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Peter Gaube

Principal Oceanographer






B.A. Ecology and Evolutionary Biology, University of Arizona, 2003

M.S. Physical Oceanography, Nova Southeastern University, 2007

Ph.D. Oceanography, Oregon State University, 2012

Peter Gaube's Website



2000-present and while at APL-UW

Marine phytoplankton down regulate core photosynthesis and carbon storage genes upon rapid mixed layer shallowing

Diaz, B.P., E. Zelzion, K. Halsey, P. Gaube, M. Behrenfeld, and K.D. Bidle, "Marine phytoplankton down regulate core photosynthesis and carbon storage genes upon rapid mixed layer shallowing," ISME J., EOR, doi:10.1038/s41396-023-01416-x, 2023.

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8 May 2023

Marine phytoplankton are a diverse group of photoautotrophic organisms and key mediators in the global carbon cycle. Phytoplankton physiology and biomass accumulation are closely tied to mixed layer depth, but the intracellular metabolic pathways activated in response to changes in mixed layer depth remain less explored. Here, metatranscriptomics was used to characterize the phytoplankton community response to a mixed layer shallowing (from 233 to 5 m) over the course of two days during the late spring in the Northwest Atlantic. Most phytoplankton genera downregulated core photosynthesis, carbon storage, and carbon fixation genes as the system transitioned from a deep to a shallow mixed layer and shifted towards catabolism of stored carbon supportive of rapid cell growth. In contrast, phytoplankton genera exhibited divergent transcriptional patterns for photosystem light harvesting complex genes during this transition. Active virus infection, taken as the ratio of virus to host transcripts, increased in the Bacillariophyta (diatom) phylum and decreased in the Chlorophyta (green algae) phylum upon mixed layer shallowing. A conceptual model is proposed to provide ecophysiological context for our findings, in which integrated light limitation and lower division rates during transient deep mixing are hypothesized to disrupt resource-driven, oscillating transcript levels related to photosynthesis, carbon fixation, and carbon storage. Our findings highlight shared and unique transcriptional response strategies within phytoplankton communities acclimating to the dynamic light environment associated with transient deep mixing and shallowing events during the annual North Atlantic bloom.

Biophysical dynamics at ocean fronts revealed by Bio-Argo floats

McKee, D.C., S.C. Doney, A. Della Penna, E.S. Boss, P. Gaube, and M.J. Bahrenfeld, "Biophysical dynamics at ocean fronts revealed by Bio-Argo floats," J. Geophys. Res., 128, doi:10.1029/2022JC019226, 2023.

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1 Mar 2023

The straining regions of the ocean in between mesoscale eddies contain large vertical velocities that may be important in regulating phytoplankton accumulation rates. We analyze time series of variables measured by ocean Bio-Argo floats (mixed layer depths [MLDs], chlorophyll, and carbon concentrations) in conjunction with variables derived from satellite altimetry (strain rates, Lyapunov exponents, vertical velocities) to determine the evolution of mixed layer phytoplankton biomass in response to straining by the mesoscale geostrophic flow. A Lagrangian (water parcel following) framework is justified by restricting the analysis to profiles whose value of a Quasi-Planktonic Index — an index quantifying averaged distance between a float trajectory and a surface geostrophic trajectory over three consecutive time steps — is less than 5 km. Bin-averaged Lagrangian derivatives of phytoplankton biomass and chlorophyll concentration are positive for elevated strain rate and upwelling quasigeostrophic vertical velocities. Lagrangian derivatives of MLD and phytoplankton carbon averaged at straining fronts (in rotated along- and across-front coordinates) have features in common with submesoscale dynamics, including increasing phytoplankton carbon (and chlorophyll) and a shoaling mixed layer over the front. To elucidate a mechanism, we average time derivatives of modeled cell division rates, finding the pattern approximately matches the pattern of phytoplankton accumulation rates and is controlled primarily by the term modulating light stress, suggesting that frontal dynamics cause accelerations of division rates by increasing available light. Regions of increasing chlorophyll are also approximately co-located with upwelling quasigeostrophic velocity, suggesting non-Lagrangian behavior of floats causes some imprint of larger scale, more persistent mesoscale signals.

Lagrangian and Eulerian time and length scales of mesoscale ocean chlorophyll from Bio-Argo floats and satellites

McKee, D.C., S.C. Doney, A. Della Penna, E.S. Boss, P. Gaube, M.J. Behrenfeld, and D.M Glover, "Lagrangian and Eulerian time and length scales of mesoscale ocean chlorophyll from Bio-Argo floats and satellites," Biogeosciences, 19, 5927-5952, doi:10.5194/bg-19-5927-2022, 2022.

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21 Dec 2022

Phytoplankton form the base of marine food webs and play an important role in carbon cycling, making it important to quantify rates of biomass accumulation and loss. As phytoplankton drift with ocean currents, rates should be evaluated in a Lagrangian as opposed to an Eulerian framework. In this study, we quantify the Lagrangian (from Bio-Argo floats and surface drifters with satellite ocean colour) and Eulerian (from satellite ocean colour and altimetry) statistics of mesoscale chlorophyll and velocity by computing decorrelation time and length scales and relate the frames by scaling the material derivative of chlorophyll. Because floats profile vertically and are not perfect Lagrangian observers, we quantify the mean distance between float and surface geostrophic trajectories over the time spanned by three consecutive profiles (quasi-planktonic index, QPI) to assess how their sampling is a function of their deviations from surface motion. Lagrangian and Eulerian statistics of chlorophyll are sensitive to the filtering used to compute anomalies. Chlorophyll anomalies about a 31 d time filter reveal an approximate equivalence of Lagrangian and Eulerian tendencies, suggesting they are driven by ocean colour pixel-scale processes and sources or sinks. On the other hand, chlorophyll anomalies about a seasonal cycle have Eulerian scales similar to those of velocity, suggesting mesoscale stirring helps set distributions of biological properties, and ratios of Lagrangian to Eulerian timescales depend on the magnitude of velocity fluctuations relative to an evolution speed of the chlorophyll fields in a manner similar to earlier theoretical results for velocity scales. The results suggest that stirring by eddies largely sets Lagrangian time and length scales of chlorophyll anomalies at the mesoscale.

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In The News

Where food is scare, ocean predators find snacks in swirling eddies

Popular Science, Laura Baisas

New research shows how billfishes, tunas, and sharks survive in ocean 'food deserts.'

8 Sep 2022

What Are Ocean Predators Doing So Deep Underwater?

The Atlantic, Stephanie Pain

Fitted with electronic tags incorporating a suite of sensors, tracking devices, and occasionally tiny cameras, deep diving animals gather information where human researchers can't. They have revealed remarkable journeys across entire oceans, and they've shown that diving deep is pretty much ubiquitous among large marine predators of all kinds.

5 Jun 2022

Call of the Deep

Knowable Magazine, Stephanie Pain

Some of the ocean’s biggest predators dive way down into the cold, dark depths. Animals-turned-oceanographers are helping biologists find out what they do when they get there.

31 May 2022

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