Origin and evolution of Cycladophora davisiana (Radiolaria) in DSDP Hole 19-192, Northwest Pacific

This paper documents the evolutionary history of Cycladophora davisiana Ehrenberg from an uppermost Miocene to Pleistocene sedimentary record in the high-latitude Northwest Pacific. It apparently evolved from C. sakaii Motoyama through a series of intermediates. C. sakaii has a relatively large shell with an external spongy layer. The evolutionary transition is characterized by a relatively rapid decrease in thorax size with a reduction of the spongy appendage. This change occurred during about 0.4 m.y. from 2.8 to 2.4 Ma without cladogenesis. Following this interval, a decrease in thorax size continued gradually up to the Recent, resulting in a very small morphology. Although the population of C. davisiana first appeared at about 2.5 Ma, some morphotypic specimens may occur in earlier periods as indistinguishable very small endmembers in the C. sakaii populations. Timing of the first appearance events both of morphotypic specimens and of a population of C. davisiana in Site 192 and previously reported cores does not disprove the idea that C. davisiana evolved first in the Northwest Pacific region, and later migrated into other regions of the world ocean. Biometrics clearly indicate no direct phylogenetic relationships between C. davisiana and C. cornutoides Kling in the studied core. Thus, the latter species, which was originally described as a variation and later elevated to a subspecies of the former species, is separated from the former species and raised to the species rank.

(Table 1) Ice floe size and other characteristics during aerial observations in Prydz Bay, Antarctica

On the basis of aerial photographs of sea ice floes in the marginal ice zone (MIZ) of Prydz Bay acquired from December 2004 to February 2005 during the 21st Chinese National Antarctic Research Expedition, image processing techniques are employed to extract some geometric parameters of floes from two merged transects covering the whole MIZ. Variations of these parameters with the distance into the MIZ are then obtained. Different parameters of floe size, namely area, perimeter, and mean caliper diameter (MCD), follow three similar stages of increasing, flat and increasing again, with distance from the open ocean. Floe shape parameters (roundness and the ratio of perimeter to MCD), however, have less significant variations than that of floe size. Then, to modify the deviation of the cumulative floe size distribution from the ideal power law, an upper truncated power-law function and a Weibull function are used, and four calculated parameters of the above functions are found to be important descriptors of the evolution of floe size distribution in the MIZ. Among them, Lr of the upper truncated power-law function indicates the upper limit of floe size and roughly equals the maximum floe size in each square sample area. L0 in the Weibull distribution shows an increasing proportion of larger floes in squares farther from the open ocean and roughly equals the mean floe size. D in the upper truncated power-law function is closely associated with the degree of confinement during ice breakup. Its decrease with the distance into MIZ indicates the weakening of confinement conditions on floes owing to wave attenuation. The gamma of the Weibull distribution characterizes the degree of homogeneity in a data set. It also decreases with distance into MIZ, implying that floe size distributes increase in range. Finally, a statistical test on floe size is performed to divide the whole MIZ into three distinct zones made up of floes of quite different characteristics. This zonal structure of floe size also agrees well with the trends of floe shape and floe size distribution, and is believed to be a straightforward result of wave-ice interaction in the MIZ.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.