Photopic and scotopic spatiotemporal tuning of adult zebrafish vision.

Sensitivity to spatial and temporal patterns is a fundamental aspect of vision. Herein, we investigated this sensitivity in adult zebrafish for a wide range of spatial (0.014 to 0.511 cycles/degree [c/d]) and temporal frequencies (0.025 to 6 cycles/s) to better understand their visual system. Measurements were performed at photopic (1.8 log cd m(-2)) and scotopic (-4.5 log cd m(-2)) light levels to assess the optokinetic response (OKR). The resulting spatiotemporal contrast sensitivity (CS) functions revealed that the OKR of zebrafish is tuned to spatial frequency and speed but not to temporal frequencies. Thereby, optimal test parameters for CS measurements were identified. At photopic light levels, a spatial frequency of 0.116 ± 0.01 c/d (mean ± SD) and a grating speed of 8.42 ± 2.15 degrees/second (d/s) was ideal; at scotopic light levels, these values were 0.110 ± 0.02 c/d and 5.45 ± 1.31 d/s, respectively. This study allows to better characterize zebrafish mutants with altered vision and to distinguish between defects of rod and cone photoreceptors as measurements were performed under different light conditions.

Achieving a more realistic assessment of rockfall hazards by coupling three-dimensional process models and field-based tree-ring data

Sound knowledge of the spatial and temporal patterns of rockfalls is fundamental for the management of this very common hazard in mountain environments. Process-based, three-dimensional simulation models are nowadays capable of reproducing the spatial distribution of rockfall occurrences with reasonable accuracy through the simulation of numerous individual trajectories on highly-resolved digital terrain models. At the same time, however, simulation models typically fail to quantify the ‘real’ frequency of rockfalls (in terms of return intervals). The analysis of impact scars on trees, in contrast, yields real rockfall frequencies, but trees may not be present at the location of interest and rare trajectories may not necessarily be captured due to the limited age of forest stands. In this article, we demonstrate that the coupling of modeling with tree-ring techniques may overcome the limitations inherent to both approaches. Based on the analysis of 64 cells (40 m × 40 m) of a rockfall slope located above a 1631-m long road section in the Swiss Alps, we illustrate results from 488 rockfalls detected in 1260 trees. We illustrate that tree impact data cannot only be used (i) to reconstruct the real frequency of rockfalls for individual cells, but that they also serve (ii) the calibration of the rockfall model Rockyfor3D, as well as (iii) the transformation of simulated trajectories into real frequencies. Calibrated simulation results are in good agreement with real rockfall frequencies and exhibit significant differences in rockfall activity between the cells (zones) along the road section. Real frequencies, expressed as rock passages per meter road section, also enable quantification and direct comparison of the hazard potential between the zones. The contribution provides an approach for hazard zoning procedures that complements traditional methods with a quantification of rockfall frequencies in terms of return intervals through a systematic inclusion of impact records in trees.

Deep water provenance and dynamics of the (de)glacial Atlantic meridional overturning circulation

Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (εNd) and the 231Pa/230Th ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined 231Pa/230Th and εNd down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic Meridional Overturning Circulation over the past ∼25 ka. Our results provide evidence for a consistent pattern of glacial/stadial advances of Southern Sourced Water along with a northward circulation mode for all cores in the deeper (>3000 m) Atlantic. Results from shallower core sites support an active overturning cell of shoaled Northern Sourced Water during the LGM and the subsequent deglaciation. Furthermore, we report evidence for a short-lived period of intensified AMOC in the early Holocene.

Role of entorhinal cortical plasticity in spatial and contextual memory

It is well accepted that the hippocampus (HIP) is important for spatial and contextual memories, however, it is not clear if the entorhinal cortex (EC), the main input/output structure for the hippocampus, is also necessary for memory storage. Damage to the EC in humans results in memory deficits. However, animal studies report conflicting results on whether the EC is necessary for spatial and contextual memory. Memory consolidation requires gene expression and protein synthesis, mediated by signaling cascades and transcription factors. Extracellular-signal regulated kinase (ERK) cascade activity is necessary for long-term memory in several tasks, including those that test spatial and contextual memory. In this work, we explore the role of ERK-mediated plasticity in the EC on spatial and contextual memory. ^ To evaluate this role, post-training infusions of reversible pharmacological inhibitors specific for the ERK cascade that do not affect normal neuronal activity were targeted directly to the EC of awake, behaving animals. This technique provides spatial and temporal control over the inhibition of the ERK cascade without affecting performance during training or testing. Using the Morris water maze to study spatial memory, we found that ERK inhibition in the EC resulted in long-term memory deficits consistent with a loss of spatial strategy information. When animals were allowed to learn and consolidate a spatial strategy for solving the task prior to training and ERK inhibition, the deficit was alleviated. To study contextual memory, we trained animals in a cued fear-conditioning task and saw an increase in the activation of ERK in the EC 90 minutes following training. ERK inhibition in the EC over this time point, but not at an earlier time point, resulted in increased freezing to the context, but not to the tone, during a 48-hour retention test. In addition, animals froze maximally at the time the shock was given during training; similar to naïve animals receiving additional training, suggesting that ERK-mediated plasticity in the EC normally suppresses the temporal nature of the freezing response. These findings demonstrate that plasticity in the EC is necessary for both spatial and contextual memory, specifically in the retention of behavioral strategies. ^

Accumulation rates for western Dronning Maud Land from firn cores and snow pits

As a result of intensive field activities carried out by several nations over the past 15 years, a set of accumulation measurements for western Dronning Maud Land, Antarctica, was collected, based on firn-core drilling and snow-pit sampling. This new information was supplemented by earlier data taken from the literature, resulting in 111 accumulation values. Using Geographical Information Systems software, a first region-wide mean annual snow-accumulation field was derived. In order to define suitable interpolation criteria, the accumulation records were analyzed with respect to their spatial autocorrelation and statistical properties. The resulting accumulation pattern resembles well known characteristics such as a relatively wet coastal area with a sharp transition to the dry interior, but also reveals complex topographic effects. Furthermore, this work identifies new high-return shallow drilling sites by uncovering areas of insufficient sampling density.

Contusotruncana contusa abundances and morphotypes in the cretaceous mid-latitude South Atlantic

Spatial and temporal patterns in test size and shape (test conicity and spiral roundness) and absolute abundance (accumulation rate) of the planktonic foraminifer Contusotruncana contusa were studied in the South Atlantic Ocean (DSDP sites 356, 516, 525 and 527) during an interval corresponding to the last 800 kyr of the Cretaceous. The variation in absolute abundance of C. contusa was characterised by alternating periods of high and low abundance; some of these periods were traceable across the entire mid-latitude South Atlantic Ocean. While the mean spiral roundness did not show any interpretable patterns, a sudden increase of the mean test size and mean test conicity occurred between 65.3 and 65.2 Ma (based on linear interpolation within the Cretaceous part of Subchron C29R) at all sites studied, indicating a poleward migration followed by rapid withdrawal of the low-latitude C. contusa morphotypes from the mid-latitude South Atlantic Ocean. We suggest that this event was caused by a short period of surface-water warming in the southern mid-latitudes corresponding to the brief high-latitude warming event and associated faunal migrations in the Boreal and Austral realms.

Statistics on low cloud occurrence per month along the South-Western African coast at 7:00 and 14:00 UTC, 2004 to 2009

The spatial and temporal patterns of fog and low clouds along the South-Western African coast are characterized based on an evaluation of Meteosat SEVIRI satellite data. A technique for the detection of fog/low clouds in the region is introduced, and validated using 1 year of CALIOP cloud lidar products, showing reliable performance. The frequency of fog and low cloud in the study area is analyzed by systematic application of the technique to all available Meteosat SEVIRI scenes from 2004 to 2009, for 7:00 UTC and 14:00 UTC. The highest frequencies are encountered in the area around Walvis Bay, with a peak in the summer months. Fog and low clouds clear by 14:00 UTC almost everywhere over land.

Radioisotopes and He accumulation in deep sea sediments of the Ontong Java Plateau

The accumulation of extraterrestrial 3He, a tracer for interplanetary dust particles (IDPs), in sediments from the Ontong Java Plateau (OJP; western equatorial Pacific Ocean) has been shown previously to exhibit a regular cyclicity during the late Pleistocene, with a period of ~100 ka. Those results have been interpreted to reflect periodic variability in the global accretion of IDPs that, in turn, has been linked to changes in the inclination of Earth's orbit with respect to the invariable plane of the solar system. Here we show that the accumulation in OJP sediments of authigenic 230Th, produced by radioactive decay of 234U in seawater, exhibits a 100-ka cyclicity similar in phase and amplitude to that evident in the 3He record. We interpret the similar patterns of 230Th and 3He accumulation to reflect a common origin within the ocean-climate system. Comparing spatial and temporal patterns of sediment accumulation against regional patterns of biological productivity and against the well-established pattern of CaCO3 dissolution in the deep Pacific Ocean leads to the further conclusion that a common 100-ka cycle in accumulation of biogenic, authigenic and extraterrestrial constituents in OJP sediments reflects the influence of climate-related changes in sediment focusing, rather than changes in the rate of production or supply of sedimentary constituents.

Vegetation, soil and site characteristics of samples taken along the Yamal Transet in 2007-2008

The overarching goal of the Yamal portion of the Greening of the Arctic project is to examine how the terrain and anthropogenic factors of reindeer herding and resource development combined with the climate variations on the Yamal Peninsula affect the spatial and temporal patterns of vegetation change and how these changes are in turn affecting traditional herding of the indigenous people of the region. The purpose of the expeditions was to collect groundobservations in support of remote sensing studies at four locations along a transect that traverses all the major bioclimate subzones of the Yamal Peninsula. This data report is a summary of information collected during the 2007 and 2008 expeditions. It includes all the information from the 2008 data report (Walker et al. 2008) plus new information collected at Kharasavey in Aug 2008. The locations included in this report are Nadym (northern taiga subzone), Laborovaya (southern tundra = subzone E of the Circumpolar Arctic Vegetation Map (CAVM), Vaskiny Dachi (southern typical tundra = subzone D), and Kharasavey (northern typical tundra = subzone C). Another expedition is planned for summer 2009 to the northernmost site at Belyy Ostrov (Arctic tundra = subzone B). Data are reported from 10 study sites - 2 at Nadym, 2 at Laborovaya, and 3 at Vaskiny Dachi and 3 at Kharasavey. The sites are representative of the zonal soils and vegetation, but also include variation related to substrate (clayey vs. sandy soils). Most of the information was collected along 5 transects at each sample site, 5 permanent vegetation study plots, and 1-2 soil pits at each site. The expedition also established soil and permafrost monitoring sites at each location. This data report includes: (1) background for the project, (2) general descriptions and photographs of each locality and sample site, (3) maps of the sites, study plots, and transects at each location, (4) summary of sampling methods used, (5) tabular summaries of the vegetation data (species lists, estimates of cover abundance for each species within vegetation plots, measured percent ground cover of species along transects, site factors for each study plot), (6) summaries of the Normalized Difference Vegetation Index (NDVI) and leaf area index (LAI) along each transect, (7) soil descriptions and photos of the soil pits at each study site, (8) summaries of thaw measurements along each transect, and (9) contact information for each of the participants. One of the primary objectives was to provide the Russian partners with full documentation of the methods so that Russian observers in future years could repeat the observations independently.

Sedimentology of core PS2564-3 and GeoB2110-4

In the South Atlantic and adjoining Southern Ocean the kaolinite/chlorite-ratio in Late Quaternary sediments are an alternative deep water proxy to benthic foraminiferal proxies and carbonate preservation indices that is even suitable in regions with poor carbonate preservation. This paper shows the relationship between modern abyssal circulation and the kaolinite/chloriteratio and presents reconstructions of deep and bottom water advection based on the kaolinite/ chlorite proxy. We also discuss the limitations and future perspectives of the kaolinite/chlorite proxy. Latitudinal and water depth-related patterns of the kaolinite/chlorite-ratio in surface sediments correspond to the modern deep and bottom water mass distribution. Kaolinite originates from lowlatitudes and traces North Atlantic Deep Water (northern-source deep water) advection to the south. Chlorite from the southern high-latitudes is exported via northward advecting Antarctic Bottom Water and Circumpolar Deep Water (southern-source deep and bottom water). Deep-sea sedimentation in regions underlying the Antarctic Circumpolar Current was current-dominated throughout the Late Quaternary. Temporal variations of the kaolinite/chlorite-ratio in response to glacial-interglacial cycles reflect changing deep water mass configurations, suggesting a shallowing and northward retreat of northern-source deep water and accordingly wider expansion of southernsource deep and bottom water masses during glacial times relative to interglacial times. Submarine topography influenced the spatial and temporal patterns of deep water mass distribution.

The relationship between alkaloid-based chemical defenses and diet in dendrobatid poison frogs

Chemical defenses are common among organisms and represent some of the most complex adaptations for avoiding predation, yet our understanding of the ecological nature of these systems remains incomplete. Poison frogs are a group of chemically defended organisms that are dependent entirely on diet for chemical defense. In this study, I identified the dietary arthropods responsible for chemical defense in poison frogs, described spatial and temporal patterns in alkaloid composition of poison frogs, and established links between patterns of variation in alkaloid defense and arthropod diet in poison frogs. Identifying dietary sources and studying patterns of variation in alkaloid composition is fundamental to understanding the ecology and evolution of chemical defense in poison frogs. ^ The dendrobatid poison frog Oophaga pumilio shares many alkaloids in common with other poison frogs and is known to vary in alkaloid composition throughout its geographic range. I designed my dissertation to take advantage of these characteristics and use O. pumilio as a model species for the study of chemical defense in poison frogs. Here, I identified siphonotid millipedes as a source for spiropyrrolizidine alkaloids, formicine ants as a source for pumiliotoxin alkaloids, and oribatid mites as dietary sources for the majority of alkaloids found in poison frogs. I found that alkaloid composition varied spatially and temporally, on both small and large scales, within and among populations of O. pumilio. Alkaloid variation between populations was related to geographic distance, and closer populations tended to have alkaloid compositions more similar to each other than to distant populations. ^ The findings of my study suggest that oribatid mites are the most important dietary source of alkaloids in poison frogs. However, overall alkaloid defense in poison frogs is based on a combination of dietary arthropods, including mites, ants, millipedes, and beetles. Variation in chemical defenses of poison frogs is due to (1) spatial and temporal differences in the presence of alkaloids in certain arthropods and (2) differences in the availability of certain alkaloid-containing arthropods, which are likely the result of differences as well as successional changes in forest structure among locations and through time. ^

Radionuclides, Nd isotopes and biogenic Opal in Atlanic Ocean sediments

Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (epsilon-Nd) and the 231Pa/230Th ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined 231Pa/230Th and epsilon-Nd down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic Meridional Overturning Circulation over the past ~25 ka. Our results provide evidence for a consistent pattern of glacial/stadial advances of Southern Sourced Water along with a northward circulation mode for all cores in the deeper (>3000 m) Atlantic. Results from shallower core sites support an active overturning cell of shoaled Northern Sourced Water during the LGM and the subsequent deglaciation. Furthermore, we report evidence for a short-lived period of intensified AMOC in the early Holocene.

Mapped cetacean habitat suitability and richness in the Azores, links to ArcGIS files

Marine spatial planning and ecological research call for high-resolution species distribution data. However, those data are still not available for most marine large vertebrates. The dynamic nature of oceanographic processes and the wide-ranging behavior of many marine vertebrates create further difficulties, as distribution data must incorporate both the spatial and temporal dimensions. Cetaceans play an essential role in structuring and maintaining marine ecosystems and face increasing threats from human activities. The Azores holds a high diversity of cetaceans but the information about spatial and temporal patterns of distribution for this marine megafauna group in the region is still very limited. To tackle this issue, we created monthly predictive cetacean distribution maps for spring and summer months, using data collected by the Azores Fisheries Observer Programme between 2004 and 2009. We then combined the individual predictive maps to obtain species richness maps for the same period. Our results reflect a great heterogeneity in distribution among species and within species among different months. This heterogeneity reflects a contrasting influence of oceanographic processes on the distribution of cetacean species. However, some persistent areas of increased species richness could also be identified from our results. We argue that policies aimed at effectively protecting cetaceans and their habitats must include the principle of dynamic ocean management coupled with other area-based management such as marine spatial planning.

Endogenous Risk Perception, Geospatial Characteristics and Temporal Variation in Hurricane Evacuation Behavior

The main focus of this thesis was to gain a better understanding about the dynamics of risk perception and its influence on people’s evacuation behavior. Another major focus was to improve our knowledge regarding geo-spatial and temporal variations of risk perception and hurricane evacuation behavior. A longitudinal dataset of more than eight hundred households were collected following two major hurricane events, Ivan and Katrina. The longitudinal survey data was geocoded and a geo-spatial database was integrated to it. The geospatial database was composed of distance, elevation and hazard parameters with respect to the respondent’s household location. A set of Bivariate Probit (BP) model suggests that geospatial variables have had significant influences in explaining hurricane risk perception and evacuation behavior during both hurricanes. The findings also indicated that people made their evacuation decision in coherence with their risk perception. In addition, people updated their hurricane evacuation decision in a subsequent similar event.

(Table 1) Annual mean concentrations of atmospheric a- and g-Hexachlorocyclohexane at stations Alert, Canada and Zeppelin, Norway

Twelve year datasets of weekly atmospheric concentrations of alpha- and gamma-HCH were compared between the two Arctic monitoring stations of Alert, Nunavut, Canada, and Zeppelin Mountain, Svalbard, Norway. Time-series analysis was conducted with the use of dynamic harmonic regression (DHR), which provided a very good model fit, to examine both the seasonal behaviour in these isomers and the longer-term, underlying trends. Strong spatial differences were not apparent between the two sites, although subtle differences in seasonal behaviour and composition were identified. For example, the composition of gamma-HCH to total HCH (alpha + gamma) was greater at Zeppelin compared to Alert, probably reflecting this site's proximity to major use regions of lindane. Pronounced seasonality in air concentrations for gamma-HCH was marked by a 'spring maximum event' (SME), confirming earlier studies. For alpha-HCH, the SME was much weaker and only evident at Alert, whereas at Zeppelin, seasonal fluctuations for alpha-HCH were marked by elevated concentrations in summer and lower concentrations during winter, with this pattern most apparent for the years after 2000. We attribute this difference in spatial and temporal patterns to the Arctic oscillation. A similar climatic pattern was not evident at either site in the gamma-HCH data. Seasonally adjusted, long-term trends revealed declining concentrations at both sites for alpha- and gamma-HCH over the entire time-series. Recent legislation affecting lindane use appear to account for this decline in gamma-HCH, with little evidence of a delay or 'lag' between the banning of lindane in Europe (a main source region) or Canada, and a decline in air concentrations observed at both Arctic sites.