No abstract

[1] Low-oxygen and low-pH events are an increasing concern and threat in the Eastern Pacific coastal waters, and can be lethal for benthic and demersal organisms on the continental shelf. The normal seasonal cycle includes uplifting of isopycnals during upwelling in spring, which brings low-oxygen and low-pH water onto the shelf. Five years of continuous observations of subsurface dissolved oxygen off Southern California, reveal large additional oxygen deficiencies relative to the seasonal cycle during the latest La Niña event. While some changes in oxygen related to the isopycnal depression/uplifting during El Niño/La Niña are not unexpected, the observed oxygen changes are 2-3 times larger than what can be explained by cross-shore exchanges. In late summer 2010, oxygen levels at mid-depth of the water column reached values of 2.5 ml/L, which is much lower than normal oxygen levels at this time of the seasons, 4-5 ml/L. The extra uplifting of isopycnals related to the La Niña event can explain oxygen reductions only to roughly 3.5 ml/L. We find that the additional oxygen decrease beyond that is strongly correlated with decreased subsurface primary production and strengthened poleward flows by the California Undercurrent. The combined actions of these three processes created a La Niña-caused oxygen decrease as large and as long as the normal seasonal minimum during upwelling period in spring, but later in the year. With a different timing of a La Niña, the seasonal oxygen minimum and the La Niña anomaly could overlap to potentially create hypoxic events of previously not observed magnitudes.

Toxicokinetics of zinc oxide nanoparticles (ZnONP) was studied in rats via a single intravenous (iv) injection and a single oral administration (3 mg/kg or 30 mg/kg), respectively. Blood concentrations of zinc (Zn) were monitored for 7 d and tissue distribution were determined in liver, kidneys, lung, spleen, thymus, brain, and testes. To ascertain the excretion of ZnONP, Zn levels in urine and feces were measured for 7 d. ZnONP were not readily absorbed from the gastrointestinal tract (GIT) after oral administration and were excreted mostly in feces. When the nanoparticles were injected iv to rats at a dose of 30 mg/kg, peak concentration appeared at 5 min but returned to normal range by d 2 (48 h after injection). ZnONP were distributed mainly to liver, kidneys, lung, and spleen, but not to thymus, brain, and testes. The distribution level was significantly decreased to normal by d 7. Feces excretion levels after iv injection supported biliary excretion of ZnONP. In rats injected iv with 30 mg/kg, mitotic figures in hepatocytes were significantly increased and multifocal acute injuries with dark brown pigment were noted in lungs, while no significant damage was observed in rats treated orally with the same dosage.

Event-scale phenomena, of limited temporal duration or restricted spatial extent, often play a disproportionately large role in ecological processes occurring in the ocean water column. Nutrient and gas fluxes, upwelling and downwelling, transport of biogeochemically important elements, predator-prey interactions, and other processes may be markedly influenced by such events, which are inadequately resolved from infrequent ship surveys. The advent of autonomous instrumentation, including underwater gliders, profiling floats, surface drifters, enhanced moorings, coastal high-frequency radars, and satellite remote sensing, now provides the capability to resolve such phenomena and assess their role in structuring pelagic ecosystems. These methods are especially valuable when integrated together, and with shipboard calibration measurements and experimental programs

The 55-yr California Cooperative Oceanic Fisheries Investigations (CalCOFI) dataset in the southern California Current reveals a significant surface-intensified warming and stratification (buoyancy frequency) change across the 1976/77 climate regime shift. However, the average depth of the thermocline, defined as the maximum gradient of temperature, did not change significantly across the regime shift. The maximumgradient criterion for thermocline depth may be more appropriate than following an isotherm because the isotherm necessarily deepens in the presence of surface-intensified warming. As the surface heating changed the strength of stratification, it also changed the slope of the nitrate-temperature relation for the middepth waters (roughly 30-200 m). Thus, the quality of upwelled water may have been fundamentally altered after the shift.

We use autonomous nitrate (NO 3 À ), oxygen (O 2 ), and dissolved inorganic carbon (DIC) observations to examine the relationship between ratios of C:N:O at an upwelling site in the Southern California Current System. Mean ratios and 95% confidence intervals observed by sensors over 8 months were NO 3 À :O 2 = À0.11 ± 0.002, NO 3 À :DIC = 0.14 ± 0.001, and DIC:O 2 = À0.83 ± 0.01, in good agreement with Redfield ratios. Variability in the ratios on the weekly time scale is attributable to shifts in biological demand and nutrient availability and shown to exhibit a spectrum of values ranging from near 100% New Production to 100% Regenerated Production.

Recent toxicity studies of zinc oxide nanoparticles by oral administration showed relatively low toxicity, which may be resulted from low bioavailability. So, the intrinsic toxicity of zinc oxide nanoparticles needs to be evaluated in the target organs by intravenous injection for full systemic concentration of the administered dosage. Although the exposure chance of injection route is low compared to oral and/or inhalation route, it is important to see the toxicity with different exposure routes to get better risk management tool. In this study, the effects of zinc oxide nanoparticles on dams and fetuses were investigated in rats after intravenous injection (5, 10, and 20 mg/kg) from gestation day 6 to 20. Two of 20 dams in the 20 mg/kg treatment group died during the treatment period. Hematological examination and serum biochemistry showed dose-dependent toxicity in treated dams. Histopathological analysis of treated dams revealed multifocal mixed cell infiltration and thrombosis in lung, tubular dilation in kidneys, and extramedullary hemopoiesis in liver. Total dead fetuses (post-implantation loss) were increased and the body weight of fetus was decreased in the 20 mg/kg treatment group. Statistical differences in corpora lutea, resorption, placental weight, morphological alterations including external, visceral and skeletal malformations were not observed in treated groups. Based on the data, lowest observed adverse effect level of injection route was suggested to be 5 mg/kg in dams and no observed adverse effect level was suggested to be 10 mg/kg in fetal developmental toxicity.

No abstract