National Ocean Service

About: National Ocean Service is a government organization based out in Silver Spring, Maryland, United States. It is known for research contribution in the topics: Algal bloom & Population. The organization has 500 authors who have published 643 publications receiving 46096 citations.

Observation of different ceramide species from crude cellular extracts by normal-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry

Abstract: Normal-phase high-performance liquid chromatography (NP-HPLC) coupled to atmospheric pressure chemical ionization mass spectrometry (APCI-MS) allows qualitative analysis of endogenous ceramide and dihydroceramide species from crude lipid extracts utilizing chromatographic methods readily adaptable from commonly used thin layer chromatography (TLC) conditions. Qualitative information for the species comes from observation of differences in chromatographic and mass spectrometric behavior between species. Application to the analysis of ceramide and dihydroceramide from various cell lines is demonstrated. The results show the species profile in each cell line to be unique despite growth under identical conditions. The results from APCI-MS analysis corroborate and enhance information acquired from use of the diacylglycerol kinase assay for total ceramide measurement. This technique readily allows the previously difficult distinction between ceramide and dihydroceramide species.

Remote sensing estimation of surface oil volume during the 2010 Deepwater Horizon oil blowout in the Gulf of Mexico: scaling up AVIRIS observations with MODIS measurements

Abstract: The Deepwater Horizon (DWH) oil blowout in the Gulf of Mexico (GoM) led to the largest offshore oil spill in U.S. history. The accident resulted in oil slicks that covered between 10,000 and upward of 40,000 km2 of the Gulf between April and July 2010. Quantifying the actual spatial extent of oil over such synoptic scales on an operational basis and, in particular, estimating the oil volume (or slick thickness) of large oil slicks on the ocean surface has proven to be a challenge to researchers and responders alike. This challenge must be addressed to assess and understand impacts on marine and coastal resources and to prepare a response to future spills. We estimated surface oil volume and probability of occurrence of different oil thicknesses during the DWH blowout in the GoM by combining synoptic measurements (2330-km swath) from the satellite-borne NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and near-concurrent, much narrower swath (∼5 km) hyperspectral observations from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A histogram-matching approach was used to transfer AVIRIS-derived oil volume to MODIS pixel-scale dimensions, after masking clouds under both sun glint and nonglint conditions. Probability functions were used to apply the transformation to 19 MODIS images collected during the DWH event. This generated three types of MODIS oil maps: maps of surface oil volume, maps of relative oil thickness with four different classes (i.e., 0 μm, 8 μm), and maps of probability distributions of different thicknesses. The results were compared with satellite-based synthetic aperture radar measurements and evaluated with concurrent aerial photographs. Although the methods may not be ideal and the results may contain large uncertainties, the current attempt suggests that coarse-resolution optical remote sensing observations can provide estimates of relative oil thickness/volume for large oil slicks captured by satellites.

Sediment quality of North Carolina estuaries: an integrative assessment of sediment contamination, toxicity, and condition of benthic fauna

Abstract: Sediment quality of North Carolina estuaries was evaluated using synoptic data on sediment chemistry, toxicity, and macroinfaunal community structure from 175 subtidal stations sampled during the summers of 1994–1997. The study area included Currituck, Albemarle, and Pamlico Sounds; estuarine portions of major rivers (e.g., Chowan, Roanoke, Tar-Pamlico, Neuse, New, Cape Fear); and numerous smaller tributaries and coastal embayments between the Virginia and South Carolina borders. A probabilistic sampling design permitted statistical estimation of the spatial extent of degraded versus non-degraded condition across these estuaries. Over half (54 ± 7%) of the surveyed area had high sediment quality characterized by healthy benthic assemblages and low levels of sediment contamination and toxicity. The remaining 46% showed evidence of significant stress in one or more of the above sediment-quality-triad components. While this is a sizable area, portions of it (27 ± 6%) were represented by sites with no connection between presence of stressors and adverse biological responses. Only 19% of the total area showed evidence of an impaired benthos coupled to significant pollution exposure (high sediment contamination, toxicity, or both). Impaired benthic condition was more closely linked to sediment contamination than to low dissolved oxygen (based on instantaneous oxygen measurements). The most pervasive contaminants were the metals arsenic, mercury, chromium, and nickel; the pesticides lindane, dieldrin, DDT, and DDT derivatives; and total PCBs. Degraded condition in all three components of the sediment quality triad co-occurred in <10% of the study area, suggesting that strong contaminant-induced effects on the benthos are limited to a small (yet ecologically significant) percentage of total estuarine area. The spatial extent of sediment contamination and toxicity was much less in these estuaries in comparison to other U.S. coastal regions where similar studies have been performed.

Tropical atlantic water within the Benguela upwelling system at 27°S

Abstract: A CTD-O 2 and ADCP section across the African Atlantic continental margin near 27°S, obtained during R.R.S. Discovery cruise 165B in May 1987, reveals the water mass structure and associated velocity field of the shelf and upper slope of the Benguela upwelling system. Continental shelf water upwelling within the Benguela Current is drawn from the 12°C (about 200 m) level. The upwelling water is drawn from oxygen depleted, tropical South Atlantic thermocline water that is advected along the shelf floor by a southward flowing subsurface current. Lower thermocline and intermediate water from the tropical South Atlantic are also observed flowing southward over the continental slope. Tropical Atlantic water generally resides north of the Angola-Benguela Front at 16°S. A narrow band of upwelled water is observed well seaward of the shelf, along the western edge of a large Agulhas eddy, indicating that Agulhas eddies play a role in stirring eastern boundary upwelled water into the ocean interior. These eddies also draw into the interior tropical Atlantic water found over the upper continental slope. The net transport between the 120 and 350 isobaths as measured by the ship-mounted ADCP, referenced to the sea floor, is 0.9 × 10 6 m 3 s −1 1 to the south, with 1.6 × 10 6 m 3 s −1 of southward flowing tropical Atlantic water and 0.7 × 10 6 m 3 s −1 of northward flowing upwelled surface water. The tropical thermocline water mass advected to the south is not observed offshore within the northward flowing Benguela Current, in an unaltered state, thus the 0.9 × 10 6 m 3 s −1 must feed shelf upwelling south of 27°S, implying a net offshore flux of upwelled water between Ld¨eritz (26°) and Cape Columbine (33°S).