Description: Benthic foraminifera provide essential information for paleobathymetric reconstructions. However, the modern distribution of benthic foraminifera, especially at depths below 1000 meters below sea level (mbsl), is still obscure in the offshore regions near Central and South America. To characterize the bathymetric scale in the eastern equatorial Pacific Ocean, we examined the depth distribution of benthic foraminifera using piston core samples taken off the coast of Costa Rica. Foraminiferal assemblages vary according to water depth: 1) U1 (mainly composed of Ammonia beccarii, Cancris sagra, Elphidium tumidum, Hanzawaia concentrica, Pseudononion basispinata, and Planulina exorna) represent inner shelf faunas (shallower than 50 mbsl). 2) U2 (mainly composed of Ammobaculites foliaceus, Bolivina striatula, Cassidulina minuta, Hanzawaia concentrica, Uvigerina incilis, Bulimina denudata, and Cancris sagra) is correlated with mid-shelf depth assemblages, from 50 to 100 mbsl. 3) U3 (mainly composed of Uvigerina incilis, Hanzawaia concentrica, Angulogerina semitrigona, Bolivina acuminata, Bolivina bicostata, and Cibicorbis inflatus) is assigned to outer shelf assemblages from 100 to 200 mbsl. 4) U4 (mainly composed of Bolivina humilis, Bolivina seminuda, Bolivina subadvena, Cassidulina tumida, Epistominella obesa, Angulogerina carinata, and Cibicorbis inflatus) is the upper bathyal faunas (200–600 mbsl). 5) U5 (mainly composed of Brizalina argentea, Uvigerina peregrina, Uvigerina auberiana, Brizalina seminuda, Bulimina striata, Epistominella smithi and Globocassidulina subglobosa) is the mid-bathyal faunas (600–1000 mbsl). 6) U6 (mainly composed of Uvigerina auberiana, Uvigerina peregrina, Brizalina argentea, Bulimina mexicana, Cassidulina carinata, Epistominella smithi, and Lenticulina cushmani) represents the lower bathyal assemblage (1000–2000 mbsl). 7) U7 (mainly composed of Uvigerina auberiana, Brizalina argentea, and Eubuliminella tenuata) represent upper abyssal faunas (2000–3000 mbsl). 8) U8 (mainly composed of Glomospira sp. A, Lagenammina arenulata, Chilostomella oolina, Hoeglundina elegans, Melonis barleeanum, Nonion affine, Oridorsalis umbonatus, Pullenia bulloides, and Uvigerina proboscidea) is characterized by deep-water cosmopolitan faunas (deeper than 3000 mbsl). On the basis of a comparison with several environmental parameters, dissolved oxygen concentrations are likely to be the most effective factor controlling foraminiferal depth distributions in the eastern equatorial Pacific especially below the oxygen minimum zone (OMZ). Around OMZ, nitrate concentration also might be related with the benthic assemblage due to the nitrate respiration.

Description: Aberrant Zn2+ homeostasis is associated with dysregulated intracellular Ca2+ release, resulting in chronic heart failure. In the failing heart a small population of cardiac ryanodine receptors (RyR2) displays sub-conductance-state gating leading to Ca2+ leakage from sarcoplasmic reticulum (SR) stores, which impairs cardiac contractility. Previous evidence suggests contribution of RyR2-independent Ca2+ leakage through an uncharacterized mechanism. We sought to examine the role of Zn2+ in shaping intracellular Ca2+ release in cardiac muscle. Cardiac SR vesicles prepared from sheep or mouse ventricular tissue were incorporated into phospholipid bilayers under voltage-clamp conditions, and the direct action of Zn2+ on RyR2 channel function was examined. Under diastolic conditions, the addition of pathophysiological concentrations of Zn2+ (≥2 nm) caused dysregulated RyR2-channel openings. Our data also revealed that RyR2 channels are not the only SR Ca2+-permeable channels regulated by Zn2+. Elevating the cytosolic Zn2+ concentration to 1 nm increased the activity of the transmembrane protein mitsugumin 23 (MG23). The current amplitude of the MG23 full-open state was consistent with that previously reported for RyR2 sub-conductance gating, suggesting that in heart failure in which Zn2+ levels are elevated, RyR2 channels do not gate in a sub-conductance state, but rather MG23-gating becomes more apparent. We also show that in H9C2 cells exposed to ischemic conditions, intracellular Zn2+ levels are elevated, coinciding with increased MG23 expression. In conclusion, these data suggest that dysregulated Zn2+ homeostasis alters the function of both RyR2 and MG23 and that both ion channels play a key role in diastolic SR Ca2+ leakage.

Description: During the Paleocene, the plankton community recovered its diversity after a severe diversity loss at the Cretaceous/Paleogene (K/Pg) boundary. In general, changes in Paleocene deep-sea ostracode fauna are poorly understood. It is still unclear how deep-sea ostracode fauna changed during compelling events such as the K/Pg boundary (66.04 Ma) and the Latest Danian Event (LDE: ~62.18 Ma), a transient Paleocene warming event. In this report, we describe a study on the latest Cretaceous-late Paleocene ostracodes from Integrated Ocean Drilling Program Site U1407, off Newfoundland, in the northwestern Atlantic. Thirty-four ostracode taxa were obtained from 202 discrete samples that were discretely collected from the interval between 66.3 and 57.3 Ma. Near the K/Pg boundary, 8% (2 of 24) of the Maastrichtian taxa became extinct. The extinction rate is estimated to be at most 0.12 E MSY-1, which is in the same range as the background-level extinction rate. Comparing the extinction rates between different ocean basins, the ostracode extinction at the K/Pg boundary displays striking geographical heterogeneity. Between the Maastrichtian and Danian, the ostracode fauna change from a biofacies dominated by shallow bathyal taxa to one dominated by deep bathyal taxa. During the LDE, ostracode fauna display an increase in their benthic ostracode accumulation rates and taxonomic diversity as well as an increase in the relative abundance of Krithe crassicaudata simultaneously with a decline in carbonate content. A similar change is commonly documented in fauna from the northeastern Atlantic during the Paleocene-Eocene Thermal Maximum (PETM; 56.0 Ma). In contrast to the PETM fauna, an extinction event is not recognized. After the Danian, the ostracode fauna indicate changes in water mass and minor environmental disturbances with possible development of corrosive water.