and surface currents from the Siberian shelf region. The phasing of the deglaciation becomes very obvious using the dolomite and quartd phyllosilicate record. It is also supposed that the flooding of the Laptev Sea during the Holocene is manifested in a stepwise increase of sediment input at the Lomonosov Ridge between the Eurasian and Amerasian Basin. Depending on the strength of meltwater pulses from the adjacent ice sheets the Transpolar Drift can probably be relocated. These movements are traceable by the distribution of indicator minerals. Based on the outcome of this work the feasibility of bulk mineral determination can be qualified as excellent tool for paleoenvironmental reconstructions in the Arctic Ocean. The easy preparation and objective determination of bulk mineralogy provided by the QUAX software bears the potential to use this analyses as basic measuring method preceding more time consuming and highly specialised mineralogical investigations (e.g. clay mineralogy, heavy mineral determination).

Differential impacts of elevated CO2 and acidosis on the energy budget of gill and liver cells from Atlantic cod

Ocean acidification impacts fish and other marine species through increased seawater PCO2 levels (hypercapnia). Knowledge of the physiological mechanisms mediating effects in various tissues of fish is incomplete. Here we tested the effects of extracellular hypercapnia and acidosis on energy metabolism of gill and liver cells of Atlantic cod. Exposure media mimicked blood conditions in vivo, either during normo- or hypercapnia and at control or acidic extracellular pH (pHe). We determined metabolic rate and energy expenditure for protein biosynthesis, Na+/K+-ATPase and H+-ATPase and considered nutrition status by measurements of metabolic rate and protein biosynthesis in media with and without free amino acids (FAA). Addition of FAA stimulated hepatic but not branchial oxygen consumption. Normo- and hypercapnic acidosis as well as hypercapnia at control pHe depressed metabolic stimulation of hepatocytes. In gill cells, acidosis depressed respiration independent of PCO2 and FAA levels. For both cell types, depressed respiration was not correlated with the same reduction in energy allocated to protein biosynthesis or Na+/K+-ATPase. Hepatic energy expenditure for protein synthesis and Na+/K+- ATPase was even elevated at acidic compared to control pHe suggesting increased costs for ion regulation and cel- lular reorganization. Hypercapnia at control pHe strongly reduced oxygen demand of branchial Na+/K+-ATPase with a similar trend for H+-ATPase. We conclude that extracellular acidosis triggers metabolic depression in gill and metabolically stimulated liver cells. Additionally, hypercapnia itself seems to limit capacities for metabolic usage of amino acids in liver cells while it decreases the use and costs of ion regulatory ATPases in gill cells.

Seawater carbonate chemistry and impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera (Ammonia tepida and Heterostegina depressa), 2011

Laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration ([CO32-]), and thereby calcite saturation state, on Mg and Sr incorporation into calcite of two species of shallow-water benthic foraminifera: Ammonia tepida and Heterostegina depressa. Impact on Mg and Sr incorporation by increased seawater [CO32-] and thereby higher calcite saturation state, is absent in either species. Comparison to results from a similar culturing experiment, in which calcite saturation state was varied as a function of [Ca2+], reveals that saturation state affects incorporation of Mg and Sr through calcium- rather than carbonate availability. The similarity in response by both species is surprising since the average Mg/Ca ratio is ~ 70 times higher in H. depressa than in A. tepida. Furthermore, these results suggest that the ions involved in biomineralization (i.e. Ca2+ and DIC) are processed by separate cellular transport mechanisms. The similar response of Mg and Sr incorporation in this study suggests that only differences in the Ca2+ transport mechanism affect divalent cation partitioning.

Impacts of seawater acidification on mantle gene expression patterns of the Baltic Sea blue mussel: implications for shell formation and energy metabolism, link to supplementary material

Marine organisms have to cope with increasing CO2 partial pressures and decreasing pH in the oceans. We elucidated the impacts of an 8-week acclimation period to four seawater pCO2 treatments (39, 113, 243 and 405 Pa/385, 1,120, 2,400 and 4,000 µatm) on mantle gene expression patterns in the blue mussel Mytilus edulis from the Baltic Sea. Based on the M. edulis mantle tissue transcriptome, the expression of several genes involved in metabolism, calcification and stress responses was assessed in the outer (marginal and pallial zone) and the inner mantle tissues (central zone) using quantitative real-time PCR. The expression of genes involved in energy and protein metabolism (F-ATPase, hexokinase and elongation factor alpha) was strongly affected by acclimation to moderately elevated CO2 partial pressures. Expression of a chitinase, potentially important for the calcification process, was strongly depressed (maximum ninefold), correlating with a linear decrease in shell growth observed in the experimental animals. Interestingly, shell matrix protein candidate genes were less affected by CO2 in both tissues. A compensatory process toward enhanced shell protection is indicated by a massive increase in the expression of tyrosinase, a gene involved in periostracum formation (maximum 220-fold). Using correlation matrices and a force-directed layout network graph, we were able to uncover possible underlying regulatory networks and the connections between different pathways, thereby providing a molecular basis of observed changes in animal physiology in response to ocean acidification.

Biological impacts of enhanced alkalinity in Carcinus maenas

Further steps are needed to establish feasible alleviation strategies that are able to reduce the impacts of ocean acidification, whilst ensuring minimal biological side-effects in the process. Whilst there is a growing body of literature on the biological impacts of many other carbon dioxide reduction techniques, seemingly little is known about enhanced alkalinity. For this reason, we investigated the potential physiological impacts of using chemical sequestration as an alleviation strategy. In a controlled experiment, Carcinus maenas were acutely exposed to concentrations of Ca(OH)2 that would be required to reverse the decline in ocean surface pH and return it to pre-industrial levels. Acute exposure significantly affected all individuals' acid-base balance resulting in slight respiratory alkalosis and hyperkalemia, which was strongest in mature females. Although the trigger for both of these responses is currently unclear, this study has shown that alkalinity addition does alter acid-base balance in this comparatively robust crustacean species.

Crustaceans and fish abundances and species at and around artificially introduced tetrapod fields in the southern North Sea, 2010-2011

In the coming decades, artificial defence structures will increase in importance worldwide for the protection of coasts against the impacts of global warming. However, the ecological effects of such structures on the natural surroundings remain unclear. We investigated the impact of experimentally introduced tetrapod fields on the demersal fish community in a hard-bottom area in the southern North Sea. The results indicated a significant decrease in fish abundance in the surrounding area caused by migration effects towards the artificial structures. Diversity (HB) and evenness (E) values exhibited greater variation after the introduction of the tetrapods. Additionally, a distinct increase in young-of-the-year (YOY) fish was observed near the structures within the second year after introduction. We suggest that the availability of adequate refuges in combination with additional food resources provided by the artificial structures has a highly species-specific attraction effect. However, these findings also demonstrate that our knowledge regarding the impact of artificial structures on temperate fish communities is still too limited to truly understand the ecological processes that are initiated by the introduction of artificial structures. Long-term investigations and additional experimental in situ work worldwide will be indispensable for a full understanding of the mechanisms by which coastal defence structures interact with the coastal environment.

Gasterosteus aculeatus egg traits and fish lengths vs. experiment setup

1) Our study addresses the role of non-genetic and genetic inheritance in shaping the adaptive potential of populations under a warming ocean scenario. We used a combined experimental approach (transgenerational plasticity and quantitative genetics) to partition the relative contribution of maternal vs. paternal (additive genetic) effects to offspring body size (a key component of fitness), and investigated a potential physiological mechanism (mitochondrial respiration capacities) underlying whole organism growth/size responses. 2) In very early stages of growth (up to 30 days), offspring body size of marine sticklebacks benefited from maternal transgenerational plasticity (TGP): offspring of mothers acclimated to17°C were larger when reared at 17°C, and offspring of mothers acclimated to 21°C were larger when reared at 21°C. The benefits of maternal TGP on body size were stronger and persisted longer (up to 60 days) for offspring reared in the warmer (21°C) environment, suggesting that maternal effects will be highly relevant for climate change scenarios in this system. 3) Mitochondrial respiration capacities measured on mature offspring (F1 adults) matched the pattern of TGP for juvenile body size, providing an intuitive mechanistic basis for the maternal acclimation persisting into adulthood. Size differences between temperatures seen at early growth stages remained in the F1 adults, linking offspring body size to maternal inheritance of mitochondria. 4) Lower maternal variance components in the warmer environment were mostly driven by mothers acclimated to ambient (colder) conditions, further supporting our tenet that maternal effects were stronger at elevated temperature. Importantly, all parent-offspring temperature combination groups showed genotype x environment (GxE) interactions, suggesting that reaction norms have the potential to evolve. 5) To summarise, transgenerational plasticity and genotype x environment interactions work in concert to mediate impacts of ocean warming on metabolic capacity and early growth of marine sticklebacks. TGP can buffer short-term detrimental effects of climate warming and may buy time for genetic adaptation to catch up, therefore markedly contributing to the evolutionary potential and persistence of populations under climate change.

Synergistic effects of ocean acidification and warming on overwintering pteropods in the Arctic

Ocean acidification and warming will be most pronounced in the Arctic Ocean. Aragonite shell-bearing pteropods in the Arctic are expected to be among the first species to suffer from ocean acidification. Carbonate undersaturation in the Arctic will first occur in winter and because this period is also characterized by low food availability, the overwintering stages of polar pteropods may develop into a bottleneck in their life cycle. The impacts of ocean acidification and warming on growth, shell degradation (dissolution), and mortality of two thecosome pteropods, the polar Limacina helicina and the boreal L. retroversa, were studied for the first time during the Arctic winter in the Kongsfjord (Svalbard). The abundance of L. helicina and L. retroversa varied from 23.5 to 120 ind /m2 and 12 to 38 ind /m2, and the mean shell size ranged from 920 to 981 µm and 810 to 823 µm, respectively. Seawater was aragonite-undersaturated at the overwintering depths of pteropods on two out of ten days of our observations. A 7-day experiment [temperature levels: 2 and 7 °C, pCO2 levels: 350, 650 (only for L. helicina) and 880 ?atm] revealed a significant pCO2 effect on shell degradation in both species, and synergistic effects between temperature and pCO2 for L. helicina. A comparison of live and dead specimens kept under the same experimental conditions indicated that both species were capable of actively reducing the impacts of acidification on shell dissolution. A higher vulnerability to increasing pCO2 and temperature during the winter season is indicated compared with a similar study from fall 2009. Considering the species winter phenology and the seasonal changes in carbonate chemistry in Arctic waters, negative climate change effects on Arctic thecosomes are likely to show up first during winter, possibly well before ocean acidification effects become detectable during the summer season.

Geochemical and palynological results of IODP Hole 302-M0004A from Lomonosov Ridge, Arctic Ocean

Several episodes of abrupt and transient warming, each lasting between 50,000 and 200,000 years, punctuated the long-term warming during the Late Palaeocene and Early Eocene (58 to 51 Myr ago) epochs**1,2. These hyperthermal events, such as the Eocene Thermal Maximum 2 (ETM2) that took place about 53.5 Myr ago**2, are associated with rapid increases in atmospheric CO2 content. However, the impacts of most events are documented only locally**3,4. Here we show, on the basis of estimates from the TEX86' proxy, that sea surface temperatures rose by 3-5 °C in the Arctic Ocean during the ETM2. Dinoflagellate fossils demonstrate a concomitant freshening and eutrophication of surface waters, which resulted in euxinia in the photic zone. The presence of palm pollen implies**5 that coldest month mean temperatures over the Arctic land masses were no less than 8 °C, in contradiction of model simulations that suggest hyperthermal winter temperatures were below freezing**6. In light of our reconstructed temperature and hydrologic trends, we conclude that the temperature and hydrographic responses to abruptly increased atmospheric CO2 concentrations were similar for the ETM2 and the better-described Palaeocene-Eocene Thermal Maximum**7,8, 55.5 Myr ago.