Abstract: Abstract. IIn recent years, pelagic tunicates (mostly salps, but potentially doliolids, appendicularians and pyrosomes as well) have been used in isotopic studies as a baseline consumer (trophic position 2) when recreating food web dynamics to overcome the challenges of using particulate organic matter (POM). While pelagic tunicates are continuous filter feeders, recent evidence has shown that they have selective feeding behaviors, and preferentially assimilate certain particles. In this review, we combine available stable isotope data for POM and pelagic tunicates and identify that trophic enrichment in 13C and 15N relative to POM is highly variable, and suggests tunicates prefer to consume smaller, heterotrophic organisms. Here we propose that it is not appropriate to consider pelagic tunicates as representative first level consumers in the classical pelagic food web in stable isotope analyses. Rather it needs acknowledgment that they are members of the microbial food web, and thus reflect an alternate food chain.

Abstract: Abstract We investigate the Mw 7.8, 2016 Kaikoura (New Zealand) earthquake by using optical satellite imagery and seismology to reveal the main features of the rupture process. Correlation of Landsat8 images reveals a 30?40?km surface rupture on the Kekerengu Fault and Jordan Thrust, with up to 12?m of right?lateral slip. A previously unrecognized conjugate strike?slip fault, the Papatea Fault, also slipped coseismically (3?4?m). The global centroid moment tensor (gCMT) centroid indicates both thrust and right?lateral slip and is located ~100?km NE of the main shock epicenter. The significant non?double?couple component of the gCMT (25%) suggests that the main shock is not well represented by a single planar fault. Back projection of teleseismic P waves reveals two main bursts of seismic radiation: (1) at 10?20?s, near the main shock epicenter, and (2) at ~70?s, close to the observed surface ruptures. We determine a finite source kinematic model of the rupture from the inversion of seismic waveforms. We use two faults in our model, defined to match the observed slip on the Kekerengu Fault, and a deeper offshore fault with a lower dip angle to satisfy the long period seismological observations. We compute the equivalent moment tensor from our finite source model and find it to be remarkably consistent with the gCMT solution. Although little is known about the geometry of these faults at depth, if the Kekerengu Fault splays from the deeper thrust, then it provides a rare example where the contribution of slip on a splay fault can be clearly isolated in the seismological waveforms.

Abstract: AbstractTide gauge records are the primary source of sea level information over multidecadal to century timescales. A critical issue in using this type of data to determine global climate?related contributions to sea level change concerns the vertical motion of the land upon which the gauges are grounded. Here we use observations from the Global Positioning System for the correction of this vertical land motion. As a result, the spatial coherence in the rates of sea level change during the twentieth century is highlighted at the local and the regional scales, ultimately revealing a clearly distinct behavior between the Northern and the Southern Hemispheres with values of 2.0?mm/yr and 1.1?mm/yr, respectively. Our findings challenge the widely accepted value of global sea level rise for the twentieth century.

Abstract: The species of the genus Aequiyoldia Soot-Ryen, 1951, previously known as Yoldia, are common, soft-substratum, sareptid bivalves. In the Southern Ocean, Aequiyoldia eightsii (Jay, 1839) was originally described from the Antarctic Peninsula and has also been reported in southern South America. The species A. woodwardi (Hanley, 1960) was reported for the Falkland/Malvinas Islands and Tierra del Fuego, but this taxon has been recently synonymised within the broadly distributed A. eightsii. Aequiyoldia has received little attention across its distribution in the Southern Ocean, and although its taxonomy and systematics remain uncertain, all the species have been grouped under a single and broadly distributed unit: A. eightsii. Nevertheless, preliminary mtDNA comparisons demonstrated a marked genetic divergence (>7%) between A. eightsii populations from South America and Antarctic Peninsula. In order to further understand the diversity and biogeography of Aequiyoldia, we analyzed A. eightsii populations from different provinces of the Southern Ocean including South America (SA), the Falkland/Malvinas Islands (FI), the Antarctic Peninsula (AP), and Kerguelen Islands (KI). Individuals were characterized according to typical diagnostic morphological measurements and phylogenetic relationships were reconstructed based on mtDNA (cytochrome c oxidase subunit I). Patterns of genetic divergence of nucDNA intergenic transcribed spacers (ITS1, ITS2) were also estimated. The statistical analysis of external diagnostic characteristics revealed two morphotypes: (1) individuals with the morphology recorded for the nominal FI species, A. woodwardi, and (2) individuals from SA, AP, and KI, with the morphology recorded for A. eightsii. However, phylogenetic reconstructions based on mtDNA and nucDNA suggest the presence of at least five lineages within A. eightsii including: one lineage in Kerguelen Island, two lineages in the Antarctic Peninsula, one lineage in South America, and the last one restricted to the Falkland/Malvinas Islands. Such results are evidence that the Antarctic Polar Front represents an historical biogeographic barrier for this group and that after the separation of these lineages, they followed independent evolutionary pathways in different provinces of the Southern Ocean. Estimates of divergence time suggest that KI separated from other Aequiyoldia lineages close to the middle Miocene. Following this, the separation between the AP and SA lineages occurred at the end of the Miocene around 7.5?Ma. Finally, Aequiyoldia diversified during the Pliocene in Antarctic Peninsula (?4.5?Ma) and South America (?3.0?Ma). Individuals from FI exhibited morphological differences, and 4% of divergence from South American individuals, suggesting that A. woordwardi could be revalidated. Similarly, the marked molecular divergence between the KI and the rest of the recorded lineages also support the validity of A. kerguelensis (Thiele, 1931).