The Influence of Climate Variability on Holoplanktonic Polychaetes Populations of Ocean Sector of the Colombian Pacific Basin

Studies of holoplanktonic polychaetes in the Tropical Eastern Pacific have focused on their systematics and distribution however, population responses related to climate variability are non-existent. Therefore, the present work described for the first time the influence of the climatic variability 2004-2012 on the holoplanktonic polychaetes populations, as well as their relationship to environmental variables. Species of the Alciopidae, Lopadorrhynchidae and Iospilidae families were identified from 85 samples collected in the Pacific Basin of Colombia, contrasting them with the presence of ENSO, and correlating them with the environmental variables of temperature, salinity and chlorophyll-α concentration. Of the 14 species identified, only Lopadorrhynchus cf. henseni and L. cf. brevis increased their densities under El Niño and correlated positively with temperature. Rhynchonereella cf. petersii correlated negatively with temperature;while R. cf. gracilis and Pelagobia cf. longicirrata were positively correlated with chlorophyll-α concentration and salinity, respectively. Additionally, with the first description of the environmental ranges of the 14 species identified for the Colombian Pacific basin, it was found that the most commons species presented broader environmental ranges. The results from the current research are consistent with previous studies in other regions of the Pacific and latitudes. The responses of the organisms suggest trophic and mobility trends that were not known for tropical holoplanktonic polychaete species.

Geophysical implications for the formation of the Tamu Massif–the Earth's largest single volcano–within the Shatsky Rise in the northwest Pacific Ocean

Recent geophysical research programs survey the Tamu Massif within the Shatsky Rise oceanic plateau in the northwest Pacific Ocean to understand the formation of this immense volcano and to test the forma- tion hypotheses of large igneous province volcanism. Massive sheet basalt flows are cored from the Tamu Massif, implying voluminous eruptions with high effusion rates. Seismic reflection data show that the Tamu Massif is the largest single volcano on Earth, characterized by a central volcanic shield with low- gradient flank slopes, implying lava flows emanating from its center and spreading massive area on the seafloor. Velocity model calculated from seismic refraction data shows that crustal thickness has a negative correlation with average velocity, implying a chemically anomalous origin of the Tamu Massif. Seismic refraction and reflection data reveal a complete crustal structure across the entire vol- cano, featured by a deep crust root with a maximum thickness of -30 kin, and Moho geometry is consis- tent with the Airy lsostasy. These recent findings provide evidence for the two end-member formation models： the mantle plume and the plate boundary, Both are supported by some results, but both are not fit with some either. Consequently, plume-ridge interaction could be a resolution that awaits future investigations.