Raymond N. Sambrotto

• Columbia University

Little is known about the bioavailability of Fe in natural dusts and the impact of dust mineralogy on Fe utilization by photosynthetic organisms. Variation in the supply of bioavailable iron (Fe) to the ocean has the potential to influence the global carbon cycle by modulating primary production in the Southern Ocean. Much of the dust deposited acr...

The nitrogen cycle on the inner shelf of the southeastern Bering Sea is complicated due to limited nutrient replenishment across this broad shelf, and substantial nitrogen loss through sedimentary processes. While diffusion at the inner front may periodically support new production, the shelf is generally hypothesized to be a regenerative system. T...

[J. Geophys. Res, 2016] A new planktonic ecosystem model was constructed for the Eastern Bering Sea based on observations from the 2007-2010 BEST/BSIERP (Bering Ecosystem Study/Bering Sea Integrated Ecosystem Research Program) field program. When run with forcing from a data-assimilative ice-ocean hindcast of 1971-2012, the model performs well agai...

Four years of data on for new (nitrate), regenerated (ammonium), and primary (carbon) productivity (2007 through 2010) confirm the elevated productivity associated with the marginal ice zone (MIZ) of the eastern Bering Sea (EBS) in spring. The greatest levels of productivity were associated with ice-melt regions along the western edge of the ice pa...

The ocean's biological pump transfers carbon to long-term storage in deep waters and sediments. Two inverse modelling studies describe the export of organic matter throughout the surface layer of the world's oceans in exceptional detail.

Spectral fluorescence measurements of phytoplankton chlorophyll a (Chl a), phytoplankton phycobilipigments and variable fluorescence (Fv/Fm), are utilized with High Performance Liquid Chromatography (HPLC) estimates of phytoplankton pigments and microscopic cells counts to construct a comprehensive picture of summer-time phytoplankton communities a...

We conduct a stratigraphic paleoecological investigation at a Hudson River National Estuarine Research Reserve (HRNERR) site, Tivoli Bays, spanning the past 1100 years. Marsh sediment cores were analyzed for ecosystem changes using multiple proxies, including pollen, spores, macrofossils, charcoal, sediment bulk chemistry, and stable carbon and nit...

The SCICEX submarine Arctic science program originated in the 1990s when six dedicated science cruises were conducted in the Arctic Ocean aboard US Navy Sturgeon class submarines. After the cold war era Sturgeon class submarines were retired, several Science Accommodation cruises, for which a few days for scientific measurements were added to plann...

We investigate the cycling of nutrients through a brackish tidal wetland about 40 km north of Manhattan in the Hudson River estuary. As part of a long-term ecological study of Piermont Marsh, a NOAA reference wetland managed by the NY State DEC, we are measuring dissolved inorganic nutrients on the Marsh surface and its drainage channels. The marsh...

The significant increase in the extent of ice-free water during summer in the Arctic Ocean is expected to increase surface biological productivity. The magnitude and pattern of the response is difficult to predict however, given the sparse sampling of nutrient levels in this region, and the likelihood that nutrient availability may constrain the pr...

The ratio of nutrient elements in marine subsurface waters is much the same everywhere, even though biogeochemically distinct ocean biomes exist. A modelling study that includes mixing solves this conundrum. See Article p.550

We use stable carbon and nitrogen isotopes from a Kenai Peninsula, Alaska fen spanning the late-glacial and Holocene to enhance our understanding of peatland hydrology and nutrient cycling. We find that isotopic values for carbon and nitrogen are lighter in the late-glacial and early Holocene (−28 to −34‰ and 0 to −4‰, respectively) than the remain...

A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in ge...

Columbia University's Lamont-Doherty Earth Observatory has established educational partnerships with 6 New York City high schools, focused on engagement of science teachers and students in real (rigorous, publicly funded, publishable) research projects. The partnering schools are all "regular" public schools (non competitive entry, predominantly Ti...

The Bering Sea's position at the end of the global ocean "conveyor belt" and shoaling of nutrient rich water masses onto its broad shelf make the Eastern Bering Sea shelf one of the most productive regions of the polar oceans, with reported annual primary production rates of 150 to 500 gC*m-2 yr-1. Much of this production occurs during spring bloom...

The lower Hudson River is a well-flushed temperate estuary that continues to support diverse wildlife populations although its shores are home to the nation's most populated metropolitan area. Data sets from the last hundred years clearly demonstrate extreme nutrient concentrations, pathogen loading, and periods of persistent hypoxia. These data al...

Measurements of nutrients, primary (14C) productivity and new (nitrate) productivity collected in the southeastern Bering Sea in July and August 2004 together with measurements from July 1981 are used to characterize the regional production system during summer and to analyze the major physical and nutrient factors controlling biological patterns....

Hydrologic changes resulting from climate change have important effects on vegetation change and global feedback cycles in the high latitudes. In an attempt to move beyond pollen analysis to interpret past climate, a number of geochemical and biological proxies were used, including bulk peat delta 13C, delta15N, and bryophytes, to make paleohydrolo...

Knowledge of foraging ecology of endangered mammals is often based on limited data because of logistical constraints of accessing animals, their stomach contents, or fecal samples. Here we use a stable isotope approach to examine feeding habits of a rare mammal, gaining insights over a greater temporal scale than a traditional fecal analysis would...

We analyzed the relationship between the estimated export (e(i)) of carbon, nitrogen, silica and phosphorus from the surface similar to 90m in the Antarctic Circumpolar Current (ACC) region along 170 degrees W and the seasonal development of the epipelagic community. Export was based on nutrient budgets from repeat sections during the 1997-1998 aus...

The net impact of biological production and regeneration (Net Community Production) on surface water dissolved inorganic carbon, nitrogen, phosphorus, and silica (NCPDIC, NCPDIN, NCPPO4, and NCPSi(OH)4, respectively) were evaluated from nutrient data collected in the Antarctic Circumpolar Current (ACC) along 170°W between October 1997 and March 199...

As a tropical ocean margin influenced by seasonal upwelling, the plankton productivity of the Cariaco Basin varies greatly between some of the largest rates measured in ocean waters, to near oligotrophic conditions, over the course of a year. The fluxes of carbon and nitrogen associated with these biological variations also change significantly and...

Summary • Here, we compared the carbon isotope ratios of leaf respiratory CO2 (13CR) and leaf organic components (soluble sugar, water soluble fraction, starch, protein and bulk organic matter) in five C3 plants grown in a glasshouse and inside Biosphere 2. One species, Populus deltoides, was grown under three different CO2 concentrations. • The K...

The Triassic-Jurassic mass extinction event ( ˜200 Ma) had a profound effect on biotic evolution, and herein we describe trends in cheirolepidaceous conifer leaf physiognomy from the Pangean tropics (present northeastern USA) that at least broadly parallel a negative delta 13C excursion recorded in the same strata. The physiognomic changes appear a...

We report on a biological and nutrient survey conducted off the eastern Adélie and George V Coasts of East Antarctica in late December 2000 and January 2001. The region was dominated by the Mertz Glacier Tongue (MGT) and its associated polynya that controlled the amount of open water through the season and influenced stratification near forming and...

Vertical profiles of water temperature, salinity, beam transmission, density, pressure, wind speed, wind direction, phytoplankton biomass (chlorophyll a (Chl a) plus phaeophytin a), and photosynthetic competency (by fast repetition-rate fluorometry) are presented for the Mertz Glacier region, East Antarctica, for a 3-week period during the austral...

Significant departures from the expected 16:1 (by mole) ratio between nitrogen and phosphorus consumption in surface waters have been recorded during several independent studies in ice-impacted regions of the Southern Ocean. Both the marginal ice zone near the Polar Front as well as near shore polynyas exhibit low N/P ratios (below 8 for the latter...

We present a synthesis of the rates of gross, new, net and primary production along with particulate organic carbon (POC) flux at 100 m from four cruises along 170°W in the Southern Ocean. Concurrent satellite pigment data, a primary productivity model, and a nitrate mass balance are used to extrapolate daily production estimates in space and time...

Nutrient uptake ratios and the Si:C:N composition ratios of particulate matter were measured within a diatom bloom located between the Antarctic Polar Front and the edge of the receding pack ice in the Pacific sector of the Southern Ocean along 170°W from 2 December 1997 to 3 January 1998. Rates of silicic acid, nitrate, ammonium and urea uptake we...

During the 1996–1998 Antarctic Environment and Southern Ocean Process Study (AESOPS), a component of US JGOFS, we obtained seasonal or longer-term data sets on the rates of production, vertical transport, remineralization and burial of particulate organic carbon (POC) and biogenic silica (BSiO2) in the Southern Ocean at 170°W between 55°S and 68°S....

The effect of feeding on the carbon isotopic composition of zooxanthellae, animal tissue and skeleton was investigated in the scleractinian coral Stylophora pistillata. Two sets of corals were grown with filtered seawater under controlled conditions. One group of colonies was fed Artemia sp. nauplii and compared to a control group that was starved....

Routine determination of dissolved organic nitrogen (DON) is performed in numerous laboratories around the world using one of three families of methods: UV oxidation (UV), persulfate oxidation (PO), or high temperature combustion (HTC). Essentially all routine methods measure total dissolved nitrogen (TDN) and calculate DON by subtracting the disso...

We examined particles from approximately 1 L of ice from 3587 m depth in core 5G from the NSF-supported National Ice Core Laboratory (NICL) (http://www.nicl-smo.sr.unh.edu). The segment dated at approximately 430 kyrs. and its del18O suggested a precipitation temperature of -37 deg. C, similar to present day conditions in the region. Microscopic an...

In this paper we examine the relationships among oxygen, carbon and nitrogen production and respiration rate measurements made in the Arabian Sea during the 1995 Northeast (NEM) and Southwest (SWM) Monsoons. Increased biological production characterized the SWM, with rates 12–53% higher than the NEM. In most cases, we found remarkable similarity in...

Planktonic nitrogen productivity and regeneration were measured with 15NO3, 15NH4 and 15N-urea tracers during the Spring Intermonsoon (SI) and Southwest Monsoon (SWM) seasons in the northern Arabian Sea from the Omani coast southeast to 10°N. On an areal basis, new (nitrate) productivity and the nitrogen f-ratio varied from 0.1 to 13 mmol m−2 d−1 a...

The Cariaco Basin, historically a natural laboratory for biogeochemists, also contains a record of past climate change. Under interglacial conditions, the formation of sediment varves at the bottom of the basin is related to variability near the ocean's surface, and appears to reflect variations on the scale of the Atlantic Ocean. The CARIACO (CArb...

Oceanographic samples were collected across the Antarctic Polar Front (APF) region in the vicinity of ∼60°S, 170°W during the US JGOFS program from December 1997 to March 1998. This paper reports the uptake rates of new (nitrate) and regenerated (ammonium and urea) nitrogen measured by 15N tracer techniques together with the levels of ammonium, ure...

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We measured dissolved inorganic carbon (DIC), combined inorganic nitrogen, O2, chlorophyll a (Chl a), particulate carbon and nitrogen (PCN) along with selected additional parameters on Georges Bank during April. Summer conditions were developing in the region as reflected by elevated biological production at the margins of the Bank (Chl a and O2 le...

Oceanographic sampling at 59.5°N, 21°W over the spring and summer months of 1989 provided the basis to quantify the amount of new (nitrate) production and to evaluate the effect of selected environmental factors on new production. Surface water nitrate decreased linearly from 14μM in early April to ∼2.5 μM in August, and suggested that new producti...

A gas exchange experiment was performed on Georges Bank using deliberate tracers sulfer hexafluoride (SF{sub 6}) and helium 3 ({sup 3}He). The concentrations of the tracers were measured in the water column over a period of 10 days. During this time the patch grew from an 8-km-long injection streak to an area of about 500 km{sup 2}. The gas transfe...

UPTAKE of atmospheric CO2 by the ocean's 'biological pump' is driven by export of carbon from the euphotic zone to deeper waters1,2. As nitrate is a limiting nutrient in large regions of the ocean, measurements of nitrate uptake are often used to estimate the amount of carbon exported in this way3-6. This presupposes knowledge of the molar C: N rat...

A simple device has been developed to facilitate in situ incubations. The hydraulic in situ time‐series sampler (HINTS) facilitates collection and incubation of a large volume of water (16 liters) without need of manipulating the sample at the surface. Injection of isotopic tracers and subsampling can be accomplished remotely via tubing connected t...

Twenty-one Coastal Zone Color Scanner (CZCS) images of the southeastern Bering Sea are examined in order to map the near-surface distribution of phytoplankton during 1979 and 1980. The information is compared with the mesoscale (100-1000 km) distribution of phytoplankton inferred from pooled ship sampling obtained during the Processes and Resources...

The U.S. results of a joint U.S.-U.S.S.R. expedition to the Bering Sea in 1984 investigated the chemical and biological interactions in the south, east, north and west regions. The nutrients, phytoplankton biomass and primary productivity were enhanced near the ends of a north-south transect of stations. The southern end of the transect had charact...

The temporal development of a spring diatom bloom in the southeast Bering Sea middle shelf for three consecutive ice-free years is analyzed. Physical and chemical criteria are used to divide the bloom period into prebloom, bloom, and postbloom stages. At this shelf depth, the shallowing of the mixed layer was most important in triggering bloom cond...

Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12x 104 square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the area's large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nut...

Interactions beween a high latitude, continental shelf, spring phytoplankton bloom and water column physics and chemistry were studied using /sup 15/N measured rates of nitrogen uptake. Peak bloom conditions commenced when the mixed layer shallowed and minimized respirational losses. Integrative light-mixing growth models were accurate during early...

1] We propose that temporal variations within the marine plankton system can induce intraseasonal variations in sea surface temperature (SST) through the effect on solar penetration due to chlorophyll and other optically active organic components. Sensitivity studies with a simple model suggest that these small oscillations in SST may stimulate rad...