The concentrations of dissolved Fe ([D‐Fe]), total dissolvable Fe ([T‐Fe]), humic‐type fluorescence intensity (humic F intensity) as humic‐type fluorescent dissolved organic matter, and nutrients were vertically determined in the shelf, slope, and basin regions (Chukchi Sea and Canada Basin) of the western Arctic Ocean during 1–27 September 2008. In all stations, the remarkably high [D‐Fe] and humic F intensity were found at depths between 25 and 200 m with the subsurface maxima of [D‐Fe] (1.0–3.2 nM) and humic F intensity (4–5 quinine sulfate units) in the upper halocline layer (upper HL), being associated with a prominent nutrient maximum. The high [D‐Fe] and humic F intensity within the upper HL are probably attributed to the Fe(III) complexation with natural organic ligands, such as marine dissolved humic substances, resulting from main processes of the brine rejection during sea ice formation and interactions with sediments on the shelves. However, subsurface maxima (10–50 nM) of [T‐Fe] were found in the lower halocline layer, beneath the upper HL, of all slope and basin regions and are mainly attributed to the resuspension of sedimentary particles in the shelf region. The finding of subsurface iron maxima in the halocline water of all regions may be the first confirmation for the lateral iron transport into the halocline layer from the shelves to the Arctic Basin.

Global inhibition is a fundamental physiological mechanism that has been proposed to shape odor representation in higher-order olfactory centers. A pair of mushroom bodies (MBs) in insect brains, an analog of the mammalian olfactory cortex, are implicated in multisensory integration and associative memory formation. With the use of single/multiple intracellular recording and staining in the cockroach Periplaneta americana, we succeeded in unambiguous identification of four tightly bundled GABA-immunoreactive giant interneurons that are presumably involved in global inhibitory control of the MB. These neurons, including three spiking neurons and one nonspiking neuron, possess dendrites in termination fields of MB output neurons and send axon terminals back to MB input sites, calyces, suggesting feedback roles onto the MB. The largest spiking neuron innervates almost exclusively the basal region of calyces, while the two smaller spiking neurons and the second-largest nonspiking neuron innervate more profusely the peripheral (lip) region of the calyces than the basal region. This subdivision corresponds well to the calycal zonation made by axon terminals of two populations of uniglomerular projection neurons with dendrites in distinct glomerular groups in the antennal lobe. The four giant neurons exhibited excitatory responses to every odor tested in a neuron-specific fashion, and two of the neurons also exhibited inhibitory responses in some recording sessions. Our results suggest that two parallel olfactory inputs to the MB undergo different forms of inhibitory control by the giant neurons, which may, in turn, be involved in different aspects of odor discrimination, plasticity, and state-dependent gain control. J. Comp. Neurol. 525:204-230, 2017. © 2016 Wiley Periodicals, Inc.

[1] In the Japan and Yamato basins (Japan Sea), dissolved Fe ([D-Fe], <0.22 mm fraction) was characterized by surface depletion, mid-depth maxima, then a slight decrease with depth in deep water and uniform concentration in bottom waters because of biological uptake in the surface water and release by microbial decomposition of sinking organic matter in mid-depth waters. Total Fe concentrations ([T-Fe]) in the surface water of the Japan Sea were 1-4 nM, a little higher than those in the surface waters of the nutrient-deficient subtropical western North Pacific and extremely higher than the nutrient-rich subarctic western North Pacific and the nutrient-deficient subtropical central North Pacific, resulting from high atmospheric Fe input to nutrient-depleted surface water of the Japan Sea. In the Japan Basin, the [T-Fe] in bottom water were lower than those in deep water, resulting from (1) the injection of new bottom water with the lower [T-Fe] into the Japan Basin bottom water, (2) the particulate Fe removal by particle scavenging during the bottom water circulation of the Japan Basin, or (3) the injection of deep water with the higher [T-Fe] into the Japan Basin deep water. On the other hand, the [T-Fe] in deep water of the Yamato Basin and the slope regions were variable with different [T-Fe] levels among stations and depths. We found a significant relationship between [T-Fe] and water transmittance in deep water, probably resulting from the iron supply into the deep water because of the lateral transport of resuspended sediment from the slope.

Iron [dissolved Fe (D-Fe) This result is also consistent with robust in situ phytoplankton growth and Chl-a production due to the presence of high iron levels in the COW. The most important mechanisms transporting iron to the surface water, which would regulate the primary production during spring bloom in the Oyashio region, are the surface intrusions of iron-and nutrient-rich COW derived from vertical and lateral mixing processes and vertical mixing in MKW during winter and spring.

We investigated the nutrient and diatom dynamics during late winter and spring These results suggest that the spring bloom in the cold water system with high macronutrients and iron concentrations would progress rapidly and intensely, and then be terminated by nitrogenous nutrient depletion. However, the diatom bloom in warmer waters with lower macronutrients and iron concentrations would be terminated by Si-and/or iron-limitation of heavily-silicified diatoms. In the OECOS study, variation of macronutrients and iron due to the surface intrusions of several water masses and modification from different chemical conditions during winter were the most important factors regulating the progression, magnitude and probably fate of the spring phytoplankton bloom in the Oyashio region.2