Enzyme-labeled fluorescence (ELF) and bulk alkaline phosphatase (AP) activity enzyme assays were used to evaluate the phosphorus (P) status of phytoplankton communities in San Francisco and Monterey bays. Both regions exhibit spatial and temporal variability in bulk AP activity with maximum activities during the early spring and summer periods of high biological productivity. ELF analysis revealed pronounced differences in the makeup of organisms responsible for AP activity in these two environments. In Monterey Bay dinoflagellates are responsible for the bulk of the AP activity. Diatoms infrequently exhibited AP activity. Dinoflagellates that comprised only 14% of all cells counted in Monterey Bay accounted for 78% of AP-producing cells examined. The presence of AP activity in this group suggests that changes in P sources, concentrations, and bioavailability could disproportionably influence this group relative to diatoms in Monterey Bay. In San Francisco Bay, AP production, indicated by ELF, was associated primarily with bacteria attached to suspended particles, potentially used to hydrolyze organic compounds for carbon, rather than to satisfy P requirements. Our results highlight the importance of organic P as a bioavailable nutrient source in marine ecosystems and as a component of the marine P cycle.

[1] The triple oxygen isotopic composition of dissolved oxygen ( 17 D) is a promising tracer of gross oxygen productivity (P) in the ocean. Recent studies have inferred a high and variable ratio of P to 14 C net primary productivity (12-24 h incubations) (e.g., P:NPP( 14 C) of 5-10) using the 17 D tracer method, which implies a very low efficiency of phytoplankton growth rates relative to gross photosynthetic rates. We added oxygen isotopes to a one-dimensional mixed layer model to assess the role of physical dynamics in potentially biasing estimates of P using the 17 D tracer method at the Bermuda Atlantic Time-series Study (BATS) and Hawaii Ocean Time-series (HOT). Model results were compared to multiyear observations at each site. Entrainment of high 17 D thermocline water into the mixed layer was the largest source of error in estimating P from mixed layer 17 D. At both BATS and HOT, entrainment bias was significant throughout the year and resulted in an annually averaged overestimate of mixed layer P of 60 to 80%. When the entrainment bias is corrected for, P calculated from observed 17 D and 14 C productivity incubations results in a gross:net productivity ratio of 2.6 (+0.9 À0.8) at BATS. At HOT a gross:net ratio decreasing linearly from 3.0 (+1.0 À0.8) at the surface to 1.4 (+0.6 À0.6) at depth best reproduced observations. In the seasonal thermocline at BATS, however, a significantly higher gross:net ratio or large lateral fluxes of 17 D must be invoked to explain 17 D field observations.

Seagliders, deployed through most of 2005 in the subtropical North Pacific gyre, made measurements of temperature, salinity, and dissolved oxygen to quantify net community production (NCP) at Station A LongTerm Oligotrophic Habitat Assessment (ALOHA) of the Hawaii Ocean Time-series (HOT) using an oxygen mass balance approach. A 'bowtie'-shaped pattern, 50 km by 50 km in size was repeatedly traversed at two week intervals with the goal of observing the influence of Rossby waves and eddies on the productivity of the study region. Rossby waves and eddies in the region cause a vertical displacement of isopycnal depth of ,650 m at the base of the euphotic zone. Shoaling of isopycnals is demonstrated to drive productivity in the deep euphotic zone. Four mesoscale shoaling events were observed between February and November in 2005. During each event when isopycnals shoaled, oxygen concentrations on isopycnals increased, fluorescence in the deep euphotic zone was higher, and net community production was elevated. Productivity in the deep euphotic zone was strongly influenced by Rossby waves and eddies, but this influence was not observed to extend into the mixed layer.

We compared the accuracy and precision of low-dose insulin administration using various devices including, for the first time, an insulin pump. We dispensed 1, 2, and 5 unit(s) of soluble insulin (100 units/mL) 15 times each from a NovoPen (3.0 mL), a BD-Mini Pen (1.5 mL), a Humalog Pen (100 units/mL), 30G Precision Sure-Dose Insulin Syringes, 30G BD Ultra-Fine II Short Needle Syringes, and a H-TRON-plus V100 insulin pump. Each dose was weighed on an analytical scale, and the delivered and target doses were compared. Accuracy was defined by the absolute percent difference from the target dose. Precision was defined as the absolute percent difference from the group sample mean. Overall, we found that the pen and pump devices were more accurate, and the pump more precise, than the syringes at the 1- and 2-unit doses. Syringes were dangerously inaccurate, clinically, at the 1-unit dose. The use of pens and syringes with very fine increment markings (1/2 unit) did not improve accuracy or precision. Earlier researchers used multiple individuals to draw and weigh the samples. In an effort to eliminate the potential introduction of significant error; our study used only 2 investigators: 1 to draw up the doses and another to weigh them. The conclusions in our study were similar to prior studies.

We measured triple oxygen isotopes and oxygen/argon dissolved gas ratios as nonincubation-based geochemical tracers of gross oxygen production (GOP) and net community production (NCP) on 16 container ship transects across the North Pacific from 2008 to 2012. We estimate rates and efficiency of biological carbon export throughout the full annual cycle across the North Pacific basin (35°N-50°N, 142°E-125°W) by constructing mixed layer budgets that account for physical and biological influences on these tracers. During the productive season from spring to fall, GOP and NCP are highest in the Kuroshio region west of 170°E and decrease eastward across the basin. However, deep winter mixed layers (>200 m) west of 160°W ventilatẽ 40-90% of this seasonally exported carbon, while only~10% of seasonally exported carbon east of 160°W is ventilated in winter where mixed layers are <120 m. As a result, despite higher annual GOP in the west than the east, the annual carbon export (sequestration) rate and efficiency decrease westward across the basin from export of 2.3 ± 0.3 mol C m À2 yr À1 east of 160°W to 0.5 ± 0.7 mol C m À2 yr À1 west of 170°E. Existing productivity rate estimates from time series stations are consistent with our regional productivity rate estimates in the eastern but not western North Pacific. These results highlight the need to estimate productivity rates over broad spatial areas and throughout the full annual cycle including during winter ventilation in order to accurately estimate the rate and efficiency of carbon sequestration via the ocean's biological pump.