Description: The snow crab Chionoecetes opilio and Arctic lyre crab Hyas coarctatus are prominent members of the Chukchi Sea epifaunal community. A better understanding of their life history will aid in determining their role in this ecosystem in light of the changing climate and resource development. In this study, the size frequency distribution, growth, and mortality of these two crab species was examined in 2009, 2010, 2012, and 2013 to determine temporal and spatial patterns within the eastern Chukchi Sea, and to identify potential environmental drivers of the observed patterns. Temporally, the mean size of both sexes of C. opilio and H. coarctatus decreased significantly from 2009 to 2013, with the number of rare maximum sized organisms decreasing significantly to near absence in the latter two study years. Spatially, the mean size of male and female crabs of both species showed a latitudinal trend, decreasing from south to north in the investigation area. Growth of both sexes of C. opilio and H. coarctatus was linear over the sampled size range, and mortality was highest in the latter two study years. Life history features of both species related to different environmental parameters in different years, ranging from temperature, the sediment carbon to nitrogen ratio of the organic content, and sediment grain size distribution. Likely explanations for the observed temporal and spatial variability are ontogenetic migrations of mature crabs to warmer areas possibly due to cooler water temperatures in the latter two study years, or interannual fluctuations, which have been reported for C. opilio populations in other areas where successful waves of recruitment were estimated to occur in eight year intervals. Further research is suggested to determine if the spatial and temporal patterns found in this study are part of the natural variability in this system or if they are an indication of long-term trends.

Description: Macrofaunal sediment reworking activity is a key driver of ecosystem functioning in marine systems. So far sediment reworking rates can only accurately be assessed by measurements as inference from community parameters is limited. In this case study we test the applicability of 2-D optical florescent sediment profile imaging (f-SPI) on multi corer type incubation cylinders. f-SPI has to date been applied to flat-surfaced (i.e. rectangular) cores only, while multi corer type incubation cylinders were analyzed by the spatially low resolved and invasive slicing technique. Here we apply both methods to cylindrical sediment cores (10 cm diameter). Cores were taken from by two common communities (i.e. Nucula-community and Amphiura-community) in the southern German Bight. Both f-SPI and the slicing technique showed similar vertical luminophore profiles. However the slicing technique found no significant differences between the two communities, whereas f-SPI showed significant differences for all investigated sediment reworking parameters: sediment reworking rate, non-locality index, mean weighted luminophore depth, and the maximal luminophore depth. Consequently, this may lead to different conclusions about the sediment reworking behaviors of the two communities. Likely the slicing method failed to detect significant differences between the Nucula- and Amphiura-community, owing to insufficient spatial accuracy. The f-SPI method, on the other hand, did not capture the full extent of maximal sediment reworking depth due to wall-effects. We conclude that both methods have specific drawbacks and advantages. While slicing is preferable when focusing on the absolute maximal sediment reworking depth especially with predominantly sessile communities, f-SPI is better suited to capture general sediment reworking patterns of most other communities. We demonstrate further that the bias, which is introduced by the distortion effect on imaging due to optical perspective and cylinder wall curvature of rounded cylinders using f-SPI, is negligible. Accordingly our results indicate that the distortion effects by curvature of the rounded cylinder walls will not cause underestimations of sediment reworking parameters in the f-SPI approach. Consequently f-SPI is suitable for the investigation of sediment reworking in natural communities by means of multi corer type samples.

Description: Understanding past seasonal temperature variability in the ocean is essential to evaluate the effects of future climate change on marine ecosystems. Here, we estimate seasonal water temperature amplitudes from stable oxygen isotope (δ18Oshell) values of fossil shells of Arctica islandica (assuming δ18Owater = + 0.9 ± 0.1‰ V-SMOW). Specimens were collected from three Pleistocene successions (Emilian and Sicilian substages of the Calabrian) in Central and Southern Italy (i.e., Rome, Lecce and Sicily). Biostratigraphic analyses from Rome Quarry deposits indicate an age between 1.6 and 1.2 Ma, whereas Sicily and Lecce successions are slightly more recent (between 1.1 and 0.62 Ma). Prior to carbonate geochemical analysis, we checked the shells for potential diagenetic alterations (e.g., from aragonite to calcite) using confocal Raman microscopy. δ18Oshell transects indicate an annual temperature amplitude of about 3 °C during the Early Pleistocene. This is in sharp contrast to reconstructions based on faunal assemblages, according to which the simultaneous occurrence of boreal and warm-water species in the Calabrian Mediterranean Sea suggests a much higher seasonality (ca. 10 °C). The low seasonality and the relatively cold water (9–10 °C) indicate the outcrops represent colder climatic conditions compared to modern times, and suggest the occurrence of a maximum glacial phase.