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Introduction
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January 2014 - present
Publications
Publications (20)
We determined the net rate of biogenic silica (bSiO2) production and estimated the diatom contribution to new production and organic matter export in the Costa Rica Dome during
summer 2010. The shallow thermocline significantly reduces bSiO2 dissolution rates below the mixed layer, leading to significant enhancement of bSiO2 relative to organic mat...
We investigated biomass and composition of heterotrophic microbes in the Costa Rica Dome during June–July 2010 as part of
a broader study of plankton trophic dynamics. Because picophytoplankton (<2 μm) are known to dominate in this unique upwelling
region, we hypothesized tight biomass relationships between size-determined predator–prey pairs (i.e....
The Costa Rica Dome is a picophytoplankton-dominated, open-ocean upwelling system in the Eastern Tropical Pacific that overlies
the ocean's largest oxygen minimum zone. To investigate the efficiency of the biological pump in this unique area, we used
shallow (90–150 m) drifting sediment traps and 234Th:238U deficiency measurements to determine expo...
We investigated phytoplankton production rates and grazing fates in the Costa Rica Dome (CRD) during summer 2010 based on
dilution depth profiles analyzed by flow cytometry and pigments and mesozooplankton grazing assessed by gut fluorescence.
Three community production estimates, from 14C uptake (1025 ± 113 mg C m−2 day−1) and from dilution experi...
We investigated biomass, size-structure, composition, depth distributions and spatial variability of the phytoplankton community
in the Costa Rica Dome (CRD) in June–July 2010. Euphotic zone profiles were sampled daily during Lagrangian experiments in
and out of the dome region, and the community was analyzed using a combination of digital epifluor...
During summer 2010, we investigated phytoplankton production and growth rates at 19 stations in the eastern tropical Pacific,
where winds and strong opposing currents generate the Costa Rica Dome (CRD), an open-ocean upwelling feature. Primary production
(14C-incorporation) and group-specific growth and net growth rates (two-treatment seawater dilu...
In the offshore waters of Southern California, sub-mesoscale processes associated with fronts may stimulate phytoplankton blooms and lead to biomass shifts at multiple trophic levels. Here we report the results of a study on the cycling of biogenic silica (bSiO2) with estimates of the contributions of diatoms to primary and new production in water...
As part of the California Current Ecosystem Long Term Ecological Research (CCE-LTER) Program, samples for epifluorescence microscopy and flow cytometry (FCM) were collected at ten ‘cardinal’ stations on the California Cooperative Oceanic Fisheries Investigations (CalCOFI) grid during 25 quarterly cruises from 2004 to 2010 to investigate the biomass...
Ocean fronts with accumulated biomass and organic matter may be significant sites of enhanced microbial activity. We sampled a frontal region (the A-Front) separating oligotrophic and mesotrophic water masses within the California Current Ecosystem (CCE) to assess the influence of frontal hydrography on several microbial parameters. Samples for het...
Spatial variability of plankton biomass, community composition and size structure was investigated across a strong frontal
transition (A-Front) in the southern California Current Ecosystem in October 2008. Depth profiles were taken across a 25-km
transect of nine stations sampled semi-synoptically during one night and for 3 days following drifter a...
Spatial variability of chlorophyll, phycobiliproteins, chromophoric dissolved organic matter and variable fluorescence (Fv/Fm) was analyzed across a deep-water density front in the Southern California Current Ecosystem using an Advanced Laser Fluorometer
(ALF) calibrated to assess chlorophyll concentration (Cchl), total autotrophic carbon (AC) and...
We investigated the biomass, size structure and composition of microbial communities over a broad area of the eastern equatorial Pacific (4°N-4°S, 110-140°W) during cruises in December 2004 (EB04) and September 2005 (EB05). Vertical-profile samples were collected at 30 stations at depths extending from the surface to the 0.1% light level, and each...
Phytoplankton dynamics were investigated in the eastern equatorial Pacific at 32 stations sampled during two cruises (December 2004 and September 2005). Based on standing stock analyses from HPLC pigments, flow cytometry and microscopy, we used a modified 2-treatment approach of the seawater dilution method to estimate taxon-specific phytoplankton...
The relative roles of silicon (Si) and iron (Fe) as limiting nutrients in the eastern equatorial Pacific (EEP) were examined in a series of nine microcosm experiments conducted over two years between 110 degrees W and 140 degrees W longitude. Si and Fe additions had consistently different but synergistic effects on macronutrient use, phytoplankton...
We investigate the hypothesis that phytoplankton growth and grazing processes are strongly balanced in high-nutrient low-chlorophyll (HNLC) waters of the equatorial Pacific using euphotic-zone estimates of rates and biomass determined for 30 stations during EB04 (December 2004) and EB05 (September 2005). As predicted by the balance hypothesis, dept...
[1] To understand and quantify plankton community dynamics in the ocean, high-resolution models are needed to capture the temporal and spatial variations of physical, biological, and biogeochemical processes. However, ecosystem models often fail to agree with observations. This failure can be due to inadequacies in the data and/or inadequacies in t...
Two novel and independent couplings of field data sets suggest that only ~10-20% of the biogenic silica (bSi) in the surface waters of the eastern equatorial Pacific upwelling zone is associated with living diatoms. Accounting for the ~80-90% contribution of detrital bSi reconciles discrepancies between estimates of diatom growth rates obtained by...
To understand and quantify plankton community dynamics in the ocean, high-resolution models are needed to capture the temporal and spatial variations of physical, biological, and biogeochemical processes. However, ecosystem models often fail to agree with observations. This failure can be due to inadequacies in the data and/or inadequacies in the m...
The equatorial Pacific plays a central role in the global carbon cycle as the largest oceanic source of CO2 to the atmosphere. The region has been described as a HNLC (High Nutrient, Low Chlorophyll) region with low chlorophyll being explained by either Fe limitation, Si(OH)4 limitation, or a combination of the two. The autotrophic community in the...
Questions
Question (1)
I am having some problems deciding which type of regression to use, OLS or RMA. I find support for each one with my dataset and goals. I am regressing nitricline depth against C:Chl ratios. The thoughts for using RMA are that there is error in both measurements and the objective is to possibly define a mutual and codependent underlying the interaction between X and Y (Sprent, 1966). However, the thoughts for using OLS are X (NC) is being used to predict Y (C:Chl) (Smith, 1994), the purpose of the regression is to understand the range of Y values at a given X, and the error in X is << than error in Y. Any thoughts would be helpful.
