ALBERT

Description: A detailed reconstruction of West African monsoon hydrology over the past 155,000 years suggests a close linkage to northern high-latitude climate oscillations. Ba/Ca ratio and oxygen isotope composition of planktonic foraminifera in a marine sediment core from the Gulf of Guinea, in the eastern equatorial Atlantic (EEA), reveal centennial-scale variations of riverine freshwater input that are synchronous with northern high-latitude stadials and interstadials of the penultimate interglacial and the last deglaciation. EEA Mg/Ca-based sea surface temperatures (SSTs) were decoupled from northern high-latitude millennial-scale fluctuation and primarily responded to changes in atmospheric greenhouse gases and low-latitude solar insolation. The onset of enhanced monsoon precipitation lags behind the changes in EEA SSTs by up to 7000 years during glacial-interglacial transitions. This study demonstrates that the stadial-interstadial and deglacial climate instability of the northern high latitudes exerts dominant control on the West African monsoon dynamics through an atmospheric linkage.

Description: 〈jats:p〉Sustained harmonic tremor signals were recorded by the seismographs of the German Neumayer Base seismological network in western Dronning Maud Land, Antarctica. These tremor episodes, lasting up to 16 hours, were recorded up to 820 kilometers from the source. Their spectra show narrow peaks with fundamental frequencies ranging from 0.5 to 6 hertz, more than 30 integer harmonic overtones, and frequency gliding, resembling volcanic tremor. Frequency‐wave number analysis suggested a moving source, which was recognized as iceberg B-09A traveling along the coast of eastern Antarctica. The most probable tremor sources are fluid-flow‐induced vibrations inside the iceberg's tunnel/crevasse systems.〈/jats:p〉

Description: Here we report bipedal movement with a hydrostatic skeleton. Two species of octopus walk on two alternating arms using a rolling gait and appear to use the remaining six arms for camouflage. Octopus marginatus resembles a coconut, and Octopus (Abdopus) aculeatus, a clump of floating algae. Using underwater video, we analyzed the kinematics of their strides. Each arm was on the sand for more than half of the stride, qualifying this behavior as a form of walking.

Description: Sponges (phylum Porifera) are among the most ancient of the multicellular animals, or Metazoa, with a fossil record dating back at least 580 million years (1). Found both in marine and freshwater environments, they filter-feed by pumping water through their bodies, which can contain a remarkable number of microbial symbionts. Sponges lack many of the characteristics typical of animals, but recent genomic studies—including the report by Jackson et al. on page 1893 of this issue (2)—have shown that they possess many major metazoan gene families. Sponges are thus invaluable systems for studying the evolution of metazoans and their interactions with microorganisms. Furthermore, their highly stable skeletons are of interest to materials scientists. Biomineralization is an important feature of metazoan life. Animals including vertebrates, insects, mollusks, and sponges use minerals [such as calcium carbonate, iron, and silica] to form skeletal structures such as bones, seashells, and coral reefs (3). Biocalcification arose among many metazoan lineages during the “Cambrian explosion,” between 530 and 520 million years ago, when the ancestors of today's animals first appeared in the fossil record. Did these lineages share the same gene(s) for biocalcification, or did multiple independent evolutionary events give rise to the ability to biocalcify? Recent studies, including that by Jackson et al., are beginning to provide an answer to this question. Jackson et al. use the Indo- Pacific sponge Astrosclera willeyana to show that the last common ancestor of the metazoans possessed a precursor to the α-carbonic anhydrases. This gene family is used by animals today in a range of processes including ion transport, pH regulation, and biomineralization (4). By integrating molecular techniques ranging from protein sequencing to gene expression, the authors identified a group of closely related α-carbonic anhydrase sequences in A. willeyana. These sequences are similar to those recovered from a whole-genome project on another sponge, Amphimedon queenslandica (5). Together, the sponge α-carbonic anhydrases form a sister group to those of all other metazoans.

Description: Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.

Description: The open oceans comprise most of the biosphere, yet patterns and trends of species diversity there are enigmatic. Here, we derive worldwide patterns of tuna and billfish diversity over the past 50 years, revealing distinct subtropical "hotspots" that appeared to hold generally for other predators and zooplankton. Diversity was positively correlated with thermal fronts and dissolved oxygen and a nonlinear function of temperature (~25°C optimum). Diversity declined between 10 and 50% in all oceans, a trend that coincided with increased fishing pressure, superimposed on strong El Niño–Southern Oscillation–driven variability across the Pacific. We conclude that predator diversity shows a predictable yet eroding pattern signaling ecosystem-wide changes linked to climate and fishing.

Description: The oceans are a major sink for atmospheric carbon dioxide (CO2). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO2 sink for those ocean basins that are well covered by shipping routes.